892
FXUS63 KGRR 081054
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
654 AM EDT Sat Aug 8 2026
.KEY MESSAGES...
- Showers and storms possible today
- Strong storms possible Sunday and Monday
&&
.DISCUSSION...
Issued at 358 AM EDT Sat Aug 8 2026
- Showers and storms possible today
A cold front is situated from Northern Lake Michigan extending
southward to near Chicago and then to the southwest into portions
of southeast Iowa. Along and ahead of the front dew points have
surged to near 70f. MUCAPE values remain well over 1000 j/kg.
Convection continues to develop ahead of the front over Southern
Lake Michigan. So far, the convection has been rather tame. These
storms and additional activity that forms will work its way across
Southwest Lower Michigan this morning. Most of the activity will
be over by 16Z or so. We are not expecting severe weather today,
but some locally heavy rain could occur given PWAT values around
1.5 inches. We should see fair weather from this afternoon through
tonight.
- Strong storms possible Sunday and Monday
Strong to severe storms are possible both on Sunday and Monday
across portions of Southwest Lower Michigan. On Sunday, the cold
front that moves through this afternoon and tonight, slows off to
our south and returns north as a warm front. The warm front will
be the driving mechanism for thunderstorm initiation. There is
fairly high confidence amongst the members of the HREF in bringing
an MCS through the region during the afternoon and early evening.
There could be multiple rounds of showers and storms Sunday as a
25-35 knot LLJ impinges on the warm front. Organized storms are
likely due to a mid level jet which leads to increasing deep layer
shear to in excess of 40 knots by evening. The details and
magnitude of the threat will be determined by how convection
develops upstream tonight into Sunday morning. SPC has much of our
southern CWA in a marginal threat for severe weather. We will be
monitoring trends in the forecast as we head into tomorrow.
Another threat exists for severe weather on Monday as the warm
front stalls over the area. The low level jet is situated over
Southern Lower Michigan and will likely continue to be a focus for
lift as it encounters the warm front over our Southern CWA. A
Slight risk for severe weather exists on Monday roughly over our
southern half of the forecast area or from I-96 to the south.
Could be a second day of rounds of strong storms.
PWAT values will approach 2.0 inches over next two days and with
training of precipitation we could see some localized flooding.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 648 AM EDT Sat Aug 8 2026
A cold front is moving east of the TAF sites as we approach 11Z.
The front is near the line of showers and thunderstorms along the
U.S. 127 corrider from St. Johns to Jackson. We are not expecting
more convection at this time given drier air is trying to press
in behind the front. The showers and isolated storms are largely
over for the TAF sites at this time. We expect VFR conditions and
benign weather for the remainder of the TAF period. The only item
of note is that southwest to west winds will be gusty in the 10-20
knot range today.
&&
.MARINE...
Issued at 358 AM EDT Sat Aug 8 2026
An increase in southwest to west flow early this morning with the
passage of a cold front will build waves from around 1 foot at
300am to the 1-3 foot range through the course of the morning.
Winds and waves will then remain below advisory levels from this
afternoon through Sunday morning. It is Sunday afternoon and night
that is our next concern for building waves. At this time waves
are expected to reach 2 to 4 feet north of Whitehall.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Duke
AVIATION...Duke
MARINE...Duke
NWS GRR Office Area Forecast Discussion
