129
FXUS63 KGRR 030742
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
342 AM EDT Mon Jun 3 2024

.KEY MESSAGES...

- Morning Fog, Warm and Rain-Free Daytime, Chance Storm Tonight

- Medium/High Confidence in evolution of upper troughing this week

&&

.DISCUSSION...
Issued at 342 AM EDT Mon Jun 3 2024

- Morning Fog, Warm and Rain-Free Daytime, Chance Storm Tonight

Airport observations, webcams, and nighttime microphysics satellite
imagery indicate regions of fog in a few different parts of the
area, and variable visibilities within those regions including
occasional dips to a quarter mile. Fog should mix out over land by 8
or 9 AM with a fair amount of sunshine today.

Keeping the forecast rain-free until after 7 or 8 PM based on the
00Z HREF, which is slightly later with the timing than the previous
12Z run. Convection from Iowa to Wisconsin and northern Illinois
today will struggle to make it into Michigan with slight ridge
amplification over the eastern Great Lakes and a lack of upper-level
jet support. Somewhat better dynamics and 850-700 mb moisture
advection arriving after 8 PM will provide better chances of a
thunderstorms from Wisconsin being maintained, especially northwest
of Grand Rapids. CAPE less than 500 J/kg would be a limiting factor
especially with eastward extent. Each model within the HREF has its
own take on the decay of the Wisconsin convection over Michigan
tonight, so confidence in the details is low.

- Medium/High Confidence in evolution of upper troughing this week

There remains good agreement among model solutions with the closed
upper low approaching from the northwest this week. This low figures
in the evolution of persistent troughing across the Great Lakes by
the end of the week with lower 500 mb heights and low level
northwest flow indicating cooler than normal temperatures into early
next week.

As far as rain chances,Tuesday will see some showers and
thunderstorms in moist southerly flow ahead of the upper low with
the best chances on Wednesday as a cold front will focus rain and
embedded thunderstorms. Deep layer shear is progged to be 25 to 30
knots on Wednesday afternoon so some organized convection is
possible, although severe storm threat appears low.

The upper low will bring showery and seasonably cool weather for
several days from late week into early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 115 AM EDT Mon Jun 3 2024

Patchy IFR conditions are expected overnight in areas of fog and
low stratus. The fog will dissipate after sunrise with VFR
conditions during Monday. Winds will be light and variable tonight
and generally from the south AOB 10 knots on Monday.

&&

.MARINE...
Issued at 342 AM EDT Mon Jun 3 2024

Areas of dense fog are present along the shore especially between
Holland and Ludington, as indicated by satellite images and webcams.
Expecting the fog should diminish later this morning as southerly
winds increase. Waves build to 1 to 3 feet today, highest near the
Sable Points. May have to contend with thunderstorms crossing the
lake after 7 PM, though models suggest they will be on a weakening
trend. Additional thunderstorms could affect the nearshore waters
between Tuesday evening and Wednesday morning.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Dense Fog Advisory until 9 AM EDT this morning for LMZ845>849.

&&

$$

DISCUSSION...CAS/Ostuno
AVIATION...Ostuno
MARINE...CAS