000
FXUS63 KGRR 132329
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
729 PM EDT Sat Apr 13 2024

.KEY MESSAGES...

- Most Stay Dry, Isolated Showers and Storms Tonight

- Beautiful Weather to End the Weekend

- Mild Temperatures to Begin the Week

- Showers and Storms Tuesday into Thursday

- Cooler with a Chance for Showers Late Week into the Weekend

&&

.DISCUSSION...
Issued at 303 PM EDT Sat Apr 13 2024

- Most Stay Dry, Isolated Showers and Storms Tonight

Tonight a shortwave trough and associated positive vorticiy
advection pass mainly north of the area late tonight. There will
be plenty of low level lift with the low level jet and warm air
advection, but there is a question as to if there is enough
moisture to pop off a few isolated showers and thunderstorms.
Looking at soundings there should be enough lift to overcome any
CIN, but overall moisture is lacking except toward Gaylord`s area.
The best window of time for showers and storms to occur will be
between 11 PM and 5 AM, afterwards we lose our main sources of
lift and drier air advects into the area aloft.

- Beautiful Weather to End the Weekend

Sunday a weak front will move through the area during the morning
and afternoon with southwest winds shifting to the northwest. With
the front expect some cloud cover, otherwise mostly sunny skies
are expected behind the front. Temperatures tomorrow will be a
little warmer than today with highs getting into the 70s across
most inland areas with upper 50s and 60s closer to the lake. Clear
skies continue into Sunday night with lows in the 40s for most
and in the mid to upper 30s along and north of the US 10 corridor.

- Mild Temperatures to Begin the Week

A negatively tilted upper level ridge will build over the region
late Sunday into Tuesday. This ridge will allow for high pressure
at the surface and mild springtime temperatures. Expect Max temps
on Monday and Tuesday to be around 10 degrees above normal, in the
upper 60s to low 70s.

- Showers and Storms Tuesday into Thursday

The ridge and and mild weather will be short lived as a strong upper
level low will be moving through the great plains and through the
mid west Tuesday through Thursday. Models continue to be in fair
agreement on the placement of the upper level lows and the
corresponding low level pattern. The system at this time seems
fairly barotropic with a decent gradient along with it. There
seems to be decent 500 mb vorticity with mid level moisture that
should cause some overrunning Tuesday. NAEFS PWATS are upwards of
1.25 inches and are +3 anomalous Tuesday evening into Wednesday.
So there remains a good chance for showers Tuesday

The low is still on track to move through late Tuesday night into
Wednesday. This cold front should correspond with a strong low
level jet. A decent amount of instability remains likely. Given
the potential for storm organization strong winds and hail are
possible.

The system looks to become an open wave with more zonal flow into
Thursday with a chance for lingering showers.

- Cooler with a Chance for Showers Late Week into the Weekend

Cold air advection will be the main story behind the front as
850mb temps by daytime Friday will be below zero. These will
continue to drop into the weekend. Maximum temperatures could be
around 10 degrees below normal. Overnight lows, especially with
dry air aloft and subsequent clearing could create some
frost/freeze potential north of the I 96 corridor.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 730 PM EDT Sat Apr 13 2024

Primary aviation concern over the next 24 hours is LLWS. Strong
LLWS develops at all terminals after 03-04z tonight around 40-45
knots, and peaks around 50-60 knots below 2000 ft after 05z. The
strongest winds at 2000 ft will be in the 07-10z timeframe before
LLWS subsides around 12-14z, lasting longest for JXN/BTL/AZO.
Southerly winds of 5-10 knots this evening become west-
northwesterly at 10-15 knots Sunday morning with gusts of 20-25
knots expected early Sunday morning through near the end of the
TAF window. Otherwise, VFR conditions are expected with no cigs or
cigs above 20000 ft expected at all TAF sites. Given the dry air
in place, showers should remain north of the TAF sites except for
the chance of showers approaching the vicinity of MKG overnight.

&&

.MARINE...
Issued at 303 PM EDT Sat Apr 13 2024

Southwest winds and waves may briefly approach Small Craft
Advisory criteria late tonight into early Sunday morning, but
overall the stronger gusts are not expected to mix down to the
surface. There is a low chance for an isolated shower or storm
tonight, but better chances look to be north of Pentwater. Winds
are then expected to shift to the northwest behind the front
Sunday morning and into the afternoon. Small Craft Advisory
conditions look to hold off until Tuesday when southeasterly
winds build with our next chance for showers and thunderstorms.

&&

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

&&

$$

DISCUSSION...Ceru/RAH
AVIATION...Thomas
MARINE...RAH