Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 151806

Area Forecast Discussion
National Weather Service Cheyenne WY
1206 PM MDT Tue Aug 15 2017

Issued at 1200 PM MDT Tue Aug 15 2017

Went ahead and added hail to areas east of the Laramie Range for
this afternoon and evening and increased PoPs some too. The best
chance of severe storms with large hail will be across the
southern Panhandle in the late aftn and early evening. With large
scale forcing and llvl warm air advection overspreading the CWA,
expect initially discrete storms to develop upscale into a larger
area of rain by the evening.


.SHORT TERM...(Today through Thursday)
Issued at 240 AM MDT Tue Aug 15 2017

Some showers along with a tstm or two lifting northeastward across
the CWA early this morning, likely in association with a shortwave
now moving into southern Wyoming.  Expect these to continue moving
northeast early this morning with a short lull in pcpn after that.

The main upper trough currently over the western CONUS will move
east today and tonight and will bring another round of showers
and tstms to much of the CWA.  Instabilities not as great today
with the highest amounts over the southeast half of the Panhandle,
where CAPEs around 1500-2000J/kg progged there this afternoon.
Shear not impressive but could still see a few strong storms in
that area later today. CAPE falls off fairly quickly this evening
with pcpn being more showers as the evening progresses.  A cool
front will slide east over the area this evening bringing a little
cooler air for Weds.  Warmer again Thursday as return flow sets up
with some isolated convection possible.

.LONG TERM...(Thursday night through Monday)
Issued at 240 AM MDT Tue Aug 15 2017

Drier pattern setting up for the long term as upper ridge builds
in from the west. Getting back to normal August like weather.

Could be some showers and thunderstorms Sunday and Monday, but
overall, the ridge is forecast to hold and believe most locations
should stay dry.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1200 PM MDT Tue Aug 15 2017

The main concern with this forecast package will be the timing of
the convection this afternoon.

Latest visible imagery was showing convection already developing
along the Laramie Range/Snowy Ranges, and between Rock Springs and
Wamsutter. This convection is progged to continue developing during
the course of the afternoon and move east-northeast at speeds at 15
to 20 kts. However, some of the stronger stronger storms may move in
a more easterly fashion. This convection should begin to affect the
CYS/LAR/RWL TAF sites between 20-23z. The Nebraska TAF sites may see
some stronger convection, but the convection will probably be mainly
after 22Z. We will have to keep an eye on how things evolve today
and make adjustments as necessary. Most of the convection should
clear out by around sunset.


Issued at 240 AM MDT Tue Aug 15 2017

Fire weather concerns expected to remain low for the rest of the
week with non-critical weather conditions. Scattered to numerous
showers and storms today with wetting rains likely from most of
them. A drier pattern will then ensue to close out the week.




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