Detailed Update On Next Week’s Storm Potential

If you are hoping for a significant storm to arrive mid-week, I can tell you that the models are digging in their heels and while they are handling the storm differently, they are reaching pretty similar conclusions. I have a lot of content today and if you want to scroll down to the summary portion of the post I will share my thoughts.

A couple of weeks ago, I talked about mid to long-range forecasting (10-16) days and the good reasons to use an ensemble version of a model, I also talked about my own take on ensembles and my experience with the best time to switch over to individual model runs from the ensembles. Basically, in the early stages, I use the ensembles while also tracking the trend of the underlying deterministic models. The closer we get to the storm arrival the more heavily I rely on the run to run consistency of the deterministic model runs.

The Euro has 50 family model member under its umbrella, the GFS has 25. According to the Euro’s site here is the proper definition of the ensemble:

“An ensemble weather forecast is a set of forecasts that present the range of future weather possibilities. Multiple simulations are run, each with a slight variation of its initial conditions and with slightly perturbed weather models. These variations represent the inevitable uncertainty in the initial conditions and approximations in the models. They produce a range of possible weather conditions.”

The downside and this is according to me, is that in my opinion, the extremely low resolution that is used in all ensemble models plays a big role in missed forecasts in our area because of our topography. At this stage, I am watching both the deterministic models and the ensemble models and as I mentioned, and as you will soon see all of the models are doubling down on this storm.

We will start with the Euro ensemble mean run. This displays the average of the 50 models. The onset of precipitation starts sometime between overnight Tuesday into Wednesday but may be delayed.

We’ll start with total liquid precipitation regionally. This is the average of the 50 euro models

1116euroensqpf

Here is how that translates to snow

 

1116euroenstotalsnow

Next to the GFS ensemble for QPF (total liquid precipitation)

1116gefsqpf.png

GFS ensemble snow

1116gefssnoqreg

Here are the zoomed-in versions, as you will see using the ensembles I can’t show you the level of detail that I do with the deterministic models, which is fine because we are watching the trend with the ensembles. Later in the post, I will show you both of the latest operational model runs.

Euro ensemble precip

1116euroensqpf

GFS ensemble (GEFS) precip

1116gefsqpfzoom

Euro ensemble snow

1116euroenssnowzoom

 

GFS ensemble snow

gefssnowzoom

This would be a really good time to remind you not to take this 100 % at face value, rather it just instills some confidence about our first major snow event for the mountains next week. It will probably be Tuesday or Wednesday before I attempt a snowfall forecast. The NWS is keeping an eye on this system, depending on who you talk to, and we may hear some early talk about the need to issue a Winter Storm Watch by Monday or Tuesday.

Summary

What do I think? Well, while it is great to see the models pick up on the moist sub-tropical air getting involved, the dry conditions that we have experienced for months are difficult to overcome with the first major storm. There seems to be a feedback mechanism we get where if our soil moisture is abnormally dry, as it has been, it takes a considerable amount of moisture to overcome the tendency to evaporate the moisture before and as it falls. If you have followed me for a while you know the opposite is true as well, when the soil is excessively wet it takes very little energy to revive or enhance a storm as it moves across the area. Some of the model runs I have seen generate a HUGE amount of precipitation in Arizona, as much as 3-5 inches from some of the models, this is the type of set up that would be enough to overcome the dry conditions, similar to last New Years. So I am cautiously optimistic, and I will be watching every model run between now and then to observe any trend that arises.

I promised you a look at the deterministic model runs, here were last night’s Euro and GFS for precip and snow.

Euro precip

1116europrecipcol.png

Euro snow1116eurocol

GFS precip

1116europrecipcol

GFS snow

1116gfscolsnow

What is amazing to me is how similar the model runs are this far out.

Beginning Monday I will update every day. For those traveling, it appears once you get out of our area you should be fine, assuming the models continue to trend in this direction.

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A Change Is Coming

Last week there were a couple of model runs, especially the Euro that showed a storm trying to develop in our area. Those couple of model runs turned out to be anomalies, it is likely the small system won’t make it over the continental divide, in a best-case scenario flurries fall over the 550 passes Saturday.  A change is coming but it’s 5-8 days away.

So far, November has had a trough in the midwest and east and a ridge in the west.  To determine these forecasters look at a 500 mb height map (mb stands for millibars, which is a unit for measuring air pressure). These maps are very good for getting a picture of the large-scale “weather pattern” over the United States, North America, or even the Northern Hemisphere. 500 mb maps are especially nice for studying wintertime weather patterns in the middle latitudes (between about 30° and 60° latitude).  The colors correlate with air-pressure NOT TEMPERATURE. So red doesn’t necessarily mean warm nor does blue mean cold. Red means above-average heights (ridge) and blue means below-average heights (trough). Ridge’s are usually associated with tranquil weather and troughs are associated with stormy weather.

Here is the current 500 mb height map

GFS500current.png

As I said earlier the pattern has looked similar to this all month.

The pattern will start to change at the beginning next week and one week from now is forecasted by the GFS model to look like this.

gfs5001121.png

Here is the current GFS run for next Thursday using different parameters that you are more familiar with seeing on this site.

gfs-deterministic-namer-instant_ptype-4337600

You can clearly see the low pressure in Arizona, in the northeast and a massive, nasty storm in the Bering Sea, in weather terms, this storm is “bombing out” and is the equivalent of a category 3 hurricane in intensity. It is not at all unusual to sea storm like this in the Bering Sea, they usually are the result of a recurving typhoon from the SW Pacific.

Here is a zoomed-in version of the map above.

zoom.png

There are four circles, one over the four corners one in southern Arizona one in New Mexico and one in eastern Colorado and western Kansas. Those are closed areas of circulation of low pressure. Above the low pressure over the four corners, you see a red line and if you follow along the red line you will see a 552, which tells me that below the 552 line the snow level will be approximately 8,000 feet. The red line above the 552 is the 546 line which is important for us because the snow level drops to 6500 feet.

All said and done here is what the GFS is currently showing for snow from that storm

GFSsnow.png

Here is the Euro

eurosnow.png

 

When we are this far out the models will often agree with outcomes but disagree with how they arrive at that outcome. That is exactly what is going on right now, they are seeing the strong potential for this event but one or all of the models will likely be right, for the wrong reasons. That happened several times during the 2016-2017 winter. So I would not take this to the bank yet but it is sure fun to see on the maps.

Looking out for the rest of November is exciting if you like stormy weather

Now that you know how to interpret the upper air pattern maps check out the last week of November.

gfs-ensemble-all-avg-namer-z500_anom-1573711200-1574445600-1575093600-40

Check back on Saturday for my next update. Thanks for following and supporting the site!

 

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Purgatory Opening Day

Purg’s planned opening day is 11/23/19, a week from Saturday. The Euro operational model run has a 10 day (240 hours) lead time for forecasts, the Canadian model is the same, the GFS model has a longer window 16 days (384 hours).

The biggest mistake new weather enthusiasts (who have weather model access) make, is seeing one particular long term (10-16 day) model run and getting too excited about what they see. As I have preached over and over, you have to look for model agreement with itself (consistency) and model agreement among other weather models. You then need to take into consideration model bias. The GFS bias is nearly exactly opposite what the Euro bias is. The GFS likes to move storms from west to east too quickly, this can cause an issue with timing and intensity. The Euro has its own issues with timing and intensity, its bias is to place storms further west and hold them deeper in the west for too long before tracking them east across the country. These biases show more prominently in the early stages and slowly correct, at times having a final correction in the last 24 hours before arrival.

Take a look at the GFS for next Wednesday 11/20/19

GFS1120

The important thing to look at is the position of the closed low-pressure system in SW Utah (look for 1001).

Now look at the Euro for the exact same time

euro111212z198

The low position is still off the California coast (the L with 1006)

Fast forward to hour 240 GFS

 

gfs240na

The GFS has already moved the storm well into the midwest.

 

Here is the Euro at 240 hours

euro1121240.png

The main low is still spinning offshore circulating deep moisture all of the way into our area, btw if you are concerned about all of the green versus blue, don’t be too concerned, on this particular model run the snow level is 8,000 feet.

So 10 days out there is roughly an 1800 mile difference between the location of the storm centers.

Of course, it is right at the very end of the model run that things start to get good on the Euro (240 hours). Looking at the GFS it has had some very impressive snow totals for this storm over the last several runs.  In fact, the GFS has shown storm totals between 10-30 inches. Since the GFS runs are 6 days longer than the Euro, of course, I had to look and it showed another decent storm around Thanksgiving.

At this point, I am cautiously optimistic that we will see a pattern change and I am pleased that I have something to talk about, I also find it interesting that we had snow at the same time last year.

I will do another update on Thursday it will be interesting to compare the same models for the same times next week.

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Factors Affecting Winter 2019-2020

Meteorological Winter officially starts December 1st, but I am sick of waiting so let’s look into the upcoming Winter a little more closely! Weather nerds will enjoy this post, not all of you fall into that category so I have added headings, at the end will be a summary plus a look at the last half of November if you wish, scroll down to the end.

Before I start I wanted to share a conversation I recently had with Mrs. Weatherguy. Me: “I am so sick of this horrible weather.” Mrs. WG: “The weather is going to be horrible?” Me: “It IS horrible, and it is going to continue to be horrible for another week or so”  Mrs. WG: “What do you mean there are no clouds, no wind and it is close to 60 degrees” Me: “I know isn’t it horrible?”

This conversation led me to look back at fall last year, was it this boring? What were we talking about at this time last year? Were conditions similar and if so does that mean we could be setting up for a similar winter to last year?

 

Last Year

October 2018 Temps

october2018.png

The last 30 days have looked like this

Screenshot 2019-11-08 at 11.14.51 AM

Not a match, but certainly very similar temperatures

 

ENSO (El Nino Southern Oscillation)

Last year we were approaching an El Nino event, but it was an El Nino Modoki (rhymes with Okey-dokey).  A typical El Nino shows warming along the equator in the Pacific off the coast of South America. There are four regions that makeup El Nino: 1+2, 3, 3.4 and 4.

nino-regions.gif

If the warming is more pronounced in the blue area above than the white and red areas it is a Modoki. Below is a good illustration of the difference.

 

modoki

Here are the current Sea Surface Temps.

anomnight.11.7.2019

 

Here is the forecast for the Sea Surface Temps in the El Nino region this year, this is measured as a blend of the temperatures in the 3.4 region. It is important to mention that there was still some disagreement at this time last year whether or not we would make it to an El Nino.

figure4_1.png

Every colored line is a forecast from a weather model. Everything above the .5 on the left is a forecast for an El Nino, everything below the -.5 on the left is a forecast for a La Nina. The letters on the bottom are three-month overlapping periods (SON=September, October, November etc.) The problem I have with the formal classification of an El Nino or La Nina is it has to occur for 5 of the 3 month overlapping periods in a row to be considered an El Nino or La Nina. You can experience El Nino or La Nina conditions without it meeting the several month criteria. Some of the snowiest winters here have been in Neutral or Modoki years. In this forecast, the majority of the models are between +.5 degrees and -.5 degrees. It will be very interesting to see the next ENSO forecast.

NOAA has been predicting an 85% chance of a neutral (La Nada) winter. However, in the latest update this week it is starting to show Modoki conditions developing. The warmer temperatures are located further west in the 3.4 region and into the 4.0 Nino region.

enso-stats-11.4.19.jpg

In the illustration above the Modoki region is in yellow.

Wait It Gets More Complicated

It sure would be nice if that was all we have to take into consideration, but as I have said ENSO status is a very simplistic way to predict what will happen in the Winter. Of course, El Nino and La Nina are the most recognized of all climate modes so they are the most hyped by the media, in reality they are a very small piece of the puzzle. There are many other climate modes you have to take into consideration. the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO) and Antarctic Oscillation (AAO), the Pacific North American Oscillation (PNA) pattern, the Eastern Pacific Oscillation (EPO), the Western Pacific Oscillation (WPO) and the Indian Ocean Dipole (IOD). All of these factors have a positive, neutral, and negative phase (just like El Nino is a positive status and La Nina is negative status) and they all feedback into the MJO (Madden Julian Oscillation).

The MJO

It is time once again for me to talk a bit about the Madden-Julian Oscillation or the “MJO” as forecasters like to refer to it.  The Madden-Julian Oscillation is a tropical disturbance that moves clouds, winds, precipitation, and pressure changes eastward around the global tropics about every 30-60 days.  Typically,  in the Northern Hemisphere the late fall, winter, and early spring have the greatest level of MJO activity.

There are phases in the MJO cycle and models predict where the cycle is headed generally 14 days in advance.  Below is the MJO forecast. The numbers 1 through 8 correspond to the 8 phases of the MJO cycle. The red and purple lines are the past, the green line with black dots is the forecast for the future.  The black dots on the green line are days  You literally have to count the dots on the green line because only the past dates are listed (on the purple and red).

Last year I did an in-depth post on the MJO, this was the forecast for November 24th to December 8th (2018) from the GFS.

MJOGEFS1124

At the time we were transitioning from phase 6 into phase 7 (don’t worry I’ll explain the phases in a minute, I have charts!). I mentioned amplitude earlier, anything close to or in that circle means the MJO will have very little effect on the weather. I labeled that “Null”. The further you go outside the circle the more the MJO affects our weather. I labeled those “Moderate Amplitude” and “High Amplitude”. By counting the dots on the green line you will see we are forecasted to go into a moderate phase 8 around 11/29 and into a moderate phase 1 December 3rd. The red line is the past, you can see that at that time we had been in phases 3,4,5,6 for the last 18 days.

I specifically used last years MJO forecast at the time so that I could contrast that with the current MJO forecasts from the Euro and the GFS

GFS

MJO Nov 9

Here is the Euro MJO forecast

euromjonov9

Not only are they similar to each other, but they are also similar to late last November. Once again we are transitioning from phase 6 to phase 7 after a couple of weeks in 3, 4, and 5, we are then forecasted to go into phase 8 and 1, so what does that mean?

The Phases change depending on what months we are in, so phase 7 in one month can be completely different than phase 7 in another month.  As you can see from a temperature perspective phases 8, 1 & 2 are colder and generally stormier phases for us.

 

MJOTempsNDJ

Remember as I said the lower amplitude of the phase we are in the lower the impact of the MJO on our weather. Also, the shorter amount of time that is spent in a particular phase the lower the impact. Going back to the forecast we are expected to zip right through phases 6 and 7, get about halfway through 8 then things start backing up and slowing down this occurs around 11/15/19 according to both of these models.

So let’s look at what happens as we get into next weekend according to the models. Fast forward to Friday through Monday.

GFS

gfs-deterministic-cw-instant_ptype-1573279200-1573819200-1574078400-80.gif

Euro

ecmwf-deterministic-cw-instant_ptype-1573257600-1573862400-1574078400-80.gif

Good News And Bad News

The good news is these forecasts team up well with the corresponding operational models, the bad news is the models can be wrong so while it is encouraging to see the models agree with not only themselves but also with each other, it is still too early to be sure. The best thing to take from this is how the MJO and all of the teleconnections (PNA AO, NAO, EPO, WPO) feedback into the MJO which can have an effect on our weather halfway around the earth. The other thing that is interesting to me is how similar the MJO phases we are in this year are to last year.

 

Other Factors

Other important factors are the Pacific Decadal Oscillation (PDO), the Atlantic Multi-Decadal Oscillation (AMO) and the Quasi-Biennial Oscillation (QBO) which can affect Stratospheric warming (Polar Vortex outbreaks). These factors, as well as some of the other teleconnections I mentioned above, also correlate with one of the biggest drivers of weather going back to the beginning, the Sun.

SC25_year

Since 1849, there have been 114 years (including 2019) with at least 1 spotless day. The chart above shows the 25 years with the highest number of spotless days. 1913 is record holder with a staggering 311 days, while 2008 ranks fourth in years with a spotless sun (265 days). With 262 days, 2009 falls just short of 2008 but it still makes it in the top 5 of years with most blanc suns, testifying of the deep minimum prior to the onset of SC24. Last year in 2018 there were 208 days  (green bar) which put it into the top 25 years with most spotless days. It’s currently ranking 15th place, well behind 2008 and 2009.

2019 is on track to be the period of the lowest solar activity since 2009. So far this year we have had 234/313 days without sunspots. This year could very well put us in the top five for low solar activity. It is easy to draw conclusions that low solar means heavy snow especially when you see 2008-09, 2009-10 and 2018-19 years which were all memorable in this area but on its own, there is no direct conclusion that can be made, what you can conclude is that it affects all of the other factors that can drive our winter.

Analog Years

When forecasters are brave enough to attempt to put out a Winter Forecast they start by going back to the past, they take into consideration all of the present and recent factors in the current state of the weather, then they compare those to similar conditions in the past, they then look at what occurred during those years and weight the significance of those events to try to forecast the upcoming winter. Those years that they identify are called Analog years. Last year we had some fun early season looking at the analog years and what is ironic is that the analog years I kept hearing from forecasters were some notable years of high snow accumulation for our area. It was because of the years listed that I came out and said I thought there would be a good chance of slightly above average snowfall for our area. Of course, no one, and I mean no one late last fall anticipated that it would be the wettest winter in recorded history for the US as a whole.

Before I get to the analog years I want to state an opinion, the majority of the Companies and individuals who issue these winter forecasts tend to focus on the east coast. I get it, that is where the population centers are,  but I do think whether they realize it or not they come up with some of these analogs based on what happened those years in the east, not necessarily the west. Last year most forecasters were sure the SE US was going to have an unusually severe winter and the storm path would direct those storms up to the NE. They also expected a dominant trough in the eastern US. Neither of those things happened.

With all of that being said here are the analog years I am hearing for the upcoming winter. From one source I follow 1962-1963, 2004-2005, 2013-2014, 2014-2015 and 2018-2019. Yes 2018-2019, and guess what? He is double weighting 62-63 and 2018-19 in his forecast, because of the low solar activity. Overall, he is calling for very slightly above average temps and average precipitation for our area. Another company I follow is using the following years as analogs 61-62, 83-84, 2002-2003, 2012-2013, 2013-2014, 2014-2015 and yep 2018-2019.

I have devised a way to score each of these years to correspond snowfall potential, soley based on analogs.

AVG= Average (0), A=Above(+1), WA=Well Above(+2),  B=Below (-1), WB= Well Below(-2)

snowscore

Using the same methodology (that I made up) let’s take a look at the analogs that were used for last year.

1819snowscore.JPG

Summary and a look ahead

As I mentioned in the MJO discussion there is a chance of some precipitation next weekend. I will be tracking it, but we are in a very nasty pattern right now, a chance is better than no chance, but it is going to take a lot to break down that ridge over the west coast, if we can weaken it bit by bit we may see that ridge allow a few systems to come underneath. Last year was pretty depressing around this time of year, our first advisory in for the mountains last November came right before Thanksgiving, and the storm did not pan out as well as had hoped. A series of systems from the NW came in December which loaded up the Central and Northern Mountains with snow, mostly missing us. Our first big break came just before New Years and as we all know it got completely ridiculous after that, then we took a break from snow from January 20th through February 5th, then it got ridiculous again. Nobody expected how much snow we got in January and February, nobody.

A number of factors will influence our winter once again this year, if you skipped over the other sections to get to the end, you may want to glance through when you have more time for a better explanation. I have concerns about a number of the analogs being used by forecasters this year, on one end of the spectrum you have 2013-2014 and 2002-2003 among others which were horrible snow years, in the last month one season has recently been added to analogs by many and that is last year, 2018-2019, in some cases it is being given double emphasis. Which gives me hope of at least an average year for snowfall. However, if I were pressed right now I would guess that we will have average to slightly below average snowfall this year from Purgatory south. Below-average snow south of 160 and slightly above average snow for Telluride, Silverton, Pagosa and Wolf Creek. This could all change in the coming 4 to 6 weeks for me but that is what I see now.

I am very much looking forward to keeping you updated this winter and if I get the support from donors like I did last winter I have plans to add some data suppliers and a few other fun things to enhance the overall experience of the site. Thanks for following and for your continued support.

 

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A Look Ahead And My Take On NOAA’s Outlook

Before I jump into this Winter let me say that I love “fall back season”. Apparently, this is a polarizing issue between night people and morning people, being the latter I love it. The other thing about it is weather models don’t observe the time change so this means I get access to weather model runs 1 hour earlier, it occurs to me that getting excited about seeing weather model runs 1 hour earlier in the morning is slightly pathetic but the nerd in me often dictates my thoughts.

We are in a stale weather pattern for sure. Over the weekend there were a couple of model runs showing a closed low moving onshore and through Arizona and New Mexico rotating moisture into our area that would fall as rain for most and snow above 9,000 feet. Lately, that has not been the case as the moisture stays south of the Colorado border, it could change, but it looks so insignificant it is almost not worth talking about. So looking ahead the next 10 days is not very exciting for precipitation. Here are the 10-day snow totals for the big three models.

Euro

ecmwf-deterministic-conus-total_snow_10to1-3689600

Canadian

gem-all-conus-total_snow_10to1-3689600

GFS

gfs-deterministic-conus-total_snow_10to1-3732800

No comment needed, dry as a bone. I do expect the pattern to try to change by the end of the month, at least for a while.

 

This is the time of year that I get questions about NOAA’s Winter Outlook. To clarify, NOAA does not make Winter Forecasts, it releases a probability scheme. Here is the latest for the upcoming Winter.

IMAGE - for 101719 - U.S. map - Temperatures likely - Winter Outlook 2019 - Climate.gov - Landscape NATIVE inset

People will quickly look at this and say “Ok, it is going to be warm in the SW US”. It is actually not that simple, what it is actually saying is that according to NOAA there is a 40%-50% chance that it will be warmer than “normal”. When I hear that I like to point out that it also means that there is a 50%-60% chance that it will not be warmer than “normal”. At best it is guidance, last year that guidance did not go well.

Here was their 2018-2019 Outlook

 

2018-2019noaa

Here is how last Winter actually turned out. It is literally almost the opposite of what the Outlook had.

actual

So much for long term forecasts. Last year at this time I was more confident in my thoughts on the upcoming Winter. This year there are a lot more wildcard scenarios, it is important to keep in mind that the oceans play the biggest role in our weather patterns. The amount of convection in the Indian Ocean has a huge impact on the weather around the world. Last year was widely reported to be an El Nino, technically it was, but it needs an asterisk because it was an El Nino-Modoki, which oftentimes mimics a La Nina. This year NOAA is saying we have an 85% chance of neutral enso-conditions. But other countries Meteorological agencies are starting to see another Modoki event. Some of the heaviest snowfalls in SW Colorado have occurred during ENSO neutral conditions.

I think that conditions are still evolving and it is too early to come to any conclusions yet about what to expect this winter. I have gone as far as saying I think the Winter will start late similar to last year. I am not entertaining any thoughts of a repeat of last year, not yet anyway. Nor do I think we are doomed. So to those of you already worried about this Winter, be patient, it is too early to worry.

 

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Update on Halloween Temps And Record October Cold

Dress warm this evening if you are going to be outside, temps between 6-8 pm will be between 24-30 in town. Temps are going to rebound on Friday and throughout the weekend.

I can honestly say I can’t remember a colder snowier October for most of the state. The near misses of storms for our area are not particularly unusual. Yesterday’s highs and this mornings low were colder than what we typically see for average temperatures December and January.

As cold as we are our neighbor to the west set an all-time low-temperature record for the Uniter States for October. At Peter Sinks, Utah, a natural sinkhole just northeast of Logan, the temperature hit 46 degrees BELOW zero. This edged out a record of -45 in Clearwater Alaska on October 31st, 1975.

There is not a lot of weather in the pipeline as I look out for the next 10 days. As soon as I signs of the pattern changing I will let everyone know. If you have any questions do not hesitate to email me, remember I don’t check Facebook regularly when we are in a boring weather pattern.

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BRRRR

I probably jumped the gun this morning when I drank the Kool-Aid from the US short term HiRes model. It’s called wishcasting and it is a problem with forecasters at all levels of experience, you see a model run that you hope is right and use that to justify a forecast. I am not immune. I deleted my FB post from this morning, only 2600 people saw it, if you are one of them refer to yesterdays post. I will not change my forecast from yesterday but based on the new Euro I have very low confidence in the accumulations I posted then. What will be correct is the cold air, tomorrow may be a bit colder than today especially in the morning.

In the coming days, we will move into yet another boring weather pattern. The rest of the state, as well as the upper midwest and the northern Rockies, have had an amazing October. Four snowstorms in Denver, Steamboat will finish the month with close to 5 feet of snow, parts of Wyoming and Montana have seen 7 feet of snow this month. I am going to do my best to provide a better look at our winter forecast next week during the boring weather pattern. At the moment it looks like the first 10-15 days of November will be pretty dry with a pattern change coming the last half of the month (right on time?) we will see.

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Storm Two And Halloween Weather

The cold air that came in with the light snow overnight will continue and likely get a bit colder as another reinforcing blast of cold and (even lighter) snow will head into the area Tuesday. As I have said I expect the light snow do be mostly north of Haviland. It will be cold dry snow so ratios will be high. At the moment I think 1-3″ for Purgatory, 2-5″ for Telluride, Silverton, Ouray and Wolf Creek.

Unfortunately, after this system moves out late Wednesday things will be quiet as we move into November, temperatures will go from substantially below average to average then slightly above average through at least the middle of next week.

See below our temps on Wednesday will be 15-25 degrees below average depending on your location, while other parts of the state will be 50 degrees below average (literally off the chart below)

ecmwf-colorado-t2m_f_anom-2458400.png

For those of you interested in the temperature for Halloween, at this time it appears after 6 pm temps will fall into the low to mid 20’s in town, and teens in the higher elevations.

I don’t expect this storm scenario to change, but I will do another update tomorrow morning just in case.

 

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Advisories Issued But It’s Complicated

At first glance, people will be jumping up and down after reading the first couple lines of this advisory.
COZ019-272300-
/O.EXB.KGJT.WW.Y.0037.191028T0600Z-191029T0000Z/
SOUTHWEST SAN JUAN MOUNTAINS-
INCLUDING THE CITIES OF SILVERTON, RICO, AND HESPERUS
144 AM MDT SUN OCT 27 2019

…WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO
6 PM MDT MONDAY…

* WHAT…SNOW. TOTAL SNOW ACCUMULATIONS OF 5 TO 10 INCHES
EXPECTED, PRIMARILY ALONG AND SOUTHEAST OF THE US 160 CORRIDOR
SOUTH OF WOLF CREEK PASS. LOWER ACCUMULATIONS OF 3 TO 6 INCHES
THROUGHOUT THE REST OF THE SAN JUAN MOUNTAINS.

* WHERE…SOUTHWEST SAN JUAN MOUNTAINS.

* WHEN…FROM MIDNIGHT TONIGHT TO 6 PM MDT MONDAY.

* IMPACTS…TRAVEL WILL BE DIFFICULT, ESPECIALLY OVER WOLF CREEK
PASS. A DETAILED MAP OF THE SNOWFALL CAN BE FOUND AT:
WWW.WEATHER.GOV/GJT/WINTER.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

SLOW DOWN AND USE CAUTION WHILE TRAVELING.

THE LATEST ROAD CONDITIONS FOR THE STATE YOU ARE CALLING FROM CAN
BE OBTAINED BY CALLING 5 1 1.

So let’s look at their detailed map

StormTotalSnowWeb

The map is a little more sobering than the misleading advisory. I have no idea why the advisory was issued for our northern forecast area. I could see them issuing it for Pagosa but you also have to remember that advisory criteria for the mountains;  >8,500′ 6-12″ of snow is a Winter Weather Advisory, >12″ is a Warning. For lower elevations, 3-6″ is an advisory >6″ is a Warning. Based on their map no location in our forecast area will reach advisory level. The models are still very uncertain where the heavier bands of snow will show up if they do at all. However, the models have consistently favored Wolf Creek Pass for heavier snow, I do think 5-10″ is very possible there, but, Wolf Creek is not in Grand Junction’s forecast area, it belongs to the Pueblo National Weather Service office.

Enough rant about the details in the advisory, let’s look at the models. The positioning of the closed circulation of the low pressure will determine where the heavier snow will set up and how far west the snow will fall. Most models indicate the heaviest snow will stretch from Pagosa to Wolf Creek.

The Euro has proven to be the most accurate model over and over, so here is the most likely scenario.

euro.png

So by late Monday afternoon, I have 0-3″ for lower elevations of La Plata County, with 2-4 for Purgatory, Telluride, Silverton and Vallecito, 3-5 for Pagosa and Ouray, 0-1 for Cortez, and 5-10 for Wolf Creek. This set up is not favorable but could be influenced by a piece of energy left behind (leftovers), the models rarely see this until the day of the event so I will have to check that in the morning.

Here is the Canadian, I actually trust the Canadian more than the GFS.

canadian

And here is the GFS which I think will be struggling all winter.

gfsold.png

You may ask why I don’t trust the GFS because the amounts look similar to the Euro, the problem is 6 hours earlier the GFS had something different, and 12 hours ago it was different still, consistency is the most important factor with weather models.

The snow will start from NW to SE beginning around 3 am with the potential for a brief heavier batch to come through around 6 -8 am tomorrow. I think if it starts on time, it will be out of La Plata County by 4 pm or earlier.

The next storm will come through overnight Tuesday, at this point, I don’t expect snow to fall south of Electra Lake, but I do expect Wolf Creek to get more snow. I will talk more about that on Monday and Tuesday.

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A Couple Chances Of Snow Next Week

For the better part of a week, the European model has been suggesting that a storm would come together and bring the Southern Mountains their first best shot of widespread snow of the year between the 28th-31st. The other models struggled with this solution but have lately come to this line of thinking over the last couple of model runs.

I am happy to see how this has come together because it indicates one thing to me, the GFS winter bias has finally caught up with the new version of the GFS. If you remember this new version of the GFS officially replaced the old version in late spring, one of the weaknesses of the favorite model of NOAA, is that it attempts to take winter storms from west to east too quickly, it usually corrects right before the storm hits but not always. If you have followed me for a while you may remember the story of the storm (I believe) in December 2009 when the GFS was predicting 1 inch of snow for the Durango in town area and the NWS swallowed that bait and used that in their point forecasts, the storm dropped in further west than expected and 15-20 inches of snow fell. That particular event was part of the impetus for creating the Facebook page that started all of this. My thought was how can anybody miss a forecast that bad?

There is a big difference in my opinion between the staff at the Grand Junction NWS then and now. My argument in the early days of the page was that they literally would run from a forecast and ignore Durango, and not follow up after making a forecast. There was a bit of a change of staffing that literally ended up with a drunk forecaster from there getting on my page and calling me an ass, to which hundreds of followers came to my defense. Most of the people there are new in the last few years especially the higher leadership and lead forecasters and I really appreciate how much more time they devote to our area.

Here is the bad news, the storm track next week still does not favor us for a lot of snow. However, Denver will likely see one of the snowiest Octobers ever and will likely set a record for all-time October low temperatures, in fact, near or below zero temps may be possible mid-week for Denver.

At the moment, it looks like flakes will be flying for most areas when we wake up Monday morning, it looks like the second storm will mainly affect areas of the northern and central mountains and areas east of the divide. I am not confident yet that we will have any accumulations south of the La Plata and San Juan County border. I will be tracking that second storm over the weekend, hopefully, we will get some more westward correction with the second storm. Either way, Wolf Creek will again be the winner next week (in our area) which will be great for their opening next Thursday!

So to recap snow should start flying in SW Colorado early Monday morning, in Denver light snow could start as early as Sunday afternoon and get heavier Sunday night into Monday. Snow should move out of the state by Monday afternoon, Tuesday afternoon/evening the second storm should move in, again mostly for Denver and the Central and Northern Mountains, but areas north of Purgatory may also see some light snow from early Wednesday morning to Wednesday evening.

Here is what that looks like. This starts on Sunday night at 8 pm and goes through Wednesday evening. The darkest areas of blue the heavier the bands of snow.

euro

I am going to hold off on posting accumulations until Sunday, but if you are going to be traveling across the state between Sunday night and Monday afternoon, and Tuesday night through Wednesday night there will likely be impacts to the highways.

Stay tuned!

 

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