008
FXUS63 KBIS 201915
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
215 PM CDT SUN SEP 20 2026
KEY MESSAGES
- LIGHT RAIN ENDING SOUTHWEST AND SOUTH CENTRAL THROUGH EARLY
TONIGHT.
- GRADUAL WARMING TREND THROUGH THE UPCOMING WORKWEEK, WITH
HIGHS MOSTLY IN THE 60S ON MONDAY INCREASING TO THE 70S AND
LOWER 80S BY THE END OF THE WEEK.
- CHANCE OF SHOWERS AND THUNDERSTORMS WEDNESDAY THROUGH
WEDNESDAY NIGHT, OTHERWISE MOSTLY DRY THROUGH THE WORKWEEK.
DISCUSSION
ISSUED AT 215 PM CDT SUN SEP 20 2026
A GENERALLY QUIET WEATHER PERIOD IS EXPECTED THROUGH THE
REMAINDER OF THE WEEK. NEAR TO SLIGHTLY BELOW NORMAL HIGHS
MAINLY IN THE 60S AND 70S WILL GRADUALLY WARM BACK INTO THE 70S
AND 80S AS WE HEAD INTO THE WEEKEND. MAINLY DRY CONDITIONS ARE
ANTICIPATED TO PREVAIL, THOUGH CHANCES FOR SHOWERS AND
POTENTIALLY SOME THUNDERSTORMS WILL DEVELOP EARLY WEDNESDAY INTO
THURSDAY, AND AGAIN LATE SATURDAY INTO SUNDAY.
FOR TODAY, AN UPPER LEVEL LOW CUTTING ACROSS SOUTH DAKOTA IS
INDUCING SCATTERED SHOWERS ACROSS PORTIONS OF WESTERN NORTH
DAKOTA. AS HIGH PRESSURE BUILDS IN ACROSS THE INTERNATIONAL
BORDER LATE THIS AFTERNOON INTO THIS EVENING, THIS LOW WILL
BEGIN TO DIVE TO THE SOUTHEAST, LIMITING PRECPITATION CHANCES TO
MAINLY THE SOUTHWEST THROUGH THE EARLY OVERNIGHT PERIOD.
OVERALL, ONLY LIGHT AMOUNTS OF ACCUMULATION ARE EXPECTED THROUGH
THE REMAINDER OF TODAY, WITH THE PROBABILITY TO EXCEED ANOTHER
0.25" OF PRECIP ACROSS THE FAR SOUTHWEST ONLY AROUND 30% OR SO
(AS PER THE LATEST CALIBRATED NBM 5.0). OTHERWISE FOR TODAY,
HIGHS FROM THE MID 50S WEST TO MID 60S CENTRAL ARE FORECAST FOR
THIS AFTERNOON. WITH OVERCAST SKIES EXPECTED TO GRADUALLY CLEAR
TO THE SOUTHEAST ALONG WITH THE RAIN THROUGH THE LATE AFTERNOON
INTO THE OVERNIGHT PERIOD, LOW TEMPERATURES TONIGHT WILL
BE MAINLY INTO THE 40S, WITH PORTIONS OF THE TURTLE MOUNTAIN
POTENTIALLY DROPPING AS LOW AS THE UPPER 30S.
CONDITIONS THROUGH THE REMAINDER OF THE WEEK ARE EXPECTED TO BE
CHARACTERIZED BY PREVAILING SOUTHWESTERLY FLOW OVER THE
NORTHERN PLAINS. WHILE MAINLY DRY CONDITIONS ARE ANTICIPATED
OVER THE FORECAST AREA WITH THIS FLOW PATTERN, THE ENSEMBLE DOES
ATTEMPT TO RESOLVE A MODEST SHORTWAVE TROUGH CUTTING ACROSS THE
REGION EARLY WEDNESDAY INTO THURSDAY, WHICH CAN BE EXPECTED TO
PROMOTE AT LEAST LOW TO MEDIUM CHANCES (33 TO 55 PERCENT) FOR
SHOWERS AND POTENTIALLY SOME ISOLATED THUNDER AT TIMES THROUGH
THAT PERIOD. THE POTENTIAL FOR SEVERE WEATHER REMAINS VERY LOW.
THE GREATEST SOURCE OF DISAGREEMENT WITHIN THE ENSEMBLE REMAINS
HOW LONG PRECPITATION WILL PERSIST OVER THE FORECAST AREA
THROUGH THURSDAY. A SLIGHT MAJORITY (APPROXIMATELY 60 PERCENT OF
ENSEMBLE MEMBERS) FAVOR SHOWERS PERSISTING WELL INTO THURSDAY
AFTERNOON OVER CENTRAL NORTH DAKOTA AS THE UPPER LEVEL FLOW
PATTERN IS SLOW TO EJECT THE SHORTWAVE OUT INTO THE SOUTHERN
CANADIAN PRAIRIES, COMPARED TO A SLIGHT MINORITY OF MEMBERS
(APPROXIMATELY 40 PERCENT) WHICH INSTEAD FAVOR THE RAPIDLY
DEVELOPMENT OF AN UPPER LEVEL RIDGE OVER THE SOUTHERN GREAT
PLAINS THAT HELPS KICK THE INCITING TROUGH WELL OUT OF THE
FORECAST AREA BY LATE WEDNESDAY EVENING. IN EITHER SCENARIO,
ONLY LIGHT PRECPITATION AMOUNTS ARE EXPECTED WITH THE STRATIFORM
SHOWERS THAT DO DEVELOP. HOWEVER, CONSIDERING MODERATELY HIGH
MODEL PWATS AROUND 1.25" WEDNESDAY AFTERNOON, SOME LOCALLY
HIGHER RAIN TOTALS CAN BE ANTICIPATED WHEN AND WHERE
THUNDERSTORMS DO END UP DEVELOPING.
BY EARLY THURSDAY THROUGH FRIDAY, TRANSIENT UPPER LEVEL RIDGING
IS EXPECTED TO SLIDE OVER THE NORTHERN PLAINS, PROMOTING
SEASONABLY WARM HIGH TEMPERATURES MAINLY IN THE MID 70S TO MID
80S. CONDITIONS THROUGH SATURDAY WILL THUS REMAIN FAIRLY DRY,
BEFORE THE RIDGE IS PROGGED TO BREAK DOWN AND FLOW OVER THE
NORTHERN PLAINS BECOMES CYCLONIC AS A FAIRLY ROBUST UPPER LEVEL
LOW MOVES ACROSS THE CANADIAN PRAIRIES STARTING SATURDAY. WHILE
THE ENSEMBLE IS FAIRLY COHESIVE ON THE TIMING OF THIS SYSTEM,
THERE IS A SPLIT BETWEEN A MORE NORTHERLY (THUS DRIER) TRACK
VERSUS A MORE SOUTHERLY (THUS WETTER) TRACK AS OF THIS FORECAST
CYCLE. AS IT STANDS, AT LEAST LOW TO MEDIUM CHANCES FOR SHOWERS
AND SOME STORMS CAN BE ANTICIPATED SATURDAY THROUGH SUNDAY. WITH
NEAR ZONAL TO SLIGHT NORTHWESTERLY FLOW THEN EXPECTED TO
DEVELOP HEADING INTO NEXT WEEK, A RETURN TO SEASONABLE HIGHS CAN
ALSO BE ANTICIPATED WITH AND BEHIND THIS WEEKEND SYSTEM.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 215 PM CDT SUN SEP 20 2026
SHOWERS AND LOW IFR TO OCCASIONAL LIFR CEILINGS LINGER OVER
PORTIONS OF SOUTHWESTERN NORTH DAKOTA TO BEGIN THE 18Z TAF
PERIOD. ELSEWHERE, LOW VFR TO MVFR CEILINGS CAN BE FOUND EARLY
THIS AFTERNOON, WITH CONDITIONS GRADUALLY IMPROVING THROUGH THE
EARLY TO MID EVENING. ACROSS THE SOUTHWEST, MVFR TO IFR CEILINGS
ARE EXPECTED TO LINGER THROUGH EARLY TONIGHT AS SHOWERS EXIT
OUT OF THE AREA. PATCHY FOG MAY DEVELOP LATE TONIGHT INTO EARLY
MONDAY MORNING ACROSS PORTIONS OF THE NORTH AND THE FAR
SOUTHWEST, THOUGH CONFIDENCE IN IMPACTS AT ANY GIVEN TAF SITE
REMAINS LOW.
LIGHT EAST TO SOUTHEAST WINDS ARE EXPECTED THIS AFTERNOON
THROUGH THIS EVENING, WITH PORTIONS OF CENTRAL NORTH DAKOTA
DIMINISHING TO BECOME VERY LIGHT AND VARIABLE OVERNIGHT. WINDS
WILL THEN REORGANIZE OUT OF THE SOUTH TO SOUTHEAST MONDAY
MORNING. REMAINING LIGHT AROUND 5 TO 10 KNOTS THROUGH THE END OF
THE TAF PERIOD.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...ADAM
AVIATION...ADAM
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