718
FXUS63 KGRR 060133
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
933 PM EDT Wed Jun 5 2024

.KEY MESSAGES...

- Clearing this evening, then showers/storms tonight

- Scattered showers and cooler Thursday

- Cooler Weekend With Some Showers Possible

&&

.UPDATE...
Issued at 933 PM EDT Wed Jun 5 2024

Continue to expect another wave of showers with some thunderstorms
passing through overnight. Water vapor imagery shows a potent
upper PV maximum entering western WI. Per cooling IR cloud tops
ahead of this feature, convection seems to be strengthening as it
begins its traverse across WI. Precipitation is expected to pass
through our region in the 1 AM to 6 AM timeframe. The 00Z DTX
sounding actually featured MUCAPE on the order of 1300 J/kg and
this is bound to hold or even increase in magnitude with the
introduction of deep forced ascent associated with the PV max.
Overall however, best thunder chances will be near the lakeshore
and towards the north. Convection allowing models have been fairly
consistent with basically everywhere getting touched with some
coverage of precipitation as it moves through southwest Lower MI
overnight.

&&

.DISCUSSION...
Issued at 915 PM EDT Wed Jun 5 2024

- Clearing this evening, then showers/storms tonight

A cold front is currently moving across Lake Michigan and will
sweep across the cwa later this afternoon/evening. Ahead of it,
showers and thunderstorms developed as expected within an
environment characterized by SBCAPE 2500 j/kg but only 25-30 knots
bulk shear. The less than robust shear is likely holding back the
storms from developing further. Radar shows a well defined MCV
moving northeast into southern Calhoun County. This MCV is running
out of real estate to produce stronger storms and the event may be
over before it gets going. Quite a bit of high clouds likely
prevented further destabilization that might have otherwise overcome
the weak shear.

Visible loop shows the back edge of the clearing moving across the
lake and we`ll likely be back in the sunshine/clearing by early
evening.

A strong short wave will move in from the northwest tonight around
midnight. CAMs show another line of showers/isold storms
developing over Wisconsin and then moving over the lake around
05z. There`s roughly 400-500 j/kg MUCAPE to work with, so we may
see some isolated thunder, but most of the precipitation will be
showers.

- Scattered showers and cooler Thursday

As the upper low settles over Lower MI, h5 temps will fall from
minus 11c to minus 16c. Those cooler temps aloft will probably be
enough to generate some instability showers as mid level lapse
rates climb to over 7c/km across northern Lower. Areas primed for
showers would be the northern cwa, closer to the higher
instability. This will continue Thursday night too.

Highs Thursday will range from the upper 60s near US-10 to mid 70s
near I-94.

- Cooler Weekend With Some Showers Possible

Upper troughing with a closed upper low settles over the region late
in the week and through the weekend leading to cooler than normal
conditions and a few chances for light rain. 850mb temperatures fall
into the low single digits late this week leading to daytime highs
in the mid to upper 60s Friday and into the low 70s by Saturday and
Sunday. Overnight lows fall into the upper 40s to low 50s.

A few chances for rain exist through the extend as several
shortwaves ripple through the parent upper trough. Moisture will be
fairly limited, so mainly light rain is expected. Most notably the
chances for rain exist for Saturday and Sunday where some diurnal
heating supports precipitation potential with some thunder possible
Saturday afternoon/evening.


&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 755 PM EDT Wed Jun 5 2024

Showers and storms have moved through so VFR will dominate through
the first half of the overnight period. However a cold front that
is moving through Wisconsin will bring some chances for showers
and storms overnight. Best chance will be between 04Z and 09Z.
Have VCTS at MKG where the best chance for storms will be among
the TAF sites. Elsewhere, while storms are possible, given the
overnight period it will be difficult for these to persist inland
and so due to confidence have left out mention. However showers
will be around after 07Z. After frontal passage expect gusty winds
upwards of 25kts tomorrow late morning.

&&

.MARINE...
Issued at 246 PM EDT Wed Jun 5 2024

A Small Craft Advisory and Beach Hazards Statement remains in
effect from midnight through 4pm Friday. A cold front will move
across the lake late this afternoon and west winds behind it will
bring in cooler air and increase to 20-25 knots. Waves in the 3-5
foot range are expected, highest between Grand Haven and South
Haven where they`ll be closer to 4-5 feet.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Beach Hazards Statement through Friday afternoon for MIZ037-043-
     050-056-064-071.
MARINE...Small Craft Advisory until 4 PM EDT Friday for LMZ844>849.

&&

$$

UPDATE...TJT
DISCUSSION...04/Thielke
AVIATION...Ceru
MARINE...04