854
FXUS63 KBIS 270514
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
1214 AM CDT SUN JUL 27 2025
KEY MESSAGES
- ISOLATED TO SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE
ACROSS WESTERN AND CENTRAL NORTH DAKOTA TONIGHT. EXPECTED
HAZARDS INCLUDE HAIL UP TO THE SIZE OF GOLF BALLS AND WIND
GUSTS UP TO 70 MPH.
- PERIODIC SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE
SUNDAY THROUGH THE FIRST HALF OF NEXT WEEK. ISOLATED SEVERE
THUNDERSTORMS ARE POSSIBLE OVER THIS TIME PERIOD.
- TEMPERATURES EXPECTED TO FALL BELOW AVERAGE BY THE MIDDLE OF
NEXT WEEK.
UPDATE
ISSUED AT 1214 AM CDT SUN JUL 27 2025
IN CLOSE COLLABORATION WITH SPC, WE HAVE ISSUED ANOTHER SEVERE
THUNDERSTORM WATCH THAT NOW ENCOMPASSES THE REST OF WESTERN AND
CENTRAL ND, THOUGH THE TOTAL COVERAGE OF SEVERE STORMS OVERNIGHT
MAY NOT BE ESPECIALLY LARGE. THE BACKGROUND ENVIRONMENT REMAINS
CHARACTERIZED BY STRONG TO EXTREME BOUYANCY (I.E., MUCAPE ON
THE ORDER OF 2000 TO 5000 J/KG) AND EFFECTIVE-LAYER SHEAR ON
THE ORDER OF 40 KT. SEVERAL CLUSTERS OF STRONG-SEVERE STORMS
ARE ONGOING AS OF 05 UTC FROM SOUTHEASTERN MT INTO NORTHERN SD
AND SOUTHERN/CENTRAL ND. WE EXPECT THOSE CLUSTERS TO CONTINUE
THE NEXT SEVERAL HOURS WITH AN ATTENDANT SEVERE RISK. SOME
RESIDUAL MIDLEVEL CAPPING APPEARS PRESENT PER FORECAST SOUNDINGS
AND RADAR REPRESENTATION OF INDIVIDUAL UPDRAFTS AT TIMES, BUT
THE OVERALL SETTING CONTINUES TO FAVOR A RISK OF BOTH LARGE HAIL
AND DAMAGING WINDS. MEANWHILE, A LONGER-LIVED COMPLEX OF
THUNDERSTORMS IN NORTHEASTERN MT IS GRADUALLY PROPAGATING INTO
THE AXIS OF HIGHER BOUYANCY, AND DOWNSTREAM EASTERLY LOW-LEVEL
FLOW DOES FAVOR SOME MAINTENANCE OF THIS COMPLEX AND A RELATED
DAMAGING WIND THREAT IN AND OF ITSELF. HOWEVER, THE GUST FRONT
WITH THIS SYSTEM HAS ALSO RECENTLY SURGED AHEAD OF THE PRIMARY
CONVECTIVE COMPLEX, WHICH WOULD SUGGEST POTENTIAL FOR IT TO
WEAKEN. THESE CONFLICTING SIGNALS SUGGEST LOWER CONFIDENCE IN
THE SEVERE-STORM RISK IN WEST CENTRAL AND NORTHWEST ND, BUT
GIVEN THE BACKGROUND THERMODYNAMIC SETTING AND WIND PROFILES,
THERE WAS ENOUGH SUPPORTIVE EVIDENCE FOR US TO INCLUDE THAT AREA
IN THE NEWLY-ISSUED SEVERE THUNDERSTORM WATCH.
UPDATE
ISSUED AT 926 PM CDT SAT JUL 26 2025
NO SIGNIFICANT CHANGES WERE NEEDED TO THE GRIDDED/PUBLIC
FORECAST WITH THIS UPDATE CYCLE, THOUGH WE DID REFRESH HOURLY
FORECASTS THROUGH THE NIGHT USING THE LATEST MODEL-BLEND
CONSENSUS. TIME-LAGGED HRRR CYCLES APPEAR TO BE CAPTURING THE
GENERAL THEME OF HOURLY PRECIPITATION CHANCES INCREASING FROM
SOUTH AND WEST TO NORTHEAST THROUGH THE NEXT SEVERAL HOURS, SO
THE FORECAST WAS WEIGHTED IN THAT DIRECTION.
AS OF 0215 UTC, THUNDERSTORM DEVELOPMENT APPEARS UNDERWAY OVER
FAR SOUTH CENTRAL ND IN THE EXTREMELY BUOYANT ENVIRONMENT.
THERE MAY BE SOME RESIDUAL CAPPING PER THE 00 UTC KBIS RAOB, BUT
THIS RECENT DEVELOPMENT CENTERED ON SIOUX COUNTY LIKELY
REPRESENTS THE ENCROACHING ASCENT ALOFT THAT IS STILL EXPECTED
TO PROMOTE SCATTERED TO NUMEROUS THUNDERSTORMS BEGINNING NOW AND
THROUGH MUCH OF THE NIGHT ACROSS MUCH OF WESTERN AND CENTRAL ND.
THE SEVERE THUNDERSTORM RISK REMAINS IN PLACE GIVEN THE CAPE-
SHEAR SETTING, WITH DAMAGING WINDS AND LARGE HAIL BOTH PROMINENT
HAZARDS, AS PREVIOUSLY DISCUSSED.
UPDATE
ISSUED AT 826 PM CDT SAT JUL 26 2025
QUICK UPDATE TO ALLOW FOR EXPIRATION OF THE HEAT ADVISORY, AS
HEAT INDEX VALUES WILL SLOWLY FALL AS SUNSET APPROACHES DESPITE
DEWPOINTS REMAINING IN THE 70S F IN SOUTH CENTRAL/SOUTHEAST ND.
OTHERWISE, A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED IN
COLLABORATION WITH SPC FOR PARTS OF SOUTHWEST AND SOUTH CENTRAL
ND. THUNDERSTORMS ARE BEGINNING TO INTENSIFY AS EXPECTED UPSTREAM
FROM SOUTHEAST MT INTO NORTHWEST SD AS STRONGER ASCENT BEGINS TO
IMPINGE ON THE AXIS OF EXTREME BOUYANCY. SPLITTING SUPERCELLS IN
NORTH CENTRAL SD HAVE THUS FAR REMAINED WELL SOUTH OF THE ND/SD
STATE LINE, BUT AS ADDITIONAL SPLITS AND/OR CLUSTERING OCCURS,
THAT AREA OF STORMS MAY ALSO MOVE INTO SOUTH CENTRAL ND IN THE
NEXT 2-3 HOURS.
UPDATE
ISSUED AT 639 PM CDT SAT JUL 26 2025
NO SIGNIFICANT CHANGES WERE MADE TO THE FORECAST WITH THIS
UPDATE CYCLE. THE HEAT ADVISORY REMAINS IN EFFECT UNTIL 01 UTC AS
LOW-LEVEL MOISTURE ADVECTION HAS RESULTED IN SURFACE DEWPOINTS
WELL INTO THE 70S F IN MUCH OF SOUTH CENTRAL ND, CONTRIBUTING TO
HEAT INDEX VALUES AROUND 100 F AS OF THIS WRITING.
OUR ATTENTION REMAINS ON POTENTIAL SEVERE THUNDERSTORMS TONIGHT.
AS OF 23 UTC, RAP OBJECTIVE MESOSCALE ANALYSIS FIELDS SUPPORT A
WIDE AXIS OF EXTREME BOUYANCY MARKED BY MUCAPE ON THE ORDER OF
4000 TO 6000 J/KG, HIGHEST IN SOUTH CENTRAL AND SOUTHEASTERN ND.
OBJECTIVE ANALYSIS OUTPUT SUGGESTS MLCIN HAS BECOME RELATIVELY
MINIMIZED, AND THE 00 UTC KBIS RAOB SUGGESTS ONLY SMALL RESIDUAL
CAPPING ALOFT. HOWEVER, UP UNTIL THIS POINT FORCING FOR ASCENT
HAS BEEN MINIMAL, THOUGH AN AREA OF SURFACE CONVERGENCE NOTED IN
WIND FIELDS CENTERED OVER MCKENZIE, DUNN, AND SOUTHERN MOUNTRAIL
COUNTIES DID YIELD ONE ATTEMPT AT CONVECTIVE INITIATION ABOUT AN
HOUR AGO. WE WILL CONTINUE MONITORING THAT ZONE OF CONVERGENCE
AS IT DOES INTERSECT WITH AN AREA OF STEEP LOW-LEVEL LAPSE
RATES, BUT SATELLITE TRENDS SUGGEST ODDS OF NEAR-TERM INITIATION
IN THAT ZONE ARE ONLY LOW. OTHERWISE, A MORE NOTABLE UPSTREAM
IMPULSE AND RELATED ASCENT ALOFT IS APPROACHING SOUTHEASTERN MT
AND WESTERN SD, AND IS EXPECTED TO YIELD GREATER THUNDERSTORM
DEVELOPMENT WHICH IS THEN EXPECTED TO MOVE INTO ND DURING THE
LATE EVENING, PROGRESSING NORTHEASTWARD OVERNIGHT. ADDITIONAL
THUNDERSTORMS HAVE DEVELOPED IN CENTRAL SD NEAR THE SURFACE LOW
AND IN AN AREA WHERE A HOT, DEEPLY-MIXED PBL OVERLAPS WITH THE
RICH MOISTURE NORTH OF THE SURFACE LOW ACROSS NORTH CENTRAL SD.
THOSE STORMS -- OR AN AGGREGATE OF THOSE STORMS AND ADDITIONAL
DEVELOPMENT AS THE UPSTREAM, PREVIOUSLY-MENTIONED IMPULSE ALL
APPROACH THE AREA -- WILL YIELD AN INCREASING SEVERE-STORM RISK
AFTER ABOUT 8 PM CDT/7 PM MDT, BEGINNING ALONG THE ND/SD BORDER
REGION. EXTREME BOUYANCY COMBINED WITH EFFECTIVE-LAYER SHEAR ON
THE ORDER OF 40 KT WILL SUPPORT LARGE HAIL AND DAMAGING WINDS.
IF CLUSTERING OF CONVECTION OCCURS, A MORE PRONOUNCED DAMAGING
WIND THREAT MAY EVOLVE GIVEN SUPPORTIVE THERMODYNAMIC PROFILES
AND 0-3-KM BULK SHEAR MAGNITUDES.
DISCUSSION
ISSUED AT 257 PM CDT SAT JUL 26 2025
CURRENTLY, IT WAS MOSTLY SUNNY ACROSS MUCH OF WESTERN AND
CENTRAL ND. SCATTERED THUNDERSTORMS CONTINUED ALONG THE
INTERNATIONAL BORDER AND ALSO IN THE SOUTHERN JAMES RIVER
VALLEY. THIS ACTIVITY MAY LINGER ALONG THE BORDERS, BUT IS NOT
EXPECTED TO BE SEVERE. OTHERWISE DRY THROUGH THE REST OF THE
AFTERNOON. HEAT INDICES WERE CURRENTLY IN THE 90S ACROSS THE
SOUTH CENTRAL AND INTO THE JAMES RIVER VALLEY. STILL A WAYS TO
GO FOR REACHING HIGHS. WILL CONTINUE THE HEAT ADVISORY.
THE MAIN FORECAST ISSUE FOR TONIGHT WILL BE THUNDERSTORMS.
CURRENTLY, THERE LOOKS TO BE A WEAK IMPULSE TRACKING THROUGH
CENTRAL ND. THE FAR NORTH MAY BE UNDER THE INFLUENCE OF THE
RIGHT ENTRANCE REGION OF AN UPPER JET OVER SOUTHERN CANADA.
OTHERWISE IT LOOKS LIKE BUILDING UPPER HEIGHTS AND LITTLE IN THE
WAY OF ANY FORCING MECHANISM TODAY. IT WILL BE, HOWEVER, QUITE
UNSTABLE THIS AFTERNOON. MLCAPES ARE ALREADY IN THE 1500-3000
J/KG ACROSS THE FORECAST AREA. FORECAST SOUNDINGS DO SHOW A BIT
OF DRY AIR IN THE LOWER LEVELS AND CURRENT CINS ARE RATHER
STOUT. EFFECTIVE SHEAR HAS BEEN INCREASING THROUGH THE DAY AND
CURRENTLY RANGES FROM 30-35KT SOUTH TO 45 KTS NORTHWEST.
NEEDLESS TO SAY, IF WE COULD SEE SOME CONVECTION TODAY IT WOULD
LIKELY BECOME SEVERE QUICKLY BUT IT'S HIGHLY CONDITIONAL UPON IF
WE CAN OVERCOME THE NEGATIVE EFFECTS OF THE LOWER LEVEL CAPPING
AND UPPER LEVEL RIDGING.
LATER ON, MOST LIKELY NOT UNTIL TONIGHT, WE DO SEE A STRONGER
IMPULSE LIFTING FROM NORTHERN COLORADO INTO EASTERN WYOMING.
THIS WILL LIKELY PROVIDE THE FORCING FOR ASCENT NEEDED TO
INITIATE CONVECTION TONIGHT. THERE MAY ALSO BE ANOTHER WAVE
OVER EASTERN IDAHO WHICH COULD AID IN CONVECTION OVER NORTHERN
WY AND SOUTHEAST MT. CONVECTION IS ALREADY FIRING OFF THE
BIGHORNS AND SOUTHWARD THROUGH EASTERN WYOMING. CAMS HAVE BEEN
PRETTY CONSISTENT IN LIFTING CONVECTION SOUTHWEST TO NORTHEAST
ACROSS THE FORECAST AREA THIS EVENING AND INTO THE EARLY
OVERNIGHT HOURS. THE MAIN THREAT APPEARS TO BE WINDS. WITH DCAPE
WELL IN EXCESS OF 1000 J/KG ACROSS THE SOUTHERN TWO THIRDS OF
THE FORECAST AREA AND A STRONG WAVE LIFTING INTO THE LOCAL AREA,
OUR CURRENTLY POSTED WINDS HAZARDS OF 70 MPH LOOK REASONABLE
FOR NOW. IF THERE WERE TO BE AN EARLY EVENING THUNDERSTORM IT'S
POSSIBLE WE COULD SEE A PERIOD OF LARGE HAIL TO GOLF BALL SIZE,
BUT ONCE WE GET INTO THE MID-EVENING HOURS, WINDS LOOK TO BE THE
MAIN THREAT.
ON SUNDAY SPC HAS PARED BACK THE MARGINAL THREAT OVER THE
EASTERN PORTION OF THE CWA, KEEPING ONLY THE FAR NORTH CENTRAL
IN THE MARGINAL RISK FOR SEVERE STORMS. NOT QUITE SURE ABOUT
THIS. COLD FRONT LOOKS TO DROP SOUTH THROUGH THE AREA BUT WE
REMAIN PRETTY WARM AND THERE LOOKS TO BE SOME PRETTY GOOD SPEED
SHEAR NORTH OF THE BOUNDARY. THERE IS SOME RATHER STRONG MID
LEVEL HEIGHT RISES, WHICH WOULD BE A LIMITING FACTOR FOR
CONVECTION. WE'LL SEE HOW THINGS PLAY OUT AND OVERALL PROBABLY
OKAY LEAVING JUST GENERAL THUNDER FOR MUCH OF THE FORECAST AREA.
THE SEVERE THREAT ON MONDAY REMAINS MARGINAL ACROSS THE FAR
SOUTH AND WE ACTUALLY SEE SOME HEIGHT FALLS TRAVERSE THE
FORECAST AREA. HOWEVER THERE MAY ALSO BE SOME CAPPING ISSUES
MONDAY AS WELL.
WE FINALLY BEGIN TO COOL OFF WITH DIMINISHING THUNDERSTORM
CHANCES AS WE HEAD INTO MID WEEK.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1214 AM CDT SUN JUL 27 2025
CLUSTERS OF SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS WESTERN
AND CENTRAL ND OVERNIGHT WITH AN ATTENDANT POTENTIAL FOR LOCAL
IFR/LIFR VISIBILITY RESTRICTIONS IN HEAVY RAIN, ALONG WITH
STRONG/ERRATIC WIND GUSTS AND POTENTIAL HAIL. THIS ACTIVITY IS
EXPECTED TO GRADUALLY END BY 12 TO 15 UTC. MOST OF SUNDAY WILL
THEN BE DRY WITH LIGHT WINDS AND PREVAILING VFR CONDITIONS. A
LOW PROBABILITY OF THUNDERSTORMS WILL RETURN SUNDAY EVENING, BUT
CONFIDENCE IN THAT IS LOW WITH A CAPPING INVERSION ALOFT.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...CJS
DISCUSSION...TWH
AVIATION...CJS
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