105
FXUS63 KDLH 091137
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
637 AM CDT TUE SEP 9 2025
KEY MESSAGES
- SHOWERS AND THUNDERSTORMS CONTINUE THROUGH TODAY, SLOWLY
SLIDING SOUTHEAST INTO NORTHWEST WISCONSIN.
- RAINFALL, HEAVY AT TIMES, MAY LEAD TO LOCALIZED FLASH FLOODING
WHERE STORMS REPEATEDLY MOVE OVER THE SAME LOCATION THIS
MORNING.
- AREAS OF DENSE FOG IN NORTH-CENTRAL MINNESOTA EARLY THIS
MORNING. MORE WIDESPREAD DENSE FOG IS POSSIBLE FOR MUCH OF THE
NORTHLAND (40-70% CHANCE) FOR TONIGHT INTO EARLY WEDNESDAY
MORNING.
- QUIETER WEATHER TAKES OVER FOR WEDNESDAY AND THURSDAY, WITH
SHOWER AND THUNDERSTORM CHANCES RETURNING FRIDAY INTO THIS
WEEKEND.
DISCUSSION
ISSUED AT 343 AM CDT TUE SEP 9 2025
TODAY - TONIGHT:
AT THE SURFACE EARLY THIS MORNING, LOW PRESSURE IS CENTERED OVER
WEST-CENTRAL MINNESOTA WITH A STATIONARY FRONT EXTENDING
EASTWARD INTO THE IRON RANGE AND WESTERN LAKE SUPERIOR.
VORTICITY ALOFT ON THE LEADING EDGE OF A MID/UPPER-LEVEL
SHORTWAVE TROUGH INTERACTING WITH THE FRONT AND ISENTROPIC
ASCENT INTO AND JUST NORTH OF THE FRONTAL ZONE ON THE NOSE OF A
LOW-LEVEL JET IS CONTINUING TO KICK OFF ELEVATED SCATTERED
SHOWERS AND STORMS FROM GRAND RAPIDS EAST TO TWO HARBORS/SILVER
BAY AND ACROSS PARTS OF THE SOUTH SHORE AND MUCH OF WESTERN LAKE
SUPERIOR. HOURLY RAINFALL WITH THIS PRECIPITATION IS GENERALLY
ON THE ORDER OF 0.5-1.25" PER HOUR DUE TO SFC-FREEZING LEVEL
SATURATION DEPTHS OF ~10 KFT, ABOVE AVERAGE PWATS OF 1.1-1.5",
AND UNIDIRECTIONAL FLOW THROUGH THE DEPTH OF THE STORMS BEING
PARALLEL TO THE SURFACE FRONT LEADING TO BOTH EFFICIENT RAINFALL
RATES AND REPEATED MOTION OF THE STORMS OVER THE SAME LOCATIONS.
WHILE WIDESPREAD HEAVY RAINFALL IS NOT EXPECTED, PONDING OF
WATER AND LOCALIZED FLASH FLOODING REMAINS POSSIBLE EAST OF THE
I-35 INTO THE SOUTH SHORE AND PORTIONS OF NORTHWEST WISCONSIN
EARLY THIS MORNING WHERE STORMS CAN REPEATEDLY MOVE OVERHEAD. WHILE
EFFECTIVE SHEAR IS STILL 25-30 KT AS OF 3:30 AM CDT, THE LOW-
LEVEL JET IS EXPECTED TO WEAKEN WITH TIME AS WE PROGRESS INTO
THE DAYLIGHT HOURS TODAY, LEADING TO DECREASING STORM COVERAGE
AND STORMS BECOMING LESS COHERENT WITH TIME. STORMS WILL ALSO
SLOWLY CONTINUE TRACKING SOUTHEAST INTO NORTHWEST WISCONSIN
TODAY AS THE STATIONARY FRONT ALSO STARTS TO TRACK THAT
DIRECTION, AS WELL. LIGHTER SHOWERS AND SOME EMBEDDED STORMS
PERSIST DURING THE DAYLIGHT HOURS BEFORE GRADUALLY EXITING TO
THE EAST OF NORTHWEST WISCONSIN TONIGHT.
ANOTHER HAZARD THROUGH EARLY THIS MORNING IS DENSE FOG OVER
NORTH-CENTRAL MINNESOTA AS WELL AS ALONG THE NORTH SHORE NORTH
OF TACONITE HARBOR/TOFTE WHERE THERE HAS BEEN CLEARING ON THE
NORTHERN EDGE OF THE CLOUD AND PRECIPITATION SHIELDS,
RESPECTIVELY. AREA WEBCAMS AND SURFACE OBSERVATIONS ALREADY
SHOW SEVERAL LOCATIONS WITH 1/4 MILE VISIBILITY OR LESS IN
NORTHERN ITASCA AND KOOCHICHING COUNTIES. IF THIS FOG CONTINUES
TO EXPAND, DENSE FOG ADVISORIES MAY BE WARRANTED.
HREF AND RRFS ENSEMBLES, AS WELL AS EVEN NBM PROBABILITIES FOR
MORE WIDESPREAD DENSE FOG (VISIBILITIES OF LESS THAN OR EQUAL TO
1/4 MILE) INCREASE AGAIN FOR TONIGHT INTO EARLY WEDNESDAY
MORNING FOR MUCH OF THE NORTHLAND, GENERALLY IN THE 40-70%
RANGE. IF THIS SIGNAL HOLDS OR INCREASES, ANOTHER DENSE FOG
ADVISORY WOULD LIKELY BE NEEDED FOR TONIGHT.
WEDNESDAY - THURSDAY:
FOG WILL BE DISSIPATING BY MID TO LATE WEDNESDAY MORNING. THE
UPPER-LEVEL PATTERN FOR WEDNESDAY INTO THURSDAY WILL FAVOR A
RIDGE MOVING THROUGH THE UPPER MIDWEST AND SURFACE HIGH PRESSURE
SLIDING EAST ACROSS ONTARIO. THIS SHOULD KEEP THE NORTHLAND
LARGELY DRY DURING THIS TIMEFRAME, THOUGH SOME LINGERING LOW-
LEVEL MOISTURE IN NORTH-CENTRAL WI COULD KEEP A FEW
SPRINKLES/SHOWERS PERSISTING INTO WEDNESDAY AFTERNOON (10-20%
CHANCE). LITTLE TO NO ADDITIONAL ACCUMULATIONS EXPECTED.
TEMPERATURES REMAIN ON THE MORE MILD SIDE THAN PREVIOUS DAYS,
WITH HIGHS IN THE MID 60S TO MID 70S AND LOWS IN THE UPPER 40S
TO 50S.
THURSDAY NIGHT - THIS WEEKEND:
TEMPERATURES TOP OUT ON FRIDAY AS THE AXIS OF THE RIDGE MOVES
OVER THE NORTHLAND, WITH HIGHS IN THE 70S FOR MOST TO EVEN
AROUND 80F FOR SOME LOCATIONS. SOME LOW-END SHOWER AND
THUNDERSTORM CHANCES (20-40%) RETURN FOR THURSDAY NIGHT THROUGH
FRIDAY AS SOME SUBTLE SHORTWAVE ENERGY ROUNDS THE TOP OF THE
MID/UPPER-LEVEL RIDGE, BUT THE SHEAR/INSTABILITY PARAMETER SPACE
AT THIS JUNCTURE DOES NOT APPEAR TO SUPPORT SEVERE WEATHER.
ENSEMBLES SHOW SOME VARIATION OF POSITIVELY-TILTED SHORTWAVE
ENERGY/TROUGHING MOVING BACK INTO THE UPPER MIDWEST AND/OR
NORTHERN PLAINS SATURDAY INTO EARLY NEXT WEEK, WHICH COULD BRING
ADDITIONAL PRECIPITATIONS CHANCES DURING THAT TIMEFRAME.
HOWEVER, THERE IS A FAIRLY STRONG SIGNAL IN AN OMEGA-BLOCKING
PATTERN SETTING UP SOMEWHERE IN THE CENTRAL/NORTH-CENTRAL CONUS
VICINITY, SO EXACT PLACEMENT OF THIS PATTERN COULD STILL VARY
ENOUGH THAT CONFIDENCE IN PRECIPITATION POTENTIAL AND TIMING
THIS WEEKEND INTO EARLY NEXT WEEK IS LOW.
AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 637 AM CDT TUE SEP 9 2025
THE STATIONARY FRONT IS STILL SITUATED FROM BWP TO GPZ TO ELO,
WITH LOCATIONS NORTH OF THE FRONT SOCKED INTO LIFR TO VLIFR
CEILINGS AND/OR VISIBILITIES. TERMINALS SOUTH OF THE FRONT ARE
LARGELY MVFR CEILINGS AND VFR VISIBILITIES, WITH POCKETS OF VFR
CEILINGS. SOME SCATTERED SHOWERS AND STORMS ARE ALSO PRESENT
ACROSS THE SOUTH SHORE, SLOWLY MOVING SOUTHEASTWARDS. AS THE
SURFACE FRONT SLOWLY MOVES SOUTHEAST TODAY, CAN'T RULE OUT A
FEW SHOWERS AND STORMS PRIMARILY IN NORTHWEST WISCONSIN.
DETERIORATING CEILINGS WILL ALSO ACCOMPANY THE FRONTAL PASSAGE,
THOUGH BRIEF IMPROVEMENT TO MVFR/VFR CONDITIONS ARE EXPECTED FOR
MANY NORTHEAST MINNESOTA TERMINALS FOR PORTIONS OF THIS
AFTERNOON AND EVENING AS THE FRONT DEPARTS. HOWEVER, THERE IS A
STRONG SIGNAL FOR MORE WIDESPREAD FOG/LOW STRATUS DEVELOPMENT
FOR MUCH OF THE AREA LATER THIS EVENING AND TONIGHT. WE HAVE
OPTED TO GO THE MORE PESSIMISTIC ROUTE WITH THIS UPDATE AND
GIVE MOST TERMINALS LIFR TO VLIFR CEILINGS AND VISIBILITIES IN
THIS PATTERN.
MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
ISSUED AT 343 AM CDT TUE SEP 9 2025
ROUNDS OF SHOWERS AND THUNDERSTORMS CONTINUE TODAY, THOUGH MUCH
OF THE ACTIVE THUNDERSTORM ACTIVITY HAS NOW FOCUSED ALONG THE
SOUTH SHORE AND WILL CONTINUE TO SLOWLY TREND SOUTHEAST WITH
TIME TODAY. CLOUD-TO-WATER LIGHTNING AND WIND GUSTS UP TO 30
KNOTS WILL BE THE PRIMARY THREATS. SOUTH TO SOUTHWEST WINDS
WITH WITH GUSTS TO 20 TO 25 KNOTS TONIGHT PERSIST THROUGH MID-
MORNING IN THE OUTER APOSTLES TO SAXON HARBOR. SMALL CRAFT
ADVISORIES REMAIN IN EFFECT. WINDS REMAIN SOUTHWESTERLY LATER
TODAY AND DECREASE TO 10 TO 20 KNOTS DURING THE AFTERNOON BEFORE
FURTHER WEAKENING TONIGHT. WINDS THEN TURN NORTHEASTERLY AT 5
TO 15 KNOTS FOR WEDNESDAY.
ANOTHER CONCERN WILL BE MARINE DENSE FOG TODAY FOR AREAS NORTH
OF THE PRECIPITATION SHIELD ALONG THE NORTH SHORE. A MARINE
DENSE FOG ADVISORY HAS BEEN ISSUED FROM TACONITE HARBOR TO GRAND
PORTAGE. WEATHER MODELS SHOW AN INCREASING POTENTIAL FOR
WIDESPREAD DENSE MARINE FOG ACROSS WESTERN LAKE SUPERIOR TONIGHT
INTO EARLY WEDNESDAY MORNING, GENERALLY A 40-70% CHANCE OF
VISIBILITIES OF 1 NM OR LESS OCCURRING. IF THIS TREND HOLDS,
MARINE DENSE FOG ADVISORIES WILL LIKELY BE NEEDED TONIGHT.
FOR THE OPEN WATER DISCUSSION, REFER TO THE NWS MARQUETTE AREA
FORECAST DISCUSSION AT WEATHER.GOV/MQT.
DLH WATCHES/WARNINGS/ADVISORIES
MN...DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR MNZ010-011-
018-021-025-026.
WI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 AM CDT THIS MORNING FOR LSZ121-
148-150.
DENSE FOG ADVISORY UNTIL 10 AM CDT THIS MORNING FOR LSZ140-141.
DISCUSSION...ROTHSTEIN
AVIATION...ROTHSTEIN
MARINE...ROTHSTEIN
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