112
FXUS63 KUNR 190506
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1006 PM MST WED DEC 18 2024
KEY MESSAGES
- A CLIPPER SYSTEM WILL BRING CHANCES FOR LIGHT RAIN/FREEZING RAIN
ACROSS NORTHWESTERN SD THIS EVENING AND STRONG NORTHWEST WINDS
ACROSS THE SD PLAINS LATE TONIGHT INTO THURSDAY
- MOSTLY DRY CONDITIONS ARE EXPECTED LATE WEEK INTO AT LEAST EARLY
NEXT WEEK WITH TEMPERATURES NEAR TO ABOVE AVERAGE ACROSS MOST
OF THE AREA.
UPDATE
ISSUED AT 1002 PM MST WED DEC 18 2024
WITH UPSTREAM WINDS OF 60+ MPH, DECIDED TO EXPAND THE HIGH WIND
WARNING TO INCLUDE NORTHERN CAMPBELL AND THE CROOK COUNTY PLAINS.
STRONGEST WINDS THERE WILL BE OVERNIGHT, SO THE WARNING GOES ONLY
UNTIL 12Z.
UPDATE ISSUED AT 536 PM MST WED DEC 18 2024
GIVEN HIRES MODEL TRENDS AND BUFR PROGS, HAVE EXPANDED THE HIGH
WIND WARNING WEST INTO THE NORTHERN AND CENTRAL BLACK HILLS.
SOUNDINGS INDICATE A HIGH PROB FOR 50+ KNOT WINDS IN THE HIGHER
TERRAIN TONIGHT WITH LIKELY STANDING WAVE MIX DOWN, COUPLED WITH
STEEPENING LOW LEVEL LAPSE RATES. SPEARFISH AND RAPID CITY SHOULD
SEE A PERIOD OF WARNING LEVEL GUSTS THUR MORNING, ESP AREAS THAT
TYPICALLY SEE DOWNSLOPING FROM THE BH (FOOTHILLS). OTHERWISE,
LEFT THE REST OF THE HAZARDS AS IS.
DISCUSSION
(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 201 PM MST WED DEC 18 2024
CURRENT SFC OBS DEPICT NORTHWEST-SOUTHEAST ORIENTED WARM FRONT
DRAPED ACROSS WESTERN SD AND PUSHING NORTHWARD. A DEVELOPING SFC
LOW IS CENTERED OVER SOUTHERN AB/NORTHWESTERN MT ASSOCIATED WITH A
SHORTWAVE TROF CROSSING THE NORTHERN ROCKIES. VISIBLE SATELLITE
IMAGERY DEPICTS ERODING BAND OF LOW CLOUDS OVER CENTRAL SD WITH
MID LEVEL WV IMAGERY SHOWING PUSH OF MOISTURE ASSOCIATED WITH THE
INCOMING SYSTEM ENTERING THE NORTHERN PLAINS.
THE UPPER LEVEL SHORTWAVE AND ATTENDANT SFC LOW/CLIPPER SYSTEM
WILL SWING SOUTHEAST THROUGH THIS AFTERNOON AND EVENING, MAKING IT
TO THE NORTHERN PLAINS BY LATE TONIGHT. THE CENTER OF THE LOW
(ALONG WITH THE STRONGEST FORCING) WILL PASS TO OUR NORTH WHICH
WILL KEEP MOST OF THE AREA DRY WITH THIS SYSTEM. HOWEVER
NORTHWESTERN INTO SOUTH CENTRAL SD MAY SEE SLIGHT CHANCES FOR
PRECIP LATER THIS EVENING AS A COLD FRONT PUSHES THROUGH. THERMAL
PROFILES FAVOR FREEZING RAIN DEVELOPING OVER NORTHWESTERN SD AS
SFC TEMPERATURES WILL DIP BELOW FREEZING WITH WARMER AIR ALOFT.
ANY ICE ACCUMULATIONS ARE EXPECTED TO BE LIGHT, GENERALLY A TRACE
TO PERHAPS A HUNDREDTH OF AN INCH.
3 HR PRESSURE RISES OF 4 TO 5 MB AND CAA BEHIND THE FRONT WILL
SUPPORT THE DEVELOPMENT OF STRONG NORTHWEST WINDS EARLY THURSDAY
MORNING. THESE PRESSURE RISES ALONG WITH A CORRIDOR OF 60-70KT
WINDS AT ~850-725 MB WILL BE SUPPORTIVE OF WIND GUSTS OF 55-65MPH
AT THE SURFACE. HREF PROBABILITIES HAVE 60-70% FOR WIND GUSTS OF
60 MPH OR GREATER ACROSS NORTHWESTERN SD THROUGH EARLY THIS
MORNING. THEREFORE HAVE OPTED TO UPGRADE THE HIGH WIND WATCH TO A
HIGH WIND WARNING. AS FOR SOUTH CENTRAL SD, THE MOST RECENT MODEL
RUNS HAVE POINTED TO MORE FAVORABLE CONDITIONS FOR STRONG WINDS TO
DEVELOP. THE 12Z RUN OF THE HREF DEPICTS 60-80% PROBABILITIES FOR
WIND GUSTS EXCEEDING 55 MPH, THOUGH THE CHANCES DROP OFF TO 10%
FOR GUSTS EXCEEDING 60 MPH. HOWEVER, WITH MODEST PRESSURE RISES OF
4 TO 5 MB/3HR AND 50-60KT WINDS JUST OFF THE SURFACE, THERE IS
THE POTENTIAL FOR HIGH WIND WARNING CRITERIA GUSTS. THEREFORE HAVE
EXPANDED THE HIGH WIND WARNING TO COVER SOUTH CENTRAL SD. WINDS
WILL DIE DOWN LATE THURSDAY AFTERNOON AS THE CLIPPER SLIDES TO THE
SOUTHEAST WITH HIGH PRESSURE BUILDING IN ITS WAKE.
ARCTIC AIR MASS WILL PUSH INTO THE NORTHERN PLAINS THURSDAY AND
FRIDAY AS THE CLIPPER MOVES OUT OF THE REGION. THE COLDEST TEMPS
SHOULD REMAIN TO OUR NORTH/NORTHEAST WITH HIGHS IN NORTHWESTERN SD
IN THE 20S AND HIGHS ACROSS NORTHWESTERN WY AND SOUTHWESTERN SD
IN THE 40S. RIDGE BUILDS OVER THE WESTERN US BY THIS WEEKEND WITH
TEMPERATURES ACROSS THE CWA WARMING INTO THE 40S TO 50S BY
SATURDAY AND SUNDAY. WEAK SHORTWAVE CROSSES THE REGION LATE FRIDAY
INTO SATURDAY. MOISTURE WITH THIS SYSTEM WILL BE LIMITED AND IT
LOOKS LIKE THE ONLY SENSIBLE WEATHER IMPACTS WILL BE BREEZY
SOUTHERLY WINDS FRIDAY AFTERNOON FOLLOWED BY A WIND SHIFT TO THE
NORTHEAST AS THE WAVE PASSES THROUGH. A SLIGHTLY STRONGER
SHORTWAVE CROSSES THE REGION SUNDAY WHICH COULD BRING CHANCES FOR
LIGHT RAIN/SNOW ACROSS PARTS OF NORTHEASTERN WY AND FAR WESTERN
SD. NEAR ZONAL FLOW WILL FACILITATE MILD CONDITIONS THROUGH
CHRISTMAS WEEK. DETERMINISTIC GUIDANCE IS STILL SHOWING A SYSTEM
DEVELOPING OVER THE CENTRAL PLAINS AND SWINGING UP NORTH BY
CHRISTMAS DAY, WHICH COULD GIVE US ANOTHER SHOT AT LIGHT RAIN
AND/OR SNOW ACROSS NORTHEASTERN WY INTO WESTERN SD.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1002 PM MST WED DEC 18 2024
A STRONG CLIPPER SYSTEM WILL WILL SUPPORT LOW LEVEL WIND SHEAR
(40-60KT AT 2000FT) BEFORE THE SURFACE FRONT MOVES THROUGH LATER
TONIGHT. EXPECT WINDS OF 30 TO 40 KNOTS WITH GUSTS OVER 50 KNOTS
BEHIND THE FRONT. WINDS WILL BEGIN TO TAPER OFF THURSDAY
AFTERNOON WEST TO EAST. LIGHT PRECIPITATION ACROSS NORTHWESTERN SD
WILL CONTINUE TO DIMINISH OVERNIGHT. MVFR CEILINGS WILL BE
POSSIBLE OVER NORTHWESTERN SD AND THE BLACK HILLS TONIGHT INTO
THURSDAY MORNING.
UNR WATCHES/WARNINGS/ADVISORIES
SD...HIGH WIND WARNING UNTIL 2 PM MST THURSDAY FOR SDZ001-002-012>014-
025-026-031-032-043-072-073-078.
HIGH WIND WARNING UNTIL 8 AM MST THURSDAY FOR SDZ024-028.
HIGH WIND WARNING FROM 8 AM MST /9 AM CST/ TO 3 PM MST /4 PM
CST/ THURSDAY FOR SDZ044-046-047-049-077.
WY...HIGH WIND WARNING UNTIL 2 PM MST THURSDAY FOR WYZ060.
HIGH WIND WARNING UNTIL 8 AM MST THURSDAY FOR WYZ057.
HIGH WIND WARNING UNTIL 5 AM MST THURSDAY FOR WYZ054-056.
UPDATE...POJORLIE
DISCUSSION/KEY MESSAGES...WONG
AVIATION...POJORLIE
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