992
FXUS63 KGRR 300753
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
353 AM EDT Mon Sep 30 2024

.KEY MESSAGES...

- Patchy fog possible this morning with Warm weather today

- Chance of showers and storms Tuesday

- Mostly Dry and Seasonal Mid to Late Week

&&

.DISCUSSION...
Issued at 352 AM EDT Mon Sep 30 2024

- Patchy fog possible this morning with Warm weather today

 Any lingering showers and most of the low clouds remains along
the Michigan border. The dropping temperatures and low level
moisture coupled with calm winds could allow for some patchy fog
this morning, especially in and around Jackson. A positively tiled
ridge will build over the region today. This will bring fair
weather with max temperatures today expected to be in the upper
70s to low 80s which is 10 to 15 degrees above normal

- Chance of showers and storms Tuesday

 The warm temps and fair weather will be short lived as an upper
level system will swing a cold front through the region tomorrow.
There is still a narrow band of moisture that will correspond
with the cold front which could spark some thunderstorms Tuesday
afternoon. Latest models continue to show a lack of moisture
through the western portion of the state which makes instability
questionable. As the front gets through the central lower
peninsula the short wave amplifies and HREF is showing then
around 500 to 1000 J/kg of CAPE. So while moisture remains limited
through the western side of the state the eastern half should 1
to 1.25 inch PWATS. That anomalous moisture could aid in
thunderstorm development Tuesday afternoon. So have trended upward
in POPS with an thunderstorms west of US 131 and mainly along and
east of the US 127 corridor. The front will cool temperatures and
move through quickly exiting the region Tuesday night.

- Mostly Dry and Seasonal Mid to Late Week

A fairly uneventful mid to late week period expected with a zonal
flow aloft dominating and the upper jet core remaining mostly to our
north along the U.S./Canadian border. High temperatures will average
near to above normal in the 65 to 75 degree range. Some patchy frost
cannot be ruled out early Wed morning north of I-96 depending on the
extent of clearing behind Tuesday`s cold front.

A weak sfc frontal boundary is shown to come into the area on
Thursday and stall out nearby into Friday. Upper jet entrance region
dynamics may come into play as the swift Pacific jet temporarily
buckles south into the Upper Midwest, but moisture looks to be
lacking and only 20 pops seem justified at this time.

A better cold front may enter the picture next Sunday which could
support a better risk of showers. However cluster analysis that far
out currently depicts considerable uncertainty as to whether or not
upper troughing to support that front digs south into the region,
and to what extent. Only 20-30 pops are justified at this time.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 149 AM EDT Mon Sep 30 2024

VFR conditions exist areawide at 06z but we expect new areas of
low stratus to develop and expand overnight...especially toward
12Z Monday. Confidence is low as to the areal coverage/extent of
the stratus and just how low the cigs/vsbys get, with highest
potential of IFR/LIFR at LAN and JXN then decreasing west from
there. MKG is expected to remain entirely VFR and GRR could go
either way being right on the edge of it. Stratus gradually
lifting Monday afternoon with most locations becoming VFR again
after 18Z.

&&

.MARINE...
Issued at 352 AM EDT Mon Sep 30 2024

The trends continue to show an increase of winds behind the cold
front Tuesday morning. Behind the front it looks like we will mix
into the 20 to 30 knot range. Combine that with cold air
advection and it`s looking like a small craft advisory is likely
going to be needed for the region.

&&

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

&&

$$

DISCUSSION...Meade/Ceru
AVIATION...Meade
MARINE...Ceru/MJS