346
FXUS65 KCYS 081124
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
524 AM MDT Mon Jul 8 2024

.KEY MESSAGES...

- Confidence is growing for a potentially significant heat wave
  to impact the region late in the week into the first half of
  the weekend.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 359 AM MDT Mon Jul 8 2024

With an exiting trough to the east and a building ridge to the west,
the CWA will enter into a period of quiet weather, with warming and
drying conditions expected. The upper-level trough axis will slowly
push into the center of the country today, keeping some lingering
cooler 700 mb air across the CWA. However, combined with abundant
sunshine expected from the dry air aloft, temperatures will begin to
rebound from Sunday`s below average temperatures. Highs for most
locations this afternoon will still be slightly below average in the
mid 70s to mid 80s. Looking at another increase in high temperatures
on Tuesday as the ridge over the West Coast strengthens and begins
to gradually shift eastward. 700 mb temperatures will climb to +12C
to +16C, which will put high temperatures right around average for
this time of year. Could also see an isolated shower or thunderstorm
develop over the high terrain as a weak disturbance passes overhead.
Any capping inversions will quickly be eliminated by rapid low-level
warming, but the lack of decent moisture will likely lead to only a
slight chance for any storms over the high terrain. Even Hi-Res
guidance isn`t too keen on anything developing in the CWA.
Rather, it keeps storm chances further south where there is a
tad more moisture and forcing.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 359 AM MDT Mon Jul 8 2024

The latest models and ensembles show no change to the medium to
long range forecast as a significant heat wave looks likely late
this week and through next weekend. Wednesday will likely be our
last "average" day for a while in terms of temperatures. Models
show the upper level high, responsible for the record heat
across the west coast, drifting eastward into the eastern Great
Basin region and the Intermountain west. 700mb temperatures will
climb to near 20c for western and central Wyoming and Colorado
on Wednesday with highs near 90 degrees across Carbon county.
Further east, mid 80s to low 90s are expected with light east to
northeast winds for the high plains. Again, can`t rule out a
quick shower or thunderstorm in and near the mountains Wednesday
afternoon due to a weak disturbance on the eastern periphery of
the upper level high, but most locations will remain dry and
likely stay that way through the weekend.

For Thursday through the weekend, all models and ensembles are
in excellent agreement...showing the center of the 598-600dm
upper level high drifting northeast into Utah and eventually
near the Utah/Wyoming/Colorado border as we head into Saturday.
The associated ridge axis will extend northward into Montana
during this time with increasing subsidence aloft across eastern
Wyoming and western Nebraska/Dakotas. Ensembles continue to show
very little, if any, spread with solutions regarding POP and max
and min temperatures. Continued to use a blend of the NBM 75th
percentile for max temperatures. This will result in afternoon
high temperatures solidly into the mid to upper 90s across most
of the forecast area with readings of 100-106 degrees for areas
below 5000 feet, such as Torrington, Scottsbluff, Alliance, and
Chadron. The best chance to see daily high temperature records
appears to be this weekend with daily records a few degrees
lower on July 13th and 14th compared to the previous days. All
time highs (monthly and yearly) are on the table as well since
current forecast highs are within a few degrees of these
records. At this time, it looks like Saturday will be the
hottest day of the week for southeast Wyoming, with Sunday
likely the hottest day for western Nebraska as afternoon
temperatures approach 110 for portions of the northern and
central panhandle.

By late in the weekend and into early next week, models continue
to be in great agreement show slight weakening of the strong
upper level high pressure, which is forecast to drift south into
Colorado and the four corners region. Some monsoon moisture
begins to make its way north, with PWATs climbing back to 0.75
to 1.00 inch next Monday. Continued to increase POP late Sunday
through next Monday as thunderstorms may return to the forecast
area. However, this is still 7-8 days away so kept POP below 35
percent for now.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 524 AM MDT Mon Jul 8 2024

High pressure aloft will begin to build across western Wyoming
today with northwesterly flow continuing for eastern Wyoming and
western Nebraska. Impacts to Aviation will be minimal early
this week with light winds and little or no precipitation.

HAZARDS/WEATHER TRENDS: VFR conditions will prevail today and
tonight.
&&

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

&&

$$

SHORT TERM...SF
LONG TERM...TJT
AVIATION...TJT