301
FXUS63 KGRR 251747
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
147 PM EDT Tue Jun 25 2024

.KEY MESSAGES...

- Early Morning Potential for Severe Thunderstorms

- Strong Storms Possible This Afternoon

- Additional Showers Early Wednesday

- Fair weather Thursday then showers and storms Friday/Saturday

&&

.UPDATE...
Issued at 1033 AM EDT Tue Jun 25 2024

The showers and storms that brought damaging winds and hail to the
region have moved to the south. Outflow in the wake of the
exiting storms will bring gusty winds at times upwards of 35 to
45 mph. This wake low will continue to dwindle into the afternoon
with the potential for gusty winds through this timeframe. Gusty
winds of 20 to 30 mph will be possible this afternoon and through
the rest of the day especially along the lakeshore. Winds will
remain out of the southwest before shifting to a more westerly
direction.

&&

.DISCUSSION...
Issued at 241 AM EDT Tue Jun 25 2024

- Early Morning Potential for Severe Thunderstorms

Much of the forecast remains unchanged while we monitor the
cluster of storms currently tracking through northern Wisconsin
that will arrive in lower Michigan within a few hours. As
expected, these storms continue to evolve into a MCS/squall line
with a projected time of arrival into West Michigan around 4 to
6am.

This will largely be a game of monitoring our environment to
estimate the persistence of storms and whether they decay or
prevail. Within the Enhanced Risk upstream of lower Michigan,
these storms are thriving and will evolve in an environment with
3000- 5000J/kg MUCAPE and 50+ knots of Bulk Shear. As the surface
low progresses further east, warm and moist advection will surge
ahead of the storms supporting some ongoing strength. We will not
be as unstable as areas to our west, but a favorable kinematic
environment will support ongoing convection as storms move onshore
and progress east through mid morning. Storms will gradually
enter a weakening stage the further east they progress into lower
Michigan. Damaging wind gusts remain the primary concern as
storms move onshore this morning, but some hail may also occur.

- Strong Storms Possible This Afternoon

The potential for thunderstorms or new convection late tonight
will be dependent on evolution of storms this morning. That is to
say, wherever the frontal boundary sets up is where the best
chance for renewed convection will occur. The strong low- level
jet will weaken as it pivots further south late this morning to
early afternoon, but instability rebounds and may support the risk
for renewed thunderstorms with a damaging wind gust and hail
potential. The main threat area will be near and south of I-96.

- Additional Showers Early Wednesday

Another trough and cold front will sweep through the area
Wednesday morning bringing chance for showers during the first
half of the day. High pressure will fill in during the second half
of the day and into Thursday.

- Fair weather Thursday then showers and storms Friday/Saturday

The flow regime across the Great Lakes this week into next week
features an enhanced belt of westerlies across the northern CONUS in
between subtropical ridging across the southern CONUS and an upper
low across central Canada. Occasional shortwave troughs embedded in
the flow will bring rain chances every couple of days from this
weekend into early next week.

Surface high pressure brings fine summer weather for Thursday into
early Friday before moving east with warm advection pattern
developing by Friday morning. Moisture advection is also increasing
with rain chances by Friday morning as moisture pools ahead of the
the next trough. THere remains some ensemble spread on timing and
and depth of the trough but the consensus has the greatest chance
for showers and storms for late Friday night.

A severe weather threat is possible late Friday night into early
Saturday  as Lower Michigan is in the warm sector and model
soundings show 30 to 35 knots of shear ahead of the cold front.

Surface high builds in behind the front with fair weather for Sunday
into Monday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 138 PM EDT Tue Jun 25 2024

Gusty winds over 25 knots will continue for a few hours through
mid afternoon but the winds will settle down later this afternoon
as the mixing height decreases. An isolated shower/storm is
possible this afternoon but overall the coverage is not expected
to warrant adding them to the TAF forecast at this time. MVFR and
possible IFR fog is now forecasted for later tonight. The recent
rain will as some moisture to the low levels tonight which will
elevated the fog risk. We are monitoring the storm risk for the
southern TAF sites of KAZO, KBTL and KJXN for Wednesday morning.
The atmosphere is forecast to destabilize there by several models
but not all are in agreement on this scenario so we will hold off
on adding them to the forecast at this time.




&&

.MARINE...
Issued at 1013 AM EDT Tue Jun 25 2024

Strong winds will continue in the wake of the exiting system and
will keep winds and waves dangerous to small craft and swimmers
through the day. Rapidly changing lake fluctuations will also
create rip currents that will be dangerous to swimmers. Additional
showers and storms possible this afternoon into the evening, and
again Wednesday morning.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement until 8 PM EDT this evening for MIZ037-
     043-050-056-064-071.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.

&&

$$

UPDATE...Ceru
DISCUSSION...Ostuno/Thielke
AVIATION...MJS
MARINE...Ceru/Thielke