Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 132052

Area Forecast Discussion
National Weather Service Cheyenne WY
152 PM MST Tue Feb 13 2018

.SHORT TERM...(This evening through Thursday)
Issued at 147 PM MST Tue Feb 13 2018

Tonight...Winds already beginning to increase at Bordeaux, and with
the Craig to Casper 850/700 mb height gradients increasing over 60
meters, inherited high wind warnings starting overnight look good.
Expect orographic light snow to start by tonight over the Sierra
Madre Range and late tonight over the Snowy Range, and with 48 hour
totals accumulating up over 12 inches, have issued a Winter Storm
Warning for these mountain ranges. Relatively mild overnight with
decent mixing and the cold air retreating.

Wednesday...With progged strong winds at low and mid levels at or
above 60 knots, and minimal cloud cover, we feel the stronger winds
will be able to mix down to the surface at Douglas and Cheyenne,
thus we have enough confidence to upgrade these locations to High
Wind Warnings. Orographic snows continue over the Snowy and Sierra
Madre Ranges. Relatively mild day with highs in the 50s east of I-25.

Wednesday night...Orographic snows look to increase over the Snowy
and Sierra Madre Ranges, with winds diminishing as gradients ease at
low levels.

Thursday...Windy and colder in the wake of a shortwave trough aloft
and cold frontal passage. Will see a chance of snow with increased
low and mid level moisture, along with cyclonic flow aloft and low
level upslope winds.

.LONG TERM...(Thursday night through Tuesday)
Issued at 147 PM MST Tue Feb 13 2018

Friday...Windy and cold again as the flow aloft turns northwest, and
with decent low and mid level gradients. Dry day with limited low
and mid level moisture.

Saturday...Although northwest flow aloft continues, heights and
thicknesses rise significantly, thus expect a warming trend, with
breezy to windy conditions due to low and mid level gradients.

Sunday...Continued dry and a bit cooler with more cloud cover.

Monday...Flow aloft backs to southwest, helping cold Canadian air to
spill westward into our counties, producing a colder day with a
chance of snow.

Tuesday...Continued cold with a chance of snow as the flow aloft
backs even further to southwest and a broad trough aloft prevails
over the Rockies with the cold airmass firmly entrenched at low
levels. Potential for significant snow due to moist overrunning of
the cold airmass.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 147 PM MST Tue Feb 13 2018

Stronger jet energy is expected to build into southern Wyoming
late tonight into tomorrow as the upper level pattern begins to
flatten out. As a result, we are looking at strong winds
developing over the Wyoming TAF`s late tonight into tomorrow.
Otherwise, VFR conditions will be the rule.


Issued at 147 PM MST Tue Feb 13 2018

No concerns based on expected winds and humidities.


WY...Winter Storm Warning from 6 PM this evening to 6 PM MST Thursday
     for WYZ112-114.

     High Wind Warning from midnight tonight to 6 PM MST Wednesday
     for WYZ107-109-115>117.

     High Wind Warning from 6 PM this evening to 6 PM MST Wednesday
     for WYZ104>106-110.

     High Wind Warning from 10 AM to 6 PM MST Wednesday for WYZ101-



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