000
FXUS63 KGRR 141522
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1122 AM EDT Sun Apr 14 2024

.KEY MESSAGES...

- Mostly sunny and mild today/Monday

- Risk for Thunderstorms Remains Late Tuesday into Wednesday

- Turning Cooler Late in the Upcoming Work Week

&&

.UPDATE...
Issued at 1116 AM EDT Sun Apr 14 2024

No changes needed with the morning update to the forecast. Skies
are mostly sunny and expected to remain that way. A cold front is
currently moving through the forecast area, stretching from near
the tip of the Thumb to near Muskegon. The front will continue to
sag south through the forecast area with little fanfare. The winds
will actually come down just a bit this afternoon and the core of
stronger winds moves south and east ahead of the frontal zone. 50s
near the immediate shoreline for highs...while inland areas reach
the 70s. Warmest readings will be toward Jackson where upper 70s
are expected.

&&

.DISCUSSION...
Issued at 314 AM EDT Sun Apr 14 2024

Discussion reissued with corrected content below...

- Mostly sunny and mild today/Monday

Interesting little system moving across northern
Wisconsin/northern Lower early this morning. A strong surge of
warm air aloft coupled with robust mid level lapse rates is
helping to produce showers/storms over northern Wisconsin/northern
Lower. Present indications are such that almost all of the rain
will remain north of the cwa, but it`s possible that the northern
row of counties could get clipped with a few showers.

We`ll be solidly in the warm sector today and temperatures will
respond by climbing into the lower to mid 70s before the trailing cold
front moves through later this afternoon.

High pressure will build into the region Monday rendering clear
skies and slightly cooler temperatures compared today. However,
highs in the upper 60s will still be 10 degrees or so above
normal.

- Risk for Thunderstorms Remains Late Tuesday into Wednesday

An upper jet at 250 mb is currently digging into CA/NV and will move
east over the coming days, strengthening as it does so. By Late
Tuesday into Wednesday, Lower Michigan is likely to be positioned in
the left exit region of this upper jet, with upper divergence
present overhead. At 500 mb, models continue to forecast upper low
development over the Rockies and central Plains by late Monday into
Tuesday with a low level jet developing as well as surface
cyclogenesis. Surface low occlusion is forecast to quickly take
place shortly thereafter across the Midwest by Tuesday night. This
low is expected to track over Lower Michigan Wednesday. The
GEFS/CMC/ECE probabilities for measurable rainfall during this
period from Tuesday night into Wednesday is 90%-100% region-wide.

During the day Tuesday, not much may be happening as we await warm
air advection aloft and a rise in low level moisture. This may be
delayed until late in the day. Areas south of I-96 are most at risk
for some showers primarily after 18z Tuesday. Model trends seem to
be delaying this threat a touch so in a reality much of the region
may stay dry for a good portion of the day before a surface warm
front is slated to arrive Tuesday night. It is during the 00z-06z
Wednesday time frame that the environment may start to be conducive
to some showers and elevated thunderstorms.

Showers and some thunderstorms are likely to be ongoing at the start
of Wednesday morning. The ECMWF and GEM have slightly slowed the
arrival of a surface cold front across the region Wednesday
afternoon, which may give areas especially near and south of I-96 a
chance to build some surface based instability depending on what
happens with the morning activity. Numerous ensemble members as well
as the deterministic runs of the GFS and GEM show the potential for
1000+ J/kg of SBCAPE to develop. Tough to say at this point whether
this will be reality, but the risk is certainly there. Fairly strong
winds aloft at 850 mb (40 kts) and 500 mb (40-50 kts) could be
tapped with any convection that develops, though deep layer shear
does not look overly impressive at 30-35 kts. Still, thunderstorms
with strong wind gusts look to be the main hazard on Wednesday. With
a warm front lifting at least as far north as I-96, we`ll also have
to watch for potential for any surface based storms that can tap
into extra low level shear and storm relative helicity along that
boundary.

- Turning Cooler Late in the Upcoming Work Week

GEFS mean 500 mb heights indicate troughing will be dominant across
the Great Lakes late in the week and weekend. Cold air advection at
850 mb looks to be slow but steady from Thursday into the weekend.
Declining temperatures at the surface can be expected during this
time as highs retreat into the 50s Thursday and Friday, then
possibly 40s for Saturday. Periodic rain showers are possible during
this time. Depending on cloud cover over the weekend, frost/freeze
conditions may develop.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 741 AM EDT Sun Apr 14 2024

LLWS will linger for a few more hours before the strong low level
jet departs the region. Otherwise, breezy conditions will be
commonplace through late morning to early afternoon before
decreasing. W winds will gradually veer NW late in the day. VFR
will hold as little in the way of any cloud cover is expected
today.

&&

.MARINE...
Issued at 413 AM EDT Sun Apr 14 2024

Strong winds aloft are getting mixed down to the surface near the
lake shore as evidenced by latest obs at MKG...g32 kts and
BIV...g39 kts. As such we have issued a Small Craft Advisory
through noon for the the lake shore south of Whitehall.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until noon EDT today for LMZ844>847.

&&

$$

UPDATE...Duke
DISCUSSION...04/Hoving
AVIATION...Hoving
MARINE...04