253
FXUS63 KGRR 191145
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
745 AM EDT Sun Apr 19 2026
.KEY MESSAGES...
- Afternoon chance of showers, isolated thunderstorm
- Freezing temperatures tonight
- Warming trend midweek, rain and thunderstorm chances around
Friday
&&
.DISCUSSION...
Issued at 359 AM EDT Sun Apr 19 2026
- Afternoon chance of showers, isolated thunderstorm
A weak shortwave trough associated with a 500 mb speed max on the
backside of the Rossby wave trough will aid in the development of
diurnal showers in the vicinity of a cold front dropping through.
Fairly steep lapse rates from surface to 600 mb (approx 13,000
feet) may yield 100-250 J/kg of CAPE over Mid Michigan during the
afternoon. Showers will tend to grow as they move east. There is a
slight chance of an isolated thunderstorm this afternoon
especially near and east of Alma, Lansing, and Jackson.
Temperatures in Central Michigan would support some snow mixing
in. Any relatively robust convective cell, whether a shower or
thunderstorm, could produce graupel / small or soft hail and
locally gustier winds closer to 40 mph, again, best chances near
and east of US-127.
- Freezing temperatures tonight
For Sunday night to Monday morning, post-cold-front air with 850
mb temperatures around -10 C and high pressure moving over the
region will support freezing temperatures. There may be some
lingering lake-effect clouds in spots and there is some
uncertainty if surface winds go completely calm. However, the
cooling overnight will be more due to the advection of a deep cold
air mass rather than radiational. Above-freezing air above tree
height will not be available to mix down mechanically, as a sharp
temperature inversion appears unlikely. In every model, early
Monday morning temperatures in the vertical profile above the
surface are entirely below freezing. It appears the best case
scenario if a local surface temperature inversion does develop
would be for mechanical mixing of air to keep temperatures in the
upper 20s rather than the lower 20s.
NBM median 2-meter temperatures at 7 AM Mon are in the range of
26- 28 degrees except are slightly warmer immediately near Lake
Michigan. The 90th percentile (the warmest 10 percent of
solutions) are about 29-31 degrees.
For the period of March 1 through April 17, this year has been
within the top 10 warmest in terms of daily average temperature,
and record wettest at every ASOS / primary climate site. This may
lead to increased susceptibility to temperatures in the 20s for
some fruit crops. The frost/freeze advisory/warning season has
begun for Muskegon, Kent, Montcalm, Gratiot counties and south.
- Warming trend midweek, rain and thunderstorm chances around
Friday
Ensembles are in good agreement of a warming trend Tuesday to
Thursday as the upper level trough progresses east. Thursday is
likely to be the warmest day of the week with highs well into the
70s. Increasing moisture and instability Thursday into Friday will
set the stage for a round of showers or thunderstorms near a cold
front extending from a northern Plains low.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 745 AM EDT Sun Apr 19 2026
Not much has changed from the previous overnight discussion. VFR
is likely much of today with daytime cumulus bases favored to be
at or above 4,000 feet. West/Northwest winds will gust during the
late morning through afternoon up to about 20-28 knots. Around
18-22 Z, scattered towering cumulus (TCU) may be present near LAN
and JXN, possibly growing into cumulonimbus (CB), as there is
about a 10-30 percent chance of a thunderstorm in that area and
toward the east. Under any TCU or CB may come briefly gustier
winds over 30 knots and graupel (small or soft hail, GS).
&&
.MARINE...
Issued at 359 AM EDT Sun Apr 19 2026
West winds become more northwest then north during today. Waves
of 2 to 5 feet will linger at least through the morning. Weaker
winds are expected tonight through Monday morning. Increasing
south winds Monday night into Tuesday may again build hazardous
waves for small craft.
&&
.HYDROLOGY...
Issued at 221 PM EDT Sat Apr 18 2026
Major flooding continues on the Muskegon River. The good news is
most locations have crested or are cresting now. It will likely
take until late next week for all locations to come under flood
stage, so the recovery process will be slow. Meanwhile, water
levels continue to rise on the Grand River, and confidence is
increasing that this will end up being another minor flood event,
slightly higher and worse than the one that happened earlier this
month, but not a record flood at any locations. However, some of
the lowest and easily flooded locations on the river like Comstock
Park and Robinson Township will have moderate flooding. Dry
conditions are expected through the next several days.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from 11 PM this evening to 11 AM EDT Monday for
MIZ050>052-056>059-064>067-071>074.
MARINE...Small Craft Advisory until 2 PM EDT this afternoon for
LMZ844>849.
&&
$$
DISCUSSION...CAS
AVIATION...CAS
MARINE...CAS
HYDROLOGY...Thomas
NWS GRR Office Area Forecast Discussion
