903
FXUS65 KCYS 302019 CCA
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
208 PM MDT Thu Jul 30 2026

.KEY MESSAGES...

- Monsoon moisture will remain in place through Friday across
  the High Plains, producing daily chances for isolated to
  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 205 PM MDT Thu Jul 30 2026

Breezier conditions are present today across the area as westerly
flow returns with the passage of a shortwave trough aloft. GOES
water vapor imagery shows the upper level circulation of this
feature located over eastern Montana at this time, with its axis
extending south across our area. Much drier air in the middle
to upper troposphere is apparent pushing into our western zones,
but surface moisture remains fairly decent today, especially
further east. As usual, instability follows the low-level
moisture, which supports about 500 to 1000 J/kg MLCAPE across
east central Wyoming and into the northern Nebraska panhandle. A
diffuse surface cold front is also moving into this area, which
should provide forcing for a few isolated storms this afternoon
and evening. Overall, the forecast has changed little. Coverage
is expected to be fairly isolated overall, and confidence is
low in where primary development will occur. The cumulus field
looks most primed over the northern Nebraska panhandle, but we
also have a region of low-level convergence located further west
more or less along the central and northern Laramie Range which
could produce a few storms. High resolution models are all over
the place in the location of thunderstorm development. In the
official forecast, most of the high plains maintains a slight
chance for thunderstorms this afternoon and early evening. The
environment is most potent for strong to severe thunderstorms in
the northern panhandle where we have the strongest instability
and modest deep layer shear. Therefore, Dawes County was
included in a severe thunderstorm watch. A few strong storms
developing further south and west cannot be ruled out, but
confidence remains low.

Overnight tonight, we are still looking at some outflow winds
pushing out of a potent MCS moving across central Nebraska. However,
timing of this differs somewhat from model to model. Moisture return
may be able to produce some areas of low clouds Friday morning in
the Nebraska panhandle, but this will depend on how overnight
convection plays out. This will setup the day on Friday with a low-
level convergence zone more or less along the Laramie Range.
Recycled monsoon moisture will remain in the picture for
another day, which should support another round of widely
scattered afternoon and evening showers and thunderstorms.
Expect Friday`s area to be further west than today with storm
activity mainly in south central and southeast Wyoming. Most
models show thunderstorms struggling once they cross into
Nebraska. As usual, storms will have a gusty wind threat, but
some isolated large hail cannot be ruled out with 0- 6km shear
pushing 40 knots and decent instability mainly along and near
the Laramie Range.

As we head into the weekend, we will enter a break period in the
monsoon pattern as the upper level ridge retrogrades further to the
west. The position of the upper level high over the Las Vegas area
combined with a significant broadening in longitudinal extent will
suppress the monsoon well to the south. Westerly flow will flood dry
air into much of the western CONUS. Our area will remain on the
periphery of the ridge, but dry northwest flow aloft will still
be quite unfavorable for convection. Temperatures will begin to
climb once again as the ridge amplifies. 700-mb temperatures
will begin to spike, especially further west in Wyoming. Expect
upper 80s to lower 90s along the I-80 corridor from Rawlins to
Sidney, with mid to upper 90s showing up along and north of the
North Platte River. While record highs are not currently
forecast, we will be within a few degrees of daily records at
several locations. Much drier air will also begin to filter into
the area, but fortunately, winds are expected to be fairly
light Saturday which should keep down fire weather concerns.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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, Dawss 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 FRIDAY/...
Issued at 1131 AM MDT Thu Jul 30 2026

Synoptically, a positively tilted shortwave trough aloft will
propagate into northeast Wyoming by supper time with its
associated cold front moving to a Douglas to Alliance line, then
the shortwave trough aloft will move to an eastern South Dakota
to western Nebraska line by dawn Friday as surface high pressure
settles in across our forecast area.

Wyoming TAFS...Confidence is high in only scattered high based
cumulus development near 9000 feet this afternoon and early
evening, with a near zero chance of thunderstorms as evidenced
by the 12Z NAM and latest HRRR runs. Expect the typical wind
gusts to near 30 knots caused by gradients and mix down winds
until sunset.

Nebraska TAFS...With an 850/700 theta-e ridge axis developing
across western Nebraska and an approaching cold front, we
anticipate isolated to widely scattered thunderstorms, producing
wind gusts to 35 knots, to be near near or affect the KCDR,
KAIA and KBFF sites. Kept PROB30s there from mid afternoon
through early evening based on the consistent HRRR run timing,
and considered lowering to VCTS though will wait for convective
development to occur as we may see the infamous Dawes County
clipper thunderstorm or two possible up near Chadron in this
pattern. Dry at Sidney. Scattered clouds near 7000 feet
anticipated through sunset. Expect the typical wind
gusts to near 25 knots caused by gradients and mix down winds
until sunset.

&&

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

&&

$$

SHORT TERM...MN
LONG TERM...RUBIN
AVIATION...RUBIN