560
FXUS63 KGRR 251936
AFDGRR

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

.KEY MESSAGES...

- Patchy fog with a chance of showers Wednesday morning/afternoon

- High Pressure tracks through Thursday into early Friday

- Thunderstorm chances increase Friday afternoon into  Saturday

&&

.DISCUSSION...
Issued at 301 PM EDT Tue Jun 25 2024

- Patchy fog with a chance of showers Wednesday morning/afternoon

Strong westerly flow will continue through the rest of the day
keeping wind gusts upwards of 30 mph. The strong flow will keep
the area mixed before winds finally start to subside mid to late
evening. Much of the area along and south of I 96 received an
inch or more with areas along the lakeshore receiving several
inches of rain. With drying in the mid levels, calm winds at the
sfc, a strengthening sfc inversion and trapped low level
moisture, patchy fog is expected along and south of I 96,
especially along the lakeshore. Patchy dense fog in low lying
regions is possible.

Any fog will lift/dissipate by late morning. A weak trough will
swing through tomorrow, late morning into the afternoon. There is
a chance for storms with this system. This trough will bring with
it a low level jet, though it is only around 30kts. MEAN CAPE
values are below 1000 J/kg. Daytime highs are expected to only get
into the low 80s. So while there is enough instability, shear and
dynamics for storm formation, there shouldn`t be enough for severe.
 Skies should clear in the wake of the exiting trough mid to late
afternoon tomorrow.

- High Pressure tracks through Thursday into early Friday

Models are in decent agreement in showing a larger Canadian high
pressure system tracking east southeast through Lower Michigan
during this timeframe.  Stronger subsidence arrives as this system
moves in Thursday leading to mainly clear skies.  Warm advection the
backside of the departing wave will support an increase the mid to
upper level clouds especially as the ridge axis will be east of the
area.  We will feature slightly below normal temperatures for this
period.

- Thunderstorm chances increase Friday afternoon into  Saturday

An impressive surge of moisture is shown to arrive ahead of the next
storm system Friday afternoon/evening.  PWAT`s are shown to climb up
to around 2 inches.  This is well above normal.  The upper level jet
strengthens as a trough builds in from the west. This trough axis
pivots east of the area by 18z Saturday. The instability axis shifts
east of the area by 18z Saturday.  As a result the bulk of the
thunderstorm activity should be prior to 18z Saturday.  As a result,
while we will feature some shower/storm activity Saturday, we will
feature falling POPs, especially in the afternoon.

&&

.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 330 PM 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
into this evening. Rapidly changing lake fluctuations will also
create rip currents that will be dangerous to swimmers.

Expect patchy fog early Wednesday morning which will reduce
visibilities into mid morning. There will be a chance for showers
and perhaps an isolated thunderstorm late Wednesday morning/early
afternoon. Another small craft advsy/ beach hazards statement may
be needed due to strong winds in the wake of an exiting system
late Wednesday into Thursday.

&&

.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.

&&

$$

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