807
FXUS63 KUNR 310443
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1043 PM MDT SAT MAY 30 2020
DISCUSSION
(THIS EVENING THROUGH SATURDAY)
ISSUED AT 157 PM MDT SAT MAY 30 2020
19Z SURFACE ANALYSIS HAD HIGH FROM EASTERN ND INTO MO. LEE
TROUGH/WARM FRONT FROM CENTRAL MT INTO NORTHEAST CO. FAIRLY TIGHT
GRADIENT BRINGING GUSTY SOUTHEASTERLY WINDS AT TIMES, UPSLOPE
FLOW, AND SLOW INCREASE IN MOISTURE. THERMAL RIDGE OVER TOPPING
CLOUD COOLED AIR PRODUCING 100-150J/KG MLCIN OVER NORTHEAST WY
WITH ABOUT 500J/KG MLCAPE. 0.5KM VISIBLE LOOP SHOWED STABLE
STRATUS/STRATOCU OVER WESTERN SD AND CLEAR SKIES OVER NORTHEAST
WY. BIG HORNS CU HAVING TROUBLE DEVELOPING. SHORTWAVE IS SUGGESTED
BY WATER VAPOUR OVER WESTERN WY, WHICH WILL HEAD NORTHEAST
TONIGHT. IT'S GOING TO BE TOUGH TO INITIATE CONVECTION OVER
NORTHEAST WY, BUT IT'S CONCEIVABLE STORMS THAT FIRE OVER THE
TERRAIN FROM NORTH CENTRAL TO CENTRAL WY MIGRATES INTO CAMPBELL
COUNTY THIS EVENING WITH ENOUGH SHEAR TO BE WATCHABLE. BRIEF
TCU/TS OVER THE HIGHEST TERRAIN OF THE BLACK HILLS ALSO POSSIBLE
EARLY. CONTINUED SOUTHEAST BOUNDARY LAYER FLOW WILL CREATE STRATUS-
FEST OVER THE SD PLAINS TONIGHT. TEMPERATURES WILL BE NEAR GUIDANCE.
SUNDAY, UPPER/THERMAL RIDGE BUILDS INTO THE CWA. STRATUS ON THE
WESTERN SD PLAINS WILL ERODE IN THE AFTERNOON AS SOLAR INSOLATION
TAKES HOLD ALONG EASTWARD MOVING WARM FRONT. IF THE WARM FRONT
DOESN'T HEAD EAST, COULD BE A HUGE BUST IN HIGH TEMPERATURES EAST OF
THE BLACK HILLS. 2KJ/KG SBCAPE FORECAST FROM THE NORTHERN BLACK
HILLS INTO NORTHWEST SD LATER SUNDAY AFTERNOON, BUT 50-100J/KG
SBCIN. INITIATING SURFACE-BASED CONVECTION WILL AGAIN BE TOUGH,
BUT DO EXPECT TSRA TO DEVELOP IN MT, WHICH WILL TRANSLATE EASTWARD
LATE AFTERNOON. IF WELL-DEFINED COLD POOL CAN DEVELOP, IT MIGHT
BE ENOUGH FOR UPSCALE GROWTH LATE IN THE DAY OVER NORTHWEST SD WITH
SEVERE WIND THREAT. CAMS INSISTENT ON THIS SCENARIO, BUT PARAMETERS
NOT SO MUCH. TEMPERATURES WILL BE NEAR GUIDANCE IF CLOUDS GO AWAY.
MONDAY THROUGH TUESDAY AFTERNOON, UPPER RIDGE SLIDES EAST AS THERMAL
RIDGE PEAKS OVER THE CWA MONDAY - THE WARMEST DAY OF THE UPCOMING
WEEK MOST LIKELY. CAN'T RULE OUT A STRAY STORM, BUT MOST AREAS WILL
BE DRY.
TUESDAY NIGHT THROUGH THE END OF NEXT WEEK, ACTIVE WEST/SOUTHWEST
FLOW EXPECTED AS A SERIES OF WAVES PUSH FRONTAL BOUNDARIES ACROSS
THE CWA. ACTIVE SEVERE WEATHER POSSIBLE GIVEN PATTERN. TEMPERATURES
WILL BE 10-15F ABOVE NORMAL.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1038 PM MDT SAT MAY 30 2020
OVER WESTERN SD, AREAS OF MVFR/IFR CONDITIONS EXPECTED DUE TO
STRATUS OVERNIGHT, ESPECIALLY IN/NEAR THE BLACK HILLS WHERE SOME
LIFR CONDITIONS/FOG WILL OCCUR. OVER NORTHEASTERN WY PLAINS,
MAINLY VFR CONDITIONS EXPECTED WITH GUSTY SOUTHERLY WINDS. SOME
MVFR CIGS ARE POSSIBLE EXTENDING OUT FROM THE HILLS. CONDITIONS
WILL IMPROVE FROM WEST TO EAST SUNDAY MORNING, AS A WARM FRONT
MOVES THROUGH THE AREA.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...HELGESON
AVIATION...MLS
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