403
FXUS63 KGRR 101858
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
258 PM EDT Wed Jul 10 2024

.KEY MESSAGES...

- Rain Ending this evening, scattered storms Thursday

- Warming Temperatures into the Weekend with Some Storms Possible

&&

.DISCUSSION...
Issued at 257 PM EDT Wed Jul 10 2024

- Rain Ending this evening, scattered storms Thursday

Dry air is being entrained from the north into the low pressure
circulation resulting in an erosion of the steady rain across
southwest Lower Michigan this afternoon. There are still some
isolated updrafts bringing heavy but quick downpours where low
level convergence combines with instability, but this will also be
diminishing by this evening. As the rain ends and water recedes
this afternoon, we can drop the FLood Advisory and Flood Watch by
4 pm.

There will be a lull in rain chances from tonight into Thursday
morning, then scattered showers and thunderstorms pop again by
Thursday afternoon as an upper trough follows quickly on the heels
of the departing low and steepens lapse rates/increases
instability. These should diminish again Thursday evening after
sunset.

- Warming Temperatures into the Weekend with Some Storms Possible

High pressure slides into the region late in the week as the
tropical low moves east of Michigan. 850mb thermal ridge builds
overhead starting around 15C and peaking at 20 to 22C by Sunday.
Reflectant surface temperatures start off in the low 80s late this
week and peak in the upper 80s to near 90 by Monday. Dewpoints will
also gradually rise into the mid to upper 70s leading to apparent T
in the mid to upper 90s early next week.

Subtle upper level troughing will remain overhead supporting
isolated showers and storms Friday afternoon as mid-level lapse
rates steepen with cold air overhead. A bit of model disagreement
beyond Friday, but there appears to be a few chances for activity
across the region as the flow turns to zonal and several shortwaves
pivot through the region. Decaying shower and storm activity
approaches from the west late Saturday to early Sunday, then an
approaching cold front Monday or Tuesday will lead to increased
storm activity early next week. Dewpoints surge Sunday through
Tuesday leading to increased instability towards 3000 to 5000 J/kg
of MUCAPE. Some severe thunderstorms may be possible Sunday to
Tuesday, especially with the approaching cold front Tuesday though
there is still uncertainty on timing and frontal placement.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 137 PM EDT Wed Jul 10 2024

The remnants of Beryl continue to work through the area but will
exit east by the start of Thursday. Ceilings have lifted towards
VFR but there are some pockets of MVFR in areas of heavy moderate
rain showers. Lingering rain will also present periodic visibility
restrictions through this afternoon before showers exit east. A
few showers across AZO, BTL and JXN may contain some flashes of
lightning. Some fog will be possible early Thursday as winds turn
calm and low level moisture lingers following recent heavy
rainfall.

&&

.MARINE...
Issued at 257 PM EDT Wed Jul 10 2024

Winds have now turned northwest and waves in the near shore waters are
approaching 4 feet at Saint Joseph. Conditions will be marginal
for the advisory further north but we will let it ride for now and
it may be cancelled before 8 pm.

&&

.HYDROLOGY...
Issued at 257 PM EDT Wed Jul 10 2024

The areal flooding will be diminishing as the rains end this
evening, but flooding of tributaries and a few points on the
mainstem rivers will continue the next few days. We expect the
crests to move down the Grand River but remain below flood stage
while going above action stage for the stretch from Ionia to Grand
Rapids.


.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch until 8 PM EDT this evening for MIZ046-051-052-
     056>059-064>067-071>074.
     Beach Hazards Statement until 8 PM EDT this evening for MIZ050-
     056-064-071.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ844>847.

&&

$$

DISCUSSION...Ostuno/Thielke
AVIATION...Thielke
MARINE...Ostuno
HYDROLOGY...Ostuno