321
FXUS63 KGRR 131834
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
234 PM EDT Mon Jul 13 2026
.KEY MESSAGES...
- Hot and humid through at least Thursday with no rain expected
- Cooler weather slowly filters in late week into the weekend
- Rain chances begin starting Thursday night and increase by Sunday
&&
.DISCUSSION...
Issued at 234 PM EDT Mon Jul 13 2026
- Hot and humid through at least Thursday with no rain expected
We issued a Heat Advisory earlier for the period of Tuesday
afternoon and evening. Additional heat headlines are very possible
through Thursday.
Our dominating weather feature is a 600 dam 500 mb ridge that is
centered just west of the state. This ridge has only strengthened
its hold as it has built over the area today. 850 mb temps are
around 19-20C this afternoon. The upper ridge will slowly build
south of the area over the next couple of days. However, the core of
the warmest air aloft (+25C) remains to our NW, and moves overhead
Tuesday.
Mid 90s F looks likely over most of the forecast area Tuesday, away
from Lake Michigan. In addition, higher dew points are also moving
in from the WNW, with upper 60s to near 70 expected. That will put
heat indices in the lower 100s.
The upper ridge axis and core of the warmest temps start to slip
south of the area by Wednesday. However, with better mixing with the
high moving away will likely keep highs in the mid 90s on Wednesday.
The trend will continue with the ridge weakening, and 850 mb temps
slowly cooling.
We feel it is likely that Heat Advisory criteria (100F) will be met
Tuesday and Wednesday, and maybe just a tad shy on Thursday as a
weak front slips through with the lowering heights. Coordination
with other offices brought a plan to deal with headlines daily, vs
over the entire period. That is due to some signal in the models of
trying to mix down much drier air. This would limit the heat indices
a tad.
- Rain chances start Thursday night with cooler temps filtering in
That front that moves through on Thursday is quite weak, with very
little convergence along it. However, it will gradually become a
potential boundary to focus convection along it with the cap
weakening with the lower heights settling in. Models are indicating
that the first chances of rain may arrive as early as Thursday night
with a weak wave embedded in the flow could act on the gradient of
better instability.
More clouds, lower heights, and cooler temps aloft will all lead to
sfc temps slowly trending cooler through the weekend. We do not see
high precipitation chances for the first half of the weekend. There
is not really a well organized upper wave/sfc low until later
Sunday. At that time, rain chances will be the best for the seven
day period.
&&
.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 206 PM EDT Mon Jul 13 2026
VFR is expected under a high pressure system and a hot and
somewhat dry atmosphere. Winds will be between SW and W with gusts
occasionally to 16 knots.
&&
.MARINE...
Issued at 234 PM EDT Mon Jul 13 2026
We are looking at a very low chance of wind/wave related headlines
through most of this week. The big area of high pressure bringing
this hot weather will also keep the gradient weak over the area
through the week. There is a little bit of wind as the center of the
high slips south over the period. The more stable conditions will
keep lighter winds over the lake with less mixing.
The next set of headlines looks to be around the Saturday time
frame. That occurs as the next organized system is poised to
approach the area.
&&
.CLIMATE...
Issued at 246 AM EDT Mon Jul 13 2026
Here are the high temperature records for July 13, 14, and 15.
Location July 13 July 14 July 15
Grand Rapids 108 (1936) 102 (1936) 95 (2013)
Lansing 99 (1936) 101 (1936) 99 (1977)
Muskegon 93 (1995) 94 (1995) 93 (1995)
Kalamazoo 109 (1936) 108 (1936) 103 (1936)
Battle Creek 103 (1936) 104 (1936) 100 (1977)
Holland 99 (1936) 98 (1995) 98 (1932)
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory from noon to 8 PM EDT Tuesday for MIZ037>040-
043>046-050>052-056>059-064>067-071>074.
MARINE...None.
&&
$$
DISCUSSION...NJJ
AVIATION...CAS
MARINE...NJJ
CLIMATE...RAH
NWS GRR Office Area Forecast Discussion
