913
FXUS63 KBIS 221133
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
633 AM CDT SAT AUG 22 2026
KEY MESSAGES
- PERIODIC LOW TO MEDIUM CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE TONIGHT THROUGH MONDAY.
- A FEW STORMS MAY BE STRONG TO SEVERE IN SOUTHWEST AND SOUTH
CENTRAL NORTH DAKOTA DURING THE DAY SUNDAY, FAR WESTERN NORTH
DAKOTA SUNDAY NIGHT, AND CENTRAL AND EASTERN NORTH DAKOTA ON
MONDAY.
- TEMPERATURES ARE FAVORED TO REMAIN NEAR TO SLIGHTLY ABOVE
NORMAL THROUGH NEXT WEEK, WITH HIGHS MOSTLY IN THE 80S.
UPDATE
ISSUED AT 633 AM CDT SAT AUG 22 2026
THE FORECAST FOR TODAY REMAINS ON TRACK. QUIET WEATHER WILL
PREVAIL UNDER SURFACE HIGH PRESSURE.
DISCUSSION
ISSUED AT 413 AM CDT SAT AUG 22 2026
A HIGHLY-AMPLIFIED UPPER LEVEL WAVE PATTERN LIES OVER NORTH
AMERICA EARLY THIS MORNING, WITH A RIDGE AXIS ALONG THE ROCKIES
AND A TROUGH AXIS FROM HUDSON BAY TO THE SOUTHERN APPALACHIAN
MOUNTAINS. SURFACE HIGH PRESSURE IS CENTERED OVER SOUTHEAST
SASKATCHEWAN, WHICH IS KEEPING THE LOCAL WEATHER VERY QUIET.
THE SURFACE HIGH WILL MORPH INTO AN ELONGATED RIDGE AND SLIDE
OVER THE RED RIVER VALLEY BY THE END OF THE DAY AS THE UPPER
RIDGE AXIS BEGINS TO PIVOT OFF THE NORTHERN ROCKIES. QUIET
WEATHER WILL CONTINUE THROUGH THE DAYTIME HOURS, WITH HIGH
TEMPERATURES THIS AFTERNOON RANGING FROM THE MID 70S NORTHEAST
TO MID 80S SOUTHWEST.
A MID LEVEL SHORTWAVE WILL EJECT OFF THE NORTHERN ROCKIES BY
THIS EVENING, CUTTING THROUGH THE RIDGE AXIS. THE INCREASING
DOWNSTREAM WARM-AIR ADVECTION, MOISTURE TRANSPORT, ISENTROPIC
LIFT, ETC. COULD GENERATE SHOWERS AND THUNDERSTORMS IN EASTERN
MONTANA TONIGHT, SPREADING INTO WESTERN NORTH DAKOTA EARLY
SUNDAY MORNING. MUCAPE COULD EXCEED 1000 J/KG WITH EFFECTIVE
BULK SHEAR NEAR 30 KTS IN THE SOUTHWEST SUNDAY MORNING, BUT
CONVECTION SHOULD REMAIN ELEVATED, AND MOST CAMS ARE ONLY
SIMULATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. THE
00Z NAMNEST IS AN OUTLIER WITH A COUPLE OF CLUSTERS OF STRONG
TO SEVERE STORMS WITH BOWING SEGMENTS IN THE SOUTHWEST SUNDAY
MORNING AND INTO THE AFTERNOON. PROXIMITY MODEL SOUNDINGS AT
DICKINSON DO SHOW HIGHER RH AT THE BASE OF THE EML AND HIGHER
EQUILIBRIUM LEVELS IN THE NAMNEST, BUT ITS HODOGRAPHS COULD
BEST BE DESCRIBED AS CHAOTIC. THEREFORE, THE RISK FOR SEVERE
WEATHER SUNDAY MORNING INTO THE EARLY AFTERNOON IS VERY LOW,
BUT NOT ZERO. THIS COULD CHANGE LATER SUNDAY AFTERNOON AS
DIURNAL HEATING OPENS THE POTENTIAL FOR SURFACE OR MIXED-LAYER
BASED CONVECTION. HOWEVER: 1) THERE IS HIGH CONFIDENCE IN A
STRONG CAPPING INVERSION ABOVE THE BOUNDARY LAYER, 2) A MOIST
SOUTHEASTERLY SURFACE FLOW IS NOT CONDUCIVE TO EFFICIENT
BOUNDARY LAYER MIXING, AND 3) MID LEVEL CLOUDS AND/OR ANVIL
SHADING FROM MORNING CONVECTION COULD LIMIT DIURNAL HEATING TO
SOME EXTENT. CAMS DO SHOW AN INCREASED PROBABILITY IN STRONGER
CONVECTION OVER SOUTH CENTRAL NORTH DAKOTA MID TO LATE SUNDAY
AFTERNOON ALONG THE EASTERN GRADIENT OF THE BUOYANCY POOL,
WHERE CIN MAY BE RELATIVELY WEAKER. STILL LOOKING AT A CAPE/
SHEAR PARAMETER SPACE SUPPORTIVE OF ONLY MARGINALLY SEVERE
STORMS THOUGH. BUT REGARDLESS OF INTENSITY, THERE ARE STILL
MEDIUM CHANCES (30 TO 60 PERCENT) FOR SHOWERS AND THUNDERSTORMS
ACROSS MUCH OF WESTERN AND CENTRAL NORTH DAKOTA SUNDAY
AFTERNOON AND EVENING AS THE SHORTWAVE MOVES THROUGH. INCREASED
CONFIDENCE IN THE AFOREMENTIONED SOUTHEASTERLY FLOW AND CLOUD
COVER HAS COOLED THE HIGH TEMPERATURE FORECAST INTO THE LOWER
AND MID 80S FOR ALL BUT FAR SOUTHWEST NORTH DAKOTA ON SUNDAY.
BY SUNDAY NIGHT, A MUCH MORE POTENT SHORTWAVE/UPPER LOW WILL BE
EJECTING OFF THE CANADIAN ROCKIES INTO THE SOUTHERN PRAIRIE
PROVINCES. CLUSTERS OF THUNDERSTORMS FORMING OFF THE MONTANA
ROCKIES LATE SUNDAY AFTERNOON COULD CROSS INTO WESTERN NORTH
DAKOTA SUNDAY NIGHT BEFORE DISSIPATING. IF THIS CONVECTION IS
MAINTAINED, IT COULD BE STRONG TO SEVERE AS IT MOVES INTO A
HIGHER BUOYANCY AIR MASS WITH INCREASING SHEAR. THE 06Z HRRR
APPEARS TO SHOW A REASONABLE WORST-CASE SCENARIO WITH A BROKEN
LINE OF STRONG TO SEVERE STORMS EXTENDING FROM THE CANADIAN TO
SOUTH DAKOTA BORDERS ENTERING THE STATE AFTER 10 PM CDT.
SIMULATED SURFACE WINDS GUSTS IN THE 06Z HRRR ARE MUCH LOWER IN
WESTERN NORTH DAKOTA THOUGH THAN THEY ARE IN EASTERN MONTANA
EARLIER IN THE EVENING.
THE THUNDERSTORM FORECAST ON MONDAY REMAINS UNCERTAIN AND MAY
END UP HIGHLY DEPENDENT ON THE EASTWARD PROPAGATION OF THE
OCCLUDED FRONT ATTENDANT TO THE POTENT CANADIAN UPPER LOW. BOTH
CAPE (~2000 J/KG) AND SHEAR (~35 KTS) DIRECTLY AHEAD OF THE
FRONT ARE PROJECTED TO BE SUFFICIENT FOR SEVERE STORMS. BUT VERY
FEW ENSEMBLE MEMBERS ARE GENERATING ANY CONVECTION ALONG THE
FRONT, LIKELY DUE TO AN ABSENCE OF MID TO UPPER LEVEL FORCING.
BROAD MID LEVEL HEIGHT FALLS DO EVENTUALLY SPREAD INTO NORTHERN
NORTH DAKOTA, BUT THAT MAY LAG BEHIND THE SURFACE FRONT. THE
LATEST NBM HAS REDUCED POPS TO ONLY 20 TO 30 PERCENT MONDAY
AFTERNOON AND EVENING, AND KEPT MENTIONABLE POPS EAST OF HIGHWAY
83. BUT LOCATION UNCERTAINTY IN THE SURFACE FRONT AT 00Z MONDAY
EVENING RANGES FROM AS FAR WEST AS MINOT TO DICKINSON (NAM) TO
AS FAR EAST AS DEVILS LAKE TO JAMESTOWN (A SMALL SUBSET OF GEFS
MEMBERS). THE PROGRESSION OF THE FRONT IS ALSO LIKELY TO PLAY A
ROLE IN HIGH TEMPERATURES ON MONDAY. STRONG MIXING IN THE DRY
POST-FRONTAL AIR MASS COULD ALLOW TEMPERATURES TO APPROACH 90
IN SOUTHWEST AND SOUTH CENTRAL NORTH DAKOTA, WITH AT LEAST
LOWER 80S ELSEWHERE. THIS IS ASSUMING A SLIGHTLY QUICKER
FRONTAL PROGRESSION, WHICH ENSEMBLES DO TILT TOWARDS.
ENSEMBLE GUIDANCE SHOWS THE CANADIAN LOW DIGGING SOUTHEASTWARD
ON TUESDAY, BUT WITH VARIANCE IN ITS TRAJECTORY. THAT
UNCERTAINTY MAY DICTATE HOW MUCH TEMPERATURES COOL OFF ON
TUESDAY, BUT THE NBM HAS TRENDED SLIGHTLY WARMER THAN PREVIOUS
ITERATIONS WITH HIGHS IN THE MID/UPPER 70S NORTH TO LOWER/MID
80S SOUTH. REGARDLESS, TUESDAY IS LIKELY TO BE A WINDIER DAY,
WITH NORTHWEST WINDS GUSTING AS HIGH AS 35 MPH. THERE COULD
ALSO BE SOME DIURNALLY-DRIVEN SHOWERS ACROSS THE NORTH TUESDAY
AFTERNOON. ENSEMBLES FAVOR A RETURN TO NORTHWEST FLOW BETWEEN
AN EASTERN CONUS TROUGH AND WESTERN CONUS RIDGE FOR THE SECOND
HALF OF NEXT WEEK, WITH UNCERTAINTY ON WHEN OR IF THE RIDGE
MIGHT GET PUSHED EASTWARD. ENSEMBLE CLUSTERS THAT ARE MORE
HEAVILY ECMWF-WEIGHTED ARE MUCH MORE PROGRESSIVE IN BREAKING
DOWN THE RIDGE, WHILE SOME GEFS-HEAVY CLUSTERS KEEP THE RIDGE
TO OUR WEST INTO NEXT WEEKEND. THE NBM BROADLY MAINTAINS NEAR
AVERAGE TEMPERATURES THROUGH THE END OF NEXT WEEK, BUT IS
STARTING TO TREND SLIGHTLY ABOVE AVERAGE IN SOUTHWEST AND SOUTH
CENTRAL NORTH DAKOTA CONSIDERING THAT AVERAGE TEMPERATURES
THEMSELVES ARE NOW BEGINNING TO COOL AT THIS TIME OF YEAR.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 633 AM CDT SAT AUG 22 2026
VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD. A FEW
SHOWERS OR THUNDERSTORMS COULD BEGIN MOVING INTO FAR WESTERN
NORTH DAKOTA LATE TONIGHT, BUT ARE UNLIKELY TO REACH KXWA OR
KDIK UNTIL AFTER 12Z SUNDAY. WINDS WILL REMAIN LIGHT AND
VARIABLE IN CENTRAL NORTH DAKOTA WHILE BECOMING SOUTHEAST
AROUND 10 KTS IN WESTERN NORTH DAKOTA THIS AFTERNOON.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...HOLLAN
DISCUSSION...HOLLAN
AVIATION...HOLLAN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page