Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 270525
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1125 PM MDT Mon Jul 26 2021

.UPDATE...
Issued at 738 PM MDT Mon Jul 26 2021

Our high temperatures were scattered by 4 degrees or higher this
afternoon. All model guidance remains too low to account for the
above-normal temperatures across the region. Therefore,
temperatures were updated. Additionally, a Heat Advisory is in
effect starting 12 PM MDT Tuesday for areas across the northern
Nebraska Panhandle and southeastern Wyoming counties, Niobrara and
Goshen, for a Heat Index up to 99. Low temperatures will trend
above 70 degrees for these areas giving no relief from the heat.
With ongoing outdoor activities, please remember to stay hydrated
and take frequent rest breaks in shaded or air conditioned
environments.

&&

.SHORT TERM...(This evening through Wednesday)
Issued at 244 PM MDT Mon Jul 26 2021

Not many changes to the previous forecast package with quiet
weather expected through early Wednesday. Current KCYS radar loop
shows some occasional shower activity developing in the mountains
early this afternoon. A few lightning strikes are noted as well,
mainly in the Snowy Range and Northern Laramie Range. Generally,
this activity has been short-lived and has dissipated pretty
quick. Added isolated showers/tstorms to the mountain zones this
evening, but not expecting much, if any, rainfall from these
showers. Otherwise, hot temperatures observed this afternoon with
readings in the 90s to around 102 across the northern Nebraska
panhandle. It has been hazy, due to the wildfires across the
intermountain west, but expect this haze to lower in concentration
through Wednesday before wind shift into the west.

Primary forecast concern Tuesday and Wednesday will be the heat
and the eventual return of the monsoon later on Wednesday. Thought
about issuing a Heat Advisory for the northern Nebraska panhandle
on Wednesday, but dewpoints will likely be pretty low and result
in heat indices around or slightly lower than 100 degrees. In
addition, an easterly breeze should keep conditions from becoming
too oppressive. Otherwise, all models show the center of the upper
level high shifting east on Wednesday. This will likely be the
hottest day of the week with mid to upper 90s possible even for
locations such as Cheyenne and portions of Carbon county. As the
center of the high moves east, monsoon moisture will slowly start
to advect northward across central Wyoming. Kept 20 to 40 percent
POP for widely scattered showers/thunderstorms for Carbon and
Albany county as PW`s increase between 0.75 to 1.00 inch.
Thunderstorms are not expected to be severe due to long/skinny
CAPE profiles and little 0-6km shear.

.LONG TERM...(Wednesday night through Sunday)
Issued at 300 AM MDT Mon Jul 26 2021

The anticipated pattern shift is still progged to commence with
the center of the upper level high over KS/NE. This will open the
door for subtropical/monsoonal moisture to advect northward over
the Central Rockies and High Plains. Isolated to scattered showers
and thunderstorms will develop during the afternoon over
southeast WY, spreading east into the NE Panhandle in the evening.
The ridge center slowly settles toward the Southern Plains and
Lower MS Valley through the remainder of the forecast period.
Precipitable water increases from 0.70 to 1.0 inch Thursday, to
1.0 to 1.3 inches this weekend. Thermodynamics are unimpressive
with tall skinny CAPEs and weak 0-6km effective shear. The main
concerns will be the potential for locally heavy rainfall and
increasing risk for burn scar flash flooding/debris flows. High
temperatures in the 90s and lower 100s Wednesday will gradually
cool into the 80s this weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1123 PM MDT Mon Jul 26 2021

VFR. Wind gusts to 25 knots at Chadron until 10Z, and to 30 knots
at all terminals after 17Z.

&&

.FIRE WEATHER...
Issued at 152 PM MDT Mon Jul 26 2021

Minimal fire weather concerns will continue this week. No fire
weather concerns expected next weekend as plentiful monsoon
moisture will push north into the Front Range and central
Wyoming. Daytime relative humidities will occasionally lower into
the teens through Wednesday afternoon mainly due to the hot and
near record high temperatures over the region. However, relatively
light winds are expected due to the position of the upper level
high over the northern and central front range. Showers and
thunderstorms will increase in coverage after Wednesday with
scattered to numerous showers and thunderstorms expected by Friday
and through next weekend.

&&

.CLIMATE...
Issued at 738 PM MDT Mon Jul 26 2021

A new record high temperature of 105 was set at Chadron Nebraska
Airport. Additionally, expected high/low temperatures for Tuesday
and Wednesday afternoon/evening may tie or break records.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Heat Advisory from noon Tuesday to midnight MDT Wednesday night
     for WYZ102-108.

NE...Heat Advisory from noon Tuesday to midnight MDT Wednesday night
     for NEZ002-003-019-095-096.

&&

$$

UPDATE...AW
SHORT TERM...TJT
LONG TERM...MAJ
AVIATION...RUBIN
FIRE WEATHER...TJT
CLIMATE...AW


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