223
FXUS63 KBIS 270938
AFDBIS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BISMARCK ND
438 AM CDT MON JUL 27 2026
KEY MESSAGES
- HOT CONDITIONS WILL CONTINUE THROUGH AT LEAST THE MIDDLE OF
THE WEEK, WITH HIGHS MOSTLY AROUND 90 TO 100.
- SMOKE FROM DISTANT WILDFIRES WILL CONTINUE TO MAKE THE SKY
HAZY AND REDUCE SURFACE VISIBILITY EARLY THIS WEEK.
- AN ISOLATED STRONG TO SEVERE THUNDERSTORM COULD ENTER FAR
SOUTHWEST NORTH DAKOTA THIS AFTERNOON AND EARLY EVENING, WITH
THE MAIN HAZARD BEING WIND GUSTS UP TO 60 MPH.
- MEDIUM CHANCES (30 TO 60 PERCENT) FOR SHOWERS AND
THUNDERSTORMS WEDNESDAY AFTERNOON THROUGH THURSDAY. A FEW
STORMS COULD BE SEVERE IN WESTERN NORTH DAKOTA WEDNESDAY
AFTERNOON AND EVENING.
DISCUSSION
ISSUED AT 438 AM CDT MON JUL 27 2026
AN AMPLIFIED UPPER LEVEL RIDGE PERSISTS FROM THE SOUTHERN
ROCKIES THROUGH THE NORTHERN HIGH PLAINS EARLY THIS MORNING,
WHILE A SURFACE RIDGE EXTENDS FROM SASKATCHEWAN INTO WESTERN
NORTH DAKOTA. THE UPPER RIDGE IS FORECAST TO REMAIN NEARLY
STATIONARY THROUGH TODAY, ALTHOUGH A MID LEVEL SHORTWAVE
CURRENTLY LOCATED BETWEEN YELLOWSTONE AND THE GREAT SALT LAKE
WILL EJECT TOWARDS THE BLACK HILLS LATER TODAY. THIS WILL INDUCE
LEE TROUGHING FROM THE BLACK HILLS INTO SOUTHWEST NORTH DAKOTA
WHILE THE SURFACE RIDGE SLIDES EASTWARD INTO CENTRAL NORTH
DAKOTA. WITH ALL THIS OCCURRING UNDERNEATH THE RIGHT ENTRANCE
REGION OF AN UPPER JET STREAK, ENOUGH FORCING SHOULD BE PRESENT
TO INITIATE STORMS ALONG THE HIGHER TERRAIN OF NORTHEAST
WYOMING/SOUTHEAST MONTANA THIS AFTERNOON, WITH EAST-
NORTHEASTWARD PROPAGATION. A CONSENSUS OF CAMS CLIPS THE
SOUTHWEST CORNER OF THE STATE WITH THIS ACTIVITY BETWEEN MID
AFTERNOON AND EARLY EVENING. FORECAST CONFIDENCE IS HIGH IN
EFFECTIVE BULK SHEAR AROUND 35-40 KTS, BUT THERE IS GREATER
UNCERTAINTY IN BUOYANCY. CAPE COULD FIRST BE REGULATED BY THE
DEGREE OF MOISTURE ADVECTION BETWEEN THE LEE TROUGH AND
DOWNSTREAM SURFACE RIDGE, THEN BY THE STRENGTH OF BOUNDARY LAYER
MIXING. ENSEMBLE AVERAGED CAPE IS GENERALLY NO GREATER THAN
1000 J/KG, AND A LINGERING WARM NOSE ALOFT COULD KEEP CONVECTION
ELEVATED. THE MAIN HAZARD WITH ANY STORM ENTERING FAR SOUTHWEST
NORTH DAKOTA LATER TODAY IS WIND GUSTS, POSSIBLY AS STRONG AS
60 MPH. THE SPC DAY 1 CONVECTIVE OUTLOOK DOES CLIP FAR SOUTHWEST
NORTH DAKOTA WITH A CONDITIONAL INTENSITY GROUP LEVEL 1 FOR
DAMAGING WINDS AS HIGH AS 75 MPH, BUT GIVEN THE LOCATION AND
FOOTPRINT OF THE POOL OF BUOYANCY, THINK SIGNIFICANT WINDS ARE
MUCH MORE LIKELY TO BE CONFINED SOUTH OF THE STATELINE. OUTSIDE
OF FAR SOUTHWEST NORTH DAKOTA, SOME CAMS HAVE BEEN SIMULATING A
VARIETY OF SHOWER OR THUNDERSTORM ACTIVITY IN OTHER PARTS OF THE
STATE THROUGHOUT THE DAY. BUT WITH FORECAST CLOUD BASES CLOSER
TO 15 KFT, NOT EXPECTING ANYTHING BEYOND JUST A FEW SPRINKLES AT
THE SURFACE, WITH MOST OF WHAT DEVELOPS BEING VIRGA.
TODAY WILL BE A FEW TO SEVERAL DEGREES COOLER FOR MOST
LOCATIONS. THE PROJECTED THICKNESS OF SMOKE ALOFT INTRODUCES
UNCERTAINTY INTO THE HIGH TEMPERATURE FORECAST FOR TODAY. GIVEN
OBSERVED CONDITIONS BOTH OVERHEAD AND UPSTREAM LAST EVENING, AND
LITTLE TO NO CHANGE IN HRRR MODELED VERTICALLY-INTEGRATED SMOKE
CONCENTRATIONS FROM THEN THROUGH THIS EVENING, OUR HIGH
TEMPERATURE FORECAST FOR TODAY IS JUST SLIGHTLY COOLER THAN THE
NBM, WITH MID AND UPPER 80S FAR NORTH TO MID 90S SOUTHWEST AND
SOUTH CENTRAL. NEAR-SURFACE SMOKE CONCENTRATIONS ARE ALSO
PROJECTED TO BE SIMILAR TO WHAT ARRIVED YESTERDAY, SO REDUCED
VISIBILITY CANNOT BE RULED OUT. THE MENTION OF SMOKE IN THE
FORECAST HAS BEEN EXTENDED THROUGH TONIGHT.
THE UPPER LEVEL RIDGE IS PROJECTED TO MORE OR LESS REMAIN IN
PLACE THROUGH WEDNESDAY. THE FORECAST FOR TUESDAY IS SIMILAR TO
THAT FOR TODAY, WITH SLIGHTLY WARMER HIGH TEMPERATURES AROUND 90
TO 100, LINGERING SMOKE BOTH AT THE SURFACE AND ALOFT, AND LOW
PROBABILITIES (LESS THAN 20 PERCENT) FOR ISOLATED AFTERNOON AND
EVENING THUNDERSTORMS ACROSS SOUTHERN NORTH DAKOTA. SYNOPTIC
SCALE FORCING LOOKS VERY WEAK ON TUESDAY, SO ANY CONVECTION THAT
DOES INITIATE WOULD LIKELY BE ON ACCOUNT OF CONVECTIVE
TEMPERATURES BEING BREACHED. SLIGHTLY HIGHER CAPE IS FORECAST ON
TUESDAY WITH DEEP LAYER SHEAR AROUND 30 KTS, SO A STRONGER
STORM CANNOT BE RULED OUT. ON WEDNESDAY, THE THERMAL RIDGE AXIS
IS FORECAST TO PIVOT INTO NORTH DAKOTA AHEAD OF STRONGER
SHORTWAVE ENERGY EJECTING FROM THE GREAT BASIN. WIDESPREAD HIGH
TEMPERATURES AND MAXIMUM HEAT INDICES AROUND 100 ARE IN THE
FORECAST FOR WEDNESDAY. CONVECTION COULD INITIATE NEAR A LEE
SURFACE TROUGH ALONG THE ND/MT BORDER WEDNESDAY AFTERNOON, AND
SHOULD BECOME MORE WIDESPREAD IN WESTERN NORTH DAKOTA WITH THE
ARRIVAL OF THE SHORTWAVE WEDNESDAY EVENING, SPREADING INTO
CENTRAL NORTH DAKOTA OVERNIGHT. FORECAST CONFIDENCE IN BOTH CAPE
AND SHEAR REMAINS LOW, BUT A MARGINAL RISK WAS INTRODUCED TO
WESTERN NORTH DAKOTA FOR THE DAY 3 CONVECTIVE OUTLOOK, AND CSU
MACHINE LEARNING GUIDANCE ALSO HIGHLIGHTS LOW SEVERE STORM
PROBABILITIES ON WEDNESDAY.
THE EASTWARD PROGRESSION OF THE SHORTWAVE COULD BE SLOW ENOUGH
TO KEEP SHOWERS AND THUNDERSTORMS IN CENTRAL AND EASTERN NORTH
DAKOTA ON THURSDAY. AFTER A SLIGHT COOL DOWN TO HIGHS IN THE MID
80S TO MID 90S FOR THURSDAY AND FRIDAY AS A RESULT OF THE
DOWNSTREAM SHORTWAVE DIGGING INTO THE GREAT LAKES AND OHIO RIVER
VALLEY, THE UPPER LEVEL RIDGE IS FORECAST TO REBOUND AND BECOME
EVEN MORE AMPLIFIED FROM THE DESERT SOUTHWEST TO THE CANADIAN
PRAIRIE THIS WEEKEND. ENSEMBLE GUIDANCE PROJECTS THE THERMAL
RIDGE AXIS TO BE OVER THE NORTHERN HIGH PLAINS ON SUNDAY, WHICH
ONCE AGAIN HAS MEDIUM CHANCES FOR TEMPERATURES EXCEEDING 100
DEGREES. A MAJOR PATTERN SHIFT COULD FINALLY BE ON THE WAY
EARLY NEXT WEEK AS ENSEMBLE GUIDANCE FAVORS DEEP TROUGHING OVER
SOUTHERN CANADA.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 438 AM CDT MON JUL 27 2026
SMOKE FROM DISTANT WILDFIRES IS EXPECTED TO REMAIN THICK ALOFT
THROUGH THE FORECAST PERIOD. SURFACE VISIBILITY RESTRICTIONS
FROM THE SMOKE ARE LESS CERTAIN, BUT MVFR COULD RETURN TO PARTS
OF THE REGION TODAY. ASIDE FROM THE SMOKE, VFR CONDITIONS ARE
EXPECTED THROUGH THE FORECAST PERIOD. A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE IN FAR SOUTHWEST NORTH DAKOTA
THROUGHOUT THE DAY, WITH VIRGA MORE LIKELY TO THE NORTH AND
EAST. SOME GUSTY WINDS COULD BE ASSOCIATED WITH SHOWERS OR
STORMS. OTHERWISE, WINDS SHOULD REMAIN AROUND 10 KTS OR LESS
WITH VARYING DIRECTIONS.
BIS WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION...HOLLAN
AVIATION...HOLLAN
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