800
FXUS63 KBIS 141011
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
511 AM CDT SUN SEP 14 2025
KEY MESSAGES
- SHOWERS AND EMBEDDED THUNDERSTORMS WILL RETURN TO MOST OF
WESTERN AND CENTRAL NORTH DAKOTA THIS MORNING AND AFTERNOON,
LASTING ON AND OFF THROUGH MONDAY.
- ISOLATED TO SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS
CENTRAL NORTH DAKOTA THIS AFTERNOON AND EARLY EVENING, WITH A
TORNADO OR TWO POSSIBLE.
- HIGHS MOSTLY IN THE 70S THROUGH TUESDAY, THEN COOLING INTO
THE 60S BY THE END OF THE WORK WEEK.
DISCUSSION
ISSUED AT 510 AM CDT SUN SEP 14 2025
LONGWAVE TROUGH AXIS EXTENDS FROM ALONG THE ALBERTA/SASKATCHEWAN
BORDER TO COLORADO EARLY THIS MORNING, PLACING THE NORTHERN PLAINS
UNDER SOUTHERLY FLOW ALOFT. A NEARLY SATURATED NEAR-SURFACE LAYER
WITH LIGHT WINDS HAS ALLOWED AREAS OF FOG TO DEVELOP ACROSS MUCH OF
WESTERN AND CENTRAL NORTH DAKOTA. THE COVERAGE OF DENSE FOG REDUCING
VISIBILITY UNDER HALF A MILE HAS NOT BEEN AS PREVALENT THUS FAR.
WOULD NOT BE SURPRISED TO SEE CONDITIONS DETERIORATE CLOSER TO
SUNRISE.
A CLOSED UPPER LOW AT THE BASE OF THE LONGWAVE TROUGH WILL TRANSLATE
NORTHWARD TODAY, KICKING THE TROUGH AXIS INTO THE NORTHERN AND
CENTRAL HIGH PLAINS AND SHORTENING ITS WAVELENGTH. THE STRONG
POLEWARD DIFFERENTIAL ADVECTION OF CYCLONIC VORTICITY COMBINED WITH
UPPER LEVEL DIVERGENCE SHOULD BRING ANOTHER ROUND OF WIDESPREAD
SHOWERS AND EMBEDDED THUNDERSTORMS TO MUCH OF WESTERN AND CENTRAL
NORTH DAKOTA LATER THIS MORNING THROUGH TONIGHT. THE ORIGINS OF THIS
CAN ALREADY BE SEEN MOVING UP THE MISSOURI RIVER VALLEY IN SOUTH
DAKOTA. THROUGH THIS AFTERNOON, THE HIGHEST PROBABILITIES FOR RAIN
ARE ALONG A LONGITUDINAL AXIS THAT ROUGHLY COVERS AREAS ALONG AND
WEST OF THE HIGHWAY 83 CORRIDOR. DIRECTLY TO THE EAST, MODEST
DIURNAL HEATING COULD YIELD SBCAPE APPROACHING 2000 J/KG, WHICH MAY
BE UNCAPPED OR ONLY VERY WEAKLY CAPPED GIVEN THE MOISTURE-RICH
BOUNDARY LAYER WITH DEWPOINTS FORECAST IN THE MID TO UPPER 60S. MOST
CAMS DEVELOP A FEW CLUSTERS OF CONVECTION ALONG AND BETWEEN THE
CORRIDORS OF HIGHWAYS 83 AND 281 BY MID AFTERNOON, WITH QUICK
NORTHWARD MOTION. STORM MODE COULD BE MESSY GIVEN THE STRONG MID TO
UPPER LEVEL FORCING AND LACK OF A WELL-DEFINED SURFACE OR LOW LEVEL
BOUNDARY. ANY SURFACE BASED STORM WOULD LIKELY HAVE ACCESS TO
EFFECTIVE BULK SHEAR AROUND 30-35 KTS, WHICH WOULD BE SUPPORTIVE OF
SEVERE STORMS. INGREDIENTS FOR LARGE HAIL AND DAMAGING WIND ARE
MOSTLY ON THE LOWER END OF THE SEVERE SPECTRUM. HOWEVER, THERE IS A
POTENTIAL THAT THE MOST PERTINENT HAZARD FROM SEVERE STORMS TODAY
COULD ACTUALLY BE TORNADOES. A CORRIDOR OF STRONG LOW LEVEL SRH
(AROUND 100 M^2/S^2) AND SHEAR (AROUND 15-20 KTS) IS FORECAST TO BE
COLLOCATED WITH MORE BUOYANT AIR MASS WITH VERY LOW LCLS, AND
FORECAST HODOGRAPHS ARE SHOWING CLASSIC LONG-LOOPING SIGNATURES. ONE
POTENTIAL LIMITING FACTOR IS THAT BOTH DETERMINISTIC AND ENSEMBLE
KINEMATIC AND THERMODYNAMIC TWO-DIMENSIONAL FIELDS INDICATE
THAT FAVORABLE CONDITIONS FOR TORNADOGENESIS MAY BE VERY LIMITED
TEMPORALLY AT ANY GIVEN LOCATION, TRANSLATING WITH THE MEAN
ATMOSPHERIC FLOW. THIS LIMITATION ALSO APPEARS IN FORECAST
HODOGRAPHS, AS THERE IS ONLY AN HOUR OR TWO OF CROSSWISE
VORTICITY AT ANY GIVEN SITE. THEREFORE, WE WILL MESSAGE THE
POTENTIAL FOR A TORNADO OR TWO ALONG WITH THE BASE SEVERE
HAZARDS OF QUARTER SIZE HAIL AND 60 MPH WINDS. LOCALLY EXCESSIVE
RAINFALL COULD ALSO BE A CONCERN YET AGAIN THIS AFTERNOON
THROUGH TONIGHT. PRECIPITABLE WATER IS PROJECTED TO REMAIN NEAR
OR AT CLIMATOLOGICAL MAXIMUM VALUES, AND THE HREF LOCALIZED
PROBABILITY-MATCHED MEAN QPF SHOWS SEVERAL POCKETS OF +2 INCHES.
SURFACE CYCLOGENESIS ATTENDANT TO THE MID/UPPER LOW IS FORECAST
BY TONIGHT, WITH THE SYSTEM QUICKLY PROJECTED TO BECOME
STACKED. COMPARED TO A TRADITIONAL LOW, THIS ONE IS FORECAST TO
BE ESSENTIALLY SIDEWAYS, WITH THE WARM FRONT POINTING DUE NORTH
AND THE WRAP-AROUND DEFORMATION BAND FOCUSED IN THE SOUTHWEST
QUADRANT. MODELS STILL SHOW TIMING UNCERTAINTY WITH THE
DEPARTURE OF THE LOW INTO CANADA, GENERALLY FROM AROUND EARLY
AFTERNOON TO LATE EVENING. THIS KEEPS HIGH CHANCES FOR SHOWERS
BUT COMPARATIVELY LOWER CHANCES FOR THUNDERSTORMS IN THE
FORECAST ON MONDAY, DECREASING FROM SOUTH TO NORTH IN THE
AFTERNOON THROUGH THE EVENING. SOME HIGH-RESOLUTION MODELS ARE
ALSO NOW SHOWING A MUCH STRONGER SURFACE LOW ENTERING SOUTHWEST
MANITOBA MONDAY AFTERNOON, WITH TIGHTLY PACKED ISOBARS ON THE
SOUTHERN FLANK ACROSS NORTHERN NORTH DAKOTA. THIS OUTCOME WOULD
LIKELY CAUSE WINDY CONDITIONS ACROSS THE NORTH MONDAY AFTERNOON,
WITH REASONABLE WORST-CASE SCENARIO GUSTS EXCEEDING 50 MPH (PER
THE 06Z HRRR). THERE IS STILL TOO MUCH UNCERTAINTY TO INCLUDE
STRONG WINDS IN THE GRIDDED FORECAST AND MESSAGING, BUT IT IS
SOMETHING THAT WILL NEED TO BE MONITORED WITH FUTURE MODEL RUNS.
NOT LONG AFTER THE DEPARTURE OF THE LOW LATE MONDAY, ANOTHER WAVE
DEEPENING OVER THE NORTHERN ROCKIES WILL BEGIN SENDING DCVA INTO THE
REGION ON TUESDAY, WHICH KEEPS A 20 TO 40 PERCENT CHANCE OF RAIN IN
THE FORECAST. GUIDANCE THEN SHOWS ANOTHER SHORTWAVE DIGGING DOWN
FROM CANADA ON WEDNESDAY. THIS WAVE IS LIKELY TO BRING A COOLER AIR
MASS INTO THE REGION, WHICH MAY HOLD THROUGH THE END OF THE WEEK AS
THE WAVE INTERACTS WITH THE OTHER AFOREMENTIONED WAVE AND
MEANDERS AROUND THE UPPER MIDWEST. THE NBM MAINTAINS A 30
PERCENT CHANCE OF RAIN ON WEDNESDAY, FOLLOWED BY ONLY A 20
PERCENT CHANCE THURSDAY THROUGH SATURDAY.
FOR TODAY THROUGH TUESDAY, HIGH TEMPERATURES ARE MOSTLY EXPECTED TO
BE IN THE 70S, THOUGH PARTS OF SOUTHWEST AND SOUTH CENTRAL NORTH
DAKOTA COULD STAY IN THE MID TO UPPER 60S SHOULD IT RAIN MOST OF THE
DAY. ENSEMBLES THEN SHOW A DISTINCT COOL DOWN FOR THE SECOND HALF OF
THE WEEK, WITH HIGHS MOSTLY IN THE 60S THURSDAY THROUGH SATURDAY.
FORECAST LOWS TONIGHT REMAIN CLOSER TO SUMMERTIME VALUES OF MID 50S
TO LOWER 60S, THEN GRADUALLY COOL TO AROUND 45 TO 50 FOR THE SECOND
HALF OF THE WEEK.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 510 AM CDT SUN SEP 14 2025
IFR TO LIFR CEILINGS ARE EXPECTED ACROSS MOST OF WESTERN AND
CENTRAL NORTH DAKOTA THIS MORNING. VISIBILITY WILL ALSO BE
REDUCED TO IFR/LIFR LEVELS AT MANY LOCATIONS BY FOG/MIST.
CEILINGS ARE EXPECTED TO IMPROVE TO AT LEAST MVFR LEVELS, BUT
PERHAPS VFR, THIS AFTERNOON. CENTRAL NORTH DAKOTA COULD THEN
SEE PREVAILING MVFR CEILINGS RETURN THIS EVENING.
SHOWERS AND EMBEDDED THUNDERSTORMS WILL ONCE AGAIN BECOME MORE
WIDESPREAD FROM SOUTH TO NORTH LATER THIS MORNING THROUGH THE
EVENING. THE HIGHEST CHANCES FOR RAIN ARE AT KBIS DURING THE
LATE MORNING AND AFTERNOON, AND AT KMOT DURING THE LATE
AFTERNOON AND EVENING. MVFR TO IFR VISIBILITY FROM RAIN CAN BE
EXPECTED AT TIMES, AND A FEW STRONGER STORMS COULD PRODUCE GUSTY
WINDS. OTHERWISE, WINDS SHOULD REMAIN LIGHT AND VARIABLE.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HOLLAN
AVIATION...HOLLAN
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