971
FXUS63 KGRR 051846
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
246 PM EDT Wed Jun 5 2024

.KEY MESSAGES...

- Clearing this evening, then showers/storms tonight

- Scattered showers and cooler Thursday

- Cooler Weekend With Some Showers Possible

&&

.DISCUSSION...
Issued at 246 PM EDT Wed Jun 5 2024

- Clearing this evening, then showers/storms tonight

A cold front is currently moving across Lake Michigan and will
sweep across the cwa later this afternoon/evening. Ahead of it,
showers and thunderstorms developed as expected within an
environment characterized by SBCAPE 2500 j/kg but only 25-30 knots
bulk shear. The less than robust shear is likely holding back the
storms from developing further. Radar shows a well defined MCV
moving northeast into southern Calhoun County. This MCV is running
out of real estate to produce stronger storms and the event may be
over before it gets going. Quite a bit of high clouds likely
prevented further destabilization that might have otherwise overcome
the weak shear.

Visible loop shows the back edge of the clearing moving across the
lake and we`ll likely be back in the sunshine/clearing by early
evening.

A strong short wave will move in from the northwest tonight around
midnight. CAMs show another line of showers/isold storms
developing over Wisconsin and then moving over the lake around
05z. There`s roughly 400-500 j/kg MUCAPE to work with, so we may
see some isolated thunder, but most of the precipitation will be
showers.

- Scattered showers and cooler Thursday

As the upper low settles over Lower MI, h5 temps will fall from
-11c to -16c. Those cooler temps aloft will probably be enough to
 generate some instability showers as mid level lapse rates climb
 to over 7c/km across northern Lower. Areas primed for showers
 would be the northern cwa, closer to the higher instability. This
 will continue Thursday night too.

Highs Thursday will range from the upper 60s near US-10 to mid 70s
near I-94.

- Cooler Weekend With Some Showers Possible

Upper troughing with a closed upper low settles over the region late
in the week and through the weekend leading to cooler than normal
conditions and a few chances for light rain. 850mb temperatures fall
into the low single digits late this week leading to daytime highs
in the mid to upper 60s Friday and into the low 70s by Saturday and
Sunday. Overnight lows fall into the upper 40s to low 50s.

A few chances for rain exist through the extend as several
shortwaves ripple through the parent upper trough. Moisture will be
fairly limited, so mainly light rain is expected. Most notably the
chances for rain exist for Saturday and Sunday where some diurnal
heating supports precipitation potential with some thunder possible
Saturday afternoon/evening.


&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 146 PM EDT Wed Jun 5 2024

After scattered showers this morning, focus turns to the isolated
heavy rain showers and storms this afternoon. We are already
seeing some isolated storms east of a line from Kalamazoo to
Saginaw, so expect lightning to impact AZO, BTL, LAN and JXN.
It`s possible MKG and GRR may see some redevelopment later on this
afternoon with lightning, but confidence is low. Any stronger
storms could feature gusts over 40 knots, with the best chance at
LAN, JXN, or BTL.

Behind the afternoon showers and storms VFR is expected.
Additional scattered showers are possible by around 05z Thursday
morning moving eastwards through about 10z.

&&

.MARINE...
Issued at 246 PM EDT Wed Jun 5 2024

A Small Craft Advisory and Beach Hazards Statement remains in
effect from midnight through 4pm Friday. A cold front will move
across the lake late this afternoon and west winds behind it will
bring in cooler air and increase to 20-25 knots. Waves in the 3-5
foot range are expected, highest between Grand Haven and South
Haven where they`ll be closer to 4-5 feet.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from midnight EDT tonight through Friday
     afternoon for MIZ037-043-050-056-064-071.
MARINE...Small Craft Advisory from midnight tonight to 4 PM EDT Friday
     for LMZ844>849.

&&

$$

DISCUSSION...04/Thielke
AVIATION...Thielke
MARINE...04