830
FXUS63 KGRR 012317
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
717 PM EDT Tue Jul 1 2025

.KEY MESSAGES...

- Scattered Showers/Storms Wednesday-Friday

- Warm This Weekend With a Chance of Showers and Storms Saturday
  Night into Sunday

&&

.DISCUSSION...
Issued at 158 PM EDT Tue Jul 1 2025

- Scattered Showers/Storms Wednesday-Friday

Subsidence from a departing trough overhead has led to plenty of
sunshine today with highs in the 80s forecasted. Conditions will
remain dry through the night and into Wednesday morning before
precipitation chances increase Wednesday afternoon.

The forcing for any precipitation will be the combination of a
few factors. 1) Lake breeze convergence 2) A weak frontal
boundary across northern Michigan and 3) a mid- level wave
providing some synoptic assistance. The Storm Prediction Center
currently has much of the area in a Marginal risk of severe
thunderstorms Wednesday. Cannot rule out an isolated strong to
severe thunderstorm, with deep layer shear around 30 knots with
MUCAPE around 1000 J/kg. However the marginal thermodynamics has
confidence in any severe storms low. If a storm can become strong to
severe, steep 0-3km lapse rates have gusty winds as the main
concern. Much of the area is likely to stay dry Wednesday with areas
near US127 and/or north of M20 having the best potential for
scattered storms as supported by HREF guidance.

The aforementioned front continues to slowly drift through the
region Thursday. This will allow the chance for widely scattered
showers and thunderstorms to develop, though once again most will
remain dry. Areas east of US131 and near and south of M46 will
have the best chance for a shower or storm.

A warm front crosses the area Friday marking the beginning of return
flow from the Gulf on the west side of a ridge. Warmer conditions
are expected with highs in the upper 80s to low 90s. A few
showers and storms are possible as this front crosses the area.
However mid-level height rises will make it difficult for
widespread precipitation to form meaning Independence Day will not
be a washout.

- Warm This Weekend With a Chance of Showers and Storms Saturday
Night into Sunday.

Warm southwesterly flow continues to take hold into the weekend as
850mb temps climb to the upper teens Celsius. highs climb into the
90s for Saturday. Sunday is a bit more uncertain as that will depend
on the exact timing of a cold frontal passage across the area.
Dewpoints near 70 will mean heat indices Friday and Saturday will
climb into the 90s.

This cold frontal passage Saturday Night into Sunday will bring the
potential for more widespread showers and storms into the area aided
by a mid-level wave, though this mid-level wave will not provide
much in the way of synoptic assistance as it`s shearing out as it
arrives.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 716 PM EDT Tue Jul 1 2025

Diurnal cu is dissipating which will leave clear skies overnight.
A weak short wave trough will approach Wednesday afternoon and may
fire a shower or storm after 18z. This would affect LAN/JXN and
perhaps BTL, but chances are only around 20 percent and so were
left out of the TAFs.

&&

.MARINE...
Issued at 108 PM EDT Tue Jul 1 2025

High pressure will remain overhead for the next few days resulting
in waves aob 2 feet. As the high moves east Friday, southwest
winds will increase and waves will respond by building to 2 to 4
feet late late Friday into Saturday.

&&

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

&&

$$

DISCUSSION...Thomas
AVIATION...04
MARINE...04