338
FXUS63 KGRR 101052
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
652 AM EDT Fri Jul 10 2026
.KEY MESSAGES...
- Isolated Showers and Storms Today South of I-96
- Heat Wave Possible Mon-Wed
&&
.DISCUSSION...
Issued at 343 AM EDT Fri Jul 10 2026
- Isolated Showers and Storms Today South of I-96
Relatively moist air lingering in southern Michigan along with
MLCAPE projected around 1000 J/kg south of Holland-Lansing,
limited convective inhibition, and weak surface convergence, means
that isolated to scattered showers or thunderstorms are possible
today. Low level wind shear will likely be minimal and 0-6 km
shear no more than 20 knots. Any storms will primarily be an
isolated microburst/wind threat, though unlikely to be severe.
With 0-3 km CAPE over 100 J/kg, LCLs around 1 km, and perhaps
zones of weak surface vorticity along converging wind fields, any
storm cells that do track along surface vorticity zones could make
an attempt at landspouts like yesterday.
- Heat Wave Possible Mon-Wed
Significant heat wave developing this weekend from the
Intermountain West to Northern High Plains, with the forecast offices
in Salt Lake, Riverton, and Billings mentioning all-time record
highs being challenged. The associated 500 mb high will migrate
toward the Dakotas with 600 dekameter heights on Monday. A plume
of very warm 850 mb air will advect toward Michigan from the
northwest, with the ECMWF favoring 21-23 C temperatures at that
level over us Mon-Tue, possibly into Wed.
The EC-ENS and GEPS have been on board for a few days now with
high temperatures in the 90s (away from Lake Michigan) Monday
through Wednesday. A growing number of GEFS members are also
pushing highs above 90 on Tue. Dew points in the lower to mid 60s
(instead of the 70s like the heat wave last week) should keep the
heat index relatively in check, though a heat index in the 90s to
near 100 for a few days still carries risk of heat illness. On but
especially after Wed, the spread in solutions grows depending on
the magnitude of the eastern Canadian trough, which makes a big
difference in how much and how quickly we cool back down later in
the week.
&&
.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 652 AM EDT Fri Jul 10 2026
ASOS/AWOS and highway webcams show a few areas with LIFR to VLIFR
fog or ceilings currently, including in between GRR and LAN,
namely Ionia (Y70). Another patch of fog east of Holland (BIV)
and south-southwest of GRR, from Zeeland to Wayland. Another patch
of fog north of South Haven (LWA). Otherwise, patchy MVFR ceilings
or vis are common in quite a number of other locations.
With sunrise, visibility should improve by 12, though ceilings
may stay between 700 and 2,000 feet until about 14 Z in some
spots.
Continues to be a chance of isolated to scattered showers and
thunderstorm cells bubbling up with daytime heating this
afternoon, mainly affecting AZO, BTL, and JXN. Can`t rule out one
developing vicinity S-SW of GRR too. A more robust thunderstorm
cell today could produce a localized microburst/LLWS.
&&
.MARINE...
Issued at 343 AM EDT Fri Jul 10 2026
Winds from the northeast this morning become northwest and
strengthen to 15 to 20 knots this afternoon with the additive
effects of a ridge of higher pressure over Wisconsin and the
daytime lake breeze. A moderate swim risk is likely to develop
by mid-late afternoon between Whitehall and South Haven,
especially affecting beaches north of north piers. Waves may build
2 to 4 feet, and some gusts may approach 22 knots per the HRRR.
This setup appears similar to Monday, which was another close call
moderate-to-high swim risk day.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...CAS
AVIATION...CAS
MARINE...CAS
NWS GRR Office Area Forecast Discussion
