658
FXUS63 KGRR 191050
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
650 AM EDT Tue May 19 2026
.KEY MESSAGES...
- Showers and storms today, some may be strong southeast of GRR
- Cooler and drier air settles in for Wednesday and Thursday
- Unsettled weather for Friday into the weekend
&&
.DISCUSSION...
Issued at 358 AM EDT Tue May 19 2026
- Showers and storms today, some may be strong southeast of GRR
A decaying area of showers and embedded thunderstorms are slowly
pushing east from Wisconsin and Illinois at 345am with some
scattered development over Lake Michigan. We expect the main area
to move into the lakeshore counties between 600am and 800am. This
activity should remain on the weak side given limited instability.
It is being aided however by strong low level moisture transport
which can never be underestimated. We will be monitoring but this
convective activity should remain below severe criteria.
The focus will then become the redevelopment this afternoon and
early evening along and ahead of the advancing cold front. We are
relying on the HREF for timing and location. We expected showers
and storms to reintensify southeast of a line from Holland to
Grand Rapids to Lansing. Storms should move through our southeast
CWA (AZO, BTL, LAN and JXN) between 400pm and 800pm. MUCAPE values
are more than adequate, forecast to be between 1,000 and 2,000
j/kg. The best shear lags the front, so deep layer values will
only be in the 20-30 knot range. Bottom line severe weather is
possible with wind being the main threat especially towards JXN.
35 knot winds at 850mb and 50 knots at 500mb support that
thinking.
- Cooler and drier air settles in for Wednesday and Thursday
850mb temperatures plunge as we head into Wednesday behind the
cold front. +2C to +3C air will be over a large portion of the CWA
on Wednesday which will hold highs to the 50s over Central Lower
and the 60s to the south. Lows Wednesday night will reach the 30s
over Central Lower and we will likely need Frost/Freeze headlines.
The cool and dry weather will continue into Thursday as surface
high pressure slides through the Great Lakes. Highs on Thursday
will be in the low to mid 60s area wide.
- Unsettled weather for Friday into the weekend
The models continue to show rain spreading back into the Great
Lakes from the south and southwest on Friday. The rain chances
will linger into the weekend. Embedded shortwaves in a developing
southwest flow will be the culprit for the precipitation as will
be weak front and surface low. Highs will warm into the 70s over
the weekend. The south could see 0.50 to 0.75 inches of rain from
Friday into Saturday.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 650 AM EDT Tue May 19 2026
Showers and a few thunderstorms moved into Western Lower Michigan
within the last hour or so. The activity is running into fairly
stable air and has largely dissipated. VCSH is what we are looking
at the next 4 to 6 hours given the widely scattered activity. It
is not until this afternoon in the 19z to 23z time frame where
showers and storms refire in earnest. AZO, BTL, LAN and JXN stand
the best chances at thunderstorms this afternoon and evening.
There is a chance of MVFR ceilings today, but conditions remain
VFR at this point across Lower Michigan. A cold front will sweep
through this evening ending any chance for showers or lower
ceilings.
Wind will be noticeable today from the southwest at 15 to 30
knots.
&&
.MARINE...
Issued at 358 AM EDT Tue May 19 2026
We have extended the Small Craft Advisory on Lake Michigan through
800am Wednesday for all zones between St. Joseph and Manistee.
Strong southwest winds to 30 knots can be expected today before
switching to the northwest behind the passage of a cold front this
evening. The northwest winds this evening will push towards 30
knots as well which is the reason for extending the SCA in time.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.
&&
$$
DISCUSSION...Duke
AVIATION...Duke
MARINE...Duke
NWS GRR Office Area Forecast Discussion
