-- Discussion containing changed information from previous version are highlighted. --
279
FXUS63 KGRR 281145
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
745 AM EDT Tue May 28 2024

.KEY MESSAGES...

- Showers and possible storms late today into tomorrow

- Dry Thursday and Friday

- Showers Possible This Weekend, Mainly Saturday

- Warmer Early Next Week; Daily Storm Risk

&&

.DISCUSSION...
Issued at 340 AM EDT Tue May 28 2024

- Showers and possible storms late today into tomorrow

 Today`s weather pattern will be dominated by a large upper level
low that is situated over eastern Canada. That low has a long wave
trough that extends across the lower Peninsula. Copious mid level
moisture will keep the region mostly cloudy today with periods of
showers today. A weak upper level ridge could allow for some
breaks in the clouds this afternoon, mainly along and west of the
US 131 corridor.

 Latest soundings are fairly moist through the sounding and
although there isn`t a ton of CAPE, there could be just enough
mid level instability to allow for storms to develop late this
afternoon into this evening, mainly along and east of the US 127
corridor. Cold air aloft behind this trough could allow for small
hail with any storms.

 Temperatures today continue to be below normal though potential
breaks in the clouds should allow for Max Temps to get into the
upper 60s to low 70s.

 A secondary trough will drop down through the region tonight
into Wednesday. A boundary will drape through southern Michigan
with showers continuing tonight into tomorrow morning along and
south of the I 94 corridor. Forecast QPF shouldn`t be significant
but upwards of a half an inch of rain is possible especially along
the I 94 corridor.


- Dry Thursday and Friday

We`ll have picture perfect weather to end the week as a Canadian
surface high passes directly overhead. Dew points in the 30s/40s and
highs 70 to 75 will make for pleasant daytime conditions, but also
chilly overnight temps in the 40s. Even some colder reading in the
mid to upr 30s and patchy front possible in nrn sections both
Wednesday Thursday nights.

- Showers Possible This Weekend, Mainly Saturday

GFS/ECMWF are in a little better agreement now regarding weekend
rain chances. Looks the main threat for showers comes on Saturday
and is related to a shortwave which tracks northeast from the
Central Plains and passes through lwr MI during the afternoon.
Southerly return flow on the back side of the departing sfc high
sends a corridor of higher PWATs in ahead of the shortwave however
instability looks quite limited so the thunder risk is low. A period
of subsidence behind the Saturday wave may support a dry Sunday,
although a few afternoon pop-up showers inland from Lk MI cannot be
ruled out.

- Warmer Early Next Week; Daily Storm Risk

Guidance is in good agreement showing a return of above normal temps
early next week as the main upper jet/stronger westerlies sets up to
our north; near or just north of the U.S./Canadian border. Daily
highs in the lower 80s are expected but rain chances/timing are
difficult to nail down given zonal flow pattern and low
predictability of potential shortwaves. Higher dew points and better
instability should support a daily risk of diurnal storms though.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
-- Changed Discussion --
Issued at 745 AM EDT Tue May 28 2024

Showers passing through this morning producing occasional IFR
cigs south of GRR and LAN through 14Z. Otherwise VFR generally
prevailing today. Scattered showers redeveloping this afternoon
with thunder also possible. The thunder threat looks to favor the
LAN and JXN terminals between about 21Z and 02Z where better sfc
convergence will be present. Scattered showers lingering tonight,
with areas of MVFR and possible IFR becoming more likely after
09Z, especially south of GRR and LAN.
-- End Changed Discussion --

&&

.MARINE...
Issued at 344 AM EDT Tue May 28 2024

Waves have subsided for now so there are no current hazards.
However the gradient will strengthen Wednesday. Winds will be
predominately from the north. Expect that gradient to continue to
increase into Wednesday afternoon. Winds and waves should
increase enough for conditions to increase to criteria Wednesday
afternoon and evening.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Meade/Ceru
AVIATION...Meade
MARINE...Ceru