172
FXUS63 KUNR 270902
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
302 AM MDT SUN APR 27 2025
KEY MESSAGES
- STRONG LOW PRESSURE WILL CROSS THE REGION LATE TODAY THROUGH
MONDAY, BRINGING POTENTIAL SEVERE WEATHER LATE TODAY AND THIS EVENING,
ALONG WITH BENEFICIAL RAIN AND GUSTY WINDS TO MANY AREAS.
- CHANCE OF SHOWERS WEDNESDAY, WITH WARMING TREND LATE WEEK INTO
THE WEEKEND.
DISCUSSION
(TODAY THROUGH SATURDAY)
ISSUED AT 302 AM MDT SUN APR 27 2025
CURRENT SURFACE ANALYSIS SHOWS WEAK LOW PRESSURE OVER SOUTHEAST
MT, WITH WARM FRONT EXTENDING SOUTH-SOUTHEAST ACROSS EASTERN WY TO
ANOTHER LOW LOCATED ACROSS NORTHEAST CO. UPPER LEVEL ANALYSIS
SHOWS LOW OVER SOUTHERN NV, WITH SOUTHWESTERLY FLOW EXTENDING
ACROSS THE ROCKIES AND INTO THE HIGH PLAINS. SKIES ARE VARIABLY
CLOUDY, WITH A GOOD AMOUNT OF LOW CLOUDS ACROSS SOUTHERN PORTIONS
OF NORTHEAST WY AND SOUTHERN SD, AS WELL AS FAR NORTHWEST SD. SOME
FOG NOTED AS WELL, ESPECIALLY ACROSS THE SOUTHERN BLACK HILLS.
TEMPS ARE MOSTLY IN THE 40S AND LOWER 50S WITH BREEZY SOUTHERLY
WINDS ACROSS PORTIONS OF THE SD PLAINS.
ACTIVE WEATHER RETURNS LATE TODAY THROUGH THE EARLY PART OF THE WEEK
AS UPPER TROUGH AND LOW PRESSURE IMPACT THE REGION. WARMER AIR
CONTINUES TO BUILD INTO THE AREA TODAY WITH SOUTH TO SOUTHWEST
WINDS. HIGHS WILL REACH THE 70S AND LOWER 80S IN MOST AREAS. BREEZY
SOUTHERLY WINDS WILL CONTINUE ACROSS AREAS TOWARD CENTRAL SD TODAY.
TO THE EAST OF THE WARM FRONT THAT WILL SETTLE OVER THE BLACK HILLS
AND SOUTHWEST SD AREA LATER TODAY, LOW LEVEL MOISTURE WILL CONTINUE
TO BUILD IN, WITH DEWPOINTS IN THE UPPER 40S AND 50S. STEEP LAPSE
RATES LATER TODAY AND INCREASING MOISTURE WILL ALLOW SBCAPE VALUES
OF 500 TO AROUND 1500 J/KG TO DEVELOP IN THE AFTERNOON, HIGHEST
VALUES TO THE EAST OF THE BLACK HILLS. FURTHER WEST, SOUTHWESTERLY
WINDS WILL DEVELOP ACROSS NORTHEAST WY INTO THE BLACK HILLS, WITH
DRY AIR SURGING IN DURING THE AFTERNOON. LACK OF FORCING THROUGH MID
TO LATE AFTERNOON SHOULD LIMIT SHOWER/STORM DEVELOPMENT UNTIL
RELATIVELY LATE IN THE DAY, LIKELY EARLY EVENING IN MANY AREAS. THAT
IS WHEN MAIN SHORTWAVE ENERGY ARRIVES AND INTERACTS WITH THE FRONTAL
BOUNDARY OVER THE AREA. SHOWERS AND STORMS SHOULD QUICKLY DEVELOP AT
THAT POINT AND EXPAND ACROSS THE BLACK HILLS AREA AND WESTERN SD
DURING THE EVENING. THE SLIGHT RISK AREA FOR SEVERE STORMS COVERS
MUCH OF THE WESTERN SD PLAINS, WITH LARGE HAIL AND STRONG WIND GUSTS
THE PRIMARY HAZARDS, ALONG WITH LOCALLY HEAVY RAINFALL. CAN'T
TOTALLY RULE OUT AN ISOLATED TORNADO EARLY IN THE EVENING ACROSS
PARTS OF FAR SOUTHWEST SD AS SURFACE LOW IS EXPECTED TO TRACK EAST-
NORTHEAST ACROSS WESTERN NE INTO SOUTH CENTRAL SD DURING THE
EVENING. AN AREA OF MARGINAL RISK COVERS THE REST OF WESTERN SD AND
THE BLACK HILLS AREA, WITH A MORE ISOLATED THREAT FOR HAIL AND WIND.
THE THREAT SHOULD START TO DISSIPATE LATE IN THE EVENING AND
ESPECIALLY TOWARD THE OVERNIGHT AS THE STRONGER ACTIVITY MOVES
QUICKLY EAST OF THE FORECAST AREA.
UPPER TROUGH AND WEAKENING EMBEDDED LOW WILL THEN TRACK ACROSS THE
REGION LATE SUNDAY NIGHT AND MONDAY, BRINGING MORE RAINFALL AND SOME
THUNDERSTORMS. THE MORE SIGNIFICANT RAINFALL WITH THIS PART OF THE
SYSTEM IS EXPECTED TO STILL BE FROM FAR NORTHEAST WY TO NORTHWEST SD
AS BETTER FORCING REMAINS ACROSS NORTHERN PORTIONS OF THE FORECAST
AREA INTO MT AND ND. PCPN POTENTIAL HAS COME DOWN SOME, THOUGH STILL
BENEFICIAL RAINFALL IS EXPECTED FOR MANY AREAS. HREF CHANCES FOR A
HALF INCH OR MORE OF RAIN LATE SUNDAY NIGHT AND MONDAY ARE AROUND 50
PERCENT OR HIGHER ACROSS FAR NORTHEAST WY, THE NORTHERN BLACK HILLS,
AND MUCH OF NORTHWEST SD. COLD FRONT MOVING THROUGH THE AREA DURING
THE DAY WILL BRING GUSTY NORTHWEST WINDS TO MUCH OF THE AREA,
ESPECIALLY THE SD PLAINS. SOME STORMS WILL LIKELY DEVELOP AHEAD OF
THE FRONT DURING THE MIDDAY AND AFTERNOON HOURS, ESPECIALLY TOWARD
SOUTH CENTRAL SD, WHERE ISOLATED STRONGER STORMS ARE POSSIBLE. AS
COLDER AIR ARRIVES LATER IN THE DAY AND INTO MONDAY NIGHT, RAIN WILL
TURN OVER TO SNOW ACROSS AT LEAST THE HIGHEST ELEVATIONS OF THE
BLACK HILLS. SOME LIGHT ACCUMULATION IS POSSIBLE ACROSS THE HIGHER
NORTHERN BLACK HILLS, ESPECIALLY ABOVE 5500 FEET, BEFORE PCPN TAPERS
OFF LATER MONDAY EVENING.
QUIETER WEATHER IS EXPECTED FOR THE REST OF THE WEEK, THOUGH A
NORTHERN STREAM TROUGH WILL BRING CHANCES FOR SHOWERS AND A FEW
STORMS WEDNESDAY INTO WEDNESDAY NIGHT. TEMPS WILL BE NEAR TO
SLIGHTLY ABOVE AVERAGE TUESDAY THROUGH THURSDAY, WITH A WARMUP TO
WELL ABOVE AVERAGE TEMPS FOR FRIDAY AND THE WEEKEND AS DEVELOPING
RIDGE TO THE WEST MOVES OVER THE REGION.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1027 PM MDT SAT APR 26 2025
MVFR/IFR CEILINGS ARE EXPANDING ACROSS THE WESTERN SD PLAINS AND
WILL CONTINUE TO DO SO OVERNIGHT. FOG WITH IFR/LIFR CONDITIONS IS
EXPECTED OVER NORTHEASTERN WY (INCLUDING KGCC), NORTHWESTERN SD,
AND SOUTHWESTERN SD. MVFR CONDITIONS IN LOW CLOUDS WILL BE
POSSIBLE AT KRAP. CEILINGS WILL LIFT LATE SUNDAY MORNING, WITH VFR
CONDITIONS THEN EXPECTED THOUGH THE AFTERNOON. SUNDAY EVENING,
THUNDERSTORMS (SOME SEVERE) ARE EXPECTED TO MOVE THROUGH MAINLY
WESTERN SD. HAIL, GUSTY WINDS, AND HEAVY RAIN WILL BE POSSIBLE,
ALONG WITH MVFR/IFR CONDITIONS.
FIRE WEATHER
ISSUED AT 302 AM MDT SUN APR 27 2025
ELEVATED FIRE WEATHER CONDITIONS ARE LIKELY ACROSS NORTHEAST WY
INTO WESTERN PORTIONS OF THE BLACK HILLS THIS AFTERNOON AS
HUMIDITY DROPS TO 12 TO 20 PERCENT. AT THIS TIME, SOUTHWESTERLY
WINDS LOOK TO MOSTLY BE IN THE 10 TO 20 MPH RANGE DURING THE
AFTERNOON.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION/KEY MESSAGES...26
AVIATION...POJORLIE
FIRE WEATHER...26
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