672
FXUS63 KBIS 272356
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
656 PM CDT SUN JUL 27 2025
KEY MESSAGES
- AN ISOLATED SEVERE THUNDERSTORM RISK EXISTS THIS EVENING IN
PARTS OF WESTERN AND CENTRAL NORTH DAKOTA, WITH THE MAIN
HAZARDS LARGE HAIL UP TO PING PONG BALL SIZE HAIL AND DAMAGING
WINDS UP TO 60 MPH.
- ISOLATED TO SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE MONDAY
IN WESTERN AND SOUTH CENTRAL NORTH DAKOTA.
- TEMPERATURES REMAIN BELOW NORMAL (MOSTLY IN THE 70S) THROUGH
THE WORK WEEK.
UPDATE
ISSUED AT 656 PM CDT SUN JUL 27 2025
AS OF EARLY EVENING, CAPPING REMAINS IN PLACE AND HAS INHIBITED
BOUNDARY LAYER CONVECTION IN WESTERN AND CENTRAL ND, WITH THE 00
UTC BISMARCK SOUNDING REVEALING A NOTABLE INVERSION JUST ABOVE
850 MB. OBJECTIVE MESOANALYSIS OUTPUT SUGGESTS ONLY NORTHWESTERN
ND HAS MINIMIZED MLCIN, CONSISTENT WITH EARLIER MODEL FORECASTS.
SATELLITE IMAGERY DOES SUGGEST A WEAK UPSTREAM IMPULSE NORTH OF
THE GLASGOW AREA IS PROGRESSING EASTWARD, SO A LOW CHANCE FOR
THUNDERSTORM DEVELOPMENT (AND CONDITIONAL SEVERE-STORM RISK) IS
CONTINUING IN PARTS OF THE AREA THIS EVENING, MAINLY NORTHWESTERN
ND. THE PRIMARY SURFACE FRONTAL ZONE STRETCHES FROM CENTRAL MN
WESTWARD TOWARD PIERRE, SD, AND THEN NORTHWEST INTO CENTRAL MT.
ONE OR MORE DIFFERENTIAL MIXING ZONES EXIST IN EASTERN MT AND
WESTERN ND, AND HAVE BEEN RESPONSIBLE FOR OCCASIONAL SHALLOW
CUMULUS DEVELOPMENT. ONE SUCH DIFFERENTIAL MIXING ZONE MAY ALSO
EXTEND FROM NEAR ESTEVAN AND CROSBY TOWARD PLENTYWOOD, MT, AND
INTO THE GLASGOW VICINITY, AND WILL BE MONITORED AS THE UPSTREAM
IMPULSE INTERACTS WITH IT THE NEXT COUPLE OF HOURS FOR SIGNS OF
CONVECTIVE INITIATION. HAVING SAID THAT, THE LACK OF MASS-FIELD
RESPONSES ACROSS THE AREA (E.G., LACK OF STRONGER SURFACE
PRESSURE FALLS), COMBINED WITH THE CAPPING, RENDERS CONFIDENCE
IN THUNDERSTORM DEVELOPMENT THIS EVENING LOW. THE MAIN CHANGE
WITH THIS FORECAST UPDATE CYCLE WAS TO FOCUS POPS THIS EVENING
IN FAR WESTERN, NORTHWEST, AND TO A LESSER-EXTENT NORTH CENTRAL
ND, AND TO LIMIT THEM TO THE 20 TO 30 PERCENT RANGE.
DISCUSSION
ISSUED AT 136 PM CDT SUN JUL 27 2025
CURRENTLY, SKIES WERE PARTLY CLOUDY ACROSS WESTERN AND CENTRAL
ND. A THUNDERSTORM THAT DEVELOPED OVER SOUTHEAST MONTANA AND
MOVED INTO SOUTHWEST ND A LITTLE EARLIER THIS AFTERNOON HAS NOW
DISSIPATED. WE REMAIN MOIST AND UNSTABLE ACROSS MOST OF THE
FORECAST AREA, ALTHOUGH THE FAR SOUTHWEST IS RELATIVELY DRY WITH
DEWPOINTS IN THE MID 50S. THERE IS A FRONTAL BOUNDARY DRAPED
ACROSS SOUTHEAST ND, WITH SCATTERED THUNDERSTORMS OVER THE FAR
SOUTHEAST PORTION OF THE STATE. GENERALLY WEAK SURFACE HIGH
PRESSURE WAS LOCATED OVER WESTERN AND CENTRAL ND. THERE IS
ABOUT 1500-2000 J/KG OF MLCAPE ACROSS WESTERN AND CENTRAL ND BUT
FORECAST SOUNDINGS INDICATE SOME WEAK MID-LEVEL CAPPING
REMAINING. SPC MESO-ANALYSIS SHOWS THE CAP ERODING OVER
NORTHWEST PORTION OF THE STATE. EFFECTIVE SHEAR IS GENERALLY
AROUND 30 KNOTS WEST TO 40 KNOTS CENTRAL. CAMS ARE NOT SHOWING
MUCH IN THE WAY OF CONVECTION THROUGH THE REST OF THIS AFTERNOON
AND EARLY EVENING. HOWEVER WITH BOUNDARIES LINGERING BEHIND
OVERNIGHT AND EARLY MORNING CONVECTION, THE AFOREMENTIONED
INSTABILITY AND SHEAR, IF A STORM COULD BREAK THE CAPPING, A
STRONG TO SEVERE STORM WOULD BE POSSIBLE WITH THE MAIN THREATS
BEING WINDS TO 60 MPH AND HAIL UP TO PING PONG BALL SIZE. IF I
WERE TO GUESS, WITH THE DISSIPATING CIN NORTHWEST, THIS WOULD BE
A GUESS FOR THE MORE LIKELY AREA FOR CI LATE AFTERNOON OR EARLY
EVENING, AND WITH THE SOUTHWEST (WITH DRIER AIR IN PLACE) THE
LEAST LIKELY. HOWEVER, CAN'T REALLY ELIMINATE ANY AREA FOR
POSSIBLE CONVECTION. COVERAGE DOES LOOK TO BE MINIMAL,
ESPECIALLY WHEN COMPARED TO LAST NIGHT.
LATER TONIGHT AND THROUGH THE DAY MONDAY WE SEE A MORE POTENT
IMPULSE IMPACTING THE LOCAL AREA. CAMS SHOW A GENERAL TIMEFRAME
OF 08-12 UTC WHEN CONVECTION MAY MOVE INTO THE WEST. THIS IS
FROM A WAVE CURRENTLY OVER THE WESTERN U.S. THAT TRACKS ACROSS
THE NORTHERN ROCKIES AND INTO THE NORTHERN HIGH PLAINS TONIGHT
AND ACROSS THE FORECAST AREA ON MONDAY. CONVECTION COULD
CONTINUE THROUGH THE DAY ON MONDAY AS THE WAVE TRACKS ALONG THE
INTERNATIONAL BORDER. THE AFTERNOON AND EVENING HOURS WOULD BE
THE FAVORED TIMEFRAME FOR STRONG TO SEVERE CONVECTION, BUT
AGAIN, I DON'T THINK YOU CAN COMPLETELY RULE OUT SEVERE MORNING
CONVECTION EITHER. AS WE DO GET INTO THE AFTERNOON HOURS, THINK
THE SEVERE POTENTIAL WILL DISSIPATE ACROSS THE NORTH, AND
EVENTUALLY IN THE SOUTH MONDAY EVENING. SPC HAS A SLIGHT RISK
OVER PORTIONS OF THE SOUTHWEST AND SOUTH CENTRAL. THIS WOULD
SEEM REASONABLE GIVING THE CURRENT TIMING. ALTHOUGH INSTABILITY
LOOKS TO DIMINISH IN THE SOUTH THROUGH THE AFTERNOON/EVENING
TIMEFRAME, THERE SHOULD BE A WINDOW WHEN WE WOULD SEE SUFFICIENT
INSTABILITY, COMBINED WITH STRONG SHEAR, TO SUPPORT LARGE HAIL
TO THE SIZE OF GOLF BALLS AND WINDS TO 70 MPH. THIS WINDOW WILL
BE GREATER TO THE SOUTH OF THE FORECAST AREA, BUT A LOT WILL
DEPEND UPON THE EVOLUTION OF THE AFOREMENTIONED SHORTWAVE AND
IT'S ATTENDANT SURFACE BOUNDARY AS WE GO THROUGH THE OVERNIGHT
HOURS AND MONDAY MORNING. PERHAPS IT'S A LITTLE SLOWER AS WE SEE
A GREATER AREA OF STRONG INSTABILITY AND SHEAR ACROSS WESTERN
AND CENTRAL ND, RESULTING IN A LONG AFTERNOON AND EVENING OF
STRONG TO SEVERE CONVECTION. ON THE OTHER HAND, PERHAPS THE
PROGRESSION OF THE SYSTEM IS SUCH THAT STRONG TO SEVERE
CONVECTION IS MOSTLY TO OUR SOUTH. FOR THE TIME BEING, INCLUDING
AT LEAST A PORTION OF THE SOUTHWEST AND SOUTH CENTRAL WITHIN
THE SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE STORMS SEEMS
REASONABLE.
ONCE CONVECTION (WHEREVER IT IS) ENDS ON MONDAY AFTERNOON OR
EVENING, IT LOOKS LIKE THE THREAT FOR STRONG TO SEVERE STORMS
WILL BE LIMITED TO THE SOUTHWEST PORTION OF THE STATE ON
TUESDAY. THEN GOING THROUGH THE REST OF THE WORK WEEK THE THREAT
FOR SEVERE STORMS LOOKS TO BE MINIMAL, AND IF ANY, ALSO
CONFINED TO THE SOUTHWEST PORTION OF THE STATE. TEMPERATURES
THROUGH THE WORK WEEK ARE EXPECTED TO REMAIN BELOW NORMAL
(MAINLY IN THE 70S TO LOWER 80S) UNTIL POSSIBLY TRENDING BACK
UP BY THE WEEKEND.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 656 PM CDT SUN JUL 27 2025
VFR CONDITIONS AND LIGHT WINDS ARE EXPECTED THROUGH THE EVENING,
WITH ONLY A LOW CHANCE OF A THUNDERSTORM. HIGHER PROBABILITIES
OF THUNDERSTORMS AND ATTENDANT LOCALIZED IFR/MVFR CONDITIONS ARE
FORECAST TO ENTER WESTERN ND LATE TONIGHT, AND CENTRAL ND MONDAY
MORNING, AS A STRONGER DISTURBANCE MOVES INTO THE AREA. SPECIFIC
TIMING AND COVERAGE OF THE LATE NIGHT AND MONDAY ACTIVITY IS
UNCERTAIN, SO ONLY PROB30 GROUPS WERE INCLUDED IN THE 00 UTC
TAFS. MVFR TO PERHAPS IFR CEILINGS IN STRATUS WILL ALSO LIKELY
(50-70% CHANCE) DEVELOP ALONG THE ND/SD BORDER, AND ESPECIALLY
INTO SOUTHWESTERN ND, LATE TONIGHT AND MONDAY MORNING ON MOIST
EAST-NORTHEAST WINDS. KDIK IS THE TERMINAL MOST LIKELY TO BE
IMPACTED BY LOW CEILINGS FROM ABOUT 12 TO 18 UTC MONDAY.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...CJS
DISCUSSION...TWH
AVIATION...CJS
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