782
FXUS63 KGRR 091726
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
126 PM EDT Thu Jul 9 2026
.KEY MESSAGES...
- Scattered Showers and Storms Today
- Mostly Dry Weekend Favored and Heating Back Up
&&
.DISCUSSION...
Issued at 350 AM EDT Thu Jul 9 2026
- Scattered Showers and Storms Today
Scattered showers and thunderstorms remain the mode today. While
not as warm as yesterday, the humidity will be a little higher. A
weak cold front slowly arriving from the northwest, weak midlevel
shortwave troughing, and remnant vorticity maxima from yesterday
evening`s convection over the Upper Miss. River valley, should
serve to initiate shower and storm development. Initially elevated
convection is possible most anywhere later this morning, then
more surface-based storms would be favored east of US-131 during
the afternoon.
CAPE should be in the range of 750-1500 J/kg. Low-level wind
shear is expected to be weak, and deep layer shear of 20 kt is
also on the marginal side. With weak forcing and weak storm-
relative inflow, storm updrafts should be smaller-scale and less
likely to produce severe hail. By afternoon, the well mixed lower
levels and DCAPE around 600 J/kg would support locally gusty winds
under any of the more robust storm cells, with a marginal risk of
severe winds near and east of Battle Creek - Lansing. Rain today
is not guaranteed in any location. However, an isolated inch or
more of rain could fall in a couple spots.
Added patchy fog into the forecast for early Friday morning as
winds go calm and skies partially clear. Isolated showers or
storms may continue to percolate in mid/southern Lower Michigan
tonight into Friday.
- Mostly Dry Weekend Favored and Heating Back Up
Rising heights in the upper levels and a strengthening surface
high over Lower Michigan this weekend will favor a dry forecast.
There is about a 10 percent chance of a shower or storm popping up
on Sunday, better chances north.
As a 500 mb high (associated with a heat wave out west)
strengthens and migrates from the SW CONUS to the Dakotas this
weekend into Monday, a plume of 20-25 C air at 850 mb will advect
into Michigan from the west-northwest Monday-Tuesday. High
temperatures in the 90s away from Lake Michigan are well supported
by the ECE and GEPS. Dew points may be a little lower than with
last week`s heat wave, but a heat index in the mid to upper 90s is
favored. Mid to late week, the spread in solutions increases (and
confidence decreases), dependent on the relative strength and
position of the central CONUS high and the eastern Canadian
trough, but now a majority of ECE members and about 25 percent of
GEPS members (not to mention a few GEFS members) keep highs in the
90s through Friday.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 126 PM EDT Thu Jul 9 2026
Scattered thunderstorms are likely through the afternoon, and
based on development trends have gone TEMPO Thunder at LAN/JXN.
Convective LLWS and microbursts with winds of 35+ knots are
possible with any storms. Thunderstorms diminish this evening
followed by a period of fog and low cloud development overnight.
MVFR conditions are likely, with IFR possible mainly at LAN. Some
discrepancy in guidance over the extent of low-level stratus vs
fog coverage, but flight category forecast remains the same. Gusts
to 15 knots, higher in thunderstorms, continue through the
afternoon with light winds overnight. Thwen winds increase to 3-8
knots from the north to northwest Friday.
&&
.MARINE...
Issued at 350 AM EDT Thu Jul 9 2026
Light winds and low waves expected over Lake Michigan today, with
wind direction variable depending on location. Can`t rule out an
isolated thunderstorm developing over the lake this morning.
Friday, north-northwest winds may build 2 to 4 foot waves and a
moderate swim risk by late afternoon. Swim risk is expected to be
low this weekend with a high pressure system over the area.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...CAS
AVIATION...Thomas
MARINE...CAS
NWS GRR Office Area Forecast Discussion
