031
FXUS63 KUNR 252318
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
518 PM MDT Wed Sep 25 2024

.KEY MESSAGES...

- Dry weather, much warmer than average temperatures, and elevated
  to critical fire weather conditions continue through the weekend.

- Cooler to start next week, then warming again.

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 220 PM MDT Wed Sep 25 2024

Current surface analysis shows lee trough from central MT to
central/eastern WY, with high pressure to the south of the region.
Upper level analysis shows ridge covering the Rockies and high
Plains. Skies are sunny with warm temps in the 80s to around 90
degrees in most areas. Winds are from the south to southeast,
breezy across much of northeast WY into portions of western SD.

A dry and warm pattern will continue through the weekend as ridging
generally persists across the southwest US/Rockies into the Plains.
Breezy south to southwest winds can be expected in some areas
tonight into early Thursday, especially from northeast WY to
southwest and south central SD. Thursday will be the warmest day of
the work week, with highs reaching into the 90s across much of the
plains. Some daily records could be broken, including in the Rapid
City area. An upper level shortwave will pass mostly north of the
region later Thursday and Thursday night, dragging a cold front
across the forecast area during the afternoon and evening. This will
bring breezy conditions and a slight cool down for Friday, with
highs in the upper 70s and 80s, but little or no chance for pcpn.
Ridge quickly returns to the region by the weekend, with highs in
the 80s and 90s, warmest on Sunday. Elevated to critical fire wx
conditions can be expected on most days through the weekend.

Another trough is progged to quickly move from southwest Canada to
south central Canada/northern Plains late this weekend into the
beginning of next week. Main energy is expected to remain north of
the forecast area Sunday night into Monday, so chances for any rain
look minimal at this point, less than 15 percent. However, passing
cold front will bring much cooler air and gusty winds for at least
Monday, with highs back closer to average levels, 60s and lower 70s.
Cooler air could linger Tuesday before weak ridging builds back into
the region. Above average temps are likely mid to late week (60
percent or higher chances).

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 518 PM MDT Wed Sep 25 2024

VFR conditions are expected through the TAF period. Breezy
southerly winds will persist tonight. Low level wind shear is
expected across the western South Dakota plains overnight, then
ending around sunrise Thursday. A cold front will work its way
through the area during the day on Thursday, with winds shifting
to the northwest.

&&

.FIRE WEATHER...
Issued At 220 PM MDT Wed Sep 25 2024

Critical or near critical fire wx conditions exist across the red
flag warning area this afternoon, with humidity in the teens and
wind gusts near or over 20 mph, especially across the northeast WY
plains. Red flag conditions will continue in these areas until
around sunset with poor humidity recovery and continued breezy
conditions leading to elevated conditions overnight. Elevated fire
wx conditions are noted across much of western SD this afternoon.

For Thursday, the drier air will shift east with the ridge and ahead
of an approaching cold front. Surface trough ahead of the front
across western SD will bring increasing southwesterly winds later in
the morning into the midday hours before the front arrives. The
front looks to move through northeast WY and much of western SD
during the midday and afternoon hours, stalling out toward central
SD later in the day. Breezy conditions, gusts of 25 to 40 mph, look
most likely behind the front over much of northeast WY and northwest
into the west central SD plains during the afternoon (near or above
70 percent). Breezy south-southwest winds can be expected toward
south central SD during the day. Humidity values will drop into the
teens across much of the area, lower teens from much of northeast WY
to southwest SD. Gustier winds may be more localized further south
across southwest SD, but some gusts to near or above 20 mph are
likely in many areas. With conditions expected to be critical or at
least near critical over much of northeast WY and western SD, will
issue a red flag warning for Thursday. For the area covered today
with a red flag warning, poor humidity recovery and periods of
breezy conditions can be expected tonight, so will just extend the
warning out through tomorrow.

Some cooler air and slightly higher humidity develop for Friday,
with very warm conditions returning over the weekend. Elevated to
near critical fire wx conditions persist through the period, with
Sunday looking to be the most favorable day for red flag conditions.
Another dry cold front will bring much cooler conditions and gusty
winds into early next week.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...     Red Flag Warning from 10 AM MDT /11 AM CDT/ to 7 PM MDT /8 PM
     CDT/ Thursday for SDZ321-323>327-329-331>334.
     Red Flag Warning until 7 PM MDT Thursday for SDZ322.
WY...     Red Flag Warning until 7 PM MDT Thursday for WYZ314>317.
&&

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...13
FIRE WEATHER...26