Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 212017
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
217 PM MDT THU JUL 21 2016

.SHORT TERM...(Tonight through Saturday night)
Issued at 215 PM MDT Thu Jul 21 2016

Very little in the way of convection over the CWA so far this
afternoon with just a bit over the Sierra Madres so far. Expect
convection to increase the rest of this afternoon into this
evening as a shortwave evident on satellite over western Colorado
lifts northeastward. Latest HRRR depicts this increase in activity
so have added some low pops mainly over the plains this evening.

Little change in the overall pattern seen for Friday as the CWA
resides under west-southwesterly flow atop an upper high that
will be building slowly westward. Next impulse coming around the
periphery of the upper high should allow for widely scattered
showers and tstms especially in the afternoon and evening.
Coverage should be a little greater with surface upslope flow
aiding in the development of this. Better shear may allow for a
few stronger storms as well. Saturday looking mainly dry as a weak
cool front moves east across the CWA in response to a shortwave
moving into the northern high plains. Not much cooling with this
front however.

.LONG TERM...(Sunday through Thursday)
Issued at 215 PM MDT Thu Jul 21 2016

Current medium range model guidance continues to show the large
upper high over the south central CONUS retrograding westward
across the Four Corners and southern Great Basin early next week.
Consequently, the flow aloft will veer from west-southwest to
west-northwest. A surface boundary draped over the Laramie Range,
relatively moist upslope flow and marginal instability will yield
isolated convection over the mountains Sunday afternoon, spreading
east onto the plains by evening. High temperatures Sunday will be
near normal with 80s. A weak shortwave dropping southeast across
the northern Great Plains will produce isolated convection
portions of eastern Wyoming and northwest Nebraska. Other isolated
late day convection will form along the I-80 corridor from Laramie
to Sidney. Temperatures Monday will begin warming as the upper
ridge builds with highs in the mid 80s-mid 90s. Tuesday will
feature similar temperatures with isolated late day convection
south and east of a Laramie-Alliance line. No precipitation is
forecast for Wednesday with above normal temperatures. A stronger
shortwave tracking east across the northern Rockies will drive a
cool front southeast across the eastern Wyoming plains and
northwest Nebraska Thursday. Temperatures will cool a few degrees
along with a slight chance of afternoon thunderstorms. It will
continue quite warm south of the North Platte River valley.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1129 AM MDT Thu Jul 21 2016

VFR. Scattered high-based cumulus becoming broken invof southeast
Wyoming mountains mid-late afternoon with isolated showers/weak
tstorms developing (VCSH Laramie and Cheyenne from 21Z-03Z).
Convection dissipates after 03Z with scattered to broken clouds
AOA 15000 ft AGL through the night. North to northeast winds will
be breezy at times, except locally gusty/erratic winds invof of
showers. Winds will become light and variable later this evening.

&&

.FIRE WEATHER...
Issued at 215 PM MDT Thu Jul 21 2016

Fire weather concerns look to remain on the low side Friday into
Saturday with generally light winds. Concerns a bit higher for
Saturday over northern districts where winds look to be a little
stronger. Isolated showers and storms over the area this evening
with somewhat higher coverage of activity Friday afternoon.

&&

.CYS Watches/Warnings/Advisories...
WY...None.
NE...None.
&&

$$

SHORT TERM...RE
LONG TERM...MAJ
AVIATION...MAJ
FIRE WEATHER...RE



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