933
FXUS63 KMQT 091739
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
139 PM EDT SAT AUG 9 2025
KEY MESSAGES
- HEAT AND HUMIDITY INCREASES THIS WEEKEND. THE CHANCE OF HEAT
INDICES EXCEEDING 90 DEGREES IS GREATER THAN 50% TODAY FOR
MOST AREAS.
- A LINE OF THUNDERSTORMS, SOME STRONG TO SEVERE, IS EXPECTED TO
MOVE ACROSS THE WEST-CENTRAL UP THIS MORNING TO EARLY
AFTERNOON.
- ADDITIONAL ROUNDS OF SHOWERS AND THUNDERSTORMS ARE POSSIBLE
THIS AFTERNOON. LOCALIZED FLOODING IS POSSIBLE WHERE TRAINING
THUNDERSTORMS OCCUR.
SHORT TERM /THROUGH SUNDAY/
ISSUED AT 139 PM EDT SAT AUG 9 2025
MORNING RAP ANALYSIS SHOWS A 1001MB LOW PRESSURE CENTERED OVER LAKE
WINNIPEG THAT HAS A SURFACE TROUGH DRAPED FROM ITS EASTERN SIDE DOWN
THROUGH THE WESTERN UP DOWN INTO THE MISSISSIPPI RIVER VALLEY. EARLY
MORNING RADAR AND SATELLITE TRENDS HAVE STRUGGLED TO MAINTAIN
CONVECTION, WHICH IS SUSPECTED TO BE A COMBINATION OF SUBSTANTIAL
LOW-TO-MID LEVEL CIN AND THE NATURE OF STORMS BEING OUTFLOW-
DOMINATED WITH NOT MUCH SHEAR PRESENT. TO THE FIRST POINT, SURFACE
DESTABILIZATION LOOKS TO BE OCCURRING IN THE CENTRAL UP PER THE RAP
WITH UP TO 2500 J/KG OF SBCAPE. HOWEVER, WITH THE NOCTURNAL LLJ
DIMINISHING, THE ALREADY POOR SHEAR IS NOT HELPING THE SECOND POINT.
STILL, WITH THE SURFACE TROUGH PROVIDING FORCING AND SURFACE DEW
POINTS IN THE MID 70S ALREADY, THE POTENTIAL FOR A VIGOROUS UPDRAFT,
EVEN IF BRIEF, IS TOO HIGH TO IGNORE. MOST OF THE MORNING CAM RUNS
HAVE BEEN TOO SLOW WITH CONVECTION AND MANY SHOWED THUNDERSTORMS
EARLY IN THE RUN OVER THE UP THAT WERE MUCH STRONGER THAN THEY
ACTUALLY WERE. THAT BEING SAID, ONCE THE ONGOING LINE OF STORMS
APPROACHES THE EASTERN UP BY AROUND 21Z THIS AFTERNOON, SOME CAMS
(NAMELY THE HRRR AND WRF ARW) SHOW A SECOND ROUND OF THUNDERSTORMS
THREATENING THE CENTRAL UP IN THE 22-00Z TIMEFRAME. THIS SECOND
ROUND, THE INSTABILITY AND SHEAR WILL BE FLIPPED ON THEIR HEADS,
WITH THE BETTER SHEAR ARRIVING WITH 0-3KM SRH VALUES JUMPING UP
AROUND 150, BUT THE INSTABILITY WILL BE WANING SOMEWHAT, WITH ONLY
AROUND 1000 J/KG EXPECTED. GIVEN THE HGZ IS STILL AROUND 500MB, HAIL
CONTINUES TO NOT BE THE PRIMARY THREAT, BUT DAMAGING WINDS AND
FREQUENT LIGHTNING WILL BE IN PLAY. SOME 1"/HR RAINFALL RATES MAY BE
OBSERVED, BUT STORM MOTION APPEARS TO KEEP MOST FLASH-FLOODING
CONCERNS AT BAY. THE CEILING OF IMPACTS IS HIGH ENOUGH TO WARRANT
THE SPC ISSUING A SLIGHT RISK (CATEGORY 2 OF 5) FOR SEVERE WEATHER
(PRIMARILY DAMAGING WIND) AND THE WPC ISSUING A MARGINAL RISK
(CATEGORY 1 OF 4) FOR EXCESSIVE RAINFALL.
THE HRRR STILL CAN'T GET ENOUGH OF CONVECTION TONIGHT THOUGH, AS IT
HAS YET ANOTHER ROUND OF ISOLATED CONVECTION IN THE 00Z-04Z RANGE
TONIGHT, THOUGH SUPPORT FOR THAT SOLUTION IS MOSTLY IGNORED BY THE
REST OF THE 12Z CAM SUITE. SCATTERED LIGHT RAIN SHOWERS ARE THEN
FORECAST INTO SUNDAY, WHERE THE CAMS ARE SOMEWHAT SPLIT ON THE
POTENTIAL FOR DIURNAL CONVECTION IN THE INTERIOR UP. SHOULD
CONVECTION OCCUR, THE CONTINUED PRESENCE OF A WARM, MOIST SURFACE
AIRMASS WILL HELP INSTABILITY VALUES OF AROUND 500-1000 J/KG PERSIST
AND HODOGRAPHS DO SHOW BETTER SHEAR PROFILES. GIVEN THE LACK OF
FORCING, CONFIDENCE REMAINS LOW.
THE OTHER HAZARD IN THE SHORT TERM IS THE HEAT RISK. GIVEN EXTENSIVE
CLOUD COVER, TEMPERATURES ARE NOT GOING TO GET OUT OF CONTROL TODAY
(HIGHS IN THE MID 80S), BUT THE AFOREMENTIONED DEW POINTS IN THE 70S
WILL MAKE IT FEEL MUGGY AND MAKE COOLING OFF MORE CHALLENGING. SOME,
BUT NOT MUCH, RELIEF IS EXPECTED OVERNIGHT AS LOWS FALL INTO THE
60S, BUT HIGHS IN THE 80S WITH DEW POINTS IN THE 70S RETURN FOR
SUNDAY. HEAT INDICES IN THE 90S WILL BE POSSIBLE, ESPECIALLY IN
AREAS ALONG LAKE SUPERIOR WHERE OCCASIONALLY GUSTY SOUTHERLY WINDS
WILL DOWNSLOPE AND WARM FURTHER THAN HIGHER ELEVATION COUNTERPARTS
FURTHER INLAND.
LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/
ISSUED AT 349 PM EDT FRI AUG 8 2025
00Z SUNDAY THROUGH 00Z MONDAY, THE CUTOFF UPPER LOW WILL LIFT INTO
THE HUDSON BAY, WITH ENSEMBLES SHOWING VARIANCES IN THE PRESENCE OF
EMBEDDED SHORTWAVES THAT KEEP POPS IN THE FORECAST BUT CONFIDENCE IN
THE PRECISE DETAILS LOW. A REINFORCING SHORTWAVE LOOKS TO DROP DOWN
FROM MANITOBA LATE MONDAY INTO TUESDAY, PROVIDING ANOTHER MECHANISM
FOR ACTIVE WEATHER, THOUGH SIGNIFICANT DIFFERENCES ARE OBSERVED IN
THE GLOBAL DETERMINISTIC SUITE WITH THE GFS SHOWING A VERY FLAT AND
WEAK WAVE WHILE THE CANADIAN SHOWS A QUITE DEEP CUTOFF LOW AND THE
EURO FALLING IN BETWEEN. INSTABILITY WILL BE PRESENT BUT NOT NEARLY
TO THE DEGREE OF SATURDAY, WITH THE 75TH PERCENTILE OF SBCAPE IN THE
LREF BEING SUB-1000 J/KG BY TUESDAY AFTERNOON. PERSISTING SOUTHWEST
FLOW ALOFT WILL KEEP WARM, MOIST AIR IN THE FORECAST, BUT THE
PRESENT CLOUD COVER WILL KEEP HIGH TEMPERATURES MAINLY AROUND THE 80
DEGREE MARK EVEN AS LOW TEMPERATURES STRUGGLE TO FALL BELOW 60
DEGREES THANKS TO THE EVER-PRESENT HUMIDITY (NAEFS HUMIDITY CHARTS
ARE ALMOST ALWAYS ABOVE THE 90TH CLIMATE PERCENTILE INTO NEXT
WEEKEND). RIDGING LOOKS TO FOLLOW FOR NEXT MIDWEEK, GIVING A DRY
PERIOD, BUT SPREAD INCREASES FURTHER GOING TOWARDS THE END OF THE
WEEK. WHILE ENSEMBLE MEAN DAILY PRECIP CHARTS SHOW SOME CHANCES OF
RAIN JUST ABOUT EVERY DAY, THE CHANCES OF OVER AN INCH OF RAINFALL
IN A DAY ARE 10 PERCENT OR LESS AFTER TUESDAY.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 139 PM EDT SAT AUG 9 2025
VFR CONDITIONS ARE OBSERVED AT ALL SITES WITH ALL SITES AFFECTED BY
SHOWERS AND THUNDERSTORMS RECENTLY. WHILE PRECIP WILL CLEAR OUT OF
IWD AND CMX THIS EVENING, FURTHER WAVES OF PRECIPITATION WILL AFFECT
SAW INTO THIS EVENING AND POTENTIALLY SUNDAY. LOW LEVEL HUMIDITY
WILL BRING WITH IT THE THREAT OF FG FORMATION AT ALL SITES, WITH
GUIDANCE SUGGESTING AROUND A 25 PERCENT CHANCE OF VISIBILITY
REDUCTIONS (AND AROUND 10 PERCENT CHANCE OF LIFR CONDITIONS).
HOWEVER, GIVEN PERSISTENT SOUTH TO SOUTHWEST WINDS GUSTING OVER 10
KT EXPECTED THROUGHOUT THE NIGHT, WILL LEAVE FG MENTION OUT OF THIS
TAF.
MARINE
ISSUED AT 139 PM EDT SAT AUG 9 2025
WIND GUSTS TO 20 KT WILL BE PRIMARILY LIMITED TO THE IMMEDIATE
VICINITY OF THUNDERSTORMS THAT WILL CONTINUE TO BE OVER THE EAST
HALF OF THE LAKE THROUGH TONIGHT, WITH THE FAR EASTERN END OF THE
LAKE RETAINING THUNDERSTORM CHANCES THROUGH SUNDAY. TUESDAY WILL
ALSO BRING CHANCES OF WIND GUSTS UP TO 25 KT OUT OF THE SOUTHWEST AS
A DISTURBANCE PASSES OVER THE LAKE. WITH THE ONGOING HOT AND HUMID
CONDITIONS FOLLOWING SHOWERS, CHANCES OF DENSE FOG INCREASE THROUGH
SUNDAY, THOUGH THE ONGOING SOUTHERLY TO SOUTHWESTERLY WINDS ARE
KEEPING FOG MOSTLY AWAY FOR THE TIME BEING.
MQT WATCHES/WARNINGS/ADVISORIES
UPPER MICHIGAN...
BEACH HAZARDS STATEMENT UNTIL 10 PM EDT THIS EVENING FOR
MIZ014.
LAKE SUPERIOR...
NONE.
LAKE MICHIGAN...
NONE.
SHORT TERM...GS
LONG TERM...GS
AVIATION...BW
MARINE...GS
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