289
FXUS63 KUNR 181000
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
300 AM MST WED DEC 18 2024
KEY MESSAGES
- MILDER TODAY FROM NORTHEAST WY TO THE BLACK HILLS AND SOUTHERN SD.
REMAINING COOL ACROSS NORTHWEST SD WITH LOW CLOUDS AND PATCHY
MORNING FOG.
- A CLIPPER SYSTEM WILL BRING A CHANCE FOR LIGHT RAIN OR FREEZING
RAIN ACROSS MAINLY NORTHWEST SD THIS EVENING AND STRONG NORTHWESTERLY
WINDS ACROSS THE SOUTH DAKOTA PLAINS LATE TONIGHT AND 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.
DISCUSSION
(TODAY THROUGH TUESDAY)
ISSUED AT 300 AM MST WED DEC 18 2024
CURRENT SURFACE ANALYSIS SHOWS DEVELOPING WARM FRONT FROM
SOUTHEASTERN MT TO NEAR BLACK HILLS AREA AND INTO FAR SOUTHWEST
SD/WESTERN NE. LOW PRESSURE IS LOCATED ALONG THE BOUNDARY OVER THE
NORTHERN ROCKIES, WITH A PACIFIC COLD FRONT MOVING ONTO THE WEST
COAST. UPPER LEVEL ANALYSIS SHOWS RIDGE AXIS OVER THE
INTERMOUNTAIN WEST, WITH LOW PRESSURE AND TROUGH OFF THE PACIFIC
NW COAST. NORTHWEST FLOW IS IN PLACE ACROSS THE NORTHERN PLAINS,
WITH STRONG JET EXTENDING OVER THE RIDGE ACROSS SOUTHWEST CANADA
INTO THE NORTHERN PLAINS. EXTENSIVE AREA OF LOW CLOUDS PERSIST TO
THE NORTHEAST OF THE FRONT, ESPECIALLY FROM NORTHWEST INTO CENTRAL
SD. PATCHY LOW CLOUDS AND FOG ARE TRYING TO DEVELOP CLOSER TO THE
FRONT NEAR THE BLACK HILLS. TEMPS ARE MOSTLY IN THE MID TEENS TO
MID 20S WITH LIGHT WINDS.
WARM FRONT WILL LIFT SLOWLY NORTHEAST ACROSS WESTERN AND SOUTHERN
PORTIONS OF THE AREA TODAY, WITH MILDER CONDITIONS ACROSS NORTHEAST
WY, THE BLACK HILLS, AND MUCH OF SOUTHERN SD. HIGHS THERE WILL REACH
THE UPPER 30S AND 40S. FARTHER NORTH AND EAST ACROSS NORTHWEST SD,
HIGHS WILL MOSTLY REACH THE UPPER 20S TO MID 30S, WITH CONSIDERABLE
LOW CLOUDS LINGERING THROUGH MUCH OF THE DAY, IF NOT ALL DAY. PATCHY
FOG COULD DEVELOP AND PERSIST INTO THE LATE MORNING. WINDS WILL BE
SOUTH TO SOUTHEAST IN MOST AREAS, BECOMING SOUTHWESTERLY ACROSS MUCH
OF NORTHEAST WY INTO THE BLACK HILLS DURING THE AFTERNOON. SOME
GUSTY WINDS ARE LIKELY ACROSS SOUTHERN CAMPBELL COUNTY LATER TODAY.
CLIPPER SYSTEM WILL QUICKLY MOVE OVER THE RIDGE TO THE WEST AND INTO
THE NORTHERN PLAINS TONIGHT. PCPN WILL START TO MOVE INTO NORTHERN
PORTIONS OF THE REGION LATE TODAY AND THIS EVENING, WITH MOST OF IT
STAYING NORTH OF THE FORECAST AREA. HOWEVER, THERE ARE STILL SOME
LOWER CHANCES FOR PCPN ACROSS MAINLY NORTHWEST SD THIS EVENING,
MOSTLY IN THE FORM OF EITHER LIGHT RAIN OR LIGHT FREEZING RAIN AS
TEMPS STAY NEAR OR BELOW FREEZING AT THE SURFACE WITH WARMER AIR
ALOFT. ANY AMOUNTS ARE EXPECTED TO BE VERY LIGHT, GENERALLY A TRACE
TO POSSIBLY A HUNDREDTH OR TWO. COLD FRONT ARRIVES LATE EVENING AND
OVERNIGHT, PUSHING ANY LINGERING PCPN EAST OF THE AREA. STRONG
NORTHWESTERLY WINDS DEVELOP BEHIND THE FRONT AROUND AND AFTER
MIDNIGHT ACROSS NORTHWEST SD. FORECAST SOUNDINGS SHOW WINDS OVER 50
KTS NOT TOO FAR OFF THE SURFACE AND HREF PROBABILITIES OF SOME GUSTS
AROUND OR ABOVE 60 MPH ARE NEAR OR ABOVE 50 PERCENT ACROSS A GOOD
PORTION OF NORTHWEST SD LATE TONIGHT INTO THURSDAY MORNING. MIXING
OF THE STRONGER WINDS COULD BE AN ISSUE OVERNIGHT WITH COLD
ADVECTION NOT VERY ROBUST UNTIL EARLY THURSDAY, BUT MORE THAN ENOUGH
POTENTIAL EXISTS TO ISSUE A HIGH WIND WATCH FOR MOST AREAS NORTH AND
NORTHEAST OF THE BLACK HILLS LATE TONIGHT THROUGH EARLY THURSDAY
AFTERNOON. STRONGER WINDS WILL SPREAD SOUTHEAST ACROSS THE REST OF
WEST CENTRAL INTO SOUTH CENTRAL SD EARLY THURSDAY. THERE IS SOME
POTENTIAL FOR WARNING CRITERIA WINDS THERE AS WELL, BUT DOES NOT
LOOK QUITE AS FAVORABLE AT THIS POINT. WILL LET LATER SHIFTS HAVE
ANOTHER LOOK TO SEE IF A WATCH OR POSSIBLE WARNING MAY BE NEEDED
THERE. WINDS SHOULD BEGIN TO DECREASE THURSDAY AFTERNOON AND
ESPECIALLY AFTER SUNSET.
THE REST OF THE WEEK AND THE WEEKEND LOOK TO BE MAINLY DRY, WITH A
WARMING TREND, AS A RIDGE BUILDS OVER THE ROCKIES LATE IN THE WEEK
AND EVENTUALLY MOVES EAST ACROSS THE PLAINS OVER THE WEEKEND. THIS
WILL EVENTUALLY BRING ABOVE AVERAGE TEMPS TO MOST AREAS BY LATE
WEEKEND, THOUGH IT COULD BE SLOW TO WARM UP TO THE NORTHEAST OF THE
BLACK HILLS FRIDAY INTO SATURDAY. AS THE RIDGE PASSES EAST OF THE
AREA ON SUNDAY, A WEAK UPPER LEVEL SHORTWAVE COULD BRING SOME
CHANCES FOR LIGHT RAIN/SNOW ACROSS PARTS OF NORTHEAST WY AND FAR
WESTERN SD LATER ON SUNDAY. MUCH OF CHRISTMAS WEEK LOOKS MILD AT
THIS POINT AS NEAR ZONAL FLOW DEVELOPS OVER THE WESTERN INTO CENTRAL
US. MANY LONGER RANGE MODELS/ENSEMBLES ARE SHOWING ANOTHER WEAKER
SYSTEM POSSIBLY MOVING ACROSS THE AREA CHRISTMAS DAY, WITH SOME
CHANCES FOR LIGHT RAIN AND/OR SNOW ACROSS AT LEAST NORTHEAST WY AND
THE BLACK HILLS.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 943 PM MST TUE DEC 17 2024
STRATUS/FOG MAY DEVELOP OVERNIGHT TONIGHT ON THE NW SD PLAINS,
WITH LOCAL MVFR/IFR CONDITIONS DEVELOPING AND PERSISTING THROUGH
THE MORNING HOURS. OTHERWISE, VFR CONDS ELSEWHERE. A STRONG
CLIPPER SYSTEM WILL APPROACH THE REGION WED EVENING WITH
INCREASING FLOW OFF THE SFC. THIS WILL SUPPORT LOCAL WIND SHEAR IN
THE LEE OF THE BLACK HILLS BEFORE THE SFC FRONT MOVES THROUGH. IN
ADDITION, LIGHT RAIN OR FREEZING RAIN WILL BE POSSIBLE ACROSS NW
SD WED EVENING.
UNR WATCHES/WARNINGS/ADVISORIES
SD...HIGH WIND WATCH FROM THIS EVENING THROUGH THURSDAY AFTERNOON FOR
SDZ001-002-078.
HIGH WIND WATCH FROM LATE TONIGHT THROUGH THURSDAY AFTERNOON FOR
SDZ012>014-031-072-073.
WY...NONE.
DISCUSSION/KEY MESSAGES...26
AVIATION...JC
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