776
FXUS63 KGRR 200611
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
211 AM EDT TUE MAY 20 2025
KEY MESSAGES
- COOL AND WET THROUGH THURSDAY.
- WEEKEND WARMING TREND
DISCUSSION
ISSUED AT 228 PM EDT MON MAY 19 2025
- COOL AND WET THROUGH THURSDAY.
LATEST VISIBLE LOOP SHOWS STRATOCU FLOWING SOUTHWESTWARD ACROSS
THE CWA AND COVERS ALL BUT THE SOUTHWEST CWA. ABUNDANT HIGH CLOUDS
COVER THE SOUTHWEST CWA. AS WE GO THROUGH THE EVENING, SOME OF THE
STRATOCU MAY DISSIPATE LEAVING PARTLY CLOUDY SKIES FOR A FEW
HOURS. HOWEVER, CLOUDS WILL INCREASE LATER TONIGHT FROM LOW
PRESSURE OVER THE PLAINS.
THAT LOW WILL MOVE EAST TUESDAY AND BEGIN TO PUSH RAIN INTO THE
CWA FROM SOUTHWEST TO NORTHEAST. THE MODEL TRACK OF THE LOW HAS
BEEN CONSISTENT FOR A FEW RUNS AFTER DEVIATING TO THE NORTH A
COUPLE DAYS AGO. GENERALLY, THE TRACK OF THE LOW WILL TAKE IT
ACROSS NORTHERN IL/IN AND SOUTH OF THE CWA, WHICH MEANS WE'LL HAVE
A STEADY EAST WIND DURING THE NEXT COUPLE OF DAYS. COOLER AIR WILL
FEED INTO THE CWA FROM ONTARIO AND WHEN COMBINED WITH THE RAIN
EXPECTED, TEMPERATURES WILL ONLY REACH THE MID TO UPPER 50S
TUESDAY THROUGH FRIDAY.
A LARGE BAND OF CONDENSATION PRESSURE DEFICITS LESS THAN 10 MB
SLOWLY ENCROACHES ON THE CWA BEGINNING LATE MORNING TUESDAY
REACHING THE NORTHERN CWA TUESDAY EVENING. ECMWF ENSEMBLES POINT
TOWARD QPF AROUND A HALF INCH TUESDAY/WEDNESDAY, EXCEPT IN THE
FAR NORTHEAST CWA WHERE ONLY A TENTH OR SO MAY FALL. GIVEN THE
LONG DURATION OF THIS EVENT, WE ARE NOT ANTICIPATING FLOODING.
CURRENTLY WE EXPECT TO BE ON THE NORTH SIDE OF THE LOW TRACK. IF
THAT LOW DRIFTS TO THE NORTH AND WE GET INTO THE WARM SECTOR,
THEN, OBVIOUSLY, TEMPERATURES WOULD BE WARMER, BUT CONVECTION
COULD ALSO BE A PLAYER, VERSUS THE STRATIFORM PRECIPITATION WE'RE
CURRENTLY ANTICIPATING.
- WEEKEND WARMING TREND
WHILE THE SURFACE LOW WILL MOVE EAST OF THE CWA THURSDAY NIGHT,
THE UPPER LOW WILL REMAIN. SEVERAL SHORT WAVES ROTATING AROUND THE
UPPER LOW WILL KEEP A CHANCE OF SHOWERS IN THE FORECAST FRIDAY
TOO, BEFORE THE TROUGH WEAKENS AND LIFTS OUT.
TEMPERATURES WILL BEGIN TO WARM SATURDAY AND CONTINUE THROUGH THE
HOLIDAY WEEKEND WITH LOWER TO MID 60S SATURDAY AND MID TO UPPER
60S BY MONDAY. THAT'S STILL COOLER THAN NORMAL, GIVEN NORMAL HIGHS
AROUND 70.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 210 AM EDT TUE MAY 20 2025
THERE REMAINS SEVERAL ISSUES OVER THIS TAF PERIOD. THE FIRST IS
THE LLWS WITH STRONG WINDS OF 40 TO 45 KTS BETWEEN 1KFT TO 2KFT.
WHILE THOSE WINDS WILL REMAIN THROUGH MOST OF THE TAF PERIOD IT
WILL BE LESS OF AN ISSUE DUE TO THE MIXING THAT WILL OCCUR
BRINGING THE GUSTY WINDS TO THE SFC. EXPECT WINDS TO MIX DOWN
AROUND 11Z AND THEN CONTINUING THROUGH THE DAY. SHOWERS WILL BE
MOVING IN FROM THE SOUTH. HEAVIEST SHOWERS WILL OCCUR AFTER 21Z
WITH MVFR CIGS AND VSBYS POSSIBLE BETWEEN 21Z UNTIL 03Z. AFTER 03Z
VSBYS SHOULD IMPROVE AS SHOWERS LIGHTEN. HOWEVER, MVFR CIGS WILL
PERSIST INTO WEDNESDAY MORNING.
MARINE
ISSUED AT 228 PM EDT MON MAY 19 2025
APPROACHING LOW PRESSURE WILL CAUSE WINDS TO INCREASE TONIGHT FROM
THE EAST UP TO 30 KNOTS; A SMALL CRAFT ADVISORY IS IN EFFECT
TONIGHT THROUGH TUESDAY EVENING. THE STRONG WINDS WILL CONTINUE
THROUGH TUESDAY EVENING, BEFORE THE LOW CENTER IS CLOSE ENOUGH
THAT THE PRESSURE GRADIENT DIMINISHES. AS THE LOW MOVES EAST
THURSDAY AND NORTH WINDS DEVELOP, WAVES WILL INCREASE SUCH THAT
ANOTHER SMALL CRAFT ADVISORY MAY BE NEEDED.
GRR WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT WEDNESDAY FOR LMZ844>849.
DISCUSSION...04
AVIATION...CERU
MARINE...04
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