355
FXUS63 KGRR 161513
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1113 AM EDT Tue Jul 16 2024

.KEY MESSAGES...

- Turning cooler and less humid; still a chance of a few
  showers/storms through Wednesday

- Dry and pleasant weather for Thursday through Sunday

&&

.UPDATE...
Issued at 1101 AM EDT Tue Jul 16 2024

Isolated showers will continue to track in off of Lake MI late
this morning into early afternoon. We earlier updated the
grids/forecasts to account for this trend. They were developing in
an area of moist low level convergence. This low level
convergence persists this afternoon/evening as the inland
locations destabilize. Thus a few storms could develop then. High
res models show very little activity. Surface based instability is
forecast to climb up to 1500 J/kg while Effective Bulk Shear
climbs up to 25 knots. Generally this setup could lead to pulse
stronger cells.


&&

.DISCUSSION...
Issued at 350 AM EDT Tue Jul 16 2024

- Turning cooler and less humid; still a chance of a few
  showers/storms through Wednesday

Widespread showers and storms will be exiting to the east early
this morning although erratic/gusty winds may occur for the next
couple hours in the wake of the departing MCS. The sfc cold front
across nrn Lwr MI has been touching off some scattered tstms and
some of these will impact areas north of I-96 early this morning.

As the cold front continues to sag southward this afternoon some
new diurnally enhanced non-severe cells may develop, although
coverage should be generally limited to areas near/east of
Highway U.S. 127. While these cells will wane/exit with sunset,
the approach of the upper trough later tonight could produce
additional scattered showers and possibly a tstm. The cold front
will bring gradually lowering dew pts after its passage tonight.

The H5 upper trough/cold pool sets up overhead on Wednesday and a
few showers and storms will remain possible despite cooler temps
in the 70s and lower dew pts in 50s behind the cold front.
Coverage should be quite limited though and generally limited to
areas east of Hwy 131 or possibly just near east of U.S. 127
again.

- Dry and pleasant weather for Thursday through Sunday

A stretch of dry and pleasant weather is expected for Thursday
through the weekend as a sprawling area of sfc high pressure
dominates the Great Lakes Region. Highs near 80 and lows in the
50s along with dew pts in the 50s and clear to partly cloudy
skies will make for comfortable/pleasant summer weather.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 749 AM EDT Tue Jul 16 2024

Numerous IFR cigs are present early this morning but these cigs
will scatter out or lift to VFR levels by afternoon. A cold front
dropping south through the area this afternoon may trigger a pop
up shower or storm, with the main risk being at the LAN and JXN
terminals. VFR expected tonight although a mid level cloud deck
approaching from the northwest could produce a few light showers
or sprinkles during the overnight period. West sfc winds of 10 to
20 knots today will diminish to 5 to 10 kts after 00Z this
evening.

&&

.MARINE...
Issued at 350 AM EDT Tue Jul 16 2024

Increased westerly flow this morning in the wake of last night`s
thunderstorms may produce 2-4 ft waves and a moderate swim risk
at west MI beaches this morning. (Latest Port Sheldon buoy ob
shows 3.6 ft.)

A cold front slides down the lake this afternoon and evening,
shifting the winds to the north-northwest. We will likely need a
Small Craft Advisory and Beach Hazard Statement for Wednesday as
the winds increase to near 20 kts along the coast in the
afternoon.

High pressure will dominate the GrtLks Rgn later this week
resulting in an extended period of relatively tranquil conditions
on Lk MI-- other than the typical afternoon/early evening
increased onshore breezes. It`s possible the northerly flow on
Wednesday will result in an upwelling event and cooler water temps
at the beaches although confidence low at this time.

&&

.HYDROLOGY...
Issued at 1113 AM EDT Tue Jul 16 2024

JACM4 has peaked and will fall below flood stage this afternoon.
Additional rainfall over the next couple of days will stay under a
tenth of an inch, limiting any additional runoff. Rises are
expected on area rivers from the rainfall over the past few days,
but at this time, only JACM4 is forecast to reach or see values
above flood stage.

&&

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

&&

$$

UPDATE...MJS
DISCUSSION...Meade
AVIATION...Meade
MARINE...Meade
HYDROLOGY...MJS