192
FXUS63 KGRR 010723
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
323 AM EDT Mon Jul 1 2024

.KEY MESSAGES...

- Sunny, Dry, Relatively Cool Today

- Shower/Thunderstorm Chances Tuesday into Wednesday

- Another Round of Storms Friday

&&

.DISCUSSION...
Issued at 323 AM EDT Mon Jul 1 2024

- Sunny, Dry, Relatively Cool Today

Center of surface high pressure will be over Lower Michigan
during the middle of today. Temperatures start off rather cool,
about 10-15 degrees below normal, but should warm up into the mid
70s (still a little below normal) with abundant sunshine. Dew
points will be on the dry side for summer, around or even below 50
degrees.

- Shower/Thunderstorm Chances Tuesday into Wednesday

As high pressure moves east of the region, southerly low-level
winds bring returning warm air on Tuesday. Cirrus and altostratus
clouds will stream in within the southwesterly upper-level flow in
advance of the next shortwave trough. There is a chance of rain
showers during the day, particularly north of Grand Rapids toward
Ludington, though initially any precip from the midlevels will
have to overcome dry low-level air on the way down. MUCAPE
appears meager but perhaps just enough for a slight chance
thunderstorm mention during the day. Rain showers become more
likely Tuesday night, especially north of GR toward Ludington,
where there may some repeating thunderstorms and narrow swaths of
rain totals over an inch.

A weakening cold front enters the CWA from the northwest and
dissipates over the area early on Wednesday. The main low level
jet pivots through the region during this time with the axis of
instability and highest PWATs pushing through as well. Ensemble
QPF plots capture this weakening trend to the system as it arrives
by showing lowering 24 hr value from Ludington to Jackson along
with decreasing number of members having measurable values. This
will be reflected in the POP forecasts for this period.

- Another Round of Storms Friday

A southwesterly upper level jet streak arrives in the Great Lakes
Region during this period. In the mid levels an associated
deepening wave tracks in during the day. From the ECMWF, the
combination of deep layer shear and instability would support some
organized convection during the day. The surface wave reflects a
warm front in the CWA, so that will need to be monitored. Modeled
ensemble QPF values show a lot of spread in the various models so
some uncertainty exists with this system. Overall though enough
confidence exists to feature a risk for thunderstorms associated
with this wave that moves in.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 134 AM EDT Mon Jul 1 2024

A large high pressure system was centered over Lower MI. Stronger
subsidence associated with this feature will act to keep the skies
mainly clear. The weaker pressure gradient will last through the
period. An onshore flow will likely develop near the lakeshore
during the afternoon.

&&

.MARINE...
Issued at 323 AM EDT Mon Jul 1 2024

Sunday`s north winds upwelled colder water along much of West
Michigan`s shoreline. The buoys a few miles offshore of Port
Sheldon and South Haven recorded a water temperature drop from the
mid-upper 60s to around 50. With a high pressure system passing
through today, light winds from the east this morning should
become light from the west this afternoon as the lake breeze
circulation sets up.

Increasing south-southeast winds Tuesday and southwest winds on
Wednesday may make parts of the shore hazardous for small craft
and swimming due to waves and currents. These south winds should
help the water temperatures gradually recover this week.

&&

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

&&

$$

DISCUSSION...CAS/MJS
AVIATION...MJS
MARINE...CAS