077
FXUS63 KBIS 311154
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
654 AM CDT FRI JUL 31 2026
KEY MESSAGES
- TEMPERATURES WILL BECOME VERY HOT AGAIN OVER THE WEEKEND,
WITH HIGHS NEAR 100 IN WESTERN NORTH DAKOTA ON SATURDAY AND
CENTRAL NORTH DAKOTA ON SUNDAY.
- IT WILL BE WINDY ON SUNDAY, WITH NEAR-CRITICAL FIRE WEATHER
CONDITIONS EXPECTED ACROSS MUCH OF THE WESTERN HALF OF THE
STATE.
- THE FIRST HALF OF THE UPCOMING WORK WEEK SHOULD BE MUCH
COOLER, WITH HIGHS IN THE 70S AND 80S.
- LOW TO MEDIUM CHANCES FOR SHOWERS AND THUNDERSTORMS LATE
SUNDAY NIGHT THROUGH MONDAY. A FEW STORMS COULD BE SEVERE IN
CENTRAL AND EASTERN PARTS OF THE STATE.
UPDATE
ISSUED AT 652 AM CDT FRI JUL 31 2026
SATELLITE IMAGERY AND SURFACE WEBCAMS SHOW VALLEY FOG
THROUGHOUT THE BADLANDS SURROUNDING THE SOUTH UNIT OF THEODORE
ROOSEVELT NATIONAL PARK. THE FOG IS REDUCING VISIBILITY ALONG
I-94 IN BILLINGS COUNTY, BUT DOES NOT APPEAR TO BE IMPACTING
TRAVEL ELSEWHERE. PATCHY GROUND FOG HAS ALSO DEVELOPED ACROSS
THE REST OF WESTERN AND CENTRAL NORTH DAKOTA WHEREVER SKIES ARE
CLEAR. THIS FOG SHOULD MOSTLY BE UNIMPACTFUL, ALTHOUGH
VISIBILITY HAS RECENTLY FALLEN BELOW A QUARTER MILE AT THE
ROLLA AWOS.
DISCUSSION
ISSUED AT 451 AM CDT FRI JUL 31 2026
A SHORTWAVE TROUGH IS LOCATED OVER THE EASTERN
DAKOTAS/MINNESOTA EARLY THIS MORNING. THE ASSOCIATED SURFACE LOW
IS ANALYZED NEAR SIOUX FALLS, WITH A BROAD HIGH PRESSURE RIDGE
FROM NORTHERN SASKATCHEWAN THROUGH WESTERN NORTH DAKOTA. SHOWER
AND THUNDERSTORM ACTIVITY HAS SHIFTED WELL OFF TO THE SOUTHEAST.
PATCHY FOG REMAINS POSSIBLE ALONG THE SURFACE RIDGE AXIS IN
WESTERN NORTH DAKOTA EARLY THIS MORNING, BUT LITTLE TO NONE HAS
BEEN OBSERVED AS OF THIS WRITING. THE SURFACE RIDGE IS FORECAST
TO SLIDE INTO CENTRAL NORTH DAKOTA THIS AFTERNOON AS THE
DOWNSTREAM SHORTWAVE DIGS SOUTHEASTWARD ALONG THE LOWER MISSOURI
RIVER VALLEY. THERE IS A LOW-AMPLITUDE SHORTWAVE TRAVELING
ALONG THE TOP OF THE UPPER LEVEL RIDGE OVER CENTRAL MONTANA
EARLY THIS MORNING THAT IS RESPONSIBLE FOR SHOWERS AND ISOLATED
THUNDERSTORMS. MODELS TEND TO DISSOLVE AND SLOW THE PROGRESSION
OF THIS SHORTWAVE AS IT APPROACHES WESTERN NORTH DAKOTA, BUT IT
APPEARS TO BE MORE POTENT AND PROGRESSIVE ON WATER VAPOR
IMAGERY. THERE IS A LOW CHANCE THAT THIS WAVE COULD BRING A FEW
SHOWERS OR THUNDERSTORMS TO WESTERN PARTS OF THE STATE TODAY,
BUT THE FORCING WILL BE RUNNING INTO RISING MID LEVEL HEIGHT
TENDENCIES, AS WELL AS THE SURFACE RIDGE. ONLY A NARROW RIBBON
OF NO GREATER THAN 1000 J/KG CAPE IS FORECAST ACROSS FAR WESTERN
NORTH DAKOTA THROUGH THIS EVENING, AND MODEL SOUNDINGS WOULD
INDICATE MID LEVEL CAPPING SHOULD PREVENT CONVECTION FROM
BECOMING SURFACE OR MIXED-LAYER BASED. IF AN UPDRAFT WERE TO
BECOME ROOTED IN THE BOUNDARY LAYER, IT WOULD EXPERIENCE
EFFECTIVE BULK SHEAR AROUND 35-40 KTS. THE 00Z HREF DOES STILL
HAVE A CONTOUR OF 10 PERCENT IN ITS NEIGHBORHOOD PROBABILITY OF
UPDRAFT HELICITY EXCEEDING 75 M^2/S^2, BUT ALMOST THE ENTIRE
CONTRIBUTION TO THAT APPEARS TO BE FROM 12Z INITIALIZED MEMBERS.
IT IS THEREFORE HIGHLY UNLIKELY THAT THERE WILL BE ANY STRONGER
STORMS TODAY, ALTHOUGH INVERTED-V THERMODYNAMIC PROFILES COULD
SUPPORT GUSTY WINDS WITH EVEN JUST SHOWERS. BUT THE PROBABILITY
OF ANY SHOWERS OR STORMS IN WESTERN NORTH DAKOTA TODAY REMAINS
UNDER 20 PERCENT. THOSE CHANCES DO INCREASE SLIGHTLY AND SHIFT
INTO NORTH CENTRAL NORTH DAKOTA TONIGHT AS THE LOW LEVEL JET
INCREASES AND TURNS TO POINT NORTHEASTWARD, INDUCING WARM AIR
ADVECTION. BUT ANY OVERNIGHT ACTIVITY WOULD LIKELY BE LIMITED TO
JUST SHOWERS AS FORECAST CAPE OVER NORTH CENTRAL NORTH DAKOTA
TONIGHT REMAINS VERY LOW.
WITH NORTH DAKOTA SITTING BETWEEN A DOWNSTREAM TROUGH AND
UPSTREAM RIDGE TODAY, HIGH TEMPERATURES ARE FORECAST TO BE
LIMITED TO THE LOWER AND MID 80S EAST BUT REACH THE LOWER 90S
WEST. OVER THE COURSE OF THE WEEKEND, THE UPPER RIDGE WILL ONCE
AGAIN BECOME HIGHLY AMPLIFIED AND PIVOT INTO A POSITIVE TILT AS
A POTENT UPPER LOW DIGS INTO BRITISH COLUMBIA. THE THERMAL RIDGE
EXPANDS INTO WESTERN NORTH DAKOTA ON SATURDAY WHERE HIGHS COULD
APPROACH 100, THEN GETS SHOVED OVER CENTRAL NORTH DAKOTA ON
SUNDAY AS THE BRITISH COLUMBIA LOW EJECTS INTO THE CANADIAN
PRAIRIE AND DRIVES A COLD FRONT INTO WESTERN NORTH DAKOTA.
RECENT NBM GUIDANCE HAS TRENDED SLIGHTLY COOLER WITH
TEMPERATURES BOTH DAYS THIS WEEKEND, WITH DAILY MAXIMA
PROJECTIONS NOW CLOSER TO 100 RATHER THAN 105. BUT STILL THINK
COMPRESSIONAL HEATING AHEAD OF THE COLD FRONT COULD PRODUCE A
CORRIDOR OF ~105 DEGREE FAHRENHEIT TEMPERATURES OVER SOUTH
CENTRAL NORTH DAKOTA SUNDAY AFTERNOON. WE WILL CONTINUE TO
MESSAGE HEAT CONCERNS THIS WEEKEND, BUT THE LATEST TRENDS
PAIRED WITH IT BEING A DRIER AIR MASS MAY PRECLUDE THE NEED FOR
ANY HEADLINES. THE OTHER CONCERN FOR SUNDAY IS THAT WINDY
CONDITIONS BOTH AHEAD OF THE FRONT (SOUTH WINDS AROUND 25 MPH
GUSTING TO 40 MPH) AND BEHIND THE FRONT (NORTHWEST AROUND 20 MPH
GUSTING TO 30 MPH) WILL COMBINE WITH THE HOT AND DRY AIR TO
PRODUCE AT LEAST NEAR-CRITICAL FIRE WEATHER CONDITIONS ACROSS
MUCH OF THE WESTERN HALF OF THE STATE. THE CURRENT FORECAST
CALLS FOR ONLY AROUND 1 TO 3 HOURS OF MEETING RED FLAG CRITERIA,
AND ONLY ON A LIMITED BASIS SPATIALLY. BUT THE WIND SHIFT WITH
THE FRONTAL PASSAGE AND VERY HOT TEMPERATURES ARE FACTORS THAT
WILL NEED TO BE CONSIDERED. AS IT STANDS NOW, THERE IS STILL
ENOUGH UNCERTAINTY IN THE MAGNITUDE OF WINDS AND THE TIMING OF
THE COLD FRONT TO PRECLUDE THE ISSUANCE OF A FIRE WEATHER WATCH,
BUT THIS COULD EASILY CHANGE WITH FUTURE FORECAST UPDATES.
THE COLD FRONT IS FORECAST TO TEMPORARILY STALL FROM NORTHEAST
TO SOUTH CENTRAL NORTH DAKOTA SUNDAY NIGHT INTO MONDAY AS THE
CANADIAN LOW OCCLUDES AND A SEPARATE SHORTWAVE LANDS ON THE
AMERICAN SIDE OF THE PACIFIC NORTHWEST. THE COLD FRONT ITSELF
IS UNLIKELY TO BE ABLE TO INITIATE CONVECTION DURING THE DAY
SUNDAY AS IT MOVES THROUGH A HIGH CIN AND LOW RH ENVIRONMENT,
BUT SOME SETS OF MODEL GUIDANCE INTRODUCE QPF LATE MONDAY NIGHT
AS STRONGER MID LEVEL HEIGHT FALLS COMMENCE OVER THE REGION AND
FLOW ALOFT TURNS SOUTHWESTERLY WITH EMBEDDED SHORTWAVE ENERGY.
EFFECTIVE BULK SHEAR CAN BE TRICKY TO FORECAST FOR ELEVATED
CONVECTION DAYS IN ADVANCE, BUT AN EXAMPLE SOUNDING (NAM AT
CARRINGTON) DOES SHOW A LENGTHENING OF THE HODOGRAPH ABOVE 3 KM
AGL WITH TIME SUNDAY NIGHT INTO MONDAY MORNING, AND THAT SAME
SOUNDING CALCULATES MUCAPE AS HIGH AS 1500 J/KG. MONDAY
AFTERNOON MAY PROVIDE A MORE FAVORABLE OPPORTUNITY FOR SEVERE
CONVECTION IN A HIGHLY-SHEARED ENVIRONMENT, BUT WHETHER THAT
IMPACTS OUR FORECAST AREA WILL DEPEND ON THE EASTWARD
PROGRESSION OF THE COLD FRONT. THE SPC HAS INTRODUCED A DAY 3
MARGINAL RISK ACROSS CENTRAL NORTH DAKOTA FOR OVERNIGHT
ELEVATED CONVECTION AND THE OFF CHANCE A SURFACE-BASED STORM
CAN DEVELOP IN THE LATE AFTERNOON/EARLY EVENING (BUT AS ALLUDED
TO ABOVE, THE LATTER HAS A VERY LOW PROBABILITY OF OCCURRENCE).
THE COLD FRONT WILL FINALLY BRING RELIEF FROM WHAT HAS BEEN ONE
OF THE HOTTEST JULYS ON RECORD. FORECAST HIGHS ON MONDAY STILL
REACH THE MID 80S NEAR THE STALLED FRONTAL BOUNDARY IN SOUTH
CENTRAL NORTH DAKOTA, BUT ARE LIMITED TO THE MID AND EVEN LOWER
70S IN THE FAR NORTHWEST. GUSTY NORTH TO NORTHWEST WINDS ARE
ALSO IN THE FORECAST FOR MONDAY, WHICH COULD PROLONG FIRE
WEATHER CONCERNS IN SOUTHWEST PARTS OF THE STATE WHERE AFTERNOON
RH IS STILL FORECAST TO FALL NEAR 20 PERCENT DESPITE THE COOLER
TEMPERATURES. THE NBM FAVORS TUESDAY TO BE THE COOLEST DAY,
WITH FORECAST HIGHS NOW NO WARMER THAN THE UPPER 70S. THE
EVOLUTION OF THE SYNOPTIC PATTERN FROM MID TO LATE NEXT WEEK
REMAINS UNCERTAIN. HIGHER-MEMBERSHIP ENSEMBLE CLUSTERS WANT TO
TRANSITION TO A NORTHWEST FLOW PATTERN AS THE UPPER RIDGE
REBUILDS OVER THE ROCKIES, WHILE LOWER-MEMBERSHIP CLUSTERS TEND
TO MAINTAIN BROAD TROUGHING OR QUASI-ZONAL FLOW OVER THE
NORTHERN PLAINS.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 652 AM CDT FRI JUL 31 2026
PATCHY FOG IS POSSIBLE ACROSS MUCH OF WESTERN AND CENTRAL NORTH
DAKOTA EARLY THIS MORNING, BUT TAF SITES ARE NOT EXPECTED TO
HAVE PREVAILING CATEGORICAL VISIBILITY RESTRICTIONS. VFR
CONDITIONS ARE OTHERWISE EXPECTED THROUGH THE FORECAST PERIOD.
WINDS TODAY WILL BE SOUTH-SOUTHEAST AROUND 10-15 KTS FROM KXWA
TO KDIK, LIGHT AND VARIABLE FROM KMOT TO KBIS, AND NORTH-
NORTHEAST AROUND 10 KTS AT KJMS.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...HOLLAN
DISCUSSION...HOLLAN
AVIATION...HOLLAN
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