074
FXUS63 KBIS 271138
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
638 AM CDT SUN JUL 27 2025
KEY MESSAGES
- AN ISOLATED SEVERE THUNDERSTORM RISK EXISTS LATE THIS
AFTERNOON AND 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.
- SEVERE THUNDERSTORMS ARE POSSIBLE MONDAY IN SOUTHWEST AND
SOUTH CENTRAL NORTH DAKOTA.
- WARM AND HUMID WEATHER IS EXPECTED TODAY, BUT TEMPERATURES ARE
EXPECTED TO COOL TO BELOW AVERAGE FOR MUCH OF THE UPCOMING
WEEK.
UPDATE
ISSUED AT 638 AM CDT SUN JUL 27 2025
SHOWERS AND THUNDERSTORMS CONTINUE IN NORTH CENTRAL, AND TO A
LESSER EXTENT, NORTHWESTERN ND THIS MORNING. SHOWERS, ALONG WITH
A FEW RUMBLES OF THUNDER, ARE ALSO PRESENT NEAR THE ND/SD
BORDER. FOR THE MOST PART, THESE SHOWERS AND THUNDERSTORMS
SHOULD END OVER THE NEXT FEW HOURS. HOWEVER, ADDITIONAL SHOWERS
AND THUNDERSTORMS, A FEW POTENTIALLY SEVERE, REMAIN POSSIBLE
ONCE AGAIN LATER THIS AFTERNOON AND EVENING.
UPDATE
ISSUED AT 501 AM CDT SUN JUL 27 2025
QUICK UPDATE FOR CANCELLATION OF SEVERE THUNDERSTORM WATCH #547
BEHIND THE PRIMARY LINEAR CONVECTIVE COMPLEX MOVING ACROSS NORTH
CENTRAL ND, AND ACROSS SOUTH CENTRAL ND (INCLUDING THE BISMARCK/
MANDAN AREA) WHERE EARLIER CONVECTIVE PROCESSING/OUTFLOW HAS
RENDERED THE AIR MASS A BIT MORE STABLE. RADAR TRENDS AND THE
PRESENCE OF LARGE BOUYANCY AND DCAPE CONTINUE TO FAVOR A THREAT
OF DAMAGING WINDS IN NORTH CENTRAL ND THE NEXT 1-2 HOURS.
DISCUSSION
ISSUED AT 322 AM CDT SUN JUL 27 2025
EARLY THIS MORNING, SEVERAL CLUSTERS OF CONVECTION ARE ONGOING
ACROSS THE REGION, AND ARE PROGRESSING THROUGH AN ENVIRONMENT
CHARACTERIZED BY STRONG TO EXTREME BOUYANCY (MUCAPE FROM 2000 TO
4000 J/KG) AND DEEP-LAYER SHEAR ON THE ORDER OF 40-50 KT. THE
STORMS IN CENTRAL AND EASTERN ND ARE OCCURRING NEAR THE TERMINUS
OF A BROAD, 30-40 KT LOW-LEVEL JET AND RELATED LOW- AND MID-
LEVEL WARM AIR ADVECTION, THOUGH CONVECTIVE PROCESSING AND
OUTFLOW FROM EARLIER ROUNDS OF STORMS IS APT TO GRADUALLY RESULT
IN SOME TEMPERING OF THERMODYNAMIC PROFILES IN SOUTH CENTRAL ND
AND THE JAMES RIVER VALLEY. MEANWHILE, ASCENT FROM A MORE WELL-
DEFINED IMPULSE ALOFT MOVING ACROSS WESTERN ND AS OF 08 UTC HAS
RESULTED IN A MORE LINEAR CONVECTIVE COMPLEX. THE BACKGROUND
ENVIRONMENT CONTINUES TO FAVOR A RISK OF LARGE HAIL AND DAMAGING
WINDS THROUGH EARLY THIS MORNING, WITH THE HAIL THREAT MORE
PROMINENT WITH ANY MORE DISCRETE STORMS. DCAPE ON THE ORDER OF
1000-1500 J/KG AND MODERATE 0-3-KM BULK WIND SHEAR CONTINUE TO
FAVOR A DAMAGING WIND RISK, PARTICULARLY WITH ANY LINEAR LINE
SEGMENTS.
THE CONVECTIVE SCENARIO EARLY THIS MORNING IS MESSY AND COMPLEX,
BUT THE OVERALL THEME IS FOR A CONTINUED STRONG-SEVERE STORM
RISK UNTIL PASSAGE OF THE MORE PROMINENT IMPULSE ALOFT. THIS
MEANS THE THREAT WILL END FROM WEST TO EAST, AND EXTRAPOLATING
TRENDS SUGGESTS IT WILL END IN WESTERN ND BY ABOUT 5 AM CDT/4 AM
MDT, AND OVER CENTRAL ND BY 7 TO 9 AM CDT.
FOR THE BETTER PART OF THE DAYTIME HOURS TODAY, THE AREA WILL BE
IN A BROAD POST-FRONTAL REGIME, AND CONVECTIVE-PROCESSING OF THE
AIR MASS FOLLOWING THE OVERNIGHT STORMS MAY ALSO STABILIZE THE
LOWER ATMOSPHERE INITIALLY. HOWEVER, THE POST-FRONTAL AIR MASS
IS EXPECTED TO REMAIN WARM, AND SEASONABL-RICH MOISTURE IS ALSO
FORECAST TO REMAIN IN PLACE. FORECAST HIGHS TODAY RANGE FROM
THE LOWER 80S F IN NORTHWEST ND TO THE UPPER 80S AND LOWER 90S F
IN SOUTHWEST AND SOUTH CENTRAL ND. AFTERNOON DEWPOINTS WILL
LIKELY REMAIN IN THE 60S F, CONTRIBUTING TO MODERATE TO STRONG
BOUYANCY WITH MLCAPE FROM 2000-3000 J/KG BY LATE AFTERNOON AND
EARLY EVENING. HEIGHT TENDENCIES ALOFT WILL BE RELATIVELY
NEUTRAL TO SLIGHTLY RISING, ESPECIALLY PRIOR TO 00 UTC, AND SOME
FORECAST SOUNDINGS SUGGEST WEAK CAPPING THROUGH THE AFTERNOON.
THIS ALL SUGGESTS THE ODDS OF CONVECTIVE INITIATION IN WESTERN
AND CENTRAL ND THIS AFTERNOON AND EVENING IS HIGHLY CONDITIONAL.
HOWEVER, SOME GUIDANCE DOES SUGGEST ANOTHER WEAK IMPULSE COULD
APPROACH WESTERN ND BY EVENING, AND THERE IS SOME SIGNAL FOR
WEAK SURFACE CONVERGENCE DEVELOPING IN EASTERN MT OR WESTERN ND,
TOO. COMBINED WITH EFFECTIVE-LAYER SHEAR ON THE ORDER OF 30-40
KT, AND THE AFOREMENTIONED BOUYANCY, THIS DOES SUGGEST A
CONDITIONAL SEVERE STORM RISK FROM LATE THIS AFTERNOON THROUGH
THE EVENING. CAMS ARE VERY DISPERSIVE IN THEIR SIMULATIONS,
FURTHER LOWERING CONFIDENCE IN THIS POTENTIAL. HOWEVER, GEFS-
BASED MACHINE LEARNING SEVERE WEATHER GUIDANCE DID INCREASE ITS
PROBABILITIES WITH ITS MOST RECENT CYCLE, ESPECIALLY IN
NORTHWEST AND NORTH CENTRAL ND.
GIVEN THE CONDITIONAL NATURE OF SEVERE STORM RISK THIS AFTERNOON
AND EVENING, WE ARE ONLY ADVERTISING LOW TO MEDIUM PROBABILITIES
OF THUNDERSTORMS. WE ARE ADVERTISING POTENTIAL THREATS AS LARGE
HAIL UP TO PING PONG BALL SIZE AND DAMAGING WINDS UP TO 60 MPH,
THOUGH SOME FORECAST SOUNDINGS WOULD SUPPORT POTENTIALLY LARGER
HAIL SIZES IF CONFIDENCE BECOMES HIGHER IN CONVECTIVE INITIATION.
GUIDANCE SUGGESTS ANOTHER IMPULSE WILL CROSS THE NORTHERN PLAINS
ON MONDAY, AND WITH STRONGER FORCING FOR ASCENT AND POTENTIALLY
STRENGTHENING FRONTAL ZONE, CONVECTIVE COVERAGE WILL LIKELY BE
GREATER. HOWEVER, GUIDANCE SUGGESTS TWO POTENTIAL OUTCOMES:
1) STRONG-SEVERE STORMS DEVELOPING OVER SOUTHERN ND DURING THE
DAYTIME WITH A FURTHER-NORTH FRONTAL ZONE, OR 2) CONVECTIVE
INITIATION REMAINING FOCUSED LATER AND FURTHER SOUTH IN SD.
MACHINE LEARNING PROBABILITIES BROADLY CAPTURE BOTH SCENARIOS,
AND WE WILL ACCORDINGLY MESSAGE THE POTENTIAL FOR SEVERE STORMS.
MODERATE CAPE AND STRONG DEEP-LAYER SHEAR WOULD FAVOR POTENTIAL
LARGE HAIL AND DAMAGING WIND GUSTS IF STORMS DEVELOP IN SOUTHWEST
AND SOUTH CENTRAL ND.
THEREAFTER, THE MAIN THEME FOR THE UPCOMING WEEK WILL BE COOLER
TEMPERATURES WITH HIGHS IN THE 70S TO LOWER 80S MOST DAYS OWING
TO A PERIOD OF NORTHWEST FLOW ALOFT THROUGH AT LEAST MIDWEEK.
LOW TO MEDIUM CHANCES OF SHOWERS AND THUNDERSTORMS WILL BE
FOCUSED IN WESTERN ND DURING THIS PERIOD.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 638 AM CDT SUN JUL 27 2025
SHOWERS AND THUNDERSTORMS CONTINUE OVER NORTH CENTRAL AND PARTS
OF NORTHWESTERN ND, WHILE SHOWERS AND A FEW RUMBLES OF THUNDER
ARE PRESENT NEAR THE ND/SD BORDER. THESE SHOWERS AND
THUNDERSTORMS SHOULD DIMINISH OVER THE NEXT FEW HOURS. AFTER
WHICH, ADDITIONAL SHOWERS AND THUNDERSTORMS, A FEW POTENTIALLY
SEVERE, ARE POSSIBLE ONCE AGAIN LATER THIS AFTERNOON AND
EVENING. OTHER THAN DURING ANY SHOWERS AND THUNDERSTORMS, WINDS
SHOULD BE LIGHT AND VARIABLE THROUGH MOST OF THE PERIOD, WHILE
VFR CEILINGS AND VISIBILITY SHOULD PREVAIL.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...TELKEN
DISCUSSION...CJS
AVIATION...TELKEN
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