042
FXUS63 KGRR 121023
AFDGRR
Area Forecast Discussion
National Weather Service Grand Rapids MI
623 AM EDT Tue May 12 2026
.KEY MESSAGES...
- Showers today; afternoon/evening thunder possible
- Frost possible north Wednesday night
- Warmer with showers/storms possible late weekend and next week
&&
.DISCUSSION...
Issued at 312 AM EDT Tue May 12 2026
- Showers today; afternoon/evening thunder possible
An approaching clipper will push isolated showers through the cwa
this morning. However, during the afternoon, coverage of the
showers will increase as the low gets closer. Although instability
isn`t overwhelming, mid level lapse rages increase to 6.5-7c/km this
afternoon that may result in a few storms 21z-03z. Lift will also
be aided by the arrival of the accompanying upper level short
wave. Expect the strongest storms to remain west and southwest of
the cwa.
- Frost possible north Wednesday night
Colder air will flow into the region once again behind the
clipper. Highs Wednesday will be in the upper 40s north to mid 50s
south and lows Wednesday night will fall into the mid 30s along
the northern row of counties. Thus, another frost advisory may be
needed Wednesday night.
- Warmer with showers/storms possible late weekend and next week
Late in the weekend, we develop a broad southwest flow as ridging
takes hold over the northeast US. This will send a plethora of
short waves moving up the ridge toward the Great Lakes. As
moisture and temperatures increase, the result will be an
increase in convective development. NCAR medium range AI ensembles
point toward Sunday and Monday as timeframes when convection
could be stronger. It`s during this time that a developing low
over the Plains begins to lift north and a warm front moves into
the cwa followed by the trailing cold front.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 618 AM EDT Tue May 12 2026
No significant changes to the forecast. Radar shows a decaying
area of light showers moving across the lake. These showers should
weaken as they move closer to MKG. More precipitation was noted
over Wisconsin, closer to the low. As this precipitation moves
over the terminals late this afternoon and evening, we`re likely
to see some thunder develop as instability increases with the
arrival of an upper short wave. Additionally, a LLJ moving across
the Lower Peninsula will create some LLWS after 00z.
&&
.MARINE...
Issued at 312 AM EDT Tue May 12 2026
No changes to the small craft advisory. Winds and waves will pick
up in speed and height as the pressure gradient tightens in
response to a clipper moving across the state. Highest waves will
be north of Holland this afternoon. After a brief lull, the winds
will shift to the northwest tomorrow and waves will build
southward during the afternoon. The small craft advisory may have
to be extended in time Wednesday.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning until 8 AM EDT this morning for MIZ037>040-045-
046.
Frost Advisory until 8 AM EDT this morning for MIZ043-044-
050>052-056>059-064>067-071>074.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.
&&
$$
DISCUSSION...04
AVIATION...04
MARINE...04
NWS GRR Office Area Forecast Discussion
