983
FXUS63 KDLH 212328
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
628 PM CDT SAT JUN 21 2025
KEY MESSAGES
- DANGEROUS HEAT TODAY AND TOMORROW WITH HEAT INDEX VALUES INTO
THE TRIPLE DIGITS ACROSS EAST-CENTRAL MINNESOTA AND NORTHWEST
WISCONSIN, WITH LITTLE RELIEF DUE TO WARM TEMPERATURES
OVERNIGHT TONIGHT. EXTREME HEAT WARNINGS AND HEAT ADVISORIES
IN EFFECT.
- A SLIGHT RISK (LEVEL 2 OUT OF 5) FOR SEVERE THUNDERSTORMS
AHEAD AND ALONG A COLD FRONT ON SUNDAY EVENING INTO SUNDAY
NIGHT FOR MUCH OF THE NORTHLAND. THIS RISK IS HIGHLY
CONDITIONAL - IF STORMS DEVELOP THEY WILL BE CAPABLE OF ALL
MODES OF SEVERE WEATHER (VERY LARGE HAIL, DAMAGING WINDS,
TORNADOES), BUT CONDITIONS ARE SUCH THAT STORMS MAY STRUGGLE
TO DEVELOP.
- SEASONABLE CONDITIONS RETURN FOR THE WORK WEEK WITH MOSTLY
SUNNY SKIES MONDAY AND TUESDAY, THEN THE NEXT CHANCE FOR
PRECIPITATION WEDNESDAY INTO THURSDAY.
DISCUSSION
ISSUED AT 147 PM CDT SAT JUN 21 2025
DANGEROUSLY HOT CONDITIONS THIS WEEKEND WILL END WITH A COLD FRONT
PASSAGE AND AT LEAST A FEW THUNDERSTORMS, WITH A COOLER, MORE
SEASONABLE WEATHER PATTERN FOR THE WORK WEEK. DRY TO START OFF THE
WEEK, THEN PRECIPITATION CHANCES RETURN WEDNESDAY INTO THURSDAY AS A
MID-LEVEL SHORTWAVE OR TWO LIFTS FROM THE CENTRAL ROCKIES INTO THE
UPPER MIDWEST HELPING TO PRODUCE SCATTERED TO WIDESPREAD SHOWERS AND
STORMS IN THE WARM SECTOR. THERE REMAINS CONSIDERABLE UNCERTAINTY IN
THE DETAILS OF TIMING, BUT THERE IS MEDIUM CONFIDENCE IN AT LEAST A
WETTING RAIN (TENTH OF AN INCH OF PRECIP OR MORE) FOR THE REGION AND
THAT THE RISK FOR SEVERE WEATHER IS LOW (LESS THAN 10 PERCENT) AT
THIS POINT. LATER IN THE WEEK INTO NEXT WEEKEND A DEEPER MID/UPPER
LEVEL TROUGH TRACKS EAST ACROSS THE HIGH PLAINS, GREAT PLAINS, AND
INTO THE GREAT LAKES, WITH THE POSSIBILITY FOR SOME KIND OF SEVERE
WEATHER THREAT TO EMERGE. BUT THERE REMAINS TOO MUCH UNCERTAINTY TO
NARROW DOWN THE LOCATION BEYOND SOMEWHERE IN THE NORTHERN GREAT
PLAINS AND MIDWEST AT THIS TIME. LEANING WARMER, BUT NOWHERE NEAR
THE EXTREME HEAT VALUES BEING EXPERIENCED THIS WEEKEND.
ON THE SYNOPTIC SCALE A FAIRLY SEASONABLE BROAD UPPER RIDGE/HIGH
EXISTS OVER THE SOUTHEAST US WITH A BROAD TROUGH OVER THE GREAT
BASIN AND INTERMOUNTAIN WEST. THIS PATTERN WILL AMPLIFY SLIGHTLY
INTO SUNDAY WITH THE TROUGH DEEPENING EASTWARD AND THE RIDGE
BUILDING NORTHEASTWARD, WITH MID/UPPER LEVEL FLOW BEING
SOUTHWESTERLY ACROSS THE GREAT PLAINS AND UPPER MIDWEST. IN THIS
FLOW, A SURFACE LOW WILL LIFT FROM THE GREAT PLAINS NORTHWEST TOWARDS
NORTHERN MINNESOTA AND WESTERN ONTARIO ON SUNDAY, WITH A VERY HOT
ENVIRONMENT AHEAD OF THE LOW. 850MB TEMPS ARE ABOVE THE 99TH
PERCENTILE RELATIVE TO CLIMATOLOGY, AND EVEN WITH PARTLY CLEAR SKIES
TONIGHT, THERE WILL BE LITTLE RELIEF FROM THE HEAT OVERNIGHT TONIGHT
AS LOWS ONLY FALL TO THE 70S IN LOCATIONS AWAY FROM LAKE SUPERIOR,
ESPECIALLY EAST-CENTRAL MN AND NORTHWEST WISCONSIN - RECORD WARM LOW
TEMP VALUES FOR BRAINERD (72, FORECAST IS 73) AND APPROACHING THE
RECORD WARM LOW AT OTHER SITES AWAY FROM LAKE SUPERIOR. THE COOLER
LAKE SUPERIOR TEMPERATURES WILL RESULT IN A STRONG LAKE INFLUENCE,
COOLING TEMPERATURES ON THE NORTH SHORE ESPECIALLY. HIGHS ON SUNDAY
WILL BE SIMILAR TO TODAY IN THE UPPER 80S TO MID 90S, WARMEST IN
NORTHWEST WISCONSIN WHERE HEAT INDEX VALUES WILL REACH THE TRIPLE
DIGITS.
AS THE SURFACE LOW APPROACHES, THE SOUTHERLY LOW LEVEL FLOW WILL
HELP TO ADVECT IN ELEVATED INSTABILITY ON THE ORDER OF 3000 TO 4500
J/KG MUCAPE - BUT WITH A VERY STRONG CAP DUE TO THE WARM
TEMPERATURES. BY 00Z SUNDAY EVENING THE WARM FRONT ASSOCIATED WITH
THE SURFACE LOW WILL BE NORTH OF THE INTERNATIONAL BORDER (OR DARN
NEAR IT), AND IF STORMS CAN DEVELOP IN THE WARM SECTOR ACROSS
NORTHERN MINNESOTA, DEEP LAYER SHEAR ON THE ORDER OF 40 KNOTS WOULD
BE MORE THAN SUFFICIENT FOR SUPERCELLS PRODUCING ALL MODES OF SEVERE
WEATHER, QUICKLY MERGING INTO A LINEAR MODE WITH SIGNIFICANT
DAMAGING WIND POTENTIAL. PWAT VALUES IN THE 1.5-1.8" RANGE MEANS
STORMS WOULD BE VERY EFFICIENT RAINFALL PRODUCERS, WITH A LOCALIZED
MINOR FLOOD THREAT DRIVEN BY INTENSE RAINFALL RATES. IN ADDITION TO
THE THREAT FOR STORMS CLOSER TO THE WARM FRONT, ADDITIONAL
THUNDERSTORMS ARE EXPECTED TO DEVELOP IN SOUTHWEST MINNESOTA THAT
COULD LIFT NORTHEAST INTO PARTS OF THE NORTHLAND OVERNIGHT, BUT WITH
A MUCH LOWER THREAT FOR SEVERE WEATHER.
THE SEVERE THREAT ON SUNDAY AFTERNOON/EVENING IS EXTREMELY
CONDITIONAL - IF STORMS DEVELOP THEY PRODUCE PRODUCE TORNADOES, VERY
LARGE HAIL, AND SIGNIFICANT DAMAGING WINDS. HOWEVER, GIVEN THE
STRONG CONVECTIVE INHIBITION PRESENT, THERE IS SIGNIFICANT
UNCERTAINTY IN WHETHER THERE WILL EVEN BE THUNDERSTORMS SOUTH OF THE
US/CANADA BORDER - IT'S POSSIBLE STORMS REMAIN NORTH OF THE BORDER
AND JUST BRUSH FAR NORTHERN MINNESOTA. CONVECTION-ALLOWING GUIDANCE
IS FAIRLY CONSERVATIVE ON THE DEVELOPMENT OF THUNDERSTORMS, BUT IF
STORMS DO DEVELOP THEY COULD PRODUCE SIGNIFICANT DAMAGE.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 627 PM CDT SAT JUN 21 2025
LARGELY VFR ACROSS THE REGION THIS EVENING WITH A FEW POCKETS OF
MVFR CEILINGS ACROSS NORTHERN MN WHERE A WARM FRONT CONTINUES TO
SURGE NORTH. SOME ECHOES MAY FORM OFF THIS BOUNDARY AND PROPAGATE
THROUGH THE NIGHT. NOT EXPECTING MUCH IMPACTS FROM THIS AS IT WILL
LIKELY BE DRIZZLE WITH SOME LOWER CEILINGS POSSIBLE. THROUGH THE
OVERNIGHT HOURS LOWER CEILINGS WILL ENVELOPE THE REGION WITH SOME
POTENTIAL OF FOG IMPACTING DLH/HIB. THESE CEILINGS WILL LINGER ACROSS
NORTHERN MN THROUGH MID MORNING BEFORE DISPERSING. ADDITIONALLY, A
STRONG LOW LEVEL JET WILL LEAD TO LOW LEVEL WIND SHEAR IN HYR
OVERNIGHT.
MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
ISSUED AT 147 PM CDT SAT JUN 21 2025
LATE TODAY INTO TONIGHT NORTHEAST WINDS INCREASE AND AT LEAST PATCHY
FOG WILL REDUCE VISIBILITY TO A MILE OR LESS IN SOME SPOTS, WITH THE
WIND GUSTS INTO THE SMALL CRAFT ADVISORY RANGE, SO WE ISSUED A SMALL
CRAFT ADVISORY FOR THE TWIN PORTS AND NORTH SHORE TONIGHT. A COLD
FRONT MOVING WEST TO EAST ON SUNDAY NIGHT WILL LEAD TO ISOLATED TO
SCATTERED THUNDERSTORMS, AND SOME OF THESE STORMS COULD PRODUCE GALE-
FORCE GUSTS. WEST WINDS 10 TO 15 KNOTS ON MONDAY IN THE WAKE OF THE
COLD FRONT WITH SKIES BECOMING SUNNY. NEXT CHANCE FOR THUNDERSTORMS
MID-WEEK.
FOR THE OPEN WATER DISCUSSION, REFER TO THE NWS MARQUETTE AREA
FORECAST DISCUSSION AT WEATHER.GOV/MQT.
DLH WATCHES/WARNINGS/ADVISORIES
MN...HEAT ADVISORY UNTIL 9 PM CDT SUNDAY FOR MNZ010>012-018-019-037.
EXTREME HEAT WARNING UNTIL 9 PM CDT SUNDAY FOR MNZ025-026-
033>036-038.
WI...EXTREME HEAT WARNING UNTIL 9 PM CDT SUNDAY FOR WIZ001>004-
006>009.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 4 AM CDT
SUNDAY FOR LSZ140>145.
DISCUSSION...JJM
AVIATION...BRITT
MARINE...JJM
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