063
FXUS63 KGRR 271748
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
148 PM EDT Mon Jul 27 2026
.KEY MESSAGES...
- Severe Thunderstorm Risk This Afternoon
- Rain and Thunderstorm Chances Return Friday into the Weekend
&&
.DISCUSSION...
Issued at 131 PM EDT Mon Jul 27 2026
- Severe Thunderstorm Risk This Afternoon
A Severe Thunderstorm Watch is in effect until 8PM this Evening.
The areas of interest are the storms that will move in from
Wisconsin and over Lake Michigan into the area. Additional
development ahead of the line is possible with remnant boundaries
in the current unstable high shear environment. The highest threat
for severe thunderstorms will be along and west of US-131 with
lower confidence further east as instability decreases.
All hazards will be in play with effective shear values around 50
knots, ML CAPE values increasing to 3000 J/kg, and 0-3km SRH
values around 100 to 200 m2/s2. Overall guidance hasn`t had a
great grasp on thunderstorm development and evolution. We are in a
high risk low confidence situation. If storms are widespread
through this afternoon and clear this evening, the rest of the
night should be largely dry. If the environment isn`t worked over
we could see additional development overnight.
- Rain and Thunderstorm Chances Return Friday into the Weekend
As the shortwave responsible for today`s thunderstorms moves east,
pressure heights increase with dry conditions expected through
most of the week. Temperatures will largely be in the 80s each day
with lows in the 50s and 60s. Rain and thunderstorm chances
increase Friday into Saturday with another trough. Chances may
linger into Sunday depending on how fast the trough clears the
area.
&&
.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 145 PM EDT Mon Jul 27 2026
A frontal boundary over the northern Great Lakes will move slowing
south during the next 12 hours. This will result in continued shower
and thunderstorm chances, as front interacts with extremely
warm/humid airmass. Expect the storms currently over Lake Michigan
to impact MKG/GRR/AZO (in particular) next 1-2 hours. It is
unclear how far east the stronger storms will persist. Gusty winds
and hail are the greatest threats. Some renewed storm development
can`t be ruled out behind the current convection into the early
evening, and will keep risk of convection through 02-03Z.
Moist airmass and light winds along and immediately behind
aforementioned front will result in MVFR ceilings/vsbys in low
clouds and fog through much of the night. Winds will eventually
become N/NW tonight and Tuesday, and expect the low (MVFR)
ceilings to gradually give way to VFR conditions by late Tuesday
morning.
&&
.MARINE...
Issued at 131 PM EDT Mon Jul 27 2026
Severe thunderstorms this afternoon will bring a risk for damaging
winds, hail, and waterspouts. This risk is expected until 8pm with
it ending earlier to the north. Wave heights of 2 to 3 feet are
expected into this evening, but higher waves will be possible with
any thunderstorm.
Tonight northerly winds behind the low pick up to 25 to 30 knots
and will bring building waves of 4 to 7 feet. These conditions
will linger through Tuesday. A Small Craft Advisory and Beach
Hazard Statement are in effect. Northwest winds Wednesday
afternoon may bring another period of Small Craft Advisory,
Moderate to High Swim Risk conditions for areas between Whitehall
and South Haven.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement from late tonight through late Tuesday
night for MIZ037-043-050-056-064-071.
MARINE...Small Craft Advisory from 4 AM Tuesday to 2 AM EDT Wednesday for
LMZ844>849.
&&
$$
DISCUSSION...RAH
AVIATION...Smith
MARINE...RAH
NWS GRR Office Area Forecast Discussion