986
FXUS63 KGRR 160653
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
253 AM EDT Fri May 16 2025

.KEY MESSAGES...

- Another round of thunderstorms Friday evening then fair and
  cooler into early next week.

&&

.DISCUSSION...
Issued at 252 AM EDT Fri May 16 2025

Severe storms have moved east and there will be a temporary lull
in the weather until a second batch of storms arrives Friday
evening, associated with a cold front trailing from the sfc
cyclone tracking across the Michigan UP.

Downburst winds will the main threat, generally between 8 pm and
11 pm, with instability waning during the evening but impressive
deep layer shear greater than 50 knots resulting in organized
convection, mostly in the form of bowing line segments, but enough
directional shear to allow for some rotating updrafts as well.

Cooler, showery weather moves in behind the front for Saturday and
Sunday then a Canadian surface high builds in with fair weather
into at least early next week. Good radiational cooling
conditions Sunday and Monday nights could bring scattered frost
with lows in the 30s across the northern zones. Rain chances
return by mid-week although some model guidance suggest most of
the precip remains south of Lower Michigan.

&&

.AVIATION /06Z TAFS SATURDAY THROUGH 06Z SUNDAY/...
Issued at 1258 AM EDT Fri May 16 2025

Strong large scale subsidence in the wake of the thunderstorm
complex will support mainly clear skies through the duration of the
night and Friday morning. Daytime heating will boost mixing depths
resulting in south winds gusting over 20 knots at times by Friday
afternoon. The passage of an upper level short wave and late day
instability will support a good chance for thunderstorms Friday
evening, primarily in the 01Z to 06Z time frame.

&&

.MARINE...
Issued at 252 AM EDT Fri May 16 2025

No changes to the Small Craft Advisory. Winds and waves will be
hazardous to small craft through Saturday evening and winds to 25
knots could persist into Sunday, though the trend will be for
conditions to improve as high pressure builds in from the north
early next week, with winds going off shore and waves decreasing.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from 11 AM this morning to 2 AM EDT Sunday
     for LMZ844>849.

&&

$$

DISCUSSION...Ostuno
AVIATION...SC
MARINE...Ostuno