000
FXUS63 KGRR 241915
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
315 PM EDT Wed Apr 24 2024

.KEY MESSAGES...

- Widespread Freezing Temperatures Tonight

- Multiple Rounds of Showers and Storms Through Monday

- Warming Trend Into Next Week

&&

.DISCUSSION...
Issued at 315 PM EDT Wed Apr 24 2024

- Widespread Freezing Temperatures Tonight

No change to the Freeze Warning as dew points have dropped into
the teens and lower 20s across the northern zones this afternoon
and this very dry air is advecting south as the cold air mass of
northern Canadian origin settles southward across Lower Michigan.

We expect lows below freezing for all of the forecast area by
daybreak on Thursday with several hours below freezing in some of
the fruit growing areas, potentially causing damage to fruit
blossoms. Thursday night will see moderating temperatures but
with the residual cold and dry airmass, still has the potential
for widespread areas below freezing late Thursday night.

- Multiple Rounds of Showers and Storms Through Monday

The overall pattern becomes more active this weekend as we
transition into southwesterly flow across the Central Great Lakes.
This brings significant moisture into the area with PWAT values
climbing to near 1.5 inches by Saturday morning (above the 97th
percentile).

The first wave of precipitation is expected Friday night into
Saturday morning as a shortwave passes to our north driving a warm
frontal boundary through the CWA. A general 0.25-0.75 inches of rain
is expected with this system and thunder is likely early Saturday as
elevated instability exceeds 1000 J/kg.

Confidence is low in convective development into the day on Saturday
as mid-level ridging in place suggests the environment remains
capped due to lack of forcing. A generally dry forecast is favored
at present given this. However, high temperatures for the day
approach model sounding convective temperatures meaning that
scattered showers and storms are possible if we can get sufficient
boundary layer heating (15-25 percent chance). Given MUCAPE values
in excess of 1000 J/kg and a strong (45-60 kt) low level jet in
place Saturday, it`ll be worth keeping an eye on. Regardless,
Saturday will be synoptically windy with the strong low-level jet
and southwest flow in place. The EPS wind gust forecasts show a high
(90+ percent) chance of 30 mph winds Saturday and low-moderate (25-
50 percent) chance of gusts exceeding 40 mph.

Confidence increases again for rainfall Sunday into Monday as an
initial shortwave brings rain shower and storm chances as we sit in
the warm sector, especially to the northwest half of the CWA,
continuing into Monday as the main trough drives a cold front across
the area. Showers wind down Monday night with dry conditions Tuesday
and Wednesday as surface ridging moves into the state.

- Warming Trend Into Next Week

The other weather trend of note for the long term will be the
temperatures. Robust warm air advection in the southwest flow
pattern causes 850 mb temps to climb into the teens Saturday into
Monday making highs in the upper 60s to 70s likely. Some guidance
like the ECMWF MOS even has lower Michigan making a run towards 80
degree highs on Sunday when the warm air is most entrenched. We then
briefly fall back into the 60s Tuesday as troughing pushes through
the region.

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 108 PM EDT Wed Apr 24 2024

The MVFR cloud deck across Lower Michigan continues to erode with
the MVFR cigs about to clear GRR in the coming hour. All sites
will transition to VFR over the next few hours with skies clearing
out this evening. A few cirrus clouds pass through tonight before
skies clear fully again into tomorrow. Winds today will be from
the north at 5-15 knots becoming northeast around 5 knots into
Thursday as high pressure moves in.

&&

.MARINE...
Issued at 315 PM EDT Wed Apr 24 2024

The SCA continues into this evening with several sites still
gusting over 25 knots at 19Z. We expect winds to slacken this
evening and remain below 25 knots into Friday. Southwest winds
will increase on Friday afternoon and a SCA may be needed for
Friday night and Saturday. We have lowered NBM winds for Saturday
since we expect the stronger winds to remain aloft in a warm
advection pattern, so we do not expect to reach gales at this
time.

&&

.CLIMATE...
Issued at 315 PM EDT Wed Apr 24 2024

RECORD LOWS FOR APRIL 25TH

Grand Rapids... 22 in 1967
Lansing... 17 in 1909
Muskegon... 24 in 1967
Kalamazoo... 22 in 1919
Battle Creek... 23 in 1967

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Freeze Warning from midnight tonight to 8 AM EDT Thursday for
     MIZ043>046-050>052-056>059-064>067-071>074.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849.

&&

$$

DISCUSSION...Ostuno/Thomas
AVIATION...Thomas
MARINE...Ostuno
CLIMATE...Ostuno