806
FXUS65 KCYS 311800
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1200 PM MDT Fri Jul 31 2026

.KEY MESSAGES...

- Monsoon moisture will remain in place through Friday across
  the High Plains, producing widely scattered thunderstorms.

- More heat returns this weekend through Monday, with some near
  record high temperatures possible along with drier conditions
  leading to elevated fire weather concerns.

- Some relief of the heat is possible during the middle of next
  week as a Canadian cold front moves towards the Front Range.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 115 AM MDT Fri Jul 31 2026

Quiet weather early this morning with generally clear skies and
light northerly winds observed. Not much has changed with the
overall forecast for Friday and this weekend, so kept most of
the forecast as is. Still expecting another round of showers and
thunderstorms this afternoon, but the outflow from the MCS
across the Great Plains is a bit more shallow than previously
expected. Dewpoints are still increasing across the area under
north to northeast winds with some low clouds around Chadron.
Further west, surface dewpoints have returned to the 50s along
the I-25 corridor. Models are now showing the subtle upper
level shortwave moving south across the area earlier in the day,
so adjusted timing for thunderstorm activity a few hours earlier
compared to yesterday. This will likely lead to weaker and more
disorganized convection with only a few storms seeing some gusty
winds and/or small hail. CAPE values have come down quite a bit
and only peak at 500 to 800 j/kg MLCAPE in the early afternoon.
Low CAPE and a cap inversion across western Nebraska should keep
conditions dry over that area with high res guidance showing
little to no activity this afternoon. After that, some drier
air is forecast to push into the area behind the shortwave,
which will reduce the coverage of thunderstorms. Most of the
activity should be finished between 6 to 8 PM.

For Saturday, all models show the upper level ridge axis, and
599dm upper level high centered across southern Utah, shifting
north and east through the day. Expect a drying trend through
the day as the midlevel subsidence is forecast to suppress
convection initiation with the drier air gradually mixing down
to the surface with inverted V soundings. After a slightly
cooler Friday, Saturday will be back to above normal
temperatures with highs in the upper 80s to upper 90s (warmest
north of I-80). Kept POP below 5 percent through the evening
hours. Sunday is forecast to be around 10 degrees warmer
compared to Saturday as the brief heat wave continues late in
the weekend.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 205 PM MDT Thu Jul 30 2026

Sunday...Main challenge will be the heat as near perfect setup for
near record high temperatures, with the dominant 5960 meter 500 mb
ridge axis prevailing and centered over the Four Corners. With quite
dry air at low and mid levels, and 700 mb temperatures near 20 to 23
Celsius, we expect maximum temperatures in the mid 90s to near 100
degrees west of I-25, with upper 90s to near 108 degrees east of I-
25, with the hottest temperatures up in Sioux, Dawes and Box
Butte Counties of the northern Nebraska Panhandle.

Current record high temperatures for August 2nd include...

98 degrees in 2008 at Cheyenne
94 degrees in 2024 at Laramie
98 degrees in 2000 at Rawlins
106 degrees in 2008 at Alliance
104 degrees in 2022 at Chadron
104 degrees in 1938 at Scottsbluff
103 degrees in 2008 at Sidney

Looking at our projected high temperatures, it looks like near
record high temperatures expected at Rawlins, Laramie, Cheyenne,
Chadron and Scottsbluff. Fortunately, dewpoints will be relatively
low and heat index temperatures will peak in the 90s to near 100
degrees east of I-25. We will need to monitor minimum temperature
trends to see about the necessity for possible Heat Advisories for
Sunday in portions of the Nebraska Panhandle.

On Monday, the ridge flattens somewhat as a weak shortwave trough
aloft and its associated cold front enter our counties from the
north, cooling off temperatures somewhat and there may be enough
available moisture for isolated late day thunderstorms over the
southern Laramie Range.

Then on Tuesday, expect a relief from the summertime heat in the
wake of a passing Canadian origin cold front, sending maximum
temperatures back into the mid 70s to mid 80s. Moisture looks scant,
perhaps enough for isolated to widely scattered late day
thunderstorms near the mountains.

For Wednesday...synoptically, we anticipate a return flow event as
low level southeast winds advect more low level moisture
northwestward into our counties and providing enough fuel to help
develop scattered afternoon and evening thunderstorms primarily from
I-25 eastward, and we will likely need to increase our POPS for this
day in the next few days.

On Thursday, a return to the heat is on tap under northwest flow
aloft and with drier air infiltrating the counties, more heat is
expected as 700 mb temperatures rise to near 15 Celsius, yielding
maximum temperatures in the 90s to near 100 degrees.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1141 AM MDT Fri Jul 31 2026

While a persistent ridge aloft stretches from western Montana to
Arizona today, a weak weather disturbance or shortwave trough
aloft will slide down our forecast area on northwest flow aloft,
producing isolated to widely scattered showers and
thunderstorms along and near the I-25 corridor this afternoon
and early evening. Ridging bulges across Wyoming and Nebraska on
Saturday, effectively ending any chances for afternoon and
evening showers and thunderstorms due to warm temperatures
aloft.

Wyoming TAFS...Only made some minor changes due to high
confidence in the long standing experience of our midnight shift
forecaster and the inherited TAFS. Looking at the 12Z NAM and
latest HRRR runs, expect isolated to widely scattered showers
and high based thunderstorms to continue to develop this
afternoon through early evening along an 850/700 mb theta-e
ridge axis parallel to I-25. So, confidence is high enough to
include PROB30s at Laramie and Cheyenne with wind gusts up to 35
knots. VFR prevails. Clouds clear out after early evening. Wind
gusts to 23 knots through sunset due to surface gradients and
adiabatic mix down winds.

Nebraska TAFS...High confidence that no showers or thunderstorms
will occur due to limited available moisture and warm
temperatures aloft producing enough convective inhibition, CIN,
to keep it dry. VFR prevails. Wind gusts to 25 knots until early
evening due to surface gradients and mix down winds. Will see
some flat cumulus development through early evening.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...TJT
LONG TERM...RUBIN
AVIATION...RUBIN