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488
FXUS63 KGRR 021147
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
747 AM EDT Thu May 2 2024

.KEY MESSAGES...

- Chance for thunderstorms later today into Friday

- Warm and Mostly Dry Weekend

- Showers and Storms Tuesday/Tuesday Night

&&

.DISCUSSION...
Issued at 347 AM EDT Thu May 2 2024

- Chance for thunderstorms later today into Friday

The first half of the day today should continue where Wednesday left
off with mild temperatures and some cloud cover in place. We will
see some smaller rain chances start to develop after noon for areas
further North and West. The reason this is the case is that the low
level jet that will be driving this round of showers and storms will
be focused much more to our NW. In addition, the lower level
moisture is lacking here, with a good deal of mid clouds moving
through. This is likely to result in a few sprinkles/light showers
falling from a mid cloud deck.

The best chance for rain will come later this evening and last
through Friday morning before starting to push east of the forecast
area. This is when the last part of the low level jet is exiting the
area, and moisture pooling ahead of the sfc front will be sufficient
for rain to be likely.

Thunder chances start to move over the area this afternoon, once
again further NW, closer to the low level jet and the better
moisture and warmth aloft. Some of the convection allowing models
are trying to bring MU CAPEs up into the 1500 J/kg toward midnight
tonight, supporting a thunder mention. The amount of instability is
likely what the Marginal Risk from the SPC is focused on. It is a
pretty healthy amount of instability present.

The limiting factors that will keep the storms likely on the more
tame side is due to the upper wave staying well west of the area.
This track will also take the core of the low level jet further
west. The entire system will take its time to move through the
entire area with the front almost nearly parallel to the upper flow.

- Warm and Mostly Dry Weekend

A secondary weak sfc cold front is shown to slowly drift in from the
west over the weekend as the nrn Plains upper low/trough moves to
Hudson Bay. Only 20-30 pct pops are in the forecast ahead of this
feature however due to lack of stronger forcing, and the bulk of the
weekend should be dry with warm temperatures in the 70s.

A weak sfc high and drier air mass builds in behind that front for
Sunday night into Monday and the baroclinic zone temporarily settles
just south of MI. Also an upper ridge builds overhead during this
time as next upper low/trough moves into the nrn Plains, suggesting
a dry day. However the warm front returns north again on Monday
night which brings a renewed chance of showers and storms.

- Showers and Storms Tuesday/Tuesday Night

A potentially active period is Tuesday afternoon and evening as a
shortwave heads northeast from KS and sends a front in our
direction. Moisture return from the Gulf via 40 kt low level jet
should result in numerous showers and storms developing and will
carry 60-70 pct pops. Fcst confidence in convective potential
decreases by the middle of next week with large ensemble QPF/timing
spread noted, but temps look to remain above normal.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
-- Changed Discussion --
Issued at 746 AM EDT Thu May 2 2024

VFR continuing today into much of tonight as incoming clouds have
bases mostly above 8000 kt. A few showers could occur this
afternoon into tonight and a few thunderstorms cannot be ruled out
as well after 00Z. Confidence is still too low to carry thunder
in the TAFs tonight with the exception of MKG which is closer to
the low level jet. Toward the end of the period MVFR cigs are
possible at MKG and GRR. Winds increasing out of the southeast
today to around 10 kts.
-- End Changed Discussion --

&&

.MARINE...
Issued at 347 AM EDT Thu May 2 2024

We are cautiously optimistic that we will not need any marine
headlines for the next couple of days. There is an increasing
pressure gradient coming in later today and tonight. This looks to
be offshore in nature, and will be warmer air riding up over the
cooler waters of Lake Michigan. Winds could be up around 20 knots,
just below criteria.

High pressure building over the area for this coming weekend will
give boaters a chance to get out on the waters with good boating
conditions expected.

&&

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

&&

$$

DISCUSSION...Meade/NJJ
AVIATION...Meade
MARINE...NJJ