12 step process for diagnosing an incoming storm in Durango

Start 4:06 am (End 5:20 am)

We wake up worried again, I have been looking out the window for the last 4 hours to see no change outside. These are the steps I take literally every time this happens.

Step one

Check the radar

RadarCapture

Step 2

Remember that there is no radar in Durango it is in Grand Junction and it only shows returns above 20,000+ feet.

Step 3

Check the National Weather Service for new info.

They were busy. They changed the wording on the advisory

301 AM MST Fri Nov 30 2018

COZ022-023-301815-
/O.EXT.KGJT.WW.Y.0033.000000T0000Z-181130T1900Z/
Animas River Basin-San Juan River Basin-
Including the cities of Durango, Bayfield, Ignacio,
and Pagosa Springs
301 AM MST Fri Nov 30 2018

...WINTER WEATHER ADVISORY NOW IN EFFECT UNTIL NOON MST TODAY
ABOVE 6500 FEET...

* WHAT...Snow expected above 6500 feet. Total snow accumulations
  of 2 to 5 inches expected.

* WHERE...San Juan River Basin and Animas River Basin.

* WHEN...Until noon MST today.

* ADDITIONAL DETAILS...Plan on slippery road conditions. The
  hazardous conditions could impact the morning commute.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Winter Weather Advisory for snow means periods of snow will
cause primarily travel difficulties. Expect snow covered roads
and limited visibilities, and use caution while driving.

 

They added a new zone

301 AM MST Fri Nov 30 2018

COZ021-301815-
/O.EXB.KGJT.WW.Y.0033.181130T1001Z-181130T1900Z/
Four Corners/Upper Dolores River-
Including the cities of Dove Creek and Mancos
301 AM MST Fri Nov 30 2018

...WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON MST TODAY ABOVE
6500 FEET...

* WHAT...Snow expected above 6500 feet. Total snow accumulations
  of 2 to 4 inches expected.

* WHERE...Four Corners/Upper Dolores River.

* WHEN...Until noon MST today.

* ADDITIONAL DETAILS...Plan on slippery road conditions. The
  hazardous conditions could impact the morning commute.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

 

Step 4

Read the forecast discussion

Blah blah, already snowing in Cortez and Telluride, blah blah. Wait here is some stuff.

The most dynamic period of this storm occurs this morning as the
mid-level trough sweeps eastward over the eastern Utah and western
Colorado. During this period, moisture associated with an
atmospheric river moving ashore over the northern Baja Peninsula
brushes the Four Corners region. Dynamically, negative mid-level
divergence of q combines with divergence associated with the
cyclonically curved jet moving through the base of the jet. Expect
this will be a period of heavy snow for the San Juans and its
southern flanks. Consequently, added CO zone 21 to the advisories
already in place for zones 22 and 23 and lowered the affected
elevations to 6500.

Sounds pretty good. 21 is Mancos, 22 and 23 are all the Durango areas.

Then I see this.

This portion of the forecast could be a bust
depending upon temperatures. Guidance was a bit higher than
previously forecast and with mild surface temperatures, melting
may inhibit accumulations.

HEDGE

He is referring to lowering the elevation of areas affected to 6,500 feet.

Step 5

Check the surface maps.WPC

sfc.PNG

Hmmm, the front seems too close, this was supposed to be at 2 am this must be at least partially wrong, but I do like the shortwave they have back in Utah (circled in red).

Step 6

Look at satellite

satCapture.PNG

Looks like the main trough is in western Utah, east of that (closer to us) is another feature I am not sure about. West of the main trough,  I think that is the shortwave I saw on the WPC map. Further west of that it looks like another weak trough.

Step 7

Look at another surface map. For me WU is great with their “fronts” feature, the algorithm is usually dialed in but unfortunately is reset to the WPC every 3 hours. So you have to look at it in a short window.

wusfcCapture

This is crazy, it verifies the main trough, it verifies the trough in Nevada, it shows that feature I mentioned near us is a WARM front, (BTW when a cold front passes an area then shoots back north over the same area it becomes a warm front) don’t worry about that yet. Attached to the south of the warm front is a cold front, heading west…

Step 8 Check models

HiRes simulated radar for 5 am

SimRadarCapture

Check time, 4:55 am.

Step 9 Look outside again

Snowing!

Step 10 Look at accumulation models

Euro

NEWeuro

GFS

new6zgfs

I don’t like the overnight HiRes run, I know it sounds stupid but for some reason, the morning run is always more accurate.

HiRes

hires_snow_colorado_34

Step 11 Draw a conclusion

It is a bit warmer than I expected it to be, and then the models had expected it to be. It looks like we will have a period of heavy snow followed by light on and off snow.

Accumulations will be on the lower end in some areas, but a westerly flow will come in after the frontal passage for a good portion of the day, there are certain areas that do well with that. Then the northwest flow will take over.

In systems like these, there are often little kicker systems that funnel out, I would not be surprised to see that happen later today after a lull and everyone thinks this over. Accumulations I have given are through Saturday at noon or when the last flakes fall Saturday before the next system decides if it is going to visit us on Sunday. As of the moment the Euro and GFS both have it in their sights!

Step 12 Pack a paper bag in my laptop case to wear today if the whole thing busts…

You knew it had to be a 12 step process…

 

 

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