871
FXUS63 KUNR 010346
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
946 PM MDT TUE JUN 30 2026
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS EXPECTED
TONIGHT, BEST CHANCES ACROSS SOUTH CENTRAL SD
- SLIGHT RISK (LEVEL 2 OF 5) OVER WESTERN SD FOR THURSDAY WITH
MAIN THREATS BEING LARGE HAIL AND DAMAGING WINDS.
- UNSETTLED WEATHER CONTINUES THROUGH THE REST OF THE WEEK WITH
NEAR DAILY CHANCES FOR AFTERNOON SHOWERS/STORMS AND TEMPERATURES
IN THE 80S TO 90S.
UPDATE
ISSUED AT 928 PM MDT TUE JUN 30 2026
UPPER TROUGH WILL PUSH THROUGH THE REGION TONIGHT, SUPPORTING POS
THETA-E ADV ACROSS MOST OF THE FA, STRONGEST ACROSS SOUTH CENTRAL
SD. MCS ONGOING ACROSS WESTERN NE. GIVEN LOCATION OF THE LL CAPE
GRADIENT, 0-3KM SHEAR VECTORS, AND FORCING ALOFT, EXPECT THE WORST
OF THIS SYSTEM WILL STAY SOUTH OF THE SCENTRAL SD, WITH MAINLY
THE NORTHERN STRATIFORM REGION AND EMBEDDED TS EXPECTED TO CLIP
THIS AREA. NW OF THIS SYSTEM, EXPECT ISOLD SHRA/TS OVERNIGHT WITH
LITTLE RAINFALL GIVEN HIGH BASED NATURE AND VERY DRY LL PROFILES.
SUBSIDENCE WILL SPREAD OVER THE REGION WED MORNING BEHIND THE
WAVE. DIURNAL HEATING MAY BE ENOUGH TO SUPPORT A FEW HIGH BASED
SHOWERS AND TS OFF THE BH IN THE AFTERNOON AND ACROSS FAR NW SD
BY EVENING. GUSTY WINDS WOULD BE THE ONLY THREAT WITH THESE CELLS.
SW FLOW WILL BECOME ESTABLISHED FOR THE END OF THE WEEK, WITH
ROUNDS OF SUBTLE MID-LEVEL IMPULSES AS LL MOISTURE RETURNS PER
ESE FLOW. SUFFICIENT CAPE WILL BE IN PLACE TO SUPPORT SEVERE CELLS
THUR AND FRIDAY, HOWEVER, BULK SHEAR IS QUESTIONABLE ATTM WITH
LACK OF STRONGER FLOW IN THE MID LEVELS. TIMING OF MID LEVEL
IMPULSES WILL BE KEY TO SEE HOW THINGS DEVELOP AS WELL AS THE
LOCATION OF THE LOW LEVEL MOISTURE AXIS.
DISCUSSION
(THIS EVENING THROUGH TUESDAY)
ISSUED AT 115 PM MDT TUE JUN 30 2026
UPPER LEVEL ANALYSIS SHOWS TROF AXIS OVER THE ROCKIES WITH
SOUTHWEST FLOW OVER THE NORTHERN PLAINS. EMBEDDED SHORTWAVE SITS
CENTERED OVER UT. THE CWA SITS UNDER MOSTLY CLEAR SKIES WITH A FEW
CUMULUS CLOUDS DEVELOPING OVER NORTHWESTERN SD. SUNNY AND WARM
WEATHER WILL PREVAIL OVER THE REGION THROUGH THE AFTERNOON BEFORE
CLOUD COVER INCREASES IN THE EVENING AS THE UPPER LEVEL WAVE
APPROACHES THE REGION. STORM CHANCES WILL INCREASE ACROSS THE
SOUTHERN TIER OF OUR CWA THROUGH THE EVENING HOURS. MU CAPE
PROGGED TO INCREASE TO 1500-3000 J/KG OVER SOUTH CENTRAL SD BY
MIDNIGHT. CAMS SHOW CONVECTION MOVING OUT OF NE INTO THE SOUTHERN
PORTIONS OF OUR CWA. WIDESPREAD SEVERE WX IS NOT EXPECTED BUT WE
COULD SEE A FEW SEVERE CALIBER GUSTS AND LARGE HAIL OVER SOUTH
CENTRAL SD OVERNIGHT.
STORM CHANCES RETURN WEDNESDAY AFTERNOON AS 500-1500 J/KG ML CAPE
AND EFFECTIVE SHEAR OF 30-45KT PROGGED TO DEVELOP OVER THE BLACK
HILLS INTO SOUTH CENTRAL SD. ISOLATED CONVECTION MAY DEVELOP OVER
THE BLACK HILLS AND ALONG A DRYLINE OVER SOUTHWESTERN INTO SOUTH
CENTRAL SD. A STRONG TO SEVERE STORM MAY DEVELOP OVER THE BLACK
HILLS AND SOUTH CENTRAL SD WITH LARGE HAIL AND DAMAGING WINDS AS
THE MAIN HAZARDS.
WEAK SHORTWAVE MOVES THROUGH THURSDAY, 1500-3000 J/KG ML CAPE
PROGGED TO DEVELOP OVER WESTERN SD BY THE AFTERNOON HOURS WITH 30-
40KT EFFECTIVE SHEAR. CONVECTION SHOULD INITIATE ALONG THE HIGHER
TERRAIN OF THE BIGHORNS AND BLACK HILLS AND MOVE EASTWARD. NAM
SHOWING A STRONG SIGNAL OF THESE CELLS GROWING INTO AN MCS AS THEY
REACH THE WESTERN SD PLAINS. THE SPC HAS MUCH OF THE WESTERN SD
PLAINS UNDER A SLIGHT RISK WITH THE MAIN HAZARDS BEING LARGE HAIL
AND DAMAGING WINDS.
DETERMINISTIC GUIDANCE IN GOOD CONSENSUS OF MOSTLY ZONAL FLOW
DEVELOPING OVER THE NORTHERN PLAINS BY THE HOLIDAY WEEKEND. WARM
TEMPERATURES (IN THE 80S TO 90S) WITH DAILY CHANCES FOR AFTERNOON
STORMS WILL RESULT.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 519 PM MDT TUE JUN 30 2026
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH MOST OF THE FORECAST
PERIOD. ISOLATED THUNDERSTORMS WILL CONTINUE TO DEVELOP THIS
EVENING AND PERSIST INTO THE OVERNIGHT HOURS; BEST CHANCES ACROSS
SW SD INTO SOUTH-CENTRAL SD. MVFR/IFR CONDITIONS WILL BE POSSIBLE
IN THE STRONGER STORMS, ALONG WITH ERRATIC GUSTY WINDS UP TO
40KTS. STARTING AROUND 01/17-19Z, ANOTHER ROUND OF ISOLATED
THUNDERSTORMS ARE POSSIBLE OVER WESTERN SOUTH DAKOTA AND THE BLACK
HILLS, LASTING THROUGH THE REMAINDER OF THE FORECAST PERIOD.
MVFR/IFR CONDITIONS WILL BE POSSIBLE IN THE STRONGER STORMS.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
UPDATE...JC
DISCUSSION...WONG
AVIATION...SCHULTZ
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