Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 240835

Area Forecast Discussion
National Weather Service Cheyenne WY
235 AM MDT Mon Jul 24 2017

.SHORT TERM...(Today through Tuesday night)
Issued at 144 AM MDT Mon Jul 24 2017

Today...Ridging and warm temperatures aloft will continue to inhibit
shower and thunderstorm development this afternoon. NAM shows a low
level convergence axis stretching across our southern counties this
afternoon and with adequate mid level moisture, expect isolated
thunderstorms to erupt along and near our Snowy, Sierra Madre and
southern Laramie Ranges this afternoon. Dry elsewhere. With plenty
of sunshine and 700 mb temperatures near 17 Celsius, expect high
temperatures well into the 90s to near 105 degrees along and east of
Interstate 25.

Tonight...Isolated evening thunderstorms possible at lower
elevations east of I-25, otherwise dry with thunderstorms
dissipating in the evening with loss of daytime heating.

Tuesday...Definite increase in low and mid level moisture, and
precipitable water values, and combined with a passing shortwave
trough aloft, will help generate scattered to numerous showers and
thunderstorms in the afternoon, mainly along and west of I-25 in the
deeper moisture. A few storms may produce locally heavy rain due to
weak steering currents aloft. Cooler temperatures, especially west
of I-25, due to cloud cover and more shower and thunderstorm
coverage compared to today.

Tuesday night...With the passing shortwave trough aloft, expect
scattered to numerous showers and thunderstorms in the evening, with
decreasing areal coverage after midnight, though still scattered
POPS after midnight over our northern counties.

.LONG TERM...(Wednesday through Sunday)
Issued at 144 AM MDT Mon Jul 24 2017

Seasonably moist west to southwest flow aloft around a flat ridge
over the southern US will keep the weather active across SE WY and
western NE on Wednesday and Thursday. Cool front will push south
into the Colorado plains by early Wednesday morning and this may
shift the best chances for showers and thunderstorms to the west
over the mountains and high valleys west of the Laramie Range.
With surface dewpoints in the 50s to low 60s and more stable NE
flow behind the front, may see some low stratus on Wednesday
morning east of the Laramie Range. Instability will increase
rapidly along and east of the Laramie Range on Thursday and moist
SE flow topped by modest westerlies may lead to a better chance
for some stronger storms. Consensus in most guidance then is to
rebuild significant ridging over the SW US for Friday into the
weekend. Warming aloft will lead to lesser chances for
precipitation and warmer temps especially as we head into Saturday
and Sunday.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1122 PM MDT Sun Jul 23 2017

VFR for all terminals through the TAF period. Gusty south winds
will develop over the plains by late Monday morning as a low
pressure trough strengthens over western SD. A few thunderstorms
will likely develop over the Snowy Range and South Laramie Range
Monday afternoon as a weak disturbance tracks overhead. Included
the mention of thunder in the WY terminals for this reason.
Variable and gusty winds are possible with this convection Monday
afternoon into early evening.


Issued at 144 AM MDT Mon Jul 24 2017

Low afternoon humidities today from 10 to 15 percent
north of a Rawlins to Alliance line, though fortunately, winds will
be relatively light, limiting concerns. Higher humidities on Tuesday
with cooler temperatures and an increase in afternoon and evening
shower and thunderstorm coverage.




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