653
FXUS63 KGRR 070748
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
348 AM EDT Sun Jul 7 2024

.KEY MESSAGES...

- Dry Sunday With Patchy Fog This Morning

- Shower/Storm Chances Return Sunday Night

- Convergent, moist flow through the first half of the week

- Remnants of Beryl and an increase of warmth mid to late week

&&

.DISCUSSION...
Issued at 347 AM EDT Sun Jul 7 2024

- Dry Sunday With Patchy Fog This Morning

Nighttime microphysics imagery shows areas of fog and stratus have
developed mainly north of I96 with other pockets on the Lake
Michigan shoreline. Additional development will be focused on the
region north of I96 and near/west of US131. Isolated pockets of
dense fog cannot be ruled out. This fog will dissipate by mid-
morning as solar heating ramps up.

Dry weather is expected today as surface and mid-level ridging slide
across the area. Expect beautiful weather in the form of partly to
mostly sunny skies with highs in the low 80s.

- Shower/Storm Chances Return Sunday Night

Low to moderate (20-40 percent) PoPs return to the forecast Sunday
night as warm air advection triggers the chance for showers mainly
north of a Holland to Mount Pleasant line. With HREF MUCAPE < 500
J/kg, thunder coverage will be isolated at worst. Highest PoPs will
be up near Ludington where low-level isentropic ascent is best.

Troughing slowly advances into the upper Great Lakes Monday, with
weak impulses ahead of this trough, combined with diurnal
enhancement from warm July sunshine, reinvigorating a chance (20-40
percent) of showers and storms Monday. The highest PoPs will be
north of I96 where the best shortwave forcing tracks. Given a
general MLCAPE <1000 J/kg and deep layer shear < 30 knots,
thunderstorms should be garden variety storms. Highs will range from
near 80 across the NW CWA where morning showers and cloud cover will
be thickest to the upper 80s across the southern CWA where sunshine
lasts longer.

- Convergent, moist flow through the first half of the week

The pattern for the upcoming week will be dominated by a building
high pressure system over the intermountain west and the
corresponding deep trough moving through the central CONUS that will
bring convergent moist flow over the midwest this week. The upper
level 500mb trough will become a conveyor belt for moisture. Through
this timeframe there is a lack of organized convection, however, the
warm air advection along with the streaming of gulf moisture should
couple with the daytime July temperatures to create an environment
for cloudy skies and daytime showers and afternoon storms. Have
scattered POPs through this timeframe. Latest WPC QPF that includes
Tuesday into Wednesday has around an inch to an inch an a half along
the I 94 corridor.

- Remnants of Beryl and an increase of warmth mid to late week

The big story mid to late week is the track of Tropical Storm
Beryl and its affects on the region as it becomes extra tropical.
The previously mentioned trough will be the main steering
mechanism for Tropical storm Beryl as it moves through the central
United States. The latest National Hurricane Center track has
Beryl barreling through the Mississippi and Ohio river valleys mid
to late this upcoming week with the cone of uncertainty covering
most of Michigan`s lower peninsula by 7 PM Thursday. The biggest
concern will be heavy rain showers due to the Gulf moisture. The
latest mid to long range models, including the various ensembles
tracks some showers from the remnants of Beryl Wednesday and
Thursday. There remains some uncertainty on the track and timing
especially when it comes to where the low will move through. Much
of the ensembles still has the low moving through Ohio through
some operational runs bring much of the moisture over southern
Michigan. Due to this have increased POPS through this timeframe.

Temperatures this week will meander around the upper 70s through
the early part of the week ending in the upper 80s into next
weekend which is just above normal for July.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 137 AM EDT Sun Jul 7 2024

Biggest forecast question overnight is the lowering of cigs and
vsbys towards sunrise. Weak flow at the surface should calm by
08Z. Expect for a strong inversion to entrench itself mainly along
and north of the I 96 corridor. MVFR to IFR cigs and vsbys are
expected between 08Z to 14Z at MKG, GRR and potentially LAN.
 The latest models continue the trend that the stratus and fog
should lift quickly after daybreak with VFR conditions returning
by 14Z. We expect a diurnal cumulus field fill in at most sites by
midday Sunday with bases around 4,000 feet.

Winds will be light and variable tonight becoming southwest on
Sunday at 5 to 10 knots.

&&

.MARINE...
Issued at 347 AM EDT Sun Jul 7 2024

Patchy fog is possible across the nearshore waters tonight thanks to
low-level moisture with satellite suggesting some has developed near
Holland/South Haven. High pressure keeps southwesterly winds at or
below 15 knots tomorrow and tomorrow night, and by extension keeps
waves below small craft criteria. Benign marine conditions continue
through at least Tuesday as no major gradient winds are expected to
develop.

&&

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

&&

$$

DISCUSSION...Ceru/Thomas
AVIATION...Ceru
MARINE...Thomas