416
FXUS63 KBIS 211951
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
251 PM CDT TUE APR 21 2026
KEY MESSAGES
- WELL ABOVE AVERAGE TEMPERATURES AND MOSTLY DRY CONDITIONS
CONTINUE THROUGH WEDNESDAY.
- CRITICAL FIRE WEATHER CONDITIONS ARE POSSIBLE ACROSS MOST OF
WESTERN AND PARTS OF SOUTHERN NORTH DAKOTA ON WEDNESDAY.
- ACTIVE WEATHER PATTERN WEDNESDAY NIGHT THROUGH THE END OF THE
WEEK, WITH MEDIUM TO HIGH PRECIPITATION CHANCES AND A STRONG
COOLING TREND.
- STRONG WEST TO NORTHWEST WINDS ARE LIKELY THURSDAY AND
FRIDAY.
DISCUSSION
ISSUED AT 251 PM CDT TUE APR 21 2026
QUIET WEATHER DAY TODAY, WITH QUASIZONAL FLOW ALOFT DOWNSTREAM
OF A DEEP CLOSED LOW MOVING ONSHORE OVER THE WESTERN CONUS.
BROAD HIGH PRESSURE WAS CENTERED OVER NORTHERN MINNESOTA, WITH A
MODEST PRESSURE GRADIENT AND BOUNDARY ORIENTED NORTHEAST-
SOUTHWEST ACROSS WESTERN NORTH DAKOTA. MOSTLY SUNNY WITH BREEZY
SOUTHERLY WINDS TODAY, AND AFTERNOON HIGHS IN THE LOWER 70S EAST
TO LOWER 80S WEST.
FORECAST CONCERNS INCREASE WEDNESDAY AND CONTINUE THROUGH THE
END OF THE WEEK. THE AFOREMENTIONED LOW APPROACHES THE REGION
AND AN UPPER RIDGE BUILDS IN JUST DOWNSTREAM OF THE TROUGH BASE,
WITH LOW-LEVEL WARM AIR ADVECTION BOOSTING HIGHS INTO THE MID
70S NORTH CENTRAL TO AROUND 90 FAR WEST AND SOUTH.
A FIRE WEATHER WATCH HAS BEEN ISSUED FOR WESTERN AND PARTS OF
SOUTHERN NORTH DAKOTA FOR WEDNESDAY, DUE TO THE COMBINATION OF LOW
RELATIVE HUMIDITY AND STRONG WINDS. SOUTHWEST NORTH DAKOTA
COMPARED TO THE NORTHWEST AND JAMES RIVER VALLEY AREAS HAVE
SLIGHTLY DIFFERENT ENVIRONMENTS. SOUTH TO SOUTHEAST WINDS WILL
BE SUSTAINED AROUND MPH ACROSS SOUTHWEST NORTH DAKOTA, WITH
MINIMUM RELATIVE HUMIDITY IN THE LOWER TEENS. FURTHER NORTH AND EAST,
WINDS WILL BE STRONGER BUT DEW POINTS SLIGHTLY HIGHER, STILL
LEADING TO POSSIBLE CRITICAL FIRE WEATHER CONDITIONS. JOINT PROBABILITIES
OF RELATIVE HUMIDITY LESS THAN 20 PERCENT AND WINDS OF AT LEAST
15 MPH FAVOR WESTERN NORTH DAKOTA, ALONG THE SD STATE LINE, AND
INTO THE SOUTHERN JAMES RIVER VALLEY, WHICH IS WHERE WE ISSUED
THE WATCH FOR. SOME UNCERTAINTY ON CONDITIONS IN THE FAR SOUTH
CENTRAL AND QUESTIONS ON WHAT DEW POINTS END UP LOOKING LIKE IN
THE JAMES RIVER VALLEY. WE ARE ALSO FAVORING THE FACT THAT IT
WILL BE THE FIRST WIDESPREAD HOT AND WINDY DAY OF THE SEASON,
WITH FORECAST HIGHS FROM MID 70S FAR NORTH CENTRAL TO THE UPPER
80S SOUTHWEST AND FAR SOUTH CENTRAL. RIGHT NOW THE MAIN CLIMATE
SITES TO POTENTIALLY BREAK RECORD HIGHS ARE DICKINSON (90
DEGREES IN 1989) AND BISMARCK (89 DEGREES IN 1990).
WE CONTINUE TO MONITOR THUNDERSTORM POTENTIAL WEDNESDAY EVENING AS
THE TROUGH BASE AND ATTENDANT LOW LIFT OVER THE NORTHERN ROCKIES AND
APPROACH THE REGION. THIS IS ALSO WHERE THE DEW POINT QUESTION COMES
INTO PLAY, WITH FORECAST INSTABILITY VARYING AMONGST
DETERMINISTIC GUIDANCE. GENERAL THOUGHT IS FOR MARGINAL
INSTABILITY AND BULK SHEAR AVAILABLE, WITH POTENTIAL FOR A FEW
STRONGER STORMS, BUT LIKELIHOOD OF AN ISOLATED SEVERE STORM IS
LOW. 12Z HREF DOES PAINT A FEW MAX UH TRACKS ACROSS THE FORECAST
AREA, BUT WILL HAVE TO SEE HOW MUCH MOISTURE RETURN WE CAN GET
IN THE NEXT 24 HOURS. DEW POINTS ACROSS SOUTHEAST NORTH DAKOTA
ARE IN THE UPPER 20S TO LOWER 30S THIS AFTERNOON, AND LOOKING
UPSTREAM ACROSS THE I-29 CORRIDOR AND SOUTHERN MINNESOTA, WE
HAVE TO LOOK PRETTY FAR SOUTH TO START SEEING DEW POINTS IN THE
50S, WHICH WOULD SEVERELY LIMIT ANY SORT OF CONVECTIVE
POTENTIAL, BUT WOULD INCREASE THE FIRE WEATHER POTENTIAL.
AS THE UPPER LOW MOVES INTO THE STATE ON THURSDAY, PRECIPITATION
CHANCES INCREASE EARLY IN THE MORNING AND THROUGH THE DAY,
ALTHOUGH ENSEMBLE GUIDANCE IS ADVERTISING A NOTICEABLE SHIFT TO
THE NORTHWEST, MOVING THE CENTER OF THE LOW OUT OF THE FORECAST
AREA COMPARED TO WHAT WAS BEING SHOWN YESTERDAY. WITH THIS SHIFT,
WE HAVE SEEN A SIGNIFICANT DECREASE IN FORECAST PRECIPITATION
AMOUNTS, WITH THE LIKELIHOOD OF EXCEEDING A HALF INCH OF QPF
ONLY AROUND 20 PERCENT IN THE NORTHWEST CORNER OF THE STATE.
PROBABILITIES FOR MORE THAN AN INCH OF SNOW ARE SIMILAR. THE
PLACEMENT OF THE SYSTEM WOULD ALSO FAVOR MUCH OF CENTRAL NORTH
DAKOTA TO BE DRY SLOTTED THROUGH THE MAIN PUSH OF MOISTURE. THE
BENEFIT OF THE SHIFTING OF THE UPPER LOW IS THAT IT'S NOT QUITE
AS SLAM DUNK OF A SCENARIO FOR VERY STRONG WINDS, ALTHOUGH
STILL HIGH CONFIDENCE IN NEEDING AN ADVISORY ON THURSDAY FOR THE
MAJORITY, IF NOT ALL OF THE FORECAST AREA.
THE CONTINUED STORY IS THEN COOLER AIR FILTERS IN, ALTHOUGH WITH THE
LOW SKEWED FURTHER TO THE NORTH WE END UP IN MORE OF A ZONAL FLOW
ALOFT / DIFFUSE SURFACE PATTERN, WITH FORECAST HIGHS A FEW DEGREES
WARMER THAN PREVIOUS UPDATES, WHICH LEADS TO MORE OF A LOWER
40S TO LOWER 50S FORECAST THROUGH THE WEEKEND. WINDS WILL STAY
BREEZY THROUGH SATURDAY BEFORE DIMINISHING MORE AS FLOW FINALLY
BEGINS TO WEAKEN. WE STILL HAVE LOW CHANCES FOR PRECIPITATION
FRIDAY AND SATURDAY, BUT WITH THE SYSTEM DISPLACED NOT AS
CONFIDENT IN AS MUCH WRAP-AROUND PRECIPITATION. STILL FAVORED AS
SNOW, ALTHOUGH NBM P-TYPES ARE SHOWING MORE OF A MIX ACROSS THE
SOUTH, ESPECIALLY DURING THE DAY AS OUR TEMPERATURES NUDGED UP.
THE OTHER NOTICEABLE CHANGE WITH THIS FORECAST PACKAGE ISSUANCE
IS INCREASING CHANCES FOR PRECIPITATION ON SUNDAY. AS THE UPPER
LOW LIFTS FURTHER TO THE NORTH, A SECONDARY WAVE WITH A SOUTHERN
STREAM TROUGH IS PROJECTED TO MOVE THROUGH THE DAKOTAS, AND IS
FURTHER NORTH THAN PREVIOUS FORECAST ITERATIONS. THIS WILL
CONTINUE CHANCES FOR RAIN AND SNOW THROUGH SUNDAY AND INTO
MONDAY. TEMPERATURES ARE FAVORED TO MODERATE FURTHER INTO NEXT
WEEK, ALTHOUGH LOOK TO STAY NEAR TO SLIGHTLY BELOW NORMAL, AND
CERTAINLY NOT AS WARM AS THEY HAVE BEEN TO START THIS WEEK.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1234 PM CDT TUE APR 21 2026
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. BREEZY SOUTHERLY
WINDS WILL DIMINISH OVERNIGHT AND BECOME MORE VARIABLE BEFORE
INCREASING AGAIN ON WEDNESDAY. A FEW HIGH CLOUDS THIS AFTERNOON,
WITH INCREASING CLOUDS LATE IN THE PERIOD AHEAD OF AN
APPROACHING SYSTEM.
BIS WATCHES/WARNINGS/ADVISORIES
FIRE WEATHER WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
EVENING FOR NDZ001-009-017-018-031>033-040>048-050-051.
DISCUSSION...JONES
AVIATION...JONES
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