641
FXUS63 KUNR 301115
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
515 AM MDT THU JUL 30 2026
KEY MESSAGES
- MARGINAL TO SLIGHT (LEVEL 1-2 OUT OF 5) RISK OF SEVERE
THUNDERSTORMS THIS AFTERNOON AND EVENING. THE PRIMARY THREAT IS
DAMAGING WINDS, BUT LARGE HAIL MAY ALSO OCCUR.
- AFTER COOLER TEMPERATURES TODAY, VERY HOT WEATHER WILL RETURN
FRIDAY AND CONTINUE THROUGH THE WEEKEND, WITH SUNDAY BEING THE
HOTTEST.
- ISOLATED THUNDERSTORMS POSSIBLE ON FRIDAY, THEN DRY WEATHER
EXPECTED FOR THE WEEKEND.
UPDATE
ISSUED AT 1030 PM MDT WED JUL 29 2026
WATER VAPOR IMAGERY AND KUDX RADAR BOTH SHOWING A MID-LEVEL
CIRCULATION ASSOCIATED WITH A STRONG SHORTWAVE CROSSING THE
WESTERN SD PLAINS AND JUST NOW MOVING INTO CENTRAL SD. THIS HAS
BEEN THE FOCUS FOR THIS EVENING'S CONVECTION, WHICH WILL EXIT TO
THE EAST OVER THE COUPLE OF HOURS OR SO. WEAK ELEVATED CONVECTION
WILL BE POSSIBLE OVERNIGHT INTO THURSDAY MORNING GIVEN RICH LOW
LEVEL MOISTURE AND MODERATE MID-LEVEL LAPSE RATES...AND ANY OLD
INTERSECTING OUTFLOW BOUNDARIES. WATER VAPOR IS ALSO SHOWING THE
NEXT STRONG WAVE NOW CROSSING UT/EASTERN ID, WHICH IS CURRENTLY
SUPPORTING SHOWERS/ISOLATED STORMS ACROSS THE HIGHER TERRAIN.
AHEAD OF THE WAVE...AMPLE MOISTURE WITH PWATS OF 150-175% OF
NORMAL AND MODERATE INSTABILITY WILL ALLOW FOR STORMS TO DEVELOP
EVEN IN THE MID/LATE MORNING HOURS. SBCAPE UP TO 1800 J/KG IS
EXPECTED BY 18Z ACROSS NE WY/FAR WESTERN SD...AND UP TO 3000 J/KG
OVER SCENTRAL SD COMBINED WITH LITTLE TO NO CIN AREAWIDE WILL HELP
GET THINGS STARTED EARLIER THAN NORMAL. HOWEVER, SHEAR IS LACKING
OVERALL WHICH WILL KEEP STORMS FROM BECOMING MORE ORGANIZED.
STILL, WITH STRONG INSTABILITY IN PLACE AND A COOL FRONT SAGGING
SOUTHWARD, COULD SEE SOME STRONG TO SEVERE STORMS DEVELOP DURING
THE AFTERNOON ACROSS THE WESTERN SD PLAINS...AND EVEN MORE SO OVER
THE SCENTRAL SD PLAINS WHERE LOW LEVEL FORCING AND SHEAR IS A
LITTLE BETTER. HIGHS WILL BE RELATIVELY COOLER TOMORROW (MID TO
UPPER 80S) DUE TO CLOUD COVER AND THE AFORMENTIONED COOL FRONT.
DISCUSSION
(THIS AFTERNOON THROUGH TUESDAY)
ISSUED AT 1106 AM MDT WED JUL 29 2026
16Z SURFACE ANALYSIS HAD TROUGH FROM EASTERN MT TO CENTRAL CO.
WATER VAPOUR LOOP HAD UPPER RIDGE FROM NM INTO EASTERN MT/WY WITH
A COUPLE OF RIDGE-RIDERS OVER SOUTHEAST MT AND WESTERN WY/UT.
0.5KM 1-MINUTE VISIBLE SATELLITE LOOP SHOWED MOST ACTIVITY WAS
ELEVATED AT THIS POINT, ALTHOUGH THERE IS A CU FIELD OVER SOUTH-
CENTRAL SD ASSOCIATED WITH OPPRESSIVE TD/S IN THE LOWER 70S.
EFFECTS OF THESE FEATURES THE MAIN SHORT TERM FORECAST CONCERN.
THIS AFTERNOON/TONIGHT, HEAT INDICES WILL BE IN THE LOWER 100S
EAST OF THE BLACK HILLS SO HOISTED A HEAT ADVISORY EARLIER TO
ACCOUNT. MAIN SHORTWAVE ROTATES AROUND UPPER RIDGE LATER THIS
AFTERNOON AND EVENING. AT LEAST 1-2KJ/KG MLCAPE POOLS AHEAD OF
SURFACE TROUGH WITH 25-35KTS OF EFFECTIVE SHEAR FORECAST. BUFKIT
SOUNDINGS SUGGEST DAMAGING WINDS WOULD BE THE MAIN THREAT WITH
SEVERE CONVECTION (MARGINAL TO SLIGHT (1-2 OUT OF 5)) RISK OVER
CWA, HIGHEST OVER NORTHWESTERN SD. LATEST CAMS/HREF EMPHASIZE THIS
THINKING. SO, EXPECT A COUPLE CLUSTERS OF SEVERE CONVECTION THIS
AFTERNOON/EVENING MOVING ACROSS THE CWA. IF COLD POOLS CAN
CONGEAL, COULD SEE A LINE OF SEVERE THUNDERSTORMS FOR A PERIOD
WHICH SOME CAM SOLUTIONS SUGGEST. ACTIVITY WILL WEAKEN OVERNIGHT,
BUT DECENT LOW LEVEL JET LIKELY TO SUSTAIN CONVECTION.
TEMPERATURES WILL BE NEAR GUIDANCE.
THURSDAY, COMPACT MID-LEVEL CIRCULATION MOVES ACROSS THE CWA WITH
CONTINUED CHANCES FOR THUNDERSTORMS AS A COLD FRONT SLICES
THROUGH THE AREA LEADING TO "COOLER" TEMPERATURES. COLD FRONT MAY
BE FOCUS FOR ACTIVE/SEVERE THUNDERSTORMS THURSDAY AFTERNOON OVER
SOUTH-CENTRAL SD. TEMPERATURES WILL BE NEAR GUIDANCE.
LINGERING POPS FRIDAY GIVEN WAY TO ROBUST THERMAL RIDGE EXPANSION
FOR THE WEEKEND WITH SUNDAY HIGHS FROM 100-110F PUTTING PRESSURE
ON SOME RECORDS. MOSTLY DRY, BUT IT IS THE NORTHERN PLAINS, SO
THUNDERSTORMS CANNOT BE COMPLETELY RULED OUT. NEXT WEEK LOOKS
"COOLER" AS UPPER RIDGE FLATTENS AND WEST/NORTHWEST FLOW ALOFT
DEVELOPS, SURE TO PROVIDE SHORTWAVES TO CREATE DAILY CHANCES OF
THUNDERSTORMS. CONFIDENCE IS GROWING FOR THE BRIEF COOLDOWN.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 513 AM MDT THU JUL 30 2026
SHOWERS OVER NE WY NEARING THE BLACK HILLS WILL CONTINUE E/NE THIS
MORNING. MORE SHOWERS AND THUNDERSTORMS WILL QUICKLY DEVELOP LATE
THIS MORNING INTO THE EARLY AFTERNOON. MVFR/IFR WILL BE POSSIBLE
NEAR ANY STORMS, ALONG WITH GUSTY, ERRATIC WINDS EVEN SOME
DISTANCE FROM THE STORMS. STORMS WILL END FROM WEST TO EAST
THROUGH THE AFTERNOON AND EVENING HOURS. A COLD FRONT CROSSING THE
AREA TODAY WILL BRING BREEZY NORTHERLY WINDS THROUGH THE
AFTERNOON.
FIRE WEATHER
ISSUED AT 1106 AM MDT WED JUL 29 2026
ELEVATED FIRE WEATHER CONDITIONS ARE EXPECTED THIS WEEK DUE TO
HOT TEMPERATURES AS WELL AS MINIMUM RELATIVE HUMIDITY IN THE TEENS
AND 20S. HOTTER WEATHER DEVELOPS FOR THE WEEKEND WITH EVEN DRIER
AIR (MINRH AS LOW AS 8%), SO CRITICAL FIRE WEATHER CONDITIONS ARE
LIKELY. THUNDERSTORM CHANCES HIGHEST THIS AFTERNOON THROUGH FRIDAY
AND THEN EARLY NEXT WEEK. THE CORES OF THUNDERSTORMS THAT OCCUR
THROUGH FRIDAY SHOULD CONTAIN WETTING RAIN, BUT LIGHTNING STRIKES
OUTSIDE OF THE CORES AS WELL AS STRONG, ERRATIC WINDS MAY CREATE
OPPORTUNITIES FOR NEW FIRES.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
UPDATE...13
DISCUSSION...HELGESON
AVIATION...13
FIRE WEATHER...HELGESON
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