050
FXUS63 KGRR 131932
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
332 PM EDT TUE MAY 13 2025
KEY MESSAGES
- SCATTERED SHOWERS AND STORMS THROUGH WEDNESDAY
- SEVERE THUNDERSTORMS POSSIBLE THURSDAY EVENING/NIGHT
- BREEZY FRIDAY WITH SHOWERS FRIDAY NIGHT INTO SATURDAY MORNING
DISCUSSION
ISSUED AT 329 PM EDT TUE MAY 13 2025
- SCATTERED SHOWERS AND STORMS THROUGH WEDNESDAY
INSTABILITY DRIVEN BY A MID-LEVEL COLD POOL WILL BRING SCATTERED
SHOWERS AND THUNDERSTORMS OVER THE NEXT 24-30 HOURS. THERE WILL BE A
DIURNAL COMPONENT TO THIS, AS IS COMMON WITH THESE EVENTS, WITH
BETTER COVERAGE IN THE AFTERNOON/EVENING EACH DAY. THERE IS ALSO A
SIGNAL FOR GREATER COVERAGE LATE THIS AFTERNOON INTO THE EARLY
EVENING ACROSS THE WESTERN HALF OF THE CWA AS THE ADVANCING LAKE
BREEZE COLLIDES WITH EASTERLY FLOW.
LITTLE IN THE WAY OF CAPPING IS PRESENT, WITH AROUND 1000-1500 J/KG
MUCAPE SUPPORTING THE POTENTIAL FOR THUNDER THIS AFTERNOON AND
WEDNESDAY. SHEAR IS MINIMAL, AT OR BELOW 15 KNOTS. STRONG STORMS ARE
NOT EXPECTED, BUT ISOLATED SMALL HAIL OR GUSTY WINDS IS NOT
COMPLETELY OUT OF THE QUESTION IN A STRONGER UPDRAFT. THE BETTER
RISK IS FOR LOCALLY HEAVY RAINFALL AS STORM MOTIONS WILL BE SLOW
GIVEN WEAK FLOW ALOFT. PRECIPITATION WINDS DOWN WEDNESDAY NIGHT AS
THE UPPER-LOW MOVES AWAY.
- SEVERE THUNDERSTORMS POSSIBLE THURSDAY EVENING/NIGHT
THE POTENTIAL FOR THE MOST IMPACTFUL WEATHER IN THE CURRENT PACKAGE
IS THURSDAY EVENING/NIGHT. A MID-LEVEL WAVE IN CONJUNCTION WITH A
COLD FRONT WILL INITIATE STORMS ACROSS WISCONSIN THURSDAY AFTERNOON.
THESE STORMS WILL MOVE EAST REACHING WEST MICHIGAN SOMETIME THURSDAY
EVENING AND MOVE ACROSS THE AREA THROUGH LATE THURSDAY NIGHT.
THE PARAMETER SPACE IS FAVORABLE FOR SEVERE STORMS WITH OUR AREA
SEEING AN OVERLAP OF BOTH GOOD FORCING AND THE BEST INSTABILITY.
OVER 1500 J/KG MLCAPE AND OVER 2000 J/KG MUCAPE ARE POSSIBLE GIVEN
DEWPOINTS IN THE 60S UNDER STEEPER MID-LEVEL LAPSE RATES. DEEP LAYER
SHEAR AROUND 30-40 KNOTS WILL BE FAVORABLE FOR ORGANIZED STORMS
WITH AMPLE SRH TO SUPPORT THE POTENTIAL FOR ROTATING HODOGRAPHS.
DAMAGING WINDS, LARGE HAIL, AND TORNADOES ARE ALL POSSIBLE IN THIS
ENVIRONMENT.
HOWEVER SOME UNCERTAINTY TO THE EXACT TIMING, COVERAGE, AND
INTENSITY OF STORMS EXISTS. GUIDANCE VARIES ON WHEN EXACTLY STORMS
ARRIVE AFFECTING THEIR POTENTIAL STRENGTH. ALSO, STORM MODE IS
UNCERTAIN. CAN THE STORMS OVER WISCONSIN GROW UPSCALE INTO A QLCS
BY THE TIME THEY ARRIVE? OR DO THEY REMAIN AT LEAST SEMI-DISCRETE
SUPERCELLS, THE DIFFERENCE HAVING IMPLICATIONS FOR TORNADO
POTENTIAL. THE EXTENT OF THE EML AND MID-LEVEL DRY AIR ON CIN IS
ALSO A FACTOR TO MONITOR. OVERALL, WHILE UNCERTAINTY REMAINS AS TO
IF AND HOW SEVERE WEATHER OCCURS, THERE IS THE POTENTIAL FOR A
SIGNIFICANT SEVERE WEATHER EPISODE ACROSS THE REGION THURSDAY
NIGHT. PEOPLE SHOULD MONITOR THE FORECAST OVER THE NEXT FEW DAYS.
- BREEZY FRIDAY WITH SHOWERS FRIDAY NIGHT INTO SATURDAY MORNING
BEHIND THE FRONT, GUSTY CONDITIONS ARE EXPECTED IN THE COLD AIR
ADVECTION PATTERN. WIND GUSTS IN EXCESS OF 30 MPH ARE POSSIBLE. A
SURFACE TROUGH THEN CROSSES THE AREA LATER FRIDAY THROUGH SATURDAY
MORNING WITH AN UPPER-LOW OVERHEAD. THIS WILL LIKELY BRING AT LEAST
SCATTERED RAIN SHOWERS ACROSS THE AREA. BY THIS WEEKEND, HIGHS WILL
FALL TO NEAR 70 UNDER THE AFOREMENTIONED TROUGH.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 217 PM EDT TUE MAY 13 2025
IFR CONDITIONS WILL CONTINUE AT JXN THROUGH THE EARLY AFTERNOON.
MVFR CIGS LINGER THROUGH MOST OTHER TAF SITES. STILL EXPECTING
CIGS TO IMPROVE AS THE AFTERNOON CONTINUES. THERE REMAINS THE
POTENTIAL FOR STORMS THOUGH THERE REMAINS SOME QUESTION ON HOW
WIDESPREAD ANY STORMS WILL BE. BEST CHANCE FOR STORMS WILL BE
BETWEEN 22Z TO 02Z WITH THE SOUTHERN TAF SITES HAVING THE BEST
CHANCE OF HAVING TSRA. THESE COULD BRING MVFR CONDITIONS WITH
ISOLATED IFR IN HEAVIER DOWNPOURS. LOW CLOUDS AND FOG WILL BRING
MORE WIDESPREAD IFR AND LIFR AFTER 06Z WITH CIGS AND VSBYS
LINGERING THROUGH MOST OF WEDNESDAY MORNING.
MARINE
ISSUED AT 329 PM EDT TUE MAY 13 2025
WINDS AND WAVES WILL REMAIN NON HAZARDOUS THROUGH THE NEXT FEW DAYS.
THERE IS SOME CONCERN FOR LINGERING SHOWERS AND STORMS LATE THIS
AFTERNOON, EARLY THIS EVENING IN THE NEARSHORE WATERS. THERE WILL
BE MORE OF A CONCERN THURSDAY EVENING AS A LINE OF STORMS COULD
BRING STRONG WINDS FOLLOWED BY WINDS GUSTING OVER 30 KNOTS AND
WAVES BUILDING OVER 4 FEET ON FRIDAY AND SATURDAY.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...THOMAS
AVIATION...CERU
MARINE...CERU
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