333
FXUS65 KCYS 161126
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
526 AM MDT Fri Aug 16 2024

.KEY MESSAGES...

- Critical fire weather conditions expected this afternoon and
  possibly Saturday as high pressure builds over central
  Wyoming.

- A few severe thunderstorms possible this afternoon across
  eastern zones where moisture will be better for storm
  development.

- Seasonable temperatures will continue through the period.
  Showers and thunderstorms will be most likely on Monday,
  Wednesday and Thursday, with less coverage for Tuesday.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 238 AM MDT Fri Aug 16 2024

Two areas of surface high pressure analyzed across the Rockies
this morning. First over northern and northeast Wyoming and a
second area of high pressure over north central Colorado up to
near Laramie. These two high pressure areas separated by a
surface trough that lays roughly from Rawlins to Douglas to
Cheyenne this morning. Dewpoints in the mid 50s east of this
surface trough in the Nebraska Panhandle. Storms have formed
along and east of this trough this past evening and continue to
slowly weaken over the southern Panhandle as of 2 AM. Across
central Wyoming...an upper level ridge continues and will slowly
shift eastward through the morning hours.

Very dry air west of the ridge axis will filter into Carbon and
Albany Counties through the morning hours. Guidance showing Tds
in the low 20s to upper 20s across Carbon and Albany Counties
after 18Z today. GFS 700mb winds still forecast to increase to
30-35kts behind the ridge axis. Decided to upgrade the Fire
Weather Watch to a Red Flag Warning from noon to 8PM today.

Further to the east...dewpoints remain high across the
Panhandle. Our forecast for this afternoon showing low to mid
50s across much of the Panhandle with low to mid 30s along the
I-25 Corridor. Looks like possibility of an upper shortwave
working through the upper ridge this afternoon. Mixed signals as
NAM MUCAPE up around 2000J/KG over the southern panhandle this
afternoon. GFS on the other hand...showing MUCAPE around
400-500J/KG. Earlier HRRR simulated radar was showing a strong
to severe cell up by Chadron and possibly Alliance...but has
since backed off on that development. Given the uncertainty in
the various models...decided to stick pretty close to SPC`s
Marginal Risk area for this afternoon.

Saturday looks mainly dry across the CWA as we stay under the
upper ridge axis. But GFS suggesting an increase in monsoonal
moisture from the southwest moving into Carbon/Albany Counties
on the west side of that ridge Saturday night into Sunday.
ANother fairly strong shortwave moves into the west side of this
ridge Sunday afternoon. ECMWF/SREF in good agreement on
increasing PoPs for Sunday as PWATS climb to 1.3 inches in the
Panhandle and near an inch here at Cheyenne. Could see heavy
rainfall returning to some areas Sunday afternoon.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Issued at 238 AM MDT Fri Aug 16 2024

Sunday night/Monday/Tuesday...Atmospheric moisture content remains
about the same for Monday, with a decrease on Tuesday. Despite
ridging aloft, we still anticipate scattered to numerous showers and
scattered thunderstorms on Monday, most numerous near the Colorado
state line, with a significant decrease in coverage for Tuesday.
Maximum temperatures will be slightly warmer for Tuesday with 700 mb
temperatures near 17 Celsius.

Wednesday...Although ridging aloft continues, precipitable water
values remain nearly the same as Tuesday, ranging from 0.8 to 1.1
inches. Thus, it looks like widely scattered to scattered late day
showers and thunderstorms again, most numerous near the Colorado
state line and west of a Douglas to Kimball line. 700 mb
temperatures remain near 19 Celsius, yielding maximum temperatures
from the mid 80s to upper 90s.

Thursday...The ridge axis aloft moves further east over the Central
Plains states, with an increase in atmospheric moisture for our
counties, thus providing more fuel for scattered afternoon and
evening showers and thunderstorms, most numerous near the Colorado
state line. With more cloud and precipitation coverage, temperatures
will be slightly cooler.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 524 AM MDT Fri Aug 16 2024

Ridging aloft will continue. Mostly clear skies will prevail.
Winds will gust to 25 knots at the Wyoming terminals from 17Z to
01Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning from noon today to 8 PM MDT this evening for
     WYZ420>423-425-427-428.
NE...None.

&&

$$

SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN