Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Cheyenne Wyoming
1104 PM MST Friday Dec 19 2014

issued at 852 PM MST Friday Dec 19 2014

No changes to the forecast this evening and no big weather
concerns through tonight. Gusty winds will be found along the
Laramie range and northern Snowy Range foothills. Gusts of 40 to
50 miles per hour will be common but not expecting high wind criteria. The
strong winds will hold off until tomorrow night and continue into
Sunday night.


Short term...(this evening through sunday)
issued at 300 PM MST Friday Dec 19 2014

Generally quiet weather expected tonight and Saturday with just
some snow showers occurring over the higher mountains at times as weak
ripples in generally west-northwesterly flow pass by with accompanying enhanced
moisture riding up west-facing slopes. Changes ensue on Sunday as
jet energy rides off the Pacific northwest and turns southeast over the region
while surface pressure falls occur over the High Plains...setting up a
favorable wind pattern in wind-prone areas. At the same time
increasing moisture will ride up the mountains late Sunday
increasing snowfall. As a result current hilites look to be in
good shape and will not alter at this time. Mild temperatures over the
plains Sunday with downsloping flow with maximums approaching 50f in a
few areas.

Long term...(sunday night through friday)
issued at 300 PM MST Friday Dec 19 2014

Sunday night...potent shortwave trough...Alberta clipper
system...moves southeast across the Dakotas...sending a cold front
across our counties and cranking up our winds. Deep moisture in
northwest flow aloft will keep the orographic snow machine cranking
across the snowy and Sierra Madre ranges with a chance of snow
elsewhere in cyclonic flow aloft.

Monday...if you Love windy...cold will enjoy this day
as brisk northwest flow from the surface to 500 mb prevails. Based
on the 700 mb gradients and deep cold air advection...we may need
high wind warnings across much of southeast Wyoming...especially
over our wind prone locales such as Arlington...vedauwoo and The
Summit of Interstate 80...along with wind advisories over western
Nebraska. Orographic snows will decrease in coverage over the snowy
and Sierra Madre ranges as moisture wanes slightly.

Tuesday...will be a good travel day for the pre Christmas travel
period. Primary issue will be winds as the 700 mb gradients suggest
a typically windy day...with perhaps our wind prone locales such as
Arlington...vedauwoo...Bordeaux and the Interstate 80 Summit
approaching high wind criteria. Only snow expected will be over the
snowy and Sierra Madre ranges...and only scattered snow
showers...dry elsewhere.

Christmas evening day...another good travel day for the pre Christmas
travel as the flow aloft backs to northwest with a transitory fast
moving shortwave ridge overhead. Aside from a few mountain snow
showers over the snowy...Sierra Madre and northern Laramie precipitation expected. Will be a warmer and windy day
based on projected gradients...but minimal travel issues.

Christmas...if you Love seeing snow on Christmas may be
pleased. While the typically drier GFS keeps Christmas evening morning
dry with the approaching shortwave trough over Idaho...the
European model (ecmwf)...typically performing better in the winter...shows a more
well pronounced shortwave trough aloft approaching from Idaho with
snow spreading into our western counties west of a Douglas to
Laramie line by Christmas day dawn...and will go with this solution
which blends well with our surrounding offices.

For the daylight hours on Christmas...the European model (ecmwf) continues to move
the well pronounced shortwave trough aloft over Wyoming with a
decent Arctic intrusion cold front and widespread snow by late
afternoon west of a Cheyenne to Chadron line...whereas the GFS is
less bullish with quantitative precipitation forecast and snowfall and brings the cold front in
later in the day. Since the European model (ecmwf) typically outperforms the more
often drier GFS in the winter...and since the European model (ecmwf) solution is
close to the one from yesterday...albeit a tad slower...will side
with our surrounding offices and paint at least a chance of
afternoon snow across most of our counties...with widespread
orographic snows across our northern Laramie...snowy and Sierra
Madre ranges.

Friday...looks like another decent travel day as both the GFS and
European model (ecmwf) show the shortwave trough aloft moving to the east of our
forecast area...with decreasing chances for snow...and windy and
cold conditions per prognosticated gradients and thicknesses.


Aviation...(for the 06z tafs through 06z Saturday night)
issued at 1102 PM MST Friday Dec 19 2014

VFR over a vast majority of the forecast area through the taf
period...but mountain tops will be obscured over south central
Wyoming. A few snow showers possible into the snowy and Sierra
Madre ranges late tonight into Saturday but snow will become
persistent with mountains obscurred Saturday night through Sunday
night with periods of heavy snow a good possibility. Strong winds
to develop over southeast Wyoming late Saturday night through
Sunday...especially in the typically wind prone areas.


Fire weather...
issued at 300 PM MST Friday Dec 19 2014

Increasing winds around the mountains will be the main concern
over the weekend but other factors expected to be non-critical.
Snow showers will increase over the mountains beginning Sunday and
persist into early next week. Elsewhere mainly dry and cool
weather will continue.


Cys watches/warnings/advisories...
Wyoming...Winter Storm Watch from late Saturday night through Monday
afternoon for wyz112-114.

High wind watch from late Saturday night through Sunday evening
for wyz106-110.

High wind watch from Sunday morning through Sunday evening for




long term...Rubin

National Weather Service Glossary of Abbreviations