005
FXUS63 KGRR 231736
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
136 PM EDT WED APR 23 2025
KEY MESSAGES
- SEVERAL CHANCES OF SHOWERS/STORMS THROUGH FRIDAY NIGHT
- WARMING THROUGH LATE WEEK
- WARM WITH SHOWER/STORM CHANCES TUESDAY
DISCUSSION
ISSUED AT 313 AM EDT WED APR 23 2025
- SEVERAL CHANCES OF SHOWERS/STORMS THROUGH FRIDAY NIGHT
SEVERAL CHANCES FOR SHOWERS AND STORMS EXIST OVER THE NEXT 72 HOURS.
THE TWO BEST CHANCES ARE LATER TODAY INTO THURSDAY, AND THURSDAY
NIGHT INTO FRIDAY.
TODAY, A WEAK FRONTAL BOUNDARY IS FORECAST TO STALL ACROSS THE UPPER-
MIDWEST. THE ARRIVAL OF A 700MB WAVE WILL BE SUFFICIENT TO FORCE
THUNDERSTORM DEVELOPMENT LATE TODAY/TONIGHT IN CONJUNCTION WITH THIS
BOUNDARY. THE BEST COVERAGE IS EXPECTED TO BE ACROSS NORTHWESTERN
PORTIONS OF OUR FORECAST AREA THAT ARE CLOSER TO SURFACE CONVERGENCE
AND THE MID-LEVEL WAVE. ISOLATED STRONG TO SEVERE STORMS CANNOT BE
RULED OUT WITH STEEP LAPSE RATES AND EFFECTIVE SHEAR OF 25-30 KNOTS,
MAINLY ACROSS OUR NORTHWESTERN FORECAST AREA. HAIL AND GUSTY WINDS
ARE THE CONCERNS IF ANY STORMS CAN ORGANIZE.
PRECIPITATION CHANCES ARE NOTABLY HIGHER, ON THE ORDER OF 70-90
PERCENT, THURSDAY NIGHT INTO FRIDAY. RAIN CHANCES ARE DUE TO A PAIR
OF MID-LEVEL SHORTWAVES DRIVING A SURFACE LOW THROUGH THE AREA. THE
BEST CHANCE OF THUNDER WITH THIS SYSTEM COMES FRIDAY AFTERNOON AS A
FEW HUNDRED JOULES OF MUCAPE BUILD ACROSS THE SOUTHEASTERN FORECAST
AREA.
SURFACE AND UPPER-LEVEL RIDGING THEN ARRIVES FOR THE WEEKEND. THIS
WILL KEEP CONDITIONS DRY ACROSS WEST MICHIGAN.
- WARMING THROUGH LATE WEEK
ABOVE NORMAL TEMPERATURES ARE EXPECTED THE NEXT SEVERAL DAYS, WITH
HIGHS INTO THE 70S TODAY AND SOME AREAS REACHING THE 80S THURSDAY.
FOR REFERENCE, NORMAL HIGHS THIS TIME OF YEAR ARE IN THE LOW SIXTIES
IN GRAND RAPIDS. TEMPERATURES THEN COOL DOWN FRIDAY INTO SATURDAY,
ALBEIT WITH TEMPS STILL NEAR TO ABOVE NORMAL, AS NORTHERLY FLOW
TAKES HOLD.
- WARM WITH SHOWER/STORM CHANCES TUESDAY
WARM AIR ADVECTION RESUMES EARLY NEXT WEEK WITH 850MB TEMPS CLIMBING
INTO THE MID TEENS TUESDAY. THIS WILL BRING PLENTY OF WARMTH AS
HIGHS CLIMB BACK INTO THE UPPER 70S OR 80S.
THE OVERALL SYNOPTIC PATTERN SHOWS THAT A MID-LEVEL WAVE WILL DRIVE
A COLD FRONT ACROSS THE REGION. LREF MEMBERS SHOW AN EXPANSIVE
WARM SECTOR DEVELOPING ACROSS THE REGION, INCLUDING LOWER
MICHIGAN, WITH MEAN DEWPOINTS IN THE LOWER 60S. WITH THE
ECMWF/GFS SHOWING SUFFICIENT DEEP LAYER SHEAR, STORMS COULD BE
STRONGER, THOUGH THIS OUTCOME IS UNCERTAIN. CLUSTER ANALYSIS SHOWS
A SPLIT IN WHEN THE SHORTWAVE AND SURFACE FRONT ARRIVE, WITH THE
TIMING BEING KEY TO WHETHER STRONGER STORMS CAN OCCUR. TUESDAY
COULD BE AN ACTIVE DAY, WITH REFINEMENT OF THE FORECAST EXPECTED
IN THE DAYS TO COME.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 136 PM EDT WED APR 23 2025
WE ARE STARTING THIS FORECAST PACKAGE OUT WITH LOTS OF MID LEVEL
CLOUDS BASED AROUND 7-10K FT AGL, AND SOME LIGHT RAIN SHOWERS
SCATTERED AROUND. THE CURRENT BATCH OF SHOWERS AND THE NEXT BATCH
OVER THE LAKE SHOULD MOVE THROUGH THE TERMINALS THROUGH ABOUT
21-23Z. VFR CONDITIONS WILL DOMINATE, BUT CAN'T RULE OUT A BRIEF
ISOLATED BOUT OF MVFR UNDER HEAVIER PARTS OF SHOWERS.
ADDITIONAL SHOWERS OCCURRING OVER SOUTHERN WI WILL TEND TO LIFT TO
THE NE, AND ARE LOOKING MORE LIKELY TO MISS THE TERMINALS LATER
THIS EVENING AND OVERNIGHT. WE HAVE ADDED IN SOME VCSH AT KMKG TO
ACCOUNT FOR THIS. THE OTHER TERMINALS ARE EXPECTED TO MISS OUT ON
THE SHOWERS LATER, AND COULD EVEN POTENTIALLY CLEAR OUT
OVERNIGHT.
MARINE
ISSUED AT 313 AM EDT WED APR 23 2025
NO MARINE CONCERNS OVER THE NEXT FEW DAYS AS WEAK GRADIENT WINDS ARE
EXPECTED ACROSS THE AREA. A STABLE PROFILE WILL LIMIT ANY MIXING
DOWN OF WINDS ALOFT AS WELL. WAVES SHOULD REMAIN TWO FEET OR LESS
OVER THE NEXT 48 HOURS. THE NEXT PERIOD OF INCREASED WINDS OVER THE
LAKE IS LATER FRIDAY INTO SATURDAY AS NORTHERLY FLOW INCREASES
BEHIND A DEPARTING LOW. SCATTERED THUNDERSTORMS ARE ALSO POSSIBLE
OVER THE LAKE THIS AFTERNOON, PARTICULARLY NORTH OF MUSKEGON.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...THOMAS
AVIATION...NJJ
MARINE...THOMAS
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