Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 141741

Area Forecast Discussion
National Weather Service Cheyenne WY
1141 AM MDT Sat Oct 14 2017

Issued at 747 AM MDT Sat Oct 14 2017

Potent vort max over SW Wyoming early this morning per GOES 16 WV
imagery. Area of snow showers accompanying this feature in an area
of DPVA aloft in the presence of decently steep lapse rates under
the cold upper trough. Think this area of showers will weaken a
bit as it encounters more downslope flow east of the Laramie Range
but still enough moisture to mention a chance of snow showers over
much of SE Wyoming this morning into early afternoon. Lowered snow
levels based on current obs and increased snow amounts to 1-2
inches over Carbon county where Rawlins is currently reporting


.SHORT TERM...(Today through Sunday night)
Issued at 300 AM MDT Sat Oct 14 2017

Today...Temperatures and dewpoints continue to come closer to each
other with areas of fog forming, thus have added mention of fog
through mid morning across far southeast Wyoming and much of the
Nebraska panhandle.

Strong and vigorous shortwave trough aloft and its associated cold
front quickly pass across our counties this morning and early
afternoon with decent 500-300 mb and 700-500 mb quasigeostrophic
forcing this morning, and with adequate low and mid level moisture,
expect scattered to numerous rain and snow showers this morning,
most numerous north of a Rawlins to Alliance line where stronger
energy and deeper moisture will be found, and least across our
southern counties due to low level downsloping winds. Strong low
level cold air advection will help temperatures to remain steady or
slowly fall during the daylight hours. Showers decrease somewhat in
coverage this afternoon as lift ends.

Tonight...Clearing skies and cold temperatures in the wake of the
shortwave trough aloft and cold front passage.

Sunday...Flow aloft remains northwest, through with rising heights
and thicknesses and plenty of sunshine, temperatures will rebound
nicely into the mid 50s to mid 60s at lower elevations with 700 mb
temperatures near 3 Celsius.

Sunday night...Northwest flow aloft continues with dry conditions
due to lack of low and mid level moisture. Not quite as cold as
Saturday night with a moderating air mass.

.LONG TERM...(Monday through Friday)
Issued at 315 AM MDT Sat Oct 14 2017

Latest numerical model/ensemble guidance is in good agreement
portraying a progressive, moderately amplified large scale flow
next week. Upper ridge axis from northwest Mexico to the Pacific
coast Monday translates eastward across the Intermountain West
and Rockies through Tuesday, and Great Plains by Wednesday. The
flow aloft will back from northwest to west mid-week, then
increase from the southwest Thursday and Friday as the next
Pacific trough and cold front move into the Great Basin. Dry and
unseasonably mild daytime temperatures are forecast. It will be
breezy most afternoons with southwest winds gusting to 25-35 mph
west of Interstate 25. Isolated showers may spread into western
Carbon County by Friday evening with return moisture.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1138 AM MDT Sat Oct 14 2017

Area of snow showers currently along and west of the Laramie Range
per surface obs and webcams. Should see visibility temporarily
reduced to IFR in snow showers through 21z mainly for KCYS and
KLAR/KRWL. Rain showers will affect the northern Panhandle with
some MVFR vis possible there as well. Elsewhere gusty north to
northwest winds will affect most sites east of the Laramie Range
this afternoon as a cold front has passed through the area.
Showers should diminish by late afternoon and skies will clear by
early evening.


Issued at 300 AM MDT Sat Oct 14 2017

No concerns today due to higher humidities with cooler temperatures
and precipitation. Increasing concerns Sunday through Tuesday with
low relative humidities and gusty winds in the afternoon.




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