793
FXUS63 KUNR 182057
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
157 PM MST MON NOV 18 2024
KEY MESSAGES
- BAND OF LIGHT RAIN/SNOW MOVES THROUGH TONIGHT
- GUSTY/HIGH WINDS TUESDAY AND WEDNESDAY
DISCUSSION
(THIS EVENING THROUGH MONDAY)
ISSUED AT 150 PM MST MON NOV 18 2024
20Z SURFACE ANALYSIS HAD 986MB LOW OVER CENTRAL KS WITH ROBUST
PRESSURE FALLS (8MB/3HR) AHEAD IT TOWARD THE SD/MN BORDER. WEAK
SURFACE TROUGH FROM EASTERN MT INTO THE NE PANHANDLE. COLD FRONT
BEHIND TROUGH FROM CENTRAL MT INTO WESTERN WY IS STARTING TO
ACCELERATE EASTWARD. WATER VAPOUR LOOP HAD COMPACT UPPER LOW OVER
WESTERN KS WITH 130KT JET STREAK AHEAD IT. NORTHERN UPPER TROUGH
SPILLING FROM THE NORTHERN ROCKIES INTO THE NORTHERN PLAINS.
REGIONAL RADAR LOOP HAD WESTERN EDGE OF PRECIPITATION SHIELD INTO
TRIPP COUNTY. WEAK RETURNS AHEAD OF SURFACE TROUGH TO OUR WEST
WITH BETTER ORGANIZATION NEAREST FORCING ASSOCIATED WITH NORTHERN
UPPER TROUGH. EFFECTS OF THESE SYSTEMS THE MAIN CONCERN.
TONIGHT, SURFACE LOW RACES INTO NORTHERN MN AS IT BECOMES STACKED
BELOW UPPER LOW AND COLD FRONT ACCELERATES THROUGH THE CWA.
NORTHERN UPPER TROUGH SAUNTERS INTO THE DAKOTAS AND COMBINES WITH
WEAK 800-600MB FRONTOGENESIS OVER THE NORTHWEST THIRD OF THE CWA
CREATING A BAND OF LIGHT PRECIPITATION, CHANGING QUICKLY TO SNOW
AFTER SUNSET. ACCUMULATIONS OF AN INCH OR TWO (MOST LIKELY OVER
THE NORTHERN BLACK HILLS AND CAMPBELL COUNTY). LESSER AMOUNTS
ELSEWHERE OVER NORTHEASTERN WY/NORTHWEST SD AND LITTLE/NONE OVER
THE WESTERN SD PLAINS, EXCEPT FOR LIGHT RAIN OVER SOUTH-CENTRAL SD
(<40% CHANCE OF 0.05" LIQUID). TUESDAY, UPPER LOWS MERGE OVER
NORTHWEST MN WITH DEEP SUBSIDING SURFACE-700MB NORTHWEST FLOW OVER
THE CWA. PRESSURE GRADIENT ROBUST WITH TWO PERIODS OF STRONG
WINDS EXPECTED. FIRST ONE OCCURS LATER TONIGHT INTO TUESDAY
MORNING AND THEN ANOTHER TUESDAY NIGHT INTO WEDNESDAY AS UPPER LOW
SPINS A DEFINED SURFACE TROUGH THROUGH THE CWA WITH RESULTANT
ISALLOBARIC FORCING TAPPING INTO 35-55KT BOUNDARY LAYER FLOW.
CONFIDENCE IS HIGH FOR A HIGH END WIND ADVISORY (GUSTS 45-55MPH)
AND WARNING CRITERIA WINDS (60-65MPH) THROUGH WEDNESDAY AFTERNOON,
BUT AS MENTIONED THERE WILL BE A LULL INBETWEEN THE TWO PERIODS
OF STRONG WINDS. HIGHLIGHTS ISSUED TO ACCOUNT. TEMPERATURES WILL
BE 5-10F BELOW NORMAL, BUT NEAR GUIDANCE.
UPPER RIDGE EXPANDS INTO THE NORTHERN ROCKIES THURSDAY THROUGH
SATURDAY, BUT BACK SIDE OF RIDGE MAY SUPPORT A BACK DOOR COLD
FRONT OR TWO RESULTING IN POTENTIAL TIGHT TEMPERATURE GRADIENT
AND STRATUS/FOG GIVEN EASTERLY COMPONENT TO BOUNDARY LAYER FLOW
BEHIND COLD FRONT. PROGRESSIVE FLOW EXPECTED SATURDAY NIGHT INTO
NEARLY NEXT WEEK PORTENDING A MORE ACTIVE PATTERN.
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY)
ISSUED AT 1036 AM MST MON NOV 18 2024
CLOUDS WILL INCREASE ACROSS THE AREA DURING THE DAY, WITH AREAS
OF MVFR/IFR CONDITIONS AND LIGHT RAIN/SNOW DEVELOPING FROM
NORTHEAST WY TO THE NORTHERN BLACK HILLS BY EARLY EVENING AND
EXPANDING INTO WESTERN SD BY MIDNIGHT. PRECIPITATION WILL TAPER
OFF BY TUESDAY MORNING. NORTHWESTERLY WINDS WILL INCREASE BEHIND
THE FRONT, ESPECIALLY ACROSS THE SD PLAINS, WHERE SOME GUSTS OF 35
TO NEAR 50 KTS WILL DEVELOP TONIGHT. STRONG WINDS WILL CONTINUE
INTO TUESDAY.
UNR WATCHES/WARNINGS/ADVISORIES
SD...HIGH WIND WARNING FROM MIDNIGHT TONIGHT TO 5 PM MST WEDNESDAY
FOR SDZ001-012-013-031-072-073-078.
HIGH WIND WARNING FROM 6 AM MST /7 AM CST/ TUESDAY TO 5 PM MST
/6 PM CST/ WEDNESDAY FOR SDZ002-014-032-043-044-046-047-049-
077.
WIND ADVISORY FROM 5 AM TO 5 PM MST TUESDAY FOR SDZ025.
WIND ADVISORY FROM 5 AM TUESDAY TO 5 PM MST WEDNESDAY FOR SDZ026.
WY...NONE.
DISCUSSION/KEY MESSAGES...HELGESON
AVIATION...POJORLIE
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