844
FXUS65 KCYS 110331
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
931 PM MDT Wed Jul 10 2024

.KEY MESSAGES...

- Very hot temperatures are likely across all of southeast
  Wyoming and the western Nebraska Panhandle this weekend
  through early next week.

- A potential monsoonal pattern may develop through into the
  early to middle portion of next week, giving way to increased
  chances for precipitation and some relief to the extreme
  temperatures.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 300 PM MDT Wed Jul 10 2024

Only minor changes were made to the forecast with this update as the
anticipated heat wave remains on track. Temperatures are climbing
back above average across the area this afternoon, with most in the
NE panhandle climbing into the 90s. Current 700-mb temperatures are
analyzed ranging from +9C in Dawes county to +16C in southeast
Carbon county. GOES water vapor satellite imagery shows the strong
ridge aloft centered over the Las Vegas area very slowly expanding
to the north and east today. northwest flow remains over our area,
with a little bit more mid to high level moisture rotating into the
area today. This small area of increased moisture is visible across
central Wyoming southward towards the Colorado mountains, and is
allowing for some convection to go up mainly over the Snowy and
Sierra Madre mountains. Expect these isolated showers and
thunderstorms to continue into the evening, with likely a little
greater coverage than the last few days. The focus of this activity
will drift slightly eastward into the evening, across Albany county
and towards western Laramie county. Due to the very dry lower
atmosphere, measurable rainfall is unlikely outside of the higher
terrain, but we may see a brief shower, gusty winds, and some
lightning near Laramie and possibly Cheyenne before this activity
wanes late this evening.

The slow eastward march of the ridge continues Thursday, with
afternoon 700-mb temperatures expected to range from +14C east to
+20C west, supporting highs about 5F warmer than today`s. This will
push the typical hot spots around Chadron and the North Platte River
Valley close to the century mark, with all remaining valleys
climbing into the 90s. A surface high sliding down into the northern
Plains tonight will turn surface winds easterly over the plains and
advect in better surface moisture. This will result in a more
defined boundary/dryline near the WY/NE border which could then
provide a focus for lifting during the afternoon. A few isolated
showers/thunderstorms may manage to develop along this and drift
southeastward Thursday afternoon, although with very deep inverted-v
soundings this looks like mainly virga leading to gusty winds and
limited chances for precipitation. Another round of isolated
showers/storms will also be possible over the higher terrain.

The heatwave will begin to peak on Friday as the ridge axis moves
into Utah. The ensemble interquartile range of 700-mb temperatures
at 00z Friday over KCYS is +18C to +20C, indicating significant heat
in any scenario. These values will be around the 90th to 97.5th
percentile of climatology, supporting highs perhaps 3-5F warmer than
Thursday. Numerous locations may go for daily record highs. While
all-time records can`t be completely ruled out, the probability is
less than 10% at this time.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 300 PM MDT Wed Jul 10 2024

The major story for the extended forecast period continues to be
the potential for a significant heat wave across southeast Wyo &
the western Neb Panhandle. Deterministic models & their ensemble
members remain in excellent agreement w/ regard to 20+ deg C 700
mb temperatures beneath a 596-598 dam H5 ridge. In general, over
all confidence in all-time record breaking heat has waned w/ the
latest model trends keeping the center of the 500-hpa ridge well
to the south and west over the Four Corners through Sunday as we
remain in the more active quasi-zonal flow aloft on the northern
fringe of the ridge. Numerous disturbances & occasional shots of
monsoonal moisture will traverse the flow, suggesting the chance
for at least fairly widespread clouds and perhaps a few showers/
thunderstorms on a daily basis through the weekend. Believe this
will significant impact our daytime highs, although there is not
a doubt that it will still be very hot w/ highs 95-105 likely at
most locations along/east of I-25 on both Saturday and Sunday w/
the latest NBM spectrum still strongly supporting these very hot
temperatures. Overnight lows should also be in the mid 60s, warm
by our standards but should remain just below thresholds leading
to excessive heat headlines. Nonetheless, still expect a longer-
term Heat Advisory to be issued in the next few forecast cycles.
Trending cooler w/ increased chances for showers & thunderstorms
after Monday next week with a decent monsoonal surge. Still warm
though on Tuesday and Wednesday w/ highs in the 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 929 PM MDT Wed Jul 10 2024

Northwest flow aloft will continue. Mostly clear skies will
prevail, with occasional periods of scattered to broken clouds
from 10000 to 12000 feet. Winds will be mainly at or below
12 knots.

&&

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

&&

$$

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