Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 211731
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1131 AM MDT Thu Mar 21 2024

.KEY MESSAGES...
225 AM MDT Thu Mar 21 2024

-Minor snow accumulations along the North Dakota border today

-Widespread/significant snow for parts of the area late Saturday
 through Sunday night/early Monday

&&

.DISCUSSION...(Today Through Wednesday)
Issued at 225 AM MDT Thu Mar 21 2024

Current surface map places low near the Big Horns with stationary
front across eastern Wyoming into the Nebraska. A few snow showers
are located across northwestern South Dakota with regional radar
showing more persistent snow band across northeast Montana into
North Dakota. Water vapor shows compact shortwave moving into the
northern Rockies. For today, shortwave zips into the western
Dakotas this afternoon and into the eastern Dakotas this evening.
Main band of frontogenisis remains north of the forecast
area with minor accumulations across far northwest South Dakota;
50-70% probability of 2" in the Lemmon area. Surface low over
northeastern Wyoming dips into the Nebraska panhandle this
afternoon, keeping most of the area on the cooler side of
guidance. Largest uncertainty in temperatures lies across
northeastern Wyoming where mixing may allow temperatures to get
into the 60s before the front surges southward. As the front moves
across the area this afternoon/tonight, some light rain/snow
showers are possible with a bit of upslope enhancement for the
Black Hills.

Friday/early Saturday northwest-southeast baroclinic zone remains
across the Northern Plains. Overall, forcing remains weak with
flat upper level ridge shifting across the area. Lingering low
level moisture and weak upslope flow may bring some very light
precipitation around the Black Hills area. Isentropic lift begins
to increase Saturday as lead impulse from western CONUS trough
crosses the Rockies. Overall, very little change in the forecast
for Saturday night through early Monday. Initial impulse lifts
into the western Dakotas with broad area of isentropic
lift/frontogenisis, with best lift and higher QPF/snowfall across
far northwest South Dakota into North Dakota. Secondary impulse
lifts through the Central Plains into eastern Nebraska Sunday
night with stronger deformation zone developing across the
central/eastern Dakotas. As that occurs, focus for higher
QPF/snowfall shifts east of the forecast area...possibly
impacting the south central South Dakota portion of the forecast
area. Probability of >=6" snowfall ranges from 50-80% across
northwest South Dakota...down to 10-30% across northeastern
Wyoming and southwestern South Dakota. Gusty winds, initially east
then shifting to the north, will create some blowing and drifting
snow.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1126 AM MDT Thu Mar 21 2024

MVFR ceilings across NW SD will persist, and MVFR visibilities
will develop around 20Z as snow moves in. VFR conditions will
prevail over the rest of the area this afternoon through this
evening, with chances for rain/snow showers. MVFR/local IFR
ceilings will spread into northeastern Wyoming, and southward
across much of western South Dakota after 09Z on Friday morning.

&&

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

$$

DISCUSSION/KEY MESSAGES...7
AVIATION...Pojorlie


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