062
FXUS63 KGRR 030015
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
815 PM EDT Tue Jul 2 2024

.KEY MESSAGES...

- Showers with scattered thunderstorms tonight into tomorrow

- Strong storms remain possible for Friday

- Unsettled weather at times next weekend and early next week

&&

.DISCUSSION...
Issued at 324 PM EDT Tue Jul 2 2024

- Showers with scattered thunderstorms tonight into tomorrow

Scattered showers continue to stream through the region, mainly
along and north of I 96. These showers will continue to move to
the northeast as the incoming trough pushes any remaining high
pressure eastward. A stronger line of showers and storms out ahead
of a frontal system will move through tonight into tomorrow
morning. None of the storms are expected to become severe,
especially given the lack of dynamics and the time of day.
 Dry air will move in behind the exiting convection with clearing
skies mid to late Wednesday.


- Strong storms remain possible for Friday

Most of the area should stay dry on Thursday, before shower/storm
chances move back in for Friday.  We will be in between systems for
the most part on Thursday. The front that moves through on Wednesday
will slip far enough south of the area to take most if not all of
the rain chances with it. There is a small chance the I-94 corridor
sees a brief shower on the northern edge of any complex riding along
the front.

There is fairly good agreement that we will have a potential period
of stronger storms on Friday. Models are in fairly good agreement in
bringing a healthy short wave and associated sfc front through the
area on Friday afternoon. The low level jet associated with the
system will help to bring a warmer and more humid air mass (implying
instability) up over the area ahead of the upper and sfc features.

In addition, an upper level jet max with the upper wave will help to
provide plenty of deep layer shear for the storms that are looking
increasingly likely to form. There are still a lot of details that
have to be worked out, (exact timing, low level flow, etc...) but it
is something we will continue to keep our eye on.

- Unsettled weather at times next weekend and early next week

The system moving through Friday looks to be the beginning of a
general pattern change that is expected to hold over the Upper
Midwest and Great Lakes into next week. We will see general long
wave upper troughing settle in over the area as a fairly extensive
upper ridge will set up over the western half of the country.

The period from Saturday through next Tuesday will see chances for
showers and storms at times. These chances will come via short waves
that will be rotating around the long wave trough. These types of
scenarios are difficult to pin down this far out due to the
evolution of the upper low and where and when if it closes off or
not, and the timing of the short waves.

Generally speaking, temperatures should be kept down slightly with
the lower heights expected. It does not look to be too cool, and
could still be warm if the sfc flow ends up from the south. Even
with multiple chances of rain expected off and on, much of the time
will be dry.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 815 PM EDT Tue Jul 2 2024

Scattered showers this evening mainly north of I-96 impacting
MKG. A few rumbles of thunder in that batch of showers should
clear east over the next hour. A lull in rain activity this
evening with some wind shear possible for northern terminals.

Additional rain will moves into the area after 06z tonight from
the west as a front approaches. All sites should drop towards MVFR
and some northern TAF sites may see a few hours of IFR ceilings.
Clouds will lift around mid-day Wednesday.

&&

.MARINE...
Issued at 324 PM EDT Tue Jul 2 2024

The small craft / beach hazards threat this afternoon into
tomorrow has two portions. The main question was to either wait to
issue the second until the first has ended or to issue an
advisory to encompass both threats. I chose the latter.

South-southeast winds over Lake Michigan will continue to
strengthen this afternoon as a pressure gradient continues to
tighten between the exiting higher pressure and the approaching
frontal system. There will be periods of gusts 25 to 30 knots
mainly at and north of Whitehall.
 There will be a lull in the winds, mainly between 8 pm and 2 am
Wednesday, then the winds will increase out of the southwest
towards sunrise. These winds will coincide with showers and
storms moving through overnight.

 After frontal passage, including the showers and storms, Winds
and waves will slowly decrease Wednesday morning into the
afternoon.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 8 AM EDT Wednesday for LMZ844>849.

&&

$$

DISCUSSION...NJJ/Ceru
AVIATION...Thielke
MARINE...Ceru