481
FXUS63 KGRR 072309
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
709 PM EDT Tue Jul 7 2026
.KEY MESSAGES...
- Slow moving front brings rain, storms late week
- Upper High builds in early next week
&&
.DISCUSSION...
Issued at 201 PM EDT Tue Jul 7 2026
- Slow moving front brings rain, storms late week
Quasi-zonal flow regime this week with upper height falls
attending a slow-moving cold front sagging south through the Great
Lakes. We will see chances for showers and thunderstorms from
Wednesday night through Friday as the front becomes almost
parallel to the flow.
By Thursday, training of storms could result in minor flooding but
in most areas rainfall should be beneficial rather than excessive.
Severe weather chances are marginal Wednesday night with limited
instability and deep layer shear.
- Upper High builds in early next week
The rains should end across the southern zones over the weekend as
the front sags south then large scale subsidence and drying begins
with an upper high across the Northern Plains edging into Lower
Michigan. Expect warm and dry for early next week before heights
fall as an upper trough amplifies across eastern Canada.
&&
.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 708 PM EDT Tue Jul 7 2026
Any remaining Cu will diminish after sunset with limited Cu
development possible again on Wednesday around 5kft. Can`t rule
out some patchy ground fog overnight, with the best signal at JXN
which climatologically is also our favored site for fog
development. Have not included restrictions at any terminal
besides JXN given low confidence (20-30% chance) of MVFR
conditions at these sites, with moderate confidence (near 50%) at
JXN. Any fog that develops will diminish shortly after daybreak
given strong July mixing with VFR conditions then expected through
the end of the TAF period. Winds will become light and variable
overnight before increasing to 5-8 knots from the southwest on
Wednesday.
&&
.MARINE...
Issued at 201 PM EDT Tue Jul 7 2026
Fairly tranquil weather this week except for the possibility of
thunderstorms with gusty winds and heavy downpours Wednesday night
into Thursday morning. Wind direction will be frequently changing
with north winds tonight going south on Wednesday then north again
on Thursday and Friday, but generally remaining at or below 15
knots.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Air Quality Alert from midnight tonight to midnight EDT
Wednesday night for MIZ050-056-057-064-065-071.
MARINE...None.
&&
$$
DISCUSSION...Ostuno
AVIATION...Thomas
MARINE...Ostuno
NWS GRR Office Area Forecast Discussion
