657
FXUS63 KGRR 231142
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
742 AM EDT Thu May 23 2024

.KEY MESSAGES...

- Potential for Storms Friday Evening / Night

- Precipitation Ends on Saturday

- Rain Likely in Sunday Through Tuesday Time Frame

&&

.DISCUSSION...
Issued at 337 AM EDT Thu May 23 2024

- Potential for Storms Friday Evening / Night

Weather conditions stay quiet today under upper ridging. Into Friday
morning an upper shortwave will pivot into the region from the
Northern Plains. A corresponding surface low will travel from
Minnesota into western Ontario with a trailing cold front sweeping
through the midwest. Surface flow across southern Michigan turns
southerly ahead of the cold front with dewpoints increasing into the
mid 60s. Mid-level lapse rates don`t look overly impressive over
lower Michigan, and there is still disagreement on instability
Friday afternoon and evening. There does appear to be agreement on
the higher instability developing over the far southwest corner of
Lower Michigan which corresponds well with the SPC Day 2 outlook
Slight Risk over southwest Michigan.

Similar to the Tuesday storms, these storms will be easily trackable
as they travel from Iowa through Illinois and into Indiana and
southern Michigan throughout the day. The primary storm mode will be
linear along the front with some bowing segments possible. Damaging
wind gusts will be the primary hazard as the storms travel into
southern Michigan.

- Precipitation Ends on Saturday

Morning showers and thunderstorms should come to an end in the
midday hours of Saturday as a cold front progresses off to the east.
Moisture is shunted to the east early in the day and there should be
plenty of sun with dry conditions for many for most of the day. Dry
weather will persist Saturday night and into Sunday.

- Rain Likely in Sunday Through Tuesday Time Frame

Model disparity exists in the Sunday through Tuesday time frame and
really event into Wednesday. The uncertainty is in how an upper
trough moving through the northern tier of the CONUS interacts with
a trough in the mid levels over Canada. The ECWMF phases with the
Canadian trough earlier which produces a deeper low earlier on
(Sunday night into Monday) vs the GFS which is later with the
stronger low (Tuesday into Tuesday night). Bottom line is the Sunday
through Tuesday time frame looks unsettled with chances for rain
throughout. Can`t rule out a few storms at times, but we are not
looking at severe weather given a lack of strong instability. Cool,
showery weather is more of what is expected. Our forecast has highs
in the 60s for Monday through Wednesday. Could see the need to lower
highs on Sunday as well, which are currently in the low to mid 70s.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 739 AM EDT Thu May 23 2024

Ideal aviation conditions (VFR) are expected the next 24 hours,
with mostly clear skies, no restrictions to visibility and winds
generally 10 knots or less. Winds will be southwest to west today
at 5 to 10 knots. A few gusts of 10 to 15 knots can be expected at
times.

&&

.MARINE...
Issued at 337 AM EDT Thu May 23 2024

Wave heights continue to fall today and into Friday with no marine
concerns to note. Storms will be possible Friday afternoon and
evening, then westerly winds build Saturday morning leading to waves
increasing towards 3 to 4 feet. Winds and waves stay marginally
below Small Craft hazards, but waves will be hazardous to any
swimmers that are brave enough to venture into 50 to 60 degree
water.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Duke/Thielke
AVIATION...Duke
MARINE...Thielke