695
FXUS63 KUNR 292100
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
300 PM MDT Mon Apr 29 2024

.KEY MESSAGES...

- Near to above average temperatures through Wednesday, with chances
  for showers and gusty winds tonight into Tuesday.

- Cooler and unsettled weather develops for the latter part of the
  week into the first half of the weekend.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 300 PM MDT Mon Apr 29 2024

Current surface analysis shows warm front moving slowly east
across western SD this afternoon, with a cold front trailing
across eastern MT and western WY. Upper level analysis shows low
pressure over northern MN, with another across southern BC. Near
zonal flow is in place across the Rockies to the high Plains.
Skies are partly to mostly sunny. Isolated light showers have
developed mostly over the Black Hills area into far northeast WY.
Temps are much milder this afternoon compared to the last couple
of days, 60s in most areas, some 50s across the higher Black
Hills. Winds are westerly and relatively light in most areas, with
variable winds across portions of southwest SD.

Mostly seasonable temperatures and unsettled weather at times for
much of the week. Upper level system to the northwest of the region
will track mostly east near and along the US/Canadian border through
midweek, with west-southwest flow over the northern Rockies into the
northern Plains. The cold front to the west will push through the
area later tonight and early Tuesday, along with shortwave energy
aloft, bringing increasing chances for showers overnight and Tuesday
morning. A little light snow could develop across the higher Black
Hills early Tuesday. Pcpn amounts look to be pretty light, with the
chances for a tenth of an inch or more rather low in most areas,
less than 30 percent. Gusty west to northwest winds will develop
behind the front on Tuesday, especially across the northwest into
west central SD plains, where some gusts around 45 mph are expected.
Will let mid shift decide if a wind advisory is needed for any of
these areas. Behind the front, much drier air will push into the
area from the west on Tuesday, with humidities dropping to 15 to 25
percent in most areas. This could result in a period of elevated
fire weather conditions, especially across northwest SD where it has
been drier of late. As the upper low moves north of the area on
Wednesday, the next shortwave swings through to the south and will
bring more chances for showers, mainly later Wednesday into
Thursday. A few thunderstorms are possible, especially across south
central SD. Medium range models have come into better agreement on
the track, with the better chances for pcpn generally across the
Black Hills area and southern SD. There is potential for at least
light accumulations of snow over the highest Black Hills Wednesday
night into Thursday, with some snow mixing in as well over the
higher elevations of northeast WY.

Some cooler air is expected late week, with near to slightly below
average temperatures through Saturday. Another upper level
disturbance could bring some showers Friday into early Saturday as
well. At this point, much of the weekend looks dry as a shortwave
ridge moves over the area, with a warmup to above average temps for
Sunday. However, another upper level system could approach the area
toward the end of the weekend or early next week, with chances for
showers and possible thunderstorms.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1042 AM MDT Mon Apr 29 2024

Isolated showers are possible this afternoon mainly over the
Black Hills. Scattered showers are then possible over northeastern
Wyoming and western South Dakota from this evening through
Tuesday morning. VFR conditions are expected through 10z Tuesday
morning. After 10z Tuesday, an area of MVFR CIGS will move into
northeastern WY and northwestern SD along with a cold front. Gusty
northwest winds will develop over western South Dakota after 12Z
Tuesday and will continue into the afternoon.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...26
AVIATION...10