474
FXUS63 KBIS 252007
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
307 PM CDT FRI JUL 25 2025
KEY MESSAGES
- SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON AND
EVENING. GOLF BALL SIZED HAIL, WIND GUSTS UP TO 70 MPH, AND A
TORNADO OR TWO ARE THE PRIMARY THREATS.
- PERIODIC SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE
THIS WEEKEND AND INTO EARLY NEXT WEEK. ISOLATED SEVERE THUNDERSTORMS
ARE POSSIBLE.
- HOT AND HUMID TODAY AND SATURDAY, WITH HIGHS IN THE MID 80S TO
MID 90S. HEAT INDICES ON SATURDAY ARE FORECAST AROUND 100
DEGREES IN PARTS OF THE SOUTH CENTRAL AND THE JAMES RIVER
VALLEY.
- A COOLING TREND BEGINS SUNDAY AND CONTINUES INTO THE MIDDLE OF
NEXT WEEK.
DISCUSSION
ISSUED AT 307 PM CDT FRI JUL 25 2025
THIS AFTERNOON, FLOW ALOFT WAS GENERALLY SOUTHWESTERLY, WITH A
SURFACE LOW ANALYZED IN CENTRAL SASKATCHEWAN. A TRAILING
SURFACE TROUGH EXTENDS FROM THE CENTER OF THE LOW, ACROSS
EASTERN MONTANA, WHERE SURFACE OBS SHOW WINDS SHIFTING FROM
SOUTHERLY TO WESTERLY. SATELLITE IMAGERY REVEALS TWO IMPULSES IN
THE IMMEDIATE AREA - ONE IN SOUTHERN MANITOBA, AND ONE IN
SOUTHEAST MONTANA. A SMALL AREA OF REFLECTIVITY CONTINUES TO
DRIFT ACROSS SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA, WITH A
THUNDERSTORM JUST ACROSS THE STATE LINE IN SOUTHEAST MONTANA.
ADDITIONAL CLOUDS AND POTENTIALLY THE START OF STORMS IS FURTHER
UPSTREAM IN NORTHERN WYOMING, AS WELL AS IN EASTERN MONTANA.
SCATTERED SHOWERS AND THUNDERSTORMS ARE LIKELY THIS AFTERNOON
AND EVENING WITH THE SURFACE TROUGH AND IMPULSE MOVING THROUGH.
SPC MESOANALYSIS PAGE HAS ANYWHERE FROM 1500-3000 J/KG OF MLCAPE
ACROSS THE AREA, ALTHOUGH MOST CAPPED IN THE SOUTHWEST. 0-6KM
SHEAR IS LOW, AS EXPECTED, WITH 25-30 KNOTS ACROSS THE NORTH
CENTRAL AND NORTHEAST, AND LOWER ELSEWHERE. THERE IS SOME MODEST
SRH, PRIMARILY FOCUSED IN THE CENTRAL AND EAST. LOW- AND MID-
LEVEL LAPSE RATES ARE GETTING TO BE STEEP IN THE SOUTHWEST, WITH
HIGHER VALUES IN MONTANA THAT WILL EVENTUALLY BE EXPANDING
ACROSS NORTH DAKOTA.
THE QUESTION IS IF THE ACTIVITY WE ARE SEEING NOW IS THE MAIN
ACTIVITY TO EXPECT, WITH THE IMPULSE MOVING THROUGH ALREADY, OR
IF TIMING IS A BIT OFFSET. HIGH-RES GUIDANCE HAS BEEN CONSISTENT
IN BRINGING IN CONVECTION TO WESTERN NORTH DAKOTA LATER THIS
EVENING, SO IF THE ONGOING ACTIVITY CONTINUES, IT WILL BE A FEW
HOURS EARLIER THAN EXPECTED. THE LACK OF SHEAR BUT VERY STRONG
BUOYANCY AND LAPSE RATES WOULD FAVOR EXPLOSIVE DEVELOPMENT
INITIALLY, WITH POTENTIAL FOR LARGE HAIL, BEFORE STORMS ARE
UNABLE TO SUSTAIN THEIR STRENGTH DUE TO THE LACK OF SHEAR. WOULD
EXPECT A LOT OF PULSE-TYPE STORMS, ESPECIALLY AT FIRST, BEFORE
CAMS FAVOR AN EVENTUAL NORTH-SOUTH ORIENTED LINE OF CONVECTION
MOVING THROUGH CENTRAL NORTH DAKOTA LATER THIS EVENING. IF THERE
ARE ANY INITIAL STORMS ACROSS THE FAR CENTRAL AND EASTERN NORTH
DAKOTA, THIS IS WHERE/WHEN THE PRIMARY TORNADO THREAT WOULD BE,
WITH MUCH LOWER SRH TO THE WEST WHERE THERE IS HIGHER
CONFIDENCE IN STORMS OCCURRING. WILL CONTINUE MESSAGING HAIL UP
TO THE SIZE OF GOLF BALLS AND WIND GUSTS UP TO 70 MPH WITH
SCATTERED SEVERE THUNDERSTORMS. HEAVY RAIN IS ALSO A POTENTIAL
THREAT, ALTHOUGH IT DOES LOOK LIKE STORMS WILL BE TRANSIENT
ENOUGH TO LIMIT TRAINING CHANCES. AFTER STORMS MOVE OFF TO THE
EAST TONIGHT, GENERALLY QUIET WEATHER WITH SEASONABLY MILD
OVERNIGHT LOWS IN THE 60S.
A TROUGH CONTINUES TO DIG ACROSS THE WESTERN CONUS ON SATURDAY, WITH
FLOW BECOMING MORE SOUTHWESTERLY AGAIN LATER IN THE DAY ACROSS THE
DAKOTAS. GUIDANCE FAVORS AN IMPULSE MOVING THROUGH LATE IN THE
AFTERNOON SATURDAY THROUGH SATURDAY NIGHT, PASSING OVER AN AIR MASS
WITH STRONG INSTABILITY LIKE TODAY BUT WITH SUFFICIENT SHEAR
FOR MORE DEVELOPED STORMS. THERE ARE SOME CAPPING CONCERNS WITH
WARM 850MB TEMPS, BUT MOST LONG-RANGE CAMS ARE DEVELOPING
CONVECTION ACROSS WESTERN NORTH DAKOTA AT SOME POINT SATURDAY
EVENING. NSSL AND CSU MACHINE LEARNING HAVE CONSISTENTLY SHOWN
SATURDAY AS THE DAY WITH THE HIGHEST SEVERE THUNDERSTORM
POTENTIAL ACROSS THE FORECAST AREA. WE ARE ONLY HIGHLIGHTED FOR
ISOLATED SEVERE THUNDERSTORMS AT THE MOMENT, BUT WOULD NOT BE
SURPRISED IF WE GOT UPGRADED TO LEVEL 2 OF 5 WITH UPDATE
TONIGHT. POPS PEAK SATURDAY NIGHT AT 40 TO 60 PERCENT ACROSS THE
AREA.
IN ADDITION TO POTENTIAL FOR SEVERE THUNDERSTORMS, HOT AND HUMID
WEATHER IS ALSO A FORECAST CONCERN FOR SATURDAY. WE HAVE ISSUED A
HEAT ADVISORY FOR PORTIONS OF SOUTH CENTRAL NORTH DAKOTA AND THE
JAMES RIVER VALLEY ON SATURDAY. DEW POINTS TODAY HAVE ALREADY BEEN A
FEW DEGREES HIGHER THAN THE NBM FORECAST, AND WITH CONTINUED
SOUTHERLY FLOW THROUGH TODAY AND TOMORROW, EXPECTING THEM TO BE EVEN
HIGHER ON SATURDAY. COMBINED WITH AIR TEMPS IN THE LOWER TO MID 90S,
APPARENT TEMPERATURES WILL BE AROUND 100 DEGREES F, WITH MOSTLY
SUNNY SKIES IN THIS AREA AS WELL.
SOUTHWEST FLOW ALOFT CONTINUES ON SUNDAY, ALTHOUGH THERE ARE SIGNS
OF THE RIDGE FLATTENING ACROSS THE DAKOTAS ON TOP OF THE BROAD
SURFACE HIGH TO OUR SOUTH. SIMILAR TO SATURDAY, IT WILL BE ANOTHER
DAY OF EMBEDDED IMPULSES THAT COULD TRIGGER CONVECTION IN AN
ENVIRONMENT WITH MODERATE INSTABILITY AND SHEAR. WE ARE
CURRENTLY ADVERTISING POTENTIAL FOR ISOLATED SEVERE
THUNDERSTORMS IN OUR EASTERN COUNTIES, WITH QUESTIONS ON
LINGERING IMPACTS ON THE ENVIRONMENT FROM CONVECTION SATURDAY
NIGHT INTO SUNDAY MORNING, AS WELL AS HINTS OF CAPPING PROBLEMS
WITH MID-LEVEL HEIGHT RISES. NSSL MACHINE LEARNING GUIDANCE HAS
THE BROADEST SIGNAL FOR SEVERE THUNDERSTORMS TO OUR EAST.
LOOKING AHEAD TO NEXT WORK WEEK, NBM TEMPERATURE PERCENTILES ARE
QUITE CONFIDENT IN A COOLING TREND THROUGH THE FIRST FEW DAYS.
ENSEMBLE CLUSTERS FAVOR FLOW STARTING ZONAL AT THE BEGINNING OF THE
WORK WEEK BEFORE TURNING NORTHWESTERLY IN RESPONSE TO A DEEP HUDSON
BAY LOW MY MIDWEEK. NSSL MACHINE LEARNING DOES STILL KEEP MODEST
PROBABILITIES FOR SEVERE WEATHER ON BOTH MONDAY AND TUESDAY, WITH
POTENTIALLY A FEW RIDGE-RIDING IMPULSES PASSING OVER MODERATE
INSTABILITY AND SHEAR CURRENTLY ADVERTISED IN DETERMINISTIC
GUIDANCE. FOR THE MAJORITY OF THE WORK WEEK, HIGHS WILL BE IN
THE MID 70S TO LOWER 80S. THE CHANCE FOR SEVERE WEATHER DROPS
OFF MIDWEEK, WITH OVERALL LOW POPS, ALTHOUGH NORTHWEST FLOW IS
TYPICALLY A BIT LOWER PREDICTABILITY OF A PRECIPITATION PATTERN.
TEMPERATURES START TO TREND WARMER FOR NEXT WEEKEND.
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 1257 PM CDT FRI JUL 25 2025
OVERALL VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. BREEZY
SOUTHERLY WINDS WILL CONTINUE INTO THIS EVENING, WITH SOME
ISOLATED SHOWERS AND A RUMBLE OF THUNDER OR TWO ACROSS SOUTHERN
NORTH DAKOTA. CONFIDENCE INCREASES IN A WAVE OF SHOWERS AND
THUNDERSTORMS MOVING THROUGH LATE THIS AFTERNOON AND EVENING
FROM WEST TO EAST, WITH PROB30 GROUPS INCLUDED AT ALL TERMINALS
IN A BEST GUESS FOR TIMING OF IMPACTS. SOME STORMS COULD BE
STRONG TO SEVERE WITH GUSTY, ERRATIC WINDS AND LARGE HAIL
POSSIBLE.
BIS WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM NOON CDT /11 AM MDT/ TO 8 PM CDT /7 PM MDT/
SATURDAY FOR NDZ023-025-034>037-042-045>048-050-051.
DISCUSSION...JONES
AVIATION...JONES
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