033
FXUS63 KBIS 111019
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
519 AM CDT THU SEP 11 2025
KEY MESSAGES
- SEVERAL ROUNDS OF SCATTERED SHOWERS AND THUNDERSTORMS THROUGH
THE MIDDLE OF NEXT WEEK.
- ISOLATED SEVERE THUNDERSTORMS ARE POSSIBLE TODAY THROUGH
FRIDAY NIGHT.
- THROUGH TONIGHT, THE HIGHEST CHANCES FOR SEVERE STORMS ARE
FROM WEST CENTRAL TO NORTH CENTRAL NORTH DAKOTA DURING THE
LATE EVENING AND OVERNIGHT HOURS.
- TEMPERATURES FAVORED TO REMAIN NEAR TO ABOVE AVERAGE THROUGH
THE MIDDLE OF NEXT WEEK.
DISCUSSION
ISSUED AT 517 AM CDT THU SEP 11 2025
..SYNOPSIS
A LONGWAVE TROUGH OVER THE WESTERN CONUS WITH AN EMBEDDED
CIRCULATION NEAR THE OR/CA/NV BORDER INTERSECTION WILL TAKE ON A
POSITIVE TILT AND SLOWLY DRIFT EASTWARD TODAY THROUGH FRIDAY,
SENDING COPIOUS AMOUNTS OF DCVA INTO THE NORTHERN PLAINS. THE TROUGH
AXIS IS THEN FORECAST TO PIVOT TO A NEGATIVE TILT THIS WEEKEND AS
THE CLOSED LOW SPINS UP INTO MONTANA AND BACK NORTHWEST INTO ALBERTA
AHEAD OF A POTENT SHORTWAVE DIGGING INTO THE PACIFIC NORTHWEST. AS
THE INITIAL TROUGH DEPARTS THE REGION TO THE NORTHEAST ON MONDAY,
THE TRAILING SHORTWAVE COULD EVOLVE INTO A CUTOFF LOW OVER THE
NORTHERN ROCKIES/HIGH PLAINS AS THE MAIN FLOW OPENS UP INTO A
GENERAL, BROAD TROUGHING PATTERN OVER THE NORTH CENTRAL CONUS.
ENSEMBLE SPREAD IN THE PROGRESSION OF THE SYNOPTIC PATTERN IS
NOTABLE BY THE MIDDLE OF NEXT WEEK, THOUGH THERE IS CONSENSUS FOR
THE BROAD CYCLONIC FLOW OVER THE NORTHERN PLAINS. THIS PATTERN SETS
THE STAGE FOR SEVERAL ROUNDS OF PRECIPITATION CROSSING THE NORTHERN
PLAINS OVER THE NEXT SEVERAL DAYS. DESPITE THE PERSISTENT CHANCES
FOR RAIN, TEMPERATURES ARE FAVORED TO REMAIN NEAR TO ABOVE AVERAGE
THROUGH THE MIDDLE OF NEXT WEEK AS IT WILL REMAIN QUITE HUMID BY MID
SEPTEMBER STANDARDS WITH DEWPOINTS CONSISTENTLY IN THE MID 50S TO
MID 60S.
..TODAY AND TONIGHT
SCATTERED THUNDERSTORMS HAVE DEVELOPED ON THE NOSE OF A LOW LEVEL
JET IN NORTH CENTRAL NORTH DAKOTA EARLY THIS MORNING. SPC
MESOANALYSIS SHOWS AN ENVIRONMENT WITH AROUND 1000 J/KG MUCAPE AND
40 KTS EFFECTIVE BULK SHEAR. A FEW STORMS HAVE BECOME STRONG AT
TIMES, AND WITHIN THE LAST HOUR, RADAR ANALYSIS SUGGESTED A SEVERE
THUNDERSTORM IN NORTHEAST BOTTINEAU COUNTY PRODUCING LARGE HAIL.
THIS ACTIVITY SHOULD MOVE OFF TO THE EAST AND/OR DISSIPATE BY MID
MORNING WITH THE WANING OF THE LOW LEVEL JET. ANOTHER BATCH OF
CONVECTION TIED TO MID LEVEL VORTICITY ADVECTION IS TRAILING BEHIND
INTO WESTERN NORTH DAKOTA. THIS CONVECTION IS MUCH WEAKER, BUT HAS A
HISTORY OF PRODUCING HEAT BURSTS WITH WIND GUSTS OVER 60 MPH.
LEE CYCLOGENESIS IS FORECAST OVER SOUTHEAST MONTANA THIS
AFTERNOON. THE PERSISTENT AND BREEZY SOUTH-SOUTHEASTERLY FLOW TO
THE EAST OF THE DEVELOPING LOW (AS HIGH AS 25 MPH SUSTAINED IN
CENTRAL NORTH DAKOTA THIS AFTERNOON) WILL BRING DEWPOINTS WELL
INTO THE 60S TO ALL BUT FAR SOUTHWEST NORTH DAKOTA, WHICH SHOULD
BE IN CLOSE PROXIMITY TO THE LOW AND ALLOW FOR BETTER MIXING OF
THE BOUNDARY LAYER. HIGH TEMPERATURES THIS AFTERNOON ARE
FORECAST TO RANGE FROM THE MID 70S IN THE TURTLE MOUNTAINS TO
NEAR 90 IN THE FAR SOUTHWEST.
AN UNSTABLE BUT CAPPED AIR MASS IS FORECAST TO DEVELOP OVER WESTERN
NORTH DAKOTA THIS AFTERNOON, WITH MLCAPE BUILDING TO AROUND 2000-
3000 J/KG. TWO-DIMENSIONAL SHEAR FIELDS ARE VARIABLE ACROSS
DETERMINISTIC MODELS, BUT FORECAST HODOGRAPHS ARE COMMONLY LONG WITH
SOME CONCAVITY IN THE LOWER LEVELS. IT IS CLEAR THAT ALL REQUISITE
INGREDIENTS FOR SEVERE CONVECTION WILL BE IN PLACE BY THIS EVENING,
BUT THE CHAOTIC NATURE OF THE FORCING MECHANISMS COMBINED WITH THE
MID LEVEL CAPPING CAUSES MUCH UNCERTAINTY IN STORM INITIATION AND
EVOLUTION. THE SUITE OF CAMS DO NOT LEND CONFIDENCE TO ANY
PARTICULAR SOLUTION BEING FAVORED OVER ANOTHER. A COMMON THEME
THOUGH IS THAT THE HIGHEST CHANCES FOR SEVERE CONVECTION ARE FROM
WEST CENTRAL TO NORTH CENTRAL NORTH DAKOTA LATE THIS EVENING THROUGH
TONIGHT, ROUGHLY IN LINE WITH SPC'S SLIGHT RISK. DOMINANT STORM MODE
IS ALSO UNCERTAIN, WITH ALL CAMS GENERALLY SHOWING MULTI-CELLULAR
CLUSTERS. IN ADDITION, THERE IS A LOW POTENTIAL FOR BACKBUILDING/
TRAINING CONVECTION TONIGHT THAT COULD RESULT IN A LOCALIZED
EXCESSIVE RAIN THREAT.
..FRIDAY THROUGH NEXT WEEK
MOST GUIDANCE FAVORS A BREAK FROM SHOWERS AND STORMS DURING THE
DAYTIME HOURS ON FRIDAY BEFORE A STRONGER SURGE OF ENERGY REACHES A
LOWER CAPE BUT HIGHER SHEAR ENVIRONMENT IN THE WESTERN DAKOTAS
FRIDAY EVENING/NIGHT. THIS COULD PRODUCE ANOTHER ROUND OF OVERNIGHT
STRONG TO AT TIMES SEVERE CONVECTION, THOUGH THERE ARE SIMILAR
UNCERTAINTIES AS FOR TODAY/TONIGHT. THE RISK FOR SEVERE WEATHER
LOOKS TO BE MUCH LOWER FOR THE WEEKEND AND BEYOND AS THE HIGH
TEMPERATURE FORECAST COOLS INTO THE 70S AND LATENT HEAT PROCESSES
WEAKEN MID LEVEL LAPSE RATES.
THE ENTIRE WEEKEND MAY NOT BE A WASHOUT, BUT WE ARE EXPECTING
SEVERAL ROUNDS OF SHOWERS STREAMING NORTH THROUGH THE REGION. FROM
SATURDAY MORNING THROUGH SUNDAY NIGHT, THE NBM MAINTAINS A 40 TO 60
PERCENT CHANCE OF AT LEAST HALF AN INCH OF RAIN, AND A 20 TO 40
PERCENT CHANCE OF AT LEAST ONE INCH. CONVECTION COULD RENDER RAIN
AMOUNTS TO BE HIGHLY VARIABLE THOUGH. A TRANSIENT RIDGE BETWEEN THE
DEPARTING TROUGH AND THE FOLLOWING SHORTWAVE/LOW COULD PROVIDE A
BREAK FROM SHOWERS ON MONDAY/MONDAY NIGHT. THE NBM MAINTAINS A 20 TO
30 PERCENT CHANCE OF RAIN OVER THIS TIME PERIOD, LIKELY ON ACCOUNT
OF TIMING UNCERTAINTY.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 141 AM CDT THU SEP 11 2025
VFR CONDITIONS ARE EXPECTED TO BEGIN THE 06Z TAF PERIOD.
CONVECTION CURRENTLY IN SOUTHEAST MONTANA IS PUSHING NORTHEAST
AND DISSIPATING ATTIM, BUT COULD MAKE IT INTO SOUTHWEST ND AFTER
MIDNIGHT, WITH A LOCALLY GUSTY WIND AND BRIEF DOWNPOURS.
CURRENTLY FORECAST IS TOO UNCERTAIN FOR THIS ACTIVITY TO MAKE IT
TO KDIK FOR INCLUSION IN THE TAF. WILL NEED TO MONITOR THOUGH
AS ATMOSPHERE ALOFT REMAINS UNSTABLE. A LOW LEVEL JET WILL BRING
WIND SHEAR TO KXWA KDIK KMOT AND KBIS IN THE 06-12 UTC
TIMEFRAME. LATE TONIGHT INTO THURSDAY MORNING CONVECTION IS
POSSIBLE ACROSS WESTERN AND NORTHERN ND. ADDED A PROB30 FOR
THUNDERSHOWERS AND KXWA AND KMOT. AT KDIK, KBIS AND KJMS,
CONVECTION MAY HOLD OFF UNTIL BEYOND THE 06Z TAF PERIOD. THERE
IS A POSSIBILITY OF SOME LOW STRATUS, MOST LIKELY EARLY THURSDAY
MORNING OVER CENTRAL ND, BUT WILL NOT INCLUDE IN TAFS AT THIS
TIME. THROUGH THE FORECAST PERIOD, EXPECT A SOUTHEAST TO EAST
SURFACE FLOW GENERALLY 10 TO 20 KNOTS, EXCEPT 15 TO 25 KNOTS
LATE MORNING THROUGH THE AFTERNOON.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HOLLAN
AVIATION...TWH
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