146
FXUS63 KGRR 121057
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
657 AM EDT Sun Apr 12 2026
.KEY MESSAGES...
- Excessive rainfall threat this week
&&
.DISCUSSION...
Issued at 151 AM EDT Sun Apr 12 2026
- Excessive rainfall threat this week
Sunday through Thursday holds the potential for more flooding
rains as Plains lows track into the Great Lakes. This is similar
to the synoptic pattern that brought flooding earlier this month
and could also result in severe weather at times.
The first batch of rain is currently across Wisconsin associated
with an area of warm advection/isentropic ascent. Expect some
elevated convection persisting into this morning north of a warm
front, across the northern half of the forecast area. Surface-
based instability is limited until the front pushes north on
Sunday afternoon.
Another round of rain and embedded thunderstorms then follows for
tonight along the front trailing the sfc low tracking into
southern Canada. Model soundings show deep moisture and this is
reflected in precipitable water of 1.5 inches. MBE vectors are
less than 5 knots during this time indicating any persistent
updrafts will result in flooding rains.
There is only a short lull before a series of surface lows move
along a baroclinic zone aligned from the Southern Plains to the
central Great Lakes from Tuesday into Thursday. Tuesday afternoon
shows wind profiles that would support severe weather threat but
this is conditional on clouds/precip limiting instability.
The wet pattern should continue even beyond that as all model
guidance depict a significant low arriving by next Saturday.
&&
.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 657 AM EDT Sun Apr 12 2026
Scattered showers and thunderstorms today, with the steadier rain
mostly north of central and southern Lower Michigan through the
afternoon. MVFR conditions, with patchy IFR are possible
overnight. LLWS can be expected overnight into this evening.
&&
.MARINE...
Issued at 151 AM EDT Sun Apr 12 2026
No changes to the SCA, but it may need to be extended beyond
Monday afternoon as southwest winds of 25 knots are forecast for
Monday night and Tuesday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 4 PM EDT Monday for LMZ844>849.
&&
$$
DISCUSSION...Ostuno
AVIATION...Ostuno
MARINE...Ostuno
NWS GRR Office Area Forecast Discussion
