104
FXUS63 KUNR 170433
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
933 PM MST SUN FEB 16 2025
KEY MESSAGES
- RECORD TO NEAR-RECORD COLD TEMPERATURES ARE POSSIBLE FOR MANY
AREAS MONDAY THROUGH THURSDAY MORNING, ESPECIALLY THE SOUTH
DAKOTA PLAINS. ALTHOUGH WINDS WILL BE RELATIVELY LIGHT THROUGH
MUCH OF THE PERIOD, WIND CHILL VALUES WILL FALL TO -20 TO NEAR
-45F AT TIMES ACROSS MUCH OF THE FORECAST AREA DURING THIS TIME.
- A PERIOD OF PROLONGED, LIGHT-TO-MODERATE SNOWFALL IS EXPECTED
THIS EVENING INTO TUESDAY EVENING, ESPECIALLY AFFECTING
NORTHEASTERN WYOMING, THE BLACK HILLS, AND SOUTHWESTERN SOUTH
DAKOTA. SNOWFALL AMOUNTS OF 2 TO 6 INCHES, WITH SPOTTY HIGHER
AMOUNTS, WILL BE POSSIBLE IN THESE AREAS OVER THE 2-DAY PERIOD.
- LINGERING LIGHT SNOW WILL COME TO AN END DURING THE MIDWEEK
PERIOD. THEREAFTER, A WARMING TREND WILL TAKE PLACE TOWARD THE
END OF THE WEEK, AND ESPECIALLY NEXT WEEKEND.
DISCUSSION
(THIS EVENING THROUGH SUNDAY)
ISSUED AT 1254 PM MST SUN FEB 16 2025
THE LATEST WATER VAPOR IMAGES AND 500-MB HEIGHT ANALYSIS SHOWS A
STRONG UPPER LOW OVER SOUTHERN MANITOBA WITH WEST-NORTHWEST FLOW
ALOFT ACROSS THE CWA. A SHORT-WAVE TROUGH OVER THE INTERMOUNTAIN
WEST WILL SKIRT THE SOUTHERN CWA TONIGHT AND MONDAY AS A LOW-LEVEL
BAROCLINIC ZONE IS THE FOCAL POINT FOR SNOW, ESPECIALLY ACROSS
THE SOUTHWESTERN HALF OF THE CWA. THE UPPER LOW WILL DROP INTO THE
UPPER MIDWEST ON WEDNESDAY, AND THEN SHIFT EAST LATE IN THE WEEK
AS UPPER RIDGING BUILDS OVER THE WEST. THE Q-VECTOR FORCING IS
FAIRLY WEAK THROUGH 06Z TUESDAY, BUT THEN INCREASES ON TUESDAY AS
THE UPPER LOW SHIFTS SOUTH. PARADOXICALLY, THE BEST LOW-LEVEL
ISENTROPIC LIFT AND FRONTOGENESIS WILL BE TONIGHT THROUGH TUESDAY
EVENING -- OUT OF PHASE WITH THE BEST UPPER FORCING.
ANYWAY, A REINFORCING SHOT OF COLDER ARCTIC AIR WILL START TO SLOWLY
SINK SOUTH ACROSS THE AREA TONIGHT AND MONDAY, THEN WILL LINGER
THROUGH THURSDAY. TEMPERATURES ARE EXPECTED TO STAY MAINLY BELOW
ZERO FOR AN EXTENDED PERIOD ACROSS MOST AREAS NORTH AND EAST OF THE
BLACK HILLS FROM TONIGHT THROUGH AT LEAST WEDNESDAY MORNING, AND
LIKELY INTO THURSDAY FOR SOME AREAS. THE COLDEST AIR IS EXPECTED
TO BE MOSTLY IN THE MONDAY NIGHT TO WEDNESDAY TIMEFRAME. AS FAR AS
COLD WEATHER HEADLINES ARE CONCERNED, WE HAVE MAINTAINED THE
WARNINGS AND ADVISORIES FROM THE PREVIOUS SHIFT. ADDITIONAL COLD
WEATHER HEADLINES THROUGH THE FIRST HALF OF THE WEEK MAY BE ISSUED
MORE ON A DAY-TO-DAY BASIS GIVEN SOME VARIABILITY IN WIND CHILL
VALUES THROUGH THE PERIOD.
BEYOND THE BITTER COLD TEMPERATURES FOR THE NEXT SEVERAL DAYS, SOME
DECENT SNOWFALL CAN BE EXPECTED OVER THE NEXT THREE DAYS AS WELL.
THE MOST IMPACTFUL SNOWFALL APPEARS TO BE ACROSS PORTIONS OF
NORTHEASTERN WY THROUGH THE BLACK HILLS TO SOUTHWESTERN SD FROM
TONIGHT THROUGH TUESDAY. THE SNOWFALL WILL BE ENHANCED AS A SERIES
OF SUBTLE SHORT-WAVE TROUGHS INTERACTS WITH A TIGHTER BAROCLINIC
ZONE IN PLACE ACROSS THIS REGION. MOST OF THE SNOWFALL IS LIKELY
TO BE LIGHT, BUT FOR A PROLONGED PERIOD OF TIME. A PERIOD OR TWO
OF MORE ENHANCED HEAVIER SNOWFALL EVENTS WILL LIKELY DEVELOP
ACROSS AT LEAST FAR SOUTHWESTERN SD, ESPECIALLY LATER TONIGHT INTO
MONDAY NIGHT. MODEL ENSEMBLES HAVE BEEN FAIRLY CONSISTENT WITH
THE TIMING, AREA, AND GENERAL AMOUNTS. LIKEWISE, WE HAVE
MAINTAINED THE WINTER WEATHER ADVISORY FOR THIS AREA IN
ANTICIPATION OF 2 TO 6 INCHES OF SNOW FROM SUNDAY NIGHT THROUGH
TUESDAY MORNING. THE HIGHEST AMOUNTS SHOULD BE ACROSS FAR
SOUTHWESTERN SD.
FINALLY, BITTER COLD TEMPERATURES WILL LINGER THROUGH MIDWEEK.
THE COLDEST AIR WILL BEGIN TO SCOUR OUT OF THE AREA LATE ON
THURSDAY, ESPECIALLY THE HIGHER ELEVATIONS OF THE FORECAST AREA.
WE WILL START TO SEE REAL IMPROVEMENT FRIDAY AND ESPECIALLY OVER
THE WEEKEND. THE ECMWF IS A BIT MORE AGGRESSIVE THAN THE GFS WITH
THE WARMING TREND. TAKING INTO ACCOUNT THE ANTICIPATED SNOWFALL,
THE SLOWER WARMING TREND (ESPECIALLY THURSDAY AND FRIDAY) APPEARS
MORE PROBABLE. HIGHS WILL LIKELY BE BACK ABOVE AVERAGE IN MANY
AREAS FOR THE WEEKEND, WITH SOME 50S POSSIBLE BY SUNDAY. THERE
WILL BE SOME LINGERING CHANCES FOR LIGHT SNOW AND FLURRIES INTO
MIDWEEK, BUT A MAINLY DRY PATTERN SHOULD DEVELOP FOR THE END OF
THE WEEK AND THE WEEKEND.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT)
ISSUED AT 931 PM MST SUN FEB 16 2025
WIDESPREAD LIGHT SNOW WILL CONTINUE TO SPREAD INTO NORTHEAST WY
AND WESTERN SD OVERNIGHT AND CONTINUE THROUGH THE REMAINDER OF THE
PERIOD. EXPECT IFR TO LOCAL LIFR CONDS TO CONTINUE TO DEVELOP
OVERNIGHT FROM WEST TO EAST. THE WORST CONDITIONS ARE EXPECTED TO
BE GENERALLY NEAR AND SOUTH OF I-90. BOTH THE KGCC AND KRAP
TERMINALS WILL BE AFFECTED.
UNR WATCHES/WARNINGS/ADVISORIES
SD...EXTREME COLD WARNING UNTIL 11 AM MST WEDNESDAY FOR SDZ001-002-
014-078.
COLD WEATHER ADVISORY UNTIL 11 AM MST /NOON CST/ MONDAY FOR
SDZ012-013-025-031-032-043-046-047-049-072-073-077.
WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR SDZ026>030-
041-042-044-074>076.
WY...WINTER WEATHER ADVISORY UNTIL 5 AM MST TUESDAY FOR WYZ058-059.
DISCUSSION/KEY MESSAGES...BUNKERS
AVIATION...JOHNSON
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