992
FXUS63 KGRR 271736
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
136 PM EDT MON APR 27 2026
KEY MESSAGES
- SHOWERS AND THUNDERSTORMS EXPECTED THIS AFTERNOON INTO TONIGHT
- RAIN SHOWERS POSSIBLE WEDNESDAY AND THURSDAY
- DRIER AND COOLER FRIDAY AND SATURDAY
DISCUSSION
ISSUED AT 401 AM EDT MON APR 27 2026
- SHOWERS AND THUNDERSTORMS EXPECTED THIS AFTERNOON INTO TONIGHT
FORECAST PARAMETERS HAVE NOT CHANGED MUCH WITH REGARD TO THE
SYSTEM MOVING IN TONIGHT. WE STILL HAVE STRONG WIND FIELDS IN
PLACE WITH 60 KNOTS FORECAST AT 850MB AND 60-70 KNOTS IN THE MID
LEVELS AT 500MB. SO, DEEP LAYER SHEAR REMAINS HIGH AT 50-60 KNOTS.
OUR ISSUE REMAINS THE LACK OF STRONGER INSTABILITY. THE HREF
CONTINUES TO SHOW 500 TO 1,000 J/KG OF MUCAPE WHICH IS NOT OVERLY
IMPRESSIVE. ANOTHER NEGATIVE FACTOR THAT IS RELATED TO THE LOWER
CAPE IS THE FACT THAT WE MAY SEE SOME RAIN MOVE IN THIS AFTERNOON
ASSOCIATED WITH THE ROBUST UPSTREAM CONVECTION. THE RAIN WOULD
OBVIOUSLY HINDER CHANCES AT BETTER DESTABILIZATION. THE SPC
OUTLOOK FOR US HAS NOT CHANGED MUCH OVER THE PAST 3 DAYS WHICH IS
INDICATIVE OF THE STEADINESS OF THE SYSTEM IN THE MODELS. WE ARE
MAINLY LOOKING AT A WIND THREAT GIVEN THE MAGNITUDE OF THE WIND
FIELDS AND THAT IS CONTINGENT ON SEEING SOME BETTER INSTABILITY
MOVE IN. HREF AND MACHINE LEARNING TOOLS LIKE NADOCAST SUPPORT AT
LEAST THE THREAT OF STRONG WINDS ACROSS WESTERN AND SOUTHERN
PORTIONS OF THE FORECAST AREA. HREF HAS A SIGNAL IN THE MAX GUSTS
THAT LAKE MICHIGAN MAY PLAY A ROLE IN SOME OF THE STRONGER WIND
GUSTS AT LEAST IN THE LAKESHORE COUNTIES. SO, WHILE THE THREAT OF
SEVERE WEATHER TONIGHT IS SOMEWHAT LOW THE WIND FIELDS HAVE OUR
INTEREST AND WE WILL BE MONITORING CLOSELY.
RIVERS HAVE BEEN STEADILY FALLING NOW FOR DAYS WHICH IS GOOD. WE
WILL SEE RAIN ON THE ORDER OF A HALF INCH TO AN INCH IN A QUARTER
IN SOME HEAVIER SWATHS. AT THIS POINT WE ARE NOT EXPECTED MAJOR
ISSUE WITH THIS RAIN. THERE MAY BE A DELAY IN THE FALL OR SLIGHT
RISES, BUT NOTHING LIKE WE SAW THE PAST COUPLE OF WEEKS.
- RAIN SHOWERS POSSIBLE WEDNESDAY AND THURSDAY
MUCH LIGHTER RAIN SHOWERS ARE POSSIBLE WEDNESDAY AND THURSDAY. THE
SHOWERS LOOK TO BE DIURNALLY DRIVEN WITH THE UPPER TROUGH
NEARBY/OVERHEAD. WEDNESDAY THE SHOWERS MAY BE AIDED BY A LOW
PASSING BY TO OUR SOUTH. THURSDAY'S CHANCES LOOKS TO BE AIDED BY
THERMALLY DRIVEN FORCING WITH HEAT OF THE DAY PRODUCING TROUGHING
AT THE SURFACE OVER THE LOWER PENINSULA.
- DRIER AND COOLER FRIDAY AND SATURDAY
WE LOOK TO BE DRIER AND COOLER FOR THE END OF THE WEEK. FROST AND
FREEZING TEMPERATURES WILL ONCE AGAIN COME INTO PLAY. WEDNESDAY
NIGHT THROUGH SATURDAY NIGHT (4 NIGHTS IN A ROW) WE COULD BE
DEALING WITH FROST/FREEZE RELATED HEADLINES. THE FRUIT CROP IS IN
FULL SWING AT MOST LOCATIONS SO ONCE WE GET BY THE THUNDER CHANCES
TONIGHT OUR FOCUS WILL PIVOT TO THE COLD AND ITS AFFECTS ON EARLY
SEASON FRUIT AND FLOWERS.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 136 PM EDT MON APR 27 2026
-------------------- KEY CHANGES ------------------------------
- SUDDEN INCREASE IN WINDS TO 35-50 KNOTS LIKELY BEHIND SHOWERS,
ADDED TEMPO MONDAY AFTERNOON
- ADJUSTED TIMING AND RESTRICTIONS FOR OVERNIGHT SHOWERS/STORMS
---------------------------------------------------------------
UPSTREAM WIND AND PRESSURE OBSERVATIONS ACROSS ILLINOIS/WISCONSIN/IOWA
SHOW A WAKE LOW HAS DEVELOPED BEHIND A LINE OF SHOWERS
APPROACHING THE AREA. THIS SUGGESTS THAT A SUDDEN JUMP IN
EAST/SOUTHEAST WIND GUSTS TO 35-50 KNOTS IS LIKELY ALONG THE BACK
EDGE OF AND BEHIND A LINE OF RAIN SHOWERS. THIS IS EXPECTED TO
REACH MKG/AZO I THE 19-20Z TIMEFRAME AND CONTINUE EAST THROUGH THE
AFTERNOON/EVENING CLEARING THE AREA BY 00Z. WINDS THEN RETURN TO
THE LARGE SCALE PATTERN OF 15G30KT ONCE THIS CLEARS. GIVEN
DECREASING INSTABILITY WITH EASTWARD EXTENT, CAN'T RULE OUT A
THUNDERSTORM EMBEDDED WITHIN THE LINE. HOWEVER, CONFIDENCE IN
THUNDER AT ANY GIVEN TERMINAL IS LOW.
A SECOND WAVE OF SHOWERS AND THUNDERSTORMS ARRIVES AFTER 23Z WITH
ISOLATED THUNDERSTORMS POSSIBLE. A SURGE OF MOISTURE WITH THIS
WILL BRING MVFR TO IFR CONDITONS TO ALL TERMINALS. SHOWERS AND
STORMS CLEAR LATE TONIGHT AS A COLD FRONT CROSSES THE TERMINALS
WITH WINDS SHIFTING TO WESTERLY BEHIND THE FRONT.
MARINE
ISSUED AT 401 AM EDT MON APR 27 2026
CONDITIONS WILL GET ROUGH ON THE BIG LAKE THIS AFTERNOON AND
EVENING AS WINDS STEADILY INCREASE. WINDS WILL BE SOUTHEAST AND
OFFSHORE THIS MORNING, BUT SPEEDS WILL INCREASE INTO THE 15 TO 25
KNOT RANGE. THIS AFTERNOON, WINDS WILL VEER JUST A BIT TO SOUTH-
SOUTHEAST AND INCREASE TO 20 TO 30 KNOTS. THIS EVENING, WE ARE
CONCERNED THAT WE WILL HIT GALE FORCE OUT OF THE SOUTH.
COORDINATED WITH SURROUNDING OFFICES AND CONSENSUS WAS TO STICK
WITH THE SMALL CRAFT ADVISORY FOR NOW GIVEN THIS IS A WARM AIR
ADVECTION WIND AND ITS HARD TO MIX INTO THE COLD AIR NEAR THE LAKE
SURFACE THIS TIME OF YEAR. THE DAY SHIFT WILL RE-EVALUATE, BUT
THERE IS 40 KNOTS IN THE MIXED LAYER. WINDS WILL DECREASE INTO
TUESDAY AS THE LOW PULLS AWAY. AS FOR WAVES...3 TO 5 FOOTERS ARE
LIKELY IN THE NEARSHORE WATERS TOWARDS SUNSET. WAVES WILL PEAK
AROUND MIDNIGHT AT 6 TO 10 FEET NORTH OF GRAND HAVEN AND 3 TO 6
FEET TO THE SOUTH.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...GALE WARNING UNTIL 8 PM EDT THIS EVENING FOR LMZ844>849.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 PM EDT TUESDAY
FOR LMZ844>849.
DISCUSSION...DUKE
AVIATION...THOMAS
MARINE...DUKE
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