Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 211758

Area Forecast Discussion
National Weather Service Cheyenne WY
1158 AM MDT TUE JUN 21 2016

.SHORT TERM...(Today Through Thursday)
Issued at 300 AM MDT Tue Jun 21 2016

Today...Primary challenges will be high temperatures and coverage of
possible thunderstorms. As mentioned by the forecasters yesterday,
we expect near record high temperatures at all of our recording
stations. Please see the climate section. 700 mb temperatures peak
around 20 Celsius with 1000-500 mb thicknesses near 5970 meters,
thus with nearly full sunshine, we project high temperatures will
into the 90s at lower elevations with a few temperatures from 100 to
105 degrees across the Nebraska panhandle at at favored locations
east of I-25 in Wyoming. Despite limited low and mid level moisture,
we may spark off isolated to widely scattered afternoon and evening
thunderstorms along a surface trough near the Wyoming and Nebraska
state line.

Tonight...Thunderstorms expected to dissipate by midnight with loss
of daytime heating and lack of a forcing mechanism. Decent cold
frontal passage during the night.

Wednesday...Considerably cooler in the wake of the cold frontal
passage with lower elevations high temperatures back into the 80s.
We may see isolated afternoon and evening thunderstorms over and
near the Snowy and southern Laramie ranges in the proximity of the
low and mid level theta-e ridge axis.

Wednesday night...Another quiet night with weak ridging aloft

Thursday...Warming trend develops as the airmass moderates and as
height and thicknesses rise with return south winds at low levels.
With an increase in low and mid level moisture, we expect a
corresponding increase in afternoon and evening thunderstorm
coverage, most numerous along the low and mid level theta-e ridge
axis over far southeast Wyoming.

.LONG TERM...(Thursday Night through Monday)
Issued at 300 AM MDT Tue Jun 21 2016

Maintained isolated to widely scattered thunderstorms in the
forecast for Thursday night as boundary pushes off to the east.
Hot temperatures return for Friday with GFS showing +18C 700mb
temperatures moving into Carbon County.

700mb winds pretty strong for this time of the year Friday as
well. By Friday afternoon...GFS forecasting 35-40kts as a low
moves across southern Montana. Could be another Red Flag day as
afternoon humidities fall to around 10 percent.

Cooler but windy Saturday behind the cold front that moves through
the area. GFS still forecasting 700mb winds 35-40kts across the
entire CWFA.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1157 AM MDT Tue Jun 21 2016

Main concern for this TAF cycle will be thunderstorms late this
afternoon and evening, and widespread gusty winds. Regarding
winds, WY terminals will see westerly winds gusting 25-35 kts
through the afternoon as a sfc trough shifts east across the
forecast area. Across the NE panhandle, south winds could get a
bit gusty as well ahead of the trough, with 20-25 kts possible
through the afternoon. The main chance for thunderstorms will be
across the WY/NE plains, particularly KCDR and KSNY, late this
afternoon through the evening. Erratic downdraft winds will be
the main threat with thunderstorms, and perhaps brief MVFR vsbys.
A cool front moving south across the plains tonight will shift
winds to the NNW, with breezy conditions likely through mid-
morning in the post-frontal environment.


Issued at 300 AM MDT Tue Jun 21 2016

Based on projected humidities and winds, we have
decided to add fire weather zones near Rawlins and Laramie to the
Red Flag warning for today. Slow improvement in humidities the next
few days with the addition of more low level moisture and cooler


Issued at 300 AM MDT Tue Jun 21 2016

Today will be the hottest day thus far and the first full day of
summer. The following are forecast and record high temperatures
for June 21...

Alliance NE Forecast High 100F / Record High 100F (1989)

Chadron NE Forecast High 103F / Record High 100F (1922)

Cheyenne WY Forecast High 95F / Record High 95F (1874)

Laramie WY Forecast High 92F / Record High 89F (2015)

Rawlins WY Forecast High 94F / Record High 91F (2015)

Scottsbluff NE Forecast High 102F / Record High 100F (1988)

Sidney NE Forecast High 99F / Record High 100F (1974)


.CYS Watches/Warnings/Advisories...
WY...Red Flag Warning until 9 PM MDT this evening for WYZ301-303-308.



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