792
FXUS63 KGRR 012350
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
750 PM EDT Wed May 1 2024

.KEY MESSAGES...

- Risk for thunderstorms later Thursday into Thursday night

- Warm with Periods of showers and storms ahead

&&

.DISCUSSION...
Issued at 259 PM EDT Wed May 1 2024

- Risk for thunderstorms later Thursday into Thursday night

A stronger mid level vort max pivots northeastward from
 SD through MN during this timeframe. An associated low level jet
lifts up through WI an into western Lower MI. Elevated instability
advects in, especially Thursday night with 925 mb/850 mb LI`s
lowering down to -2 deg C. Thus an increasing risk for
thunderstorms will exist during this period. With the low level
jet around, any stronger storm may result in stronger gusts. Deep
layer shear is shown to be quite strong well west of the CWA then,
but if a complex and track in from the west, we could see an
organized gust front, mainly Thursday night. We will expand the
likely POPs to include much of the CWA for Thursday night.

- Warm with Periods of showers and storms ahead

A slow moving upper level low moving through the upper Midwest
and along the Canadian border will dominate the weather pattern
through the weekend into next week. No major changes to forecast
ahead. Mid to long range models continue to show a shortwave
swinging around that large upper level low that will entrench
itself over the Upper Midwest Friday.

 That shortwave will strengthen a frontal system that will bring
a warm and cold front through the region Friday. There is strong
moisture through the mid levels that correspond with a mid level
shortwave, a decent mid level gradient and dry air behind the
front. This should bring for substantial showers and storms
Friday afternoon and evening. PWATs still look to be around 1.25
and dewpoints in the 60s. While upper level dynamics look to be
beneficial, looking at soundings they are fairly moist so periods
of showers look to be the trend. The cold front treks eastward
Friday afternoon with showers and storms.

As the upper level low moves northeastwards a tertiary trough
swings through late Saturday which could bring some light
scattered showers into Sunday m morning.

The next best chance for showers and storms will be early next
week as another large upper level low moves similarly as Friday`s
system and drags another trough with warm moist air into the
Great Lakes.

Max Temperatures through this timeframe will be in the 70s with
highest temperatures nearing 80 next week. Cooler air will reside
along the lakeshore.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 750 PM EDT Wed May 1 2024

High likelihood of VFR tonight and much of the day Thursday.
Clouds above 10,000 feet will be streaming in tonight and during
the morning, and by afternoon (after 16 Z), clouds around 6,000
feet should stream in, sometimes creating a ceiling. Those clouds
at 6,000 feet may be unstable and convect with weak to moderate
updrafts, possibly up to 15,000 feet, to produce scattered showers
and a slight chance of a thunderstorm. Any passing showers during
the afternoon-evening could produce downdrafts, given a fairly
dry and well-mixed lower atmosphere, and temporarily disrupt
ground-level wind speed/direction.


&&

.MARINE...
Issued at 259 PM EDT Wed May 1 2024

The winds and waves have largely fallen to under small craft
advisory so we cancelled the headline early. The winds will
increase again Thursday night as another low level jet moves in.
Mixing heights and the winds at those levels suggest we will fall
just short of small craft conditions.

&&

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

&&

$$

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