440
FXUS63 KGRR 041723
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
123 PM EDT Sat Jul 4 2026
.KEY MESSAGES...
- Pop-up Thunderstorms This Afternoon and Evening
- Showers and Thunderstorms Mainly South Tonight into Sunday
- Dry Monday through Wednesday, Showers and Thunderstorm Chances
Return Late Wednesday Night into Thursday
&&
.DISCUSSION...
Issued at 123 PM EDT Sat Jul 4 2026
- Pop-up Thunderstorms This Afternoon and Evening
A surface trough over the area and weak cold front will sink south
this afternoon. Already seeing building cumulus and showers
developing north of I-96. Surface based CAPE will increase to 1000
to 1500 J/kg this afternoon. Shear however is lacking. Therefore not
expecting anything organized or severe, just some general pop-up
thunderstorms with lightning and brief heavy downpours as the main
concern. Thunderstorms will generally taper off around sunset with
the chance for lingering showers and storms across southern Michigan.
- Showers and Thunderstorms Mainly South Tonight into Sunday
As mentioned showers and thunderstorms could linger in southern
Michigan overnight due to a disturbance moving through northern
Illinois under the surface trough. HREF probabilities are not high
though so it is possible that areas along I-94 could remain dry.
Sunday we`ll see another diurnal trend with storms mainly focused
along and east of a Kalamazoo to St. Johns line. Instability will
only be around 1000 J/kg and with similar shear values to today do
not expect any severe weather.
- Dry Monday through Wednesday, Showers and Thunderstorm Chances
Return Late Wednesday Night into Thursday
High pressure builds in for Monday through Wednesday. The ridge
weakens Wednesday night with an approaching trough. There are some
timing differences with this shortwave moving through sometime in
the late Wednesday night/Thursday timeframe. The timing will impact
whether we see lingering rain chances for Friday or if we`ll see dry
conditions. Overall with this system there will be a weak low level
jet, and upper level jet divergence may be displaced. Overall not
seeing a concern for a severe risk at this time.
High temperatures through the week will largely be in the 80s with
lows in the 50s and 60s. A nice break from the hot temperatures
this past week.
&&
.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 102 PM EDT Sat Jul 4 2026
Earlier MVFR cigs have broken up with scattered low clouds likely
to persist into the afternoon. After 20z, scattered pop up
thunderstorms are likely, especially for LAN/JXN, however
confidence in terminal impacts to a particular terminal remains
low. As such, the earlier PROB30s remain in place with amendments
made as needed. Overnight, signals suggest pockets of low clouds
may (30%) develop tonight. Have added SCT MVFR clouds for now and
will add restrictions if confidence increases. Any clouds will
lift/break up Sunday morning after daybrek.
&&
.MARINE...
Issued at 123 PM EDT Sat Jul 4 2026
Thunderstorms will be possible this afternoon and evening before
tapering off around sunset. Waves will remain below 3 feet through
next week. Northerly winds Sunday afternoon and Monday afternoon may
briefly approach Small Craft Advisory criteria toward Big and Little
Sable. Northerly winds are largely expected through Monday with
winds potentially becoming easterly each night. Tuesday winds become
westerly then southwesterly for Wednesday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...RAH
AVIATION...Thomas
MARINE...RAH
NWS GRR Office Area Forecast Discussion
