609
FXUS63 KMQT 181932
AFDMQT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MARQUETTE MI
332 PM EDT MON MAY 18 2026
KEY MESSAGES
- ISOLATED SHOWERS AND POSSIBLY A THUNDERSTORM LATE THIS
AFTERNOON.
- ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS IS EXPECTED
TONIGHT. SOME OF THE STORMS COULD BE SEVERE, MAINLY OVER THE
SOUTHERN HALF OF THE U.P. HEAVY RAINFALL IS ALSO POSSIBLE.
- COOLER THAN NORMAL TEMPERATURES TUESDAY THROUGH THE REST OF
THE WORK WEEK.
DISCUSSION
ISSUED AT 331 PM EDT MON MAY 18 2026
THE PRIMARY FOCUS OF THE FORECAST IS ON THE NEXT 24 HOURS AS A
DYNAMIC LOW PRESSURE SYSTEM LIFTS THROUGH THE REGION. QUIET AND
BENIGN WEATHER FOLLOWS FOR MOST OF THE REMAINDER OF THE WEEK.
LATEST GOES WATER VAPOR IMAGERY PLACE A DEEP TROUGH OVER THE ROCKIES
AND PLAINS WHICH IS MOVING EAST. AN EMBEDDED SHORTWAVE OVER CO IS
EMERGING WHERE A SFC LOW IS ORGANIZING. THESE TWO FEATURES LIFT TO
NORTHWEST WI BY TONIGHT, SUPPORTED BY A RIGHT ENTRANCE REGION OF THE
UPPER LEVEL JET AND STRONG LLJ, BRINGING ANOTHER ROUND OF SHOWERS
AND STORMS TO UPPER MI FOR TONIGHT. AFTERNOON VISIBLE SATELLITE
IMAGERY HAS SHOWN A BRIEF WINDOW OF CLEARING PASSING OVER THE
WESTERN UP ALLOWING FOR TEMPS TO WARM INTO THE 60S TO MID 70S
INTERIOR WEST. COOLER TEMPS ARE NOTED NEAR LAKE SUPERIOR IN THE MID
40S TO MID 50S WHERE A LAKE BREEZE IS MOVING ONSHORE. WHERE
TRANSIENT SHOWERS LINGERED THIS MORNING IN THE EAST AND CLOUD COVER
HAS BEEN STUBBORN, TEMPS ARE IN THE MID 50S TO MID 60S. NOT MUCH
FURTHER WARMING IS ANTICIPATED GIVEN THE BRIEF WINDOW OF CLEARING,
LAKE BREEZE INFLUENCES, AND STATIONARY BOUNDARY PRESSING IN FROM THE
WEST. LATEST SPC MESO-ANALYSIS INDICATES SOME SURFACE INSTABILITY
DEVELOPING, WHICH IS ANTICIPATED TO INCREASE UP TO ~1250 J/KG BY
THIS EVENING PER 12Z HREF MEAN AS TDS RISE INTO THE UPPER 50S TO LOW
60S. WHILE MARGINAL INSTABILITY BUILDS THIS AFTERNOON, SOME ISOLATED
SHOWERS AND STORMS ARE POSSIBLE (20-40% CHANCE). THAT SAID, ~30 KTS
OF SHEAR AND LITTLE FORCING WILL LEAVE CONVECTION SHORT LIVED AND
WEAK.
THE LLJ MOVING IN TONIGHT SIGNIFICANTLY INCREASES SHEAR AFTER SUNSET
WHILE INSTABILITY BEGINS DIMINISHING. WITH COLD FRONT CONVECTION
WELL TO THE SOUTH, DECREASING SBCAPE/LOW LEVEL LAPSE RATES, AND A
CAP STRENGTHENING, IT'S NO SURPRISE THE UP (AND MOST OF WI) HAS BEEN
COMPLETELY REMOVED FROM THE SPC TORNADO OUTLOOK. MUCAPE AND MID
LEVEL LAPSE RATES APPROACHING 7 C/KM LINGER INTO TONIGHT, PROVIDING
A LOW CHANCE FOR STRONG TO SEVERE STORMS WITH LARGE HAIL AND
DAMAGING WINDS. THE DOWNWARD TREND IS ALSO REFLECTED IN THE LATEST
SPC HAIL/WIND OUTLOOKS, DOWNGRADING THE NORTHERN TIER OF THE UP TO
JUST GENERAL THUNDERSTORMS WITH A MARGINAL RISK (~5%) OVER THE
SOUTH. PWATS ~1.5 INCH WITH THE MAIN WAVE TONIGHT WILL YIELD
RAINFALL TOTALS OF A FEW HUNDRETHS TO AROUND 0.5 INCHES, HIGHEST
AMOUNTS OVER THE WEST WHERE THERE IS A 25-50% CHANCE FOR AMOUNTS UP
TO 1 INCH. THIS IS CAPTURED BY THE WPC MARGINAL RISK OF EXCESSIVE
RAINFALL (~5% CHANCE OF EXCEEDING FLASH FLOOD GUIDANCE). OTHERWISE
TEMPS FALL INTO THE 40S AND 50S TONIGHT, COLDEST NORTHWEST.
ISOLATED TO SCATTERED SHOWERS LINGER INTO TUESDAY, HOWEVER
INSTABILITY WILL LIKELY BE ELEVATED AND ONLY BRIEFLY UNCAPPED IN THE
EAST/SOUTH-CENTRAL FOR A FEW HOURS AT BEST. THUNDER IS IN THE
FORECAST, BUT STRONG TO SEVERE STORMS ARE NOT EXPECTED. HIGHS IN THE
EAST HALF ON TUESDAY WILL BE IN THE UPPER 50S TO UPPER 60S, LOWER IN
THE NORTHWESTERN UP WHERE MID 40S TO MID 50S ARE EXPECTED.
FROM THERE, THE LOW DEPARTS TO THE NORTHEAST AND HIGH PRESSURE OVER
THE PLAINS REPLACES IT. THIS MAINTAINS OVER THE GREAT LAKES THROUGH
MOST OF THE WORK WEEK YIELDING DRY WEATHER UNTIL THE WEEKEND.
LINGERING TROUGHING ALOFT KEEPS COLDER NORTHWEST FLOW THROUGH
WEDNESDAY, RESULTING IN TEMPS BETWEEN 5-15 DEGREES BELOW NORMAL;
HIGHS IN THE 40S AND 50S AND LOWS IN THE 30S. A WARMING PATTERN IS
THEN EXPECTED TOWARD NEXT WEEKEND AS MID LEVEL RIDGING SLOWLY BUILDS
OVER THE SOUTHEAST AND EXTENDS UP INTO THE GREAT LAKES. ANOTHER
TROUGH OVER THE ROCKIES ON FRIDAY LOOKS TO MOVE TOWARD THE UPPER
GREAT LAKES DURING THE WEEKEND, BRINGING BACK PRECIP TO THE UP.
INSTABILITY WITH THIS IS LACKING, SO IMPACTFUL STRONG TO SEVERE
STORMS ARE NOT ANTICIPATED.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 152 PM EDT MON MAY 18 2026
VISIBLE SATELLITE REVEALS PARTIAL CLEARING TAKING PLACE OVER THE
WESTERN HALF OF UPPER MICHIGAN AS OF 18Z MON, WITH SURFACE
OBSERVATIONS SHOWING A CORRESPONDING UPWARD TREND IN FLIGHT
CATEGORIES AT AREA TERMINALS. EXPECT AN EVENTUAL TREND BACK DOWN TO
LOW END MVFR OR IFR ROUGHLY 21-00Z THIS EVENING AT KIWD AND KSAW AS
THE NEXT ROUND OF SHOWERS MOVES INTO THE REGION. PROBABILITIES FOR
STRONG TO SEVERE THUNDERSTORMS HAVE DECREASED INTO TONIGHT, BUT WILL
STILL CARRY TSRA AT KIWD AND PROB30S AT KCMX AND KSAW THROUGH ~10Z
TUE. WILL SEE GRADUAL IMPROVEMENT FROM WEST TO EAST AS THE SYSTEM
EXITS TUE MORNING, BUT CIGS WILL LIKELY HOLD AT MVFR IF NOT IFR
UNTIL AFTER 18Z TUE.
MARINE
ISSUED AT 331 PM EDT MON MAY 18 2026
A LOW PRESSURE MOVING NORTHEAST OVER UPPER MICHIGAN AND LAKE
SUPERIOR TONIGHT INTO TUESDAY. THIS TIGHTENS THE PRESSURE GRADIENT
AND INCREASES NORTHEAST WINDS OVER THE WEST AND NORTH-CENTRAL
PORTIONS OF THE LAKE TO 20-30 KTS TONIGHT. AS THE LOW MOVES
OVERHEAD, WINDS BECOME NORTHWEST AND STRONGEST WINDS SHIFT FROM THE
WEST HALF TO THE EAST AS COLDER AIR MOVES IN. PROBABILITIES OF GALES
TO 35 KTS ARE 25% OR LESS, HIGHEST IN THE EAST TUESDAY AFTERNOON.
SHOWERS AND STORMS ARE EXPECTED WITH THIS SYSTEM INTO TUESDAY
MORNING, HOWEVER SEVERE STORMS ARE NO LONGER EXPECTED. THIS RAINFALL
WILL PROLONG FOG OVER THE EAST INTO TUESDAY MORNING. HIGH PRESSURE
RETURNS WINDS TO 20 KTS OR LESS BY WEDNESDAY AFTERNOON, WINDS
LIKELY MAINTAIN LIGHT INTO THE WEEKEND.
MQT WATCHES/WARNINGS/ADVISORIES
UPPER MICHIGAN...
NONE.
LAKE SUPERIOR...
DENSE FOG ADVISORY UNTIL 11 AM EDT TUESDAY FOR LSZ244-264>266.
DENSE FOG ADVISORY FROM 1 AM TO 8 AM EDT TUESDAY FOR
LSZ245>247.
DENSE FOG ADVISORY FROM 8 PM THIS EVENING TO 8 AM EDT TUESDAY
FOR LSZ248>251.
DENSE FOG ADVISORY UNTIL 2 PM EDT TUESDAY FOR LSZ267.
LAKE MICHIGAN...
NONE.
DISCUSSION...77
AVIATION...CB
MARINE...77
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