948
FXUS63 KBIS 220017
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
717 PM CDT THU MAY 21 2026
KEY MESSAGES
- SHOWERS AND THUNDERSTORMS MAINLY IN WESTERN AND NORTH CENTRAL
NORTH DAKOTA THIS EVENING. THUNDERSTORM ACTIVITY DIMINISHES
OVERNIGHT, WHILE SHOWERS CONTINUE BEFORE SPREADING EASTWARD
FRIDAY.
- AXIS OF HIGHER RAIN AMOUNTS IN WESTERN NORTH DAKOTA,
ESPECIALLY WHERE THUNDERSTORMS OCCUR.
- BELOW AVERAGE TEMPERATURES FRIDAY, THEN WARMING TO WELL ABOVE
AVERAGE BY THE END OF THE HOLIDAY WEEKEND.
UPDATE
ISSUED AT 717 PM CDT THU MAY 21 2026
SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ALONG A STATIONARY
FRONTAL BOUNDARY OVER PARTS OF SOUTHWESTERN NORTH DAKOTA, AND
TO A LESSER EXTENT, PARTS OF THE NORTH CENTRAL. A STRONG STORM
HAD INITIALLY DEVELOPED SOUTHWEST OF DICKINSON, THOUGH HAS
SINCE DECREASED IN INTENSITY. MODEL GUIDANCE SUGGESTS
INSTABILITY SHOULD RAPIDLY DECREASE AS THE SUN SETS RESULTING
MOSTLY IN SHOWERS DURING THE OVERNIGHT HOURS. THOUGH A FEW
RUMBLES OF THUNDER CANNOT BE COMPLETELY RULED OUT. SHOWER
ACTIVITY OVERNIGHT WILL REMAIN MOSTLY CONCENTRATED ALONG THE
FRONTAL BOUNDARY BEFORE EXPANDING EASTWARD FRIDAY.
DISCUSSION
ISSUED AT 230 PM CDT THU MAY 21 2026
CURRENTLY A MEDIUM SIZE TROUGH AND UPPER LOW IS SITTING OVER
MONTANA AND WYOMING. UPSTREAM IN THE PACIFIC NORTHWEST A RIDGE
OR ZONAL FLOW IS FORMING. AT THE SURFACE THE COLLOCATED SURFACE
LOW IS IN SOUTHERN CANADA, WITH A STATIONARY FRONT SITTING IN
AN INVERTED TROUGH PLACED OVER WESTERN NORTH DAKOTA. ALONG THE
POSITIVE VORTICITY SIDE OF THE UPPER LEVEL TROUGH IN EASTERN
MONTANA, SHOWERS HAVE BEEN ON GOING. THIS AFTERNOON AS SURFACE
TEMPERATURES INCREASE, AROUND 1500 J/KG OF CAPE WILL BE PRESENT
ALONG THE FRONT. WITH SHEAR AROUND 30KTS, THUNDERSTORMS WILL
FORM AND TRAIN SOUTH TO NORTH ALONG THE FRONT SINCE THE SHEAR
VECTOR WILL BE PARALLEL TO THE FRONT. WITH VERY SKINNY CAPE
PROFILES AND HIGH RELATIVE HUMIDITIES THROUGH THE UPPER LEVELS,
THERE IS ONLY A SMALL CHANCE OF SEVERE HAZARDS. SO THE HIGHEST
RISK FROM THE STORMS WILL BE HEAVY DOWNPOURS. THE CAMS AGREE ON
THE LOCATION BEING SOMEWHERE BETWEEN BEACH, AND GLEN ULLIN.
TIMING LOOKS TO BE BETWEEN 5 AND 7PM CT. WITH THE FRONT
REMAINING STATIONARY ALONG WITH THE INVERTED TROUGH, THE STORMS
SHOULD STAY WEST OF THE MISSOURI RIVER THROUGH THE EVENING.
TONIGHT A SURFACE LOW MOVING OUT OF WYOMING FROM THE BOTTOM OF
THE UPPER LEVEL TROUGH WILL START TO MOVE NORTHEAST. BY FRIDAY
MORNING IT WILL FORM INTO IT'S OWN STACKED LOW AND BE IN
NORTHERN SOUTH DAKOTA. THEREFOR FRIDAY WILL BE SLIGHTLY COOLER
WITH WIDESPREAD RAIN ACROSS MOST OF THE STATE. THIS RAIN WILL
LAST THROUGH MOST OF THE DAY, ENDING WEST TO EAST AS THE LOW
CONTINUES INTO NORTHERN MINNESOTA FRIDAY NIGHT. AN AXIS OF
HIGHER QPF IS WILL OCCUR WITH THE THUNDERSTORMS THIS EVENING,
AND THE FRONT ENHANCING LIFT THROUGH FRIDAY IN WESTERN ND. THERE
IS A MEDIUM TO HIGH CHANCE OF 1 INCH OF QPF ON A NORTH SOUTH
LINE CENTERED ON DICKINSON BETWEEN SOUTH DAKOTA AND NEW TOWN.
ANOTHER HIGHER AREA OF QPF IS FORECAST IN SOUTHEAST ND WHEN THE
LOW WRAPS UP AND MOVES THROUGH. THE MAJORITY OF THAT QPF WILL
FALL FRIDAY AFTERNOON.
THROUGH THIS WEEKEND ZONAL FLOW WILL SETUP ACROSS THE NORTHERN
PLAINS LEADING TO VERY WARM TEMPERATURES, BOTH ALOFT AND AT THE
SURFACE. BY MONDAY EXPECT HIGHS NEAR 90 IN THE WEST AND
CENTRAL. THESE ABOVE NORMAL TEMPERATURES WILL CONTINUE THROUGH
THE WEEK. IN THE LATTER PART OF NEXT WEEK A LARGE UPPER LEVEL
LOW COULD MOVE THROUGH, ALTHOUGH THERE IS AN INCREDIBLE AMOUNT
OF UNCERTAINTY IN LOCATION AND TIMING IF IT DOES OCCUR. NBM DOES
HAVE LOW POPS FOR THIS, AND TEMPERATURES LOOK TO STAY IN THE
UPPER 70S OR LOWER 80S.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 717 PM CDT THU MAY 21 2026
SHOWERS AND THUNDERSTORMS HAVE DEVELOPED ALONG A STATIONARY
FRONT OVER PARTS OF SOUTHWESTERN AND NORTH CENTRAL NORTH
DAKOTA. SO FAR, MOST THUNDERSTORM ACTIVITY HAS BEEN CONFINED TO
THE SOUTHWEST. THUNDERSTORM ACTIVITY WILL DIMINISH AS THE SUN
SETS, THOUGH SHOWERS SHOULD PERSIST THROUGH THE NIGHT. STILL,
AN OCCASIONAL ROGUE RUMBLE OF THUNDER WILL REMAIN POSSIBLE.
SHOWERS, PERHAPS WITH A FEW RUMBLES OF THUNDER, WILL THEN EXPAND
EASTWARD ACROSS THE STATE ON FRIDAY. MVFR CEILINGS ARE EXPECTED
TO ENTER SOUTHWESTERN NORTH DAKOTA LATER TONIGHT BEFORE
MVFR/IFR CEILINGS IMPACT MOST OF THE STATE FRIDAY. CEILINGS WILL
ALSO GRADUALLY IMPROVE FROM WEST TO EAST.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
UPDATE...TELKEN
DISCUSSION...SMITH
AVIATION...TELKEN
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