744
FXUS63 KGRR 040556
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
156 AM EDT Sat May 4 2024

.KEY MESSAGES...

- Increasing Chance for Showers/Storms Later Saturday into
  Saturday night

- Dry end of the weekend

- Many chances for rain next week

&&

.UPDATE...
Issued at 1101 PM EDT Fri May 3 2024

Nighttime microphysics imagery shows low clouds beginning to fill
in across Southeast Lower Michigan this evening. Observations
confirm the low clouds with bases below 1,000 feet at several
sites. This stratus should expand and roll into Southwest Lower
Michigan from the east overnight as easterly winds advect the
clouds in. So, quite a bit of the area will be mostly cloudy at
daybreak. Some fog is expected as well, especially near and north
of I-96. Visibilities below 1 mile are expected. Maximum extent of
the stratus and fog should be around 700am. We expect clearing to
take place by midday.

&&

.DISCUSSION...
Issued at 231 PM EDT Fri May 3 2024

- Increasing Chance for Showers/Storms Later Saturday into
  Saturday night

Southerly winds ahead of an approaching cold front will draw up
moisture from the south Saturday into Saturday night. Instability
increases as well later Saturday afternoon into Saturday night,
but overall remains weak. Aloft some upper level divergence is
seen Saturday night over the CWA so that may enhance the lift.
Thus the combination of moisture, lift and instability will likely
lead to showers and a few storms. Ensemble QPF values, while low,
have been trending up with the precipitation for this period.


- Dry end of the weekend

High pressure over the upper Mississippi Valley will produce plenty
of sunshine Sunday. Highs will climb to a couple of degree either
side of 70.

- Many chances for rain next week

The persistent upper trough over the western US is progd to cut off
over the northern High Plains during the middle of the week. The
result will be several short waves that move in our direction and
bring chances for showers and storms.

Tuesday night through Wednesday night will be a time frame that will
see increased chances for precipitation. An occluded front will lift
north toward Lower MI Tuesday afternoon and this will produce some
showers/storms. Present indications are that the strongest
instability will remain south of the state. However, that could
changed this far out. SPC has already highlighted areas to the
southwest of the state for the potential of severe storms.

Another chance of showers/storms will come Thursday and Thursday
night, when the surface low over the northern Plains moves east.
Accompanying short waves and a feed of moisture rich air from the
south will spur convective development during this time.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 156 AM EDT Sat May 4 2024

Areas of IFR/LIFR cigs and vsbys expected through mid morning
Saturday due to fog and low stratus patches drifting westward from
the east side of the state. Conditions turning VFR again by
Saturday afternoon with a scattered to broken cumulus deck lifting
to around 4500 ft. An isolated shower or tstm cannot be ruled out
inland from Lk MI in the late afternoon but the potential (and
the coverage) looks too low to include in the TAFs. The primary
risk of showers and storms holds off until after 06Z Sunday with
perhaps the exception of MKG which may see that threat materialize
by 04Z.

&&

.MARINE...
Issued at 231 PM EDT Fri May 3 2024

Southerly flow will be on the increase Saturday into Saturday
night as a front moves in from the west. This will be warm air
advection and overall the values are expected to remain under 20
knots. Thus we don`t plan on needing headlines a this time.

&&

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

&&

$$

UPDATE...Duke
DISCUSSION...MJS/04
AVIATION...Meade
MARINE...MJS