278
FXUS65 KCYS 301750
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
1150 AM MDT Thu Jul 30 2026

.KEY MESSAGES...

- Monsoon moisture will remain in place through the end of the
  week across the high plains.

- More heat returns this weekend through Monday, with some near
  record high temperatures possible along with drier conditions.

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

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 215 AM MDT Thu Jul 30 2026

Current radar mosaic across the northern Front Range shows scattered
light showers over the mountains and east central Wyoming plains
at this hour with the evening thunderstorm activity moving
further east over the central plains. Lightning detection hasn`t
picked up any CG at this time with only isolated embedded thunder
expected over the next few hours. This activity is in response
to an upper level shortwave and 65 knot jet max, which is expected
to drift southeast across southeast Wyoming and western Nebraska
for Thursday. Tricky forecast this afternoon and evening with
some high res models showing a decent chance of a few severe
thunderstorms, while other guidance shows mainly dry conditions
over much of the area. Synoptic models continue to show the upper
level ridge axis rebuilding over Utah, western Colorado, and
western Wyoming today. This ridge and the upper level jet max
will provide some drier air to the forecast area, but mainly
across central and south central Wyoming...including Carbon and
Albany counties. Further east, not as confident that this dry
air will make it as far east as the Nebraska/Wyoming
border...nor the I-25 corridor to a lesser extent. Models tend
to dry things out too quick this time of the year when it comes
to monsoon patterns, and today will be no different. Convective
parameters still look good, especially east of I-25, with MLCAPE
between 1500 to 2000 j/kg for Sidney, Scottsbluff, and Chadron.
Shear is also better compared to the last several days as the
jet max moves overhead...with 0-6km shear up to 40 knots later
in the day. There is definitely a conditional risk for severe
thunderstorms today, so agree with SPC Marginal Risk for the
eastern plains. However, forcing is limited outside of east
central Wyoming and the northern/central Nebraska Panhandle as
most of the forecast area is south of the upper level shortwave,
or not under the favorable quadrant of the upper level jet max.
Any storms that do develop may contain large hail and strong
gusty winds. Also, can`t rule out a storm or two overachieving
today in these conditions...but confidence is low at this time.
Slightly warmer temperatures today with highs in the upper 80s
to middle 90s, warmest over the western Nebraska Panhandle.

For Friday, models show the upper level flow becoming more northerly
as the upper level ridge axis builds northward and amplifies through
the day. All models indicate a potent upper level shortwave digging
southeast. In addition, nocturnal convection/MCS activity across
the Great Plains expected to produce considerable northeast to
easterly outflow as a surface cool front moves into the Laramie
Range and stalls. This feature will result in enhanced surface
convergence along and east of the I-25 corridor. Another 65-70 knot
jet max is forecast to lift northeast across the Colorado/Wyoming
border, with increasing upper level diffluence. Expected
thunderstorm coverage to increase Friday afternoon and evening,
mainly from Douglas to Laramie and Lusk to Kimball Nebraska. At this
time, 0-6km shear looks to be on the marginal to on the low side, so
will keep strong to severe wording out of the forecast for now...but
will continue to monitor this trend over the next 24 hours. Current
trend has shifting the area of best thunderstorm develop further
west...to include Albany County.

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 afternoon as the midlevel subsidence is forecast to suppress
convection initiation. 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.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Issued at 211 PM MDT Wed Jul 29 2026

A ridge axis will be firmly in place for our Saturday with dam
heights above 594 decameters for a good portion of the area. This
high pressure will also suppress the monsoonal moisture flow and keep
it well to our south. The sinking and downsloping air should help
dry and heat up the afternoon atmosphere. Expect high temperatures
ranging from the mid to upper 80s in the interior basins and foot
hills to low to upper 90s north and east of the Laramie Range. Some
locations in Converse and Niobrara Counties could reach or exceed
record daily high temperatures. Another area of concern with the
excessive heat is how dry it will be. Minimum afternoon humidity
values are progged to be in the lower 20s to the low teens and
single digits for the northern and western fire zones. Winds appear
tame and are expected to preclude red flag conditions. A few
isolated storms are possible in the mountains and very southern
portions of the CWA during the afternoon hours with just enough
moisture to kick off high based thunderstorms. Would not expect
these storms to last long or produce much rainfall.

Sunday and Monday still has the ridge axis over the area. There may
be a few weak shortwave troughs that could flatten the ridge
slightly. The probability of a few more afternoon thunderstorms
could result, but chances are low and storms would be dry. The main
concern is for the excessive heat Sunday. Again temperatures soar to
the upper 90s to mid 100s for many locations. The current forecast
is for daily record highs to be broken or tied. Winds do increase
also Sunday with the increasing pressure gradients influenced by the
shortwave troughs. RH values plummet into the single digits over a
large part of the area and overnight recoveries are likely to be
poor. Therefore it is probable red flag products are issued if these
conditions hold in the forecast.

Monday evening through the rest of the forecast period has ensemble
support of a trough clipping the border and extending south through
our area. This would suppress the ridge into the deep southwest and
allow more seasonable conditions to return. Moisture remains a
scarce commodity, but perhaps there is enough along with enhanced
synoptic lift to trigger some showers and storms, especially over
the ranges. Hopefully a cold front associated with this trough can
provide some relief from the heat and increase surface humidity.

&&

.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...TJT
LONG TERM...RV
AVIATION...RUBIN