542
FXUS63 KGRR 200552
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
152 AM EDT Mon Apr 20 2026
.KEY MESSAGES...
- Freeze Warning Tonight
- Some Storminess by Friday
&&
.DISCUSSION...
Issued at 245 PM EDT Sun Apr 19 2026
- Freeze Warning Tonight
Sharp upper trough moving through today combined with sufficient
low to mid level moisture has resulted in convective updrafts
with scattered showers this afternoon. Lake shadow and high clouds
has prevented widespread deeper updrafts, lowering the potential
for ice pellet/graupel. Showers will diminish end this evening as
the trough axis moves east and with the loss of insolation.
Cold surface high builds in overnight with drying and subsidence
with winds decoupling after midnight. Radiational cooling
conditions become optimal by 12Z with the surface high progged to
be centered over southwest Lower Michigan. A hard freeze is
expected as temperatures will be below freezing for several
hours.
- Some Storminess by Friday
The surface high moves east by Tuesday with southerly flow
developing but the moisture return does not immediately result in
precipitation as shortwave ridging is expected during the middle
part of the week ahead of an upper low over the NW CONUS that
eventually moves into Upper Plains and Canada by the end of the
week. A cold front trailing a surface low moving into northern
Minnesota before it occludes and moves into Canada will
concentrate showers on Friday with the chance for thunderstorms
during the afternoon.
&&
.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 152 AM EDT Mon Apr 20 2026
VFR is expected today with light winds underneath a high pressure
system. Daytime cumulus development around 5,000 feet is unlikely
given the dry lower to middle troposphere. Clouds above 12,000
feet will increase late in the evening. About 25 knots of wind
shear between 2,000 feet and ground is possible by 06 Z Tuesday.
&&
.MARINE...
Issued at 245 PM EDT Sun Apr 19 2026
High pressure brings tranquil conditions on Lake Michigan tonight
and Monday. The high will move east and southerly winds increase and
waves will build Monday night. A SCA will be needed from late
Monday through Tuesday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning until 11 AM EDT this morning for MIZ050>052-
056>059-064>067-071>074.
MARINE...None.
&&
$$
DISCUSSION...Ostuno
AVIATION...CAS
MARINE...Ostuno
NWS GRR Office Area Forecast Discussion
