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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