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Area forecast discussion 
National Weather Service Cheyenne Wyoming
249 PM MDT Wednesday Sep 2 2015

Short term...(this evening through friday)
issued at 151 PM MDT Wednesday Sep 2 2015

A few showers or thunderstorms will be possible through early
evening mainly along and west of the the Laramie range but the
overall chance for precipitation is low across the forecast area.
That will change tomorrow as a late season push of monsoon moisture
moves across the region. Chances for thunderstorms will increase
with the main threat for precipitation late afternoon and evening
in association with shortwave energy. Models do vary a bit in the
timing and location of the shortwave so tough to pinpoint the
highest potential but confident much of the forecast area will
receive some measurable rain. Do not see a severe thunderstorm
threat based on model prognosticated soundings but the soundings are
tropical in nature such that heavy rain is likely with a few
thunderstorms. Fortunately it looks like storm will move fast enough
such that the flash flood threat will be on the low side...albeit
higher that climatology.

Shortwave energy will shift northeast of the forecast area Thursday
night with showers and thunderstorms ending after midnight. Late
Thursday night through Friday morning should be dry across the
area but continued moist southwest flow aloft will bring another
chance for afternoon and evening thunderstorms with the main
chances over southeast Wyoming. Do not see any threat for severe
thunderstorms but again a few heavy rainers will be possible.

Long term...(friday night through wednesday)
issued at 1251 PM MDT Wednesday Sep 2 2015

Latest medium range model guidance is in good agreement this weekend
progging the northwest Continental U.S. Upper low to lift northeast and weaken
through Idaho and Montana on Sunday. Moist southwest flow aloft and
accompanying shortwave will produce widely scattered showers and
thunderstorms Friday night and Saturday...followed by drier and windier
conditions Saturday night and Sunday. A tight pressure gradient
preceding a Pacific front will produce the gusty westerly winds. The
front will pass through Sunday afternoon with cooler...more seasonal
temperatures for the upcoming week. There are some model differences
by the middle of next week with the GFS digging a upper trough and
surface front south into the intermountain west. The preferred European model (ecmwf)
and ensembles maintain a dry zonal flow aloft.

&&

Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1127 am MDT Wednesday Sep 2 2015

VFR conditions will prevail through the next 24 hours. It will be
breezy at the southeast Wyoming terminals this afternoon with westerly
surface winds gusting to 25 knots or higher at times. The winds will
diminish this evening. Convective development will be isolated and
mainly confined to the higher terrain this afternoon.

&&

Fire weather...
issued at 230 PM MDT Wednesday Sep 2 2015

The threat of critical fire conditions will decrease tomorrow with
only minimal concerns the rest of this week and weekend. Subtropical
monsoon moisture will move into the area tomorrow with scattered
showers and thunderstorms developing in the afternoon and evening.
Much of southeast Wyoming and potentially the Nebraska Panhandle
will be affected by showers and thunderstorms. A few storms are
expected to produce heavy rain. The only potential fire weather
concern Thursday is into east central Wyoming where humidity
values may dip to around 15 percent before the monsoon moisture
arrives. Fortunately winds should be on the light sides in the 5
to 10 miles per hour range with only a few gusts of 15 to 20 miles per hour into western
Converse County.

Chances for showers and thunderstorms will continue right through
the weekend as moisture southwest flow aloft remains in place. The
models do show a stronger weather system moving across the northern
rockies Sunday which should bring stronger winds and cooler air to
the area.

&&

Cys watches/warnings/advisories...

Wyoming...red flag warning until 7 PM MDT this evening for wyz301>304-306-
308.

NE...none.

&&

$$

Short term...small
long term...maj
aviation...maj
fire weather...small

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