402
FXUS63 KGRR 131047
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
647 AM EDT Mon Apr 13 2026
.KEY MESSAGES...
- Excessive rainfall/severe threat this week
&&
.DISCUSSION...
Issued at 233 AM EDT Mon Apr 13 2026
- Excessive rainfall/severe threat this week
The threat of excessive rain continues through the end of the
week, along with severe storms in the vicinity of a stalled front
across central Lower Michigan.
There will be a short lull today between the rain moving through
early this morning and an expected flare up of convection this
evening as another wave of low pressure moves along the baroclinic
zone. The CAMs show convection across southern WI/northern IL this
afternoon moving east as multicell clusters or bowing lines when
they reach southwest Lower Michigan in the evening. Hail and
downburst winds are the main threat, along with localized flooding
as very moist airmass yields heavy rain rates falling on saturated
ground.
The process repeats several successive times Tuesday through
Saturday as shortwave energy ejects from with western CONUS
longwave trough persistent baroclinic zone and southwest flow
keeping deep moisture in place. A break in the action may finally
come later this weekend as sfc high builds in followed by
shortwave upper ridging early next week.
&&
.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 647 AM EDT Mon Apr 13 2026
Low ceilings will bring areas of IFR through the morning,
followed by a gradual improvement to MVFR then VFR in the
afternoon. LLWS continues this morning with some gusts over 25
knots reaching the surface at times through the afternoon.
&&
.MARINE...
Issued at 233 AM EDT Mon Apr 13 2026
No changes to the SCA. There will be a brief lull this afternoon
and evening before winds and waves pick up again tonight so
another SCA will probably be needed for tonight and Tuesday when
the current SCA expires.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Flood Watch through Wednesday morning for MIZ037>040-043>045.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for
LMZ844>849.
&&
$$
DISCUSSION...Ostuno
AVIATION...Ostuno
MARINE...Ostuno
NWS GRR Office Area Forecast Discussion
