489
FXUS63 KGRR 272352
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
752 PM EDT Thu Jun 27 2024

.KEY MESSAGES...

- Chance of showers and storms Friday night into Saturday morning

- Cooler and drier late Saturday through Monday

- Rain chances increase Tuesday-Wednesday

&&

.DISCUSSION...
Issued at 344 PM EDT Thu Jun 27 2024

- Chance of showers and storms Friday night into Saturday morning

While the mild weather will continue through the daytime Friday
with temps getting back into the upper 70s to low 80s, an
elongated mid level trough will bring instability through the
region late Friday night into early Saturday. There will be lots
of mid level moisture associated with this system. Models have
varying timing but high confidence in the feature itself.
Strongest flow will be the far southern Michigan with the main
focus through Ohio and Pennsylvania. That said, there could be
enough shear and instability to overcome any convective
inhibition. As such there is a marginal risk for severe weather
across lower Michigan south of a line extending from Saginaw Bay
to St. Joseph.


- Cooler and drier late Saturday through Monday

We will have some lingering showers and storms that will be hanging
around the area on Saturday. We should see the shower and storm
activity from Friday night move out with the low level jet shifting
east of the area. The cold front will remain NW of the area until
later in the day as it passes through. There will be a bit of
instability associated with it due to moisture pooling along the
front. However, these situations with the rain and low level jet
moving out are not usually conducive for lots of additional
convection.

Behind the frontal passage by later Saturday, we will see upper
ridging and an expansive sfc ridge build toward the area. These
features should be well entrenched over the area by Sunday. There
will be a cooler and drier flow from the north, helping to clear
things out. 850 mb temperatures dropping to +7 to +9C will support
highs in the 70s with lower humidity levels. Monday will remain dry
as the ridging starts to move east. Temperatures will warm up to
around 80 as return flow on the backside of the sfc high shifts
east.

- Rain chances increase Tuesday-Wednesday

It seems that the models and ensembles are locked on to rainfall
chances next week being centered on the Tuesday/Wednesday time
frame. The details are uncertain as to the exact timing and such.

The upper ridge that will be bringing the cool and dry weather to
the area Sunday and Monday will shift east of the area by Tuesday. A
broad long wave trough will settle in over the Upper Midwest, and
provide for a deep flow from the SW for Lower Michigan. We will see
a couple of short waves embedded in the flow lift to the NE toward
the area. In addition, the low level SSW flow will help to bring a
bit of Gulf moisture up and over the area, and with warm and humid
conditions. This will provide for showers and storms Tuesday through
Wednesday at times.

We should see a break in the rain chances for Thursday as the upper
trough lifts out of the area, and ridging builds back in temporarily
as another trough digs over the western portion of the country.
Temperatures will not cool off that much as there is never really a
push of cooler air behind the mid-week system.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 752 PM EDT Thu Jun 27 2024

VFR is likely over the next 24 hours as the atmosphere below
10,000 feet will be fairly dry. Ceilings at or above 10,000 should
occasionally produce virga during the day Friday, perhaps some
spots could see sprinkles of light rain.

&&

.MARINE...
Issued at 342 PM EDT Thu Jun 27 2024


Northwest winds peaked this afternoon and continue to diminish.
latest webcams show low waves. Waves will continue to diminish
tonight as the high builds overhead and winds shift offshore.

Models continue to show winds shifting more southerly Friday and
building into the late morning to afternoon. These southerly
winds will build wave heights early Friday into the afternoon and
continue into Friday evening. Conditions will be hazardous to
small craft and a beach hazard statement may be needed for this
time period as well.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory from noon Friday to 2 AM EDT Saturday for
     LMZ847>849.

&&

$$

DISCUSSION...NJJ/Ceru
AVIATION...CAS
MARINE...Ceru