378
FXUS63 KGRR 240721
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
321 AM EDT Tue Sep 24 2024

.KEY MESSAGES...

- Wet and Gloomy Day Ahead

- Dry Wednesday/Thursday, then rain chances increase

- Cooler next week

&&

.DISCUSSION...
Issued at 321 AM EDT Tue Sep 24 2024

- Wet and Gloomy Day Ahead

An upper level trough will amplify as it passes into the Great
Lakes Region today. Meanwhile, it`s associated surface low will
slowly track through Lower Michigan this morning and afternoon
bringing spotty showers through much of the day. As the column
gradually saturates further this morning, showers will fill in
late morning to afternoon. Some periods of heavier rain and
embedded non-severe thunderstorms will be possible as PWATS climb
to 1.5" to 1.75", especially across southern Lower Michigan.

Showers diminish in coverage late tonight to early Wednesday, but
some fog potential exists for early Wednesday morning.

- Dry Wednesday/Thursday, then rain chances increase

Models continue to show the deep upper low over the MS Valley
Thursday shearing off the northern part leaving a cutoff low over
the Missouri Valley. Surface high pressure camped out over the
western Great Lakes will result in sunny skies Thursday and early
Friday. What`s left of the Gulf hurricane is progd to move north
into the Ohio Valley, but the high over our region will slow the
northward spread of rainfall. We`ll likely see an increase in
cloudiness, however, Friday afternoon, before the ridge over us
moves east, which will enable the cutoff low to drift north. As the
low moves slowly northward, rainfall chances will increase to 30-50
percent Saturday through Tuesday. Thunder chances aren`t high, but
not zero either.

- Cooler next week

The upper low will finally get kicked east from the next upstream
wave on Monday. This short wave will push a stronger cold front
through the cwa Tuesday dropping h8 temps from 12c to 6c. Highs
Tuesday will be a bit below normal in the mid to upper 60s.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 131 AM EDT Tue Sep 24 2024

Local radar shows light rain moving north toward the terminals.
Along with the rain, MVFR/IFR ceilings will develop within the
next few hours. Look for showers throughout the day. An isolated
thunderstorm is possible too, but given low instability, we left
TSRA out of the TAFS.

Once the rain ends around 00z, fog and IFR/LIFR cigs will develop.

&&

.MARINE...
Issued at 321 AM EDT Tue Sep 24 2024

Winds and waves should be fairly low through much of this week.
Waves may become choppy Wednesday afternoon but should remain below
Small Craft Criteria. Periodic showers, fog, and low clouds may
limit visibility over the next 12 to 24 hours.

Over lake instability today and tonight will present a low chance for
waterspouts across the southern half of Lake Michigan.

&&

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

&&

$$

DISCUSSION...04/Thielke
AVIATION...04
MARINE...Thielke