031
FXUS63 KGRR 201654
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
1254 PM EDT Sat Jul 20 2024

.KEY MESSAGES...

- Humidity returns, chance of storms north Sunday

- Quiet Weather through Monday, then rain chances return

&&

.DISCUSSION...
Issued at 328 AM EDT Sat Jul 20 2024

- Humidity returns, chance of storms north Sunday

High pressure over the Great Lakes will begin to drift east today
resulting in a southerly flow developing. Dewpoints will increase
and so will the humidity. Highs around 80 and dewpoints around 60
are pretty typical of summer and that`s what we`ll have today,
along with mostly sunny skies.

Another mostly clear sky tonight will send temperatures down to
around 60. The higher dewpoints may result in some patchy fog
overnight.

A deeper upper trough over James Bay will push a weak cold front
south across Lower MI Sunday. The convergence along the frontal
boundary coupled with the higher dewpoints and SBCAPE around 900
j/kg and LI`s around -6c may result in scattered convection
developing over the northern half of the cwa Sunday afternoon.
Given shear values less than 20 kts, no severe wx is expected.


- Quiet Weather through Monday, then rain chances return

Flow regime across the CONUS is dominated by northeast troughing and
western upper high/ridging into next week. Surface anticyclone of
Canadian origin persists over the weekend with low humidity and
offers several days of drying sunshine.

The next chance for rain comes by Tuesday as a shortwave trough
diving southeast from Canada moves across the Great Lakes. Model
soundings by Wednesday afternoon  show some potential for strong
storms with deep layer shear of 30 knots and sfc-based instability
with over 1000 J/kg of CAPE...so we will continue to watch how this
evolves.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1254 PM EDT Sat Jul 20 2024

VFR expected the next 24 hours. SCT cumulus in the 6-8kft that are
presently developing will diminish after sunset with just a BKN
cirrus layer remaining through the end of the TAF window. Winds
will be below 10 knots today becoming light and variable tonight
with some form of westerly component dominating the light winds.
The one possible exception is MKG where SW winds ahead of a
stalled front bring moisture off the lake. A period of MVFR or
lower fog is possible, however confidence in restrictions does not
rise to the level needed for TAF inclusion (only 20-30 percent).
Given the favorable setup and moisture profile will highlight a
window of 6SM BR near daybreak and future packages can add
restrictions if confidence grows.

&&

.MARINE...
Issued at 328 AM EDT Sat Jul 20 2024

Light winds are expected due to high pressure overhead. Winds and
waves will increase a tad late Sunday as a weak cold front moves
south across the lake. At this time, waves should remain less than
2 feet.

&&

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

&&

$$

DISCUSSION...Ostuno/04
AVIATION...Thomas
MARINE...04