Models Are All In For More!

First of all, let’s get to the latest advisory.

NORTHWEST SAN JUAN MOUNTAINS-SOUTHWEST SAN JUAN MOUNTAINS-
LA SAL AND ABAJO MOUNTAINS-
INCLUDING THE CITIES OF VAIL, CRESTED BUTTE, TAYLOR PARK, BUFORD,
TRAPPERS LAKE, TELLURIDE, OURAY, LAKE CITY, SILVERTON, AND RICO
941 AM MST SAT DEC 7 2019

…WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM MIDNIGHT
TONIGHT TO 9 AM MST MONDAY ABOVE 8500 FEET…

* WHAT…SNOW EXPECTED. TOTAL SNOW ACCUMULATIONS OF 6 TO 10
INCHES WITH LOCALLY HIGHER AMOUNTS UP TO 14 INCHES. EXPECT
LOWER AMOUNTS BELOW 8,500 FEET.

* WHERE…PORTIONS OF SOUTHEAST UTAH AND NORTHWEST, SOUTHWEST
AND WEST CENTRAL COLORADO.

* WHEN…FROM MIDNIGHT TONIGHT TO 9 AM MST MONDAY.

* IMPACTS…TRAVEL COULD BE VERY DIFFICULT.

I like it as written, it makes sense with what the models are forecasting and leaves some room for some surprises. I am still a bit leary of the snow levels to start the night, but tomorrow morning it looks like we will be ok for snow at or above 6,500′ from about sunrise on. I will get to accumulations a little later, but snow totals are going to be dependent on the amount of time the winds blow favorably before and during the storm for each area.

Overview

In case you missed what I wrote yesterday here is the set-up for tomorrow’s storm.       “Another pacific storm will begin to come onshore this evening and start working its way into the Great Basin Saturday. This is a large system and a piece is going to go north and combine with a large longwave trough full of very cold air reaching from the east coast of the US to British Columbia. Another piece will go south, which will be the part of the system that begins to affect us Sunday morning. Late Sunday the northern trough will drop south pushing colder air into our area and flow will change from the SW to Northerly/Northwesterly shutting off the precipitation to most areas except those that prefer NNW flow.” Since I wrote this yesterday I have been seeing more westerly flow in the models.

Timing has not changed much in the models for the last 24 hours-which is surprising to me. It still looks like light precipitation will start falling late tonight mainly above 8,000′ between 11 pm and 2 am. Heavier precipitation will start between 5 am and 8 am, falling as snow mainly at or above 6,500′ accumulations will be difficult below 7,200 feet due to melting. If you wake up and it is completely dry out in the morning that probably means a delay more than a complete miss. If that is the case you can rest assured I have either written a post or am in the process of doing so to let you know the new timing. Different models are showing different temperatures by 4-5 degrees at the surface tomorrow morning at 5 am.

There are a lot of moving parts that will have to come together for any one area to get a lot of snow, the models have been trending up, I made a point of showing the NAM model yesterday with its push for higher snow totals in the areas that favor the northerly, northwesterly, and westerly flow. This could include higher elevations along as well as just north and south of 160 west of Durango. It definitely affects Telluride, Dolores County, and areas around Mancos Hill. That is why I said I liked the wording of the Advisory because it leaves room for upside surprises.

Here are three snowfall forecasts from 3 different models for your viewing pleasure, remember that these are not accumulations, they are snowfall before melting.

Euro

euro12612zsnow.png

GFS

gfs-deterministic-colorado-total_snow_10to1-5925200.png

NAM HiRes zoom

Screenshot 2019-12-07 at 11.55.49 AM.png

Screenshot 2019-12-07 at 11.56.14 AM.png

All three have an interesting take but there are a lot of differences. Some people are going to be very happy and some are going to feel cheated. If the NAM HiRes above is correct, certain mid-elevation areas are going to be very happy! We will see.

If there is anything worth sharing later today I will update, otherwise I will have something out early tomorrow morning.

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Sunday Storm and Vortex Signal

Another pacific storm will come onshore this evening and start working its way into the Great Basin Saturday.

Screenshot 2019-12-06 at 11.58.06 AM.png

This is a large system and a piece is going to go north and combine with a large longwave trough full of very cold air reaching from the east coast of the US to British Columbia.

ecmwf-deterministic-conus-instant_ptype-5720000.png

Another piece will go south, which will be the part of the system that begins to affect Sunday morning.

ecmwf-deterministic-swus-instant_ptype-5806400.png

Late Sunday and  Monday the northern trough will drop south pushing colder air into our area and flow will change from the SW to Northerly/Northwesterly shutting off the precipitation to most areas except those that prefer NNW flow.

ecmwf-deterministic-conus-instant_ptype-5903600

Notice in the above map the tightly packed blue “thickness lines” in southern Canada (Ontario) those 492 and 498 lines have very cold air and indicate that the dreaded polar vortex may center itself in the midwest with cold air filtering down covering much of the country by mid-month. We will see.

Here are the liquid precip amounts that models were predicting on their 5 am model runs Friday morning.

Euro

europrecip12612z.png

GFS

gfsprecip12612z.png

Last the NAM short term mesoscale model, I throw this in the mix because it is really highlighting the NNW flow at the end of the storm and you can see how that affects the totals in the areas that favor north and northwest flow.

namprecip12612z.png

I am not at the point where I favor one model over the other with this storm, I hope tomorrow will shed a little more light on all of these variables.

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Heading North

About 5 minutes after I posted the latest update, I looked at the new mapping data and it indicated that the top portion on the front had separated from the frontal boundaries as the system weakened and is now a part of a shortwave trough near Monticello, Utah. there is precipitation breaking out in front of and just behind the low. This looks like it will clip the northern area as it tracks further northeast into the state.

wu1257am.JPG

Here is the satellite

1257amsat.JPG

We may see a brief snow shower break out, but the air is dry to our south and will likely get caught in the flow which will deter any widespread snow event from occurring. It would likely happen in the next couple of hours if it happens at all. If you see a dramatic pick up in snow or wind let me know where what and when.

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Downgraded Advisory Amounts

NWS downgraded the advisory amounts to 3-6″ above 8,500′. As I mentioned yesterday, I have tried to keep everyone’s expectations low on this storm, the storm is going to die soon the frontal boundary is starting to erode. WU did a great job finding the low pressure and front.

1254amwumap

This is easily verified on GeoColor multi-spectral infrared satellite, I added the front and low on there.

SAT.JPG

Models are still indicating a frontal passage after 8 am, we’ll see. It could still get fast and furious for a while but there is very little moisture left for the low to tap into as it passes. Wolf Creek has been getting snow most of the night, but it has been off and on everywhere else, last I looked Purgatory had started snowing again and had 2-3 inches at 4 am.

If I had to place a bet on when the frontal passage will happen, it would be when I drop my car off at the dealership for service this morning, I will be leaving my house around 8:45 this morning if that helps anyone plan. I will try to do a wrap up this afternoon, and tomorrow we can start talking about the next storm late Sunday early Monday. Good or bad I will take any precipitation we can get in early December, it does not happen as often as you might think!

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Resort Refresh

First of the advisory from the NWS in Grand Junction. If you read it this morning, it has not changed. My ideas on this storm follow the advisory wording.

Advisory

NATIONAL WEATHER SERVICE GRAND JUNCTION CO
305 PM MST WED DEC 4 2019

COZ009-017-019-UTZ028-051200-
/O.CON.KGJT.WW.Y.0042.191205T0000Z-191206T0000Z/
GRAND AND BATTLEMENT MESAS-UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-
SOUTHWEST SAN JUAN MOUNTAINS-LA SAL AND ABAJO MOUNTAINS-
INCLUDING THE CITIES OF RIDGWAY, GLADE PARK, SILVERTON, RICO,
HESPERUS, AND MONTICELLO
305 PM MST WED DEC 4 2019

…WINTER WEATHER ADVISORY REMAINS IN EFFECT UNTIL 5 PM MST
THURSDAY…

* WHAT…SNOW EXPECTED. TOTAL SNOW ACCUMULATIONS OF 6 TO 10
INCHES ABOVE 8,500 FEET WITH LOCALLY HIGHER AMOUNTS UP TO 12
INCHES.

* WHERE…IN UTAH, LA SAL AND ABAJO MOUNTAINS. IN COLORADO,
GRAND AND BATTLEMENT MESAS, UNCOMPAHGRE PLATEAU AND DALLAS
DIVIDE AND SOUTHWEST SAN JUAN MOUNTAINS.

* WHEN…FROM 5 PM THIS AFTERNOON TO 5 PM MST THURSDAY.

* IMPACTS…TRAVEL COULD BE VERY DIFFICULT ESPECIALLY ON THE
MOUNTAIN PASSES. 

My Take

It will be nice to get a few inches of fresh snow for the Ski Areas. That being said I have struggled to get to some of the totals I have been hearing about.  Wolf Creek should get 5-8″.  I can justify 4-7″ for Purgatory and Mayday. Telluride should also hit the 4-6″ range but most of that will fall tomorrow. 2-4″ for most of the mid-elevations, and zero to a heavy inch” in Durango and lower elevations with up .40 inches of total liquid for the low elevations.

Timing and snow levels once again are the details that make this a difficult forecast, this is common in the early season. In case you had not noticed I have been trying to downplay expectations on this storm. It has some similarities in its approach to last week, but the models overproduced last week and I don’t like storms that weaken as they approach. I have to balance that with the fact that it still appears that the frontal passage could impact travel between 5-8 am tomorrow, so even if the overall totals are lower if you are stuck out in it when it comes through it could still be dicey.

Here is the storm coming onshore at 5 pm our time today.

euro5005pmwed.png

Here it is at 5 am according to the latest Euro

euro500thurs5am.png

And here is what is left of it at 2 pm on Thursday

euro500thurs2pm

Just to repeat what I said earlier, just because I am predicting some of the lower amounts you have probably read about, things could still get dicey with the frontal passage so please keep that in mind before writing off the storm. I will update early, probably before you wake up.

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Advisory Issued

The NWS has issued an advisory for 6-10″ above 8,500′ with up to a foot somewhere…

NATIONAL WEATHER SERVICE GRAND JUNCTION CO
329 AM MST WED DEC 4 2019

COZ009-017-019-UTZ028-042300-
/O.NEW.KGJT.WW.Y.0042.191205T0000Z-191206T0000Z/
GRAND AND BATTLEMENT MESAS-UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-
SOUTHWEST SAN JUAN MOUNTAINS-LA SAL AND ABAJO MOUNTAINS-
INCLUDING THE CITIES OF RIDGWAY, GLADE PARK, SILVERTON, RICO,
HESPERUS, AND MONTICELLO
329 AM MST WED DEC 4 2019

…WINTER WEATHER ADVISORY IN EFFECT FROM 5 PM THIS AFTERNOON TO
5 PM MST THURSDAY…

* WHAT…SNOW EXPECTED. TOTAL SNOW ACCUMULATIONS OF 6 TO 10 INCHES
ABOVE 8,500 FEET WITH LOCALLY HIGHER AMOUNTS UP TO 12 INCHES.

* WHERE…IN UTAH, LA SAL AND ABAJO MOUNTAINS. IN COLORADO,
GRAND AND BATTLEMENT MESAS, UNCOMPAHGRE PLATEAU AND DALLAS
DIVIDE AND SOUTHWEST SAN JUAN MOUNTAINS.

* WHEN…FROM 5 PM THIS AFTERNOON TO 5 PM MST THURSDAY.

* IMPACTS…TRAVEL COULD BE VERY DIFFICULT ESPECIALLY ON THE
MOUNTAIN PASSES.

I will update after I go through the models probably around noon.

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Wednesday/Thursday Storm

 

Overview

An area of low pressure will come onshore in Central and Southern California Wednesday morning, rotating up an initial surge of moisture that could trigger a chance of light snow showers in southwest flow by Wednesday afternoon generally north of Haviland and in La Plata Canyon. As this happens, the main piece of energy starts to move through California. The initial surge of sub-tropical air will move through New Mexico by Wednesday evening, temporarily shutting off the moisture flow as the low pressure brings snow to southern Utah late Wednesday night. The low is forecasted to continue moving east through the night with snow returning to elevations above 8,000 feet after midnight, and light drizzle to lower elevations. Snow levels will drop to 7,000 feet Thursday morning with 3-6 inches of snow above 8,500′ (perhaps a little more at Mayday). Above 7,200′ feet, 2-5 inches of snow is possible with perhaps a heavy dusting to an inch or two below 7,000 feet as the system passes us.

The models are still not in complete agreement on this system, they probably won’t be until they see exactly where the low comes onshore, just a little too far north and it will lose its intensity in our area and focus the energy to our north. I am not worried about it coming onshore too far south.

For now, it looks like the front and heavier weather will pass between 7 am-10 am. It could temporarily affect travel in the area during that time. It looks like it will move through quickly and not linger around. It is too early to determine if anything will be left behind

Last night’s Euro

12300zeuroprecip.png

Overnight Euro

euro12306zeuroprecip.png

 

Latest Euro Precipitation

euro12312zprecip.png

Now the GFS

GFS last night

12300zgfsprecip

GFS overnight

12306zgfsprecip.png

GFS latest

12312zgfsprecip.png

 

As you see the GFS and Euro models are still on a bit of a rollercoaster with their amounts and the Euro appears to be trending lower. But that is not necessarily a trend across the board, here are the last three runs of the NAM (short term model), showing the precip amounts increasing every run.

Last night’s NAM

12300znamprecip

Overnight NAM

12306znam.png

Latest NAM

12312zNamprecip.png

This run does not make a lot of sense, but I am sure it will change.

The models are starting to acknowledge the possibility of snow on Sunday, but let’s get through this one before getting too excited about Sunday.

I will update again around noon on Wednesday.

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This Week’s Storm And Snowpack Update

Before I jump into the next storm I wanted to share the new snowpack numbers for the high country.

snotel122header.JPG

snoteltable122

The column next to the end on the right is the one to look at “Percent of Today’s Median”. Cascade, Vallecito, Lemon, and the La Platas look great for now. The new drought monitor will be out tomorrow and I am hoping we will go to a D1 from the current D2 in our area.

Thursday Storm

After prolonged storms with a lot of interesting and complex twists and turns, it is difficult to get too excited about the incoming smaller storm. The struggles will be similar to what we just saw late last week. Most importantly we will start with higher snow levels (around 8,500′). As the front approaches, snow levels should drop to 6,500′ and the front should pass with a lot of fanfare (again) and even if it is short-lived (again) many people found out what nearly impossible travel conditions look like last week. Timing is the other important variable, I am already starting to see some slowing in the models. Looking at the meat of the storm it looks slightly deeper and stronger than 24 hours ago, so these are all positive signs.

Due to the uncertainty of the snow levels at this time, I am just going to show the snow water equivalent numbers (SWE) or liquid precipitation. I am expecting all snow above 8,500′ so multiply by 10 or 12 if you are above 8,500′.

I am also going to show the last two runs from the operational models.

Euro last night

1221900zeuroprecip.png

Euro overnight

1221906zeuroprecip.png

Euro this morning

12212zeuroprecip.png

 

GFS last night

12219gfs00zprecip.png

 

GFS overnight

1221906zgfsprecip

GFS this morning

1221912zGFSprecip

These are just a few of the many parameters I look at, but it is good way to see some of the solutions the models are coming up with.

After this storm, a system will try to brush by to our north on Sunday then it looks like we will be dry until at least the 15th when it looks like a stormier pattern will return.

Next Update Tuesday around noon.

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A Couple More Storms This Week?

At this stage of the game, it looks like the storm coming in Wednesday night into Thursday will not be anything to be overly concerned about. I have no confidence yet in the second storm but if the models are correct we may see some snow next Sunday. As far as the first storm goes, I expect it to slow down, but it looks like a quick mover. If it were to arrive around sunrise on Thursday it could create some travel or commuting concerns, too early to tell. The models are showing it fizzling out as it departs our area. The core of the storm, according to what I am looking at right now, will be just south of Durango, so there is a chance that most of the energy associated will be south of Hermosa. We have seen that happen a few times with smaller storms where Breen will get more than Purgatory and Vallecito because the flow is not strong enough to drive the dynamics that far north.

Here is the progression of the storm which shows weakening in both models as the system approaches.

Euro

ecmwf-ensemble-avg-west-z500_anom-1575180000-1575482400-1575590400-80

GFS

gfs-ensemble-all-avg-west-z500_anom-1575180000-1575482400-1575590400-80

So from the data available right now, the complete upside would be 2-6 inches depending on your location. The downside would be the miss to the south. I will feature some of the operational runs on Monday. BTW These cold temps are going scour out a little bit each day. 3 degrees at my house this morning was a little colder than I prefer for the first of December!

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