956
FXUS63 KGRR 080759
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
359 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 /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 212 AM EDT Sat Aug 8 2026
Some fog/stratus is certainly possible early this Saturday
morning, but it does not appear to be anywhere near as widespread
as yesterday morning. We are looking at some MVFR ceilings and
visibilities this morning from roughly 09Z to 14Z, especially from
AZO east to JXN and possibly LAN as well. VFR weather is then
forecast for the most part through the remainder of the TAF
period.
There is a chance for some isolated showers and storms to occur
this morning, but threat is small enough to not include at this
time. If showers/storms do form early this morning it will be for
MKG to GRR before 12Z. Showers and storms are also possible from
AZO to LAN and JXN a bit later this morning, but have left out of
the TAFs at this time due to low confidence in evolution.
&&
.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
