661
FXUS63 KGRR 061144
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
744 AM EDT Sat Jun 6 2026
.KEY MESSAGES...
- Isolated Thunderstorms Possible Today
- Increasing Chances for Rain and Thunderstorms Monday into
Tuesday
- Warm and Humid With Slight Chances (20 percent) for
Thunderstorms
&&
.DISCUSSION...
Issued at 308 AM EDT Sat Jun 6 2026
- Isolated Thunderstorms Possible Today
The line of thunderstorms currently moving through the area will
exit by 5am. Instability builds back in during the day with the
mean HREF surfaced based CAPE values around 1000 J/kg and shear
around 35 knots. Even with these values the HREF members are not
excited about thunderstorm chances later this morning and
afternoon. Other guidance has also decreased on convection later
today. This could be due to the lack of lift in the lower levels,
but with 500mb positive vorticity advection and the front moving
through, will keep a 20 to 30 percent chance with the best
potential east of I-69.
- Increasing Chances for Rain and Thunderstorms Monday into
Tuesday
The upper level ridge builds back in for Sunday, but the shortwave
over Texas will weaken the ridge bringing with it rain and
thunderstorms for Monday and Tuesday. Heavy rain will be possible
with precipitable water values around 2 inches. Currently we are
in the day 5 Excessive Rainfall Outlook from WPC. Depending on the
evolution of the shortwave, rain and thunderstorms could linger
into Wednesday.
- Warm and Humid With Slight Chances (20 percent) for
Thunderstorms
Temperatures gradually warm through next week with the best
potential for 90s on Thursday as 925 mb temperatures will be in
the 24 to 25 C range. However within the southwest flow and the
humid environment with dew points in the 60s and 70s,
thunderstorms chances could play a role in how warm we actually
get. Still worth monitoring as heat indices could be in the 90s
multiple days in a row and may approach the low 100s.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 744 AM EDT Sat Jun 6 2026
There is a low chance for precipitation at the terminals now that
an area of showers and thunderstorms has exited to south of the
forecast area. The biggest forecast challenge will be at MKG where
marine fog has resulted in LIFR conditions. Conditions are
expected to improve during the day but there is considerable
uncertainty regarding the exact timing. Our best guess now is that
VFR conditions will be realized by noon coincident with the onset
of a lake breeze that will promote mixing of the nearshore marine
boundary layer.
Elsewhere, predominantly VFR conditions are expected although a
brief window of MVFR ceiling restrictions this morning can`t be
completely ruled out.
&&
.MARINE...
Issued at 308 AM EDT Sat Jun 6 2026
For the rest of today thunderstorm chances are low. Winds will
shift more to the northwest with the front moving through this
afternoon. High pressure then builds into Sunday with winds and
waves remaining below Advisory and Statement levels through next
week. Thunderstorms will be likely Monday into Tuesday with lower
chances lingering through the rest of the week.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Dense Fog Advisory until 2 PM EDT this afternoon for LMZ846>849.
&&
$$
DISCUSSION...RAH
AVIATION...TJT
MARINE...RAH
NWS GRR Office Area Forecast Discussion
