Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 180547

Area Forecast Discussion
National Weather Service Cheyenne WY
1147 PM MDT Sun Sep 17 2017

Issued at 926 PM MDT Sun Sep 17 2017

We have made a few updates this evening to keep the chance of
showers and thunderstorms going across the southern Nebraska
panhandle through midnight. We have also introduced some patchy
fog over the southern panhandle due to some decoupling tonight and
moist soils from the rainfall. Otherwise, no real major concerns
as the sky should gradually clear out from west to east by


.SHORT TERM...(This evening through Tuesday night)
Issued at 242 PM MDT Sun Sep 17 2017

Early afternoon water vapor loop showed the upper trough axis
entering western WY and northern UT. Scattered convection was
developing across south-central and southeast WY. This trend will
continue, with shower and thunderstorm activity spreading east
into the western Nebraska Panhandle through late afternoon.

Scattered showers and thunderstorms will taper off from west to
east later this evening across the plains as the upper trough
moves through the CWA. A surface ridge of high pressure extending
north into southern WY will prevail Monday with dry and warm
conditions. Expect high temperatures in the 70s to mid 80s.
Southwest winds will be breezy along and west of the Laramie
Range during the afternoon.

Shortwave energy diving southeast from the Gulf of AK into the
Pacific Northwest Monday night will shift east across the northern
Rockies Tuesday. A strong Pacific cold front will race east across
WY Tuesday afternoon and western NE Tuesday night. Scattered
showers will accompany the front, along with cooler temperatures
for portions of south-central southeast WY. 700mb winds increase
to 40-50 kt along and west of the Laramie Range Tuesday, with
westerly surface gusts of 40-45 kt possible. Winds slowly ease
Tuesday night after the frontal passage.

.LONG TERM...(Wednesday through Sunday)
Issued at 242 PM MDT Sun Sep 17 2017

It will be a little cooler Weds in the wake of a Pacific cool
front. Looking breezy to windy as well as favorable southwesterly
upper flow sets up over the region ahead of a digging upper trough
over the Pacific northwest. This system will continue to amplify
Thursday while moving very little, maintaining warm and dry
weather for the CWA given the swly flow aloft. Cooler conditions
should arrive Friday as lee cyclogenesis occurs over Colorado with
the latest EC a little slower than the GFS. Showers should spread
gradually east across southeast Wy Friday with a cool and rather
wet weekend as colder air filters down the high plains under
s-swly flow aloft.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1140 PM MDT Sun Sep 17 2017

Latest radar loop shows most of the showers and thunderstorms had
exited the area. We are now looking at the potential for some
patchy fog to develop in the BFF and AIA region tonight due to
good moisture flux from the rainfall this evening and some
decoupling especially around the North Platte Valley. However, the
fog should clear out fairly quickly due to downslope flow kicking
in by mid morning. The wind is expected to be quite gusty in KRWL
tomorrow afternoon due to deep mixing ahead of the next shortwave
moving in from the Pacific northwest.


Issued at 245 PM MDT Sun Sep 17 2017

Upper level trough will shift east across the districts this
afternoon and evening with scattered showers and thunderstorms.
Drier, breezy and warmer conditions return Monday ahead of a
strong Pacific trough and cold front. Westerly winds increase
Tuesday with the frontal passage, along with scattered showers and
cooler temperatures. Mild and dry conditions Wednesday and
Thursday will be replaced by much cooler and wetter weather
Friday through next weekend.




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