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000
FXUS63 KGRR 201931
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
331 PM EDT Sat Apr 20 2024

.KEY MESSAGES...

- Cold Tonight; Breezy Sunday with Elevated Fire Danger

- A Couple Rounds of Precipitation Expected Next Week

- Typical Spring Rollercoaster Temperatures

&&

.DISCUSSION...
Issued at 331 PM EDT Sat Apr 20 2024

- Cold Tonight; Breezy Sunday with Elevated Fire Danger

Tonight`s frost/freeze set up still appears marginal given
extensive cloudiness both overhead and upstream as well as a
decent cyclonic pressure gradient in place. While sfc winds do
relax tonight, they stay up around 5-8 kts for most of the night
with 15 kt winds shown just above the sfc.

It may be difficult to form much frost overnight given dew points
only in the lower to mid 20s along with the clouds and winds so
will forego any frost or freeze headlines at this time. Early
Sunday morning lows could dip down to 30-32 in spots once some
better clearing takes place, but suspect the duration/coverage of
any sub-freezing temps will be rather brief/limited.

Brisk westerly flow ramps up again on Sunday once deeper mixing
commences with gusts up to 30 mph expected in the afternoon.
Sunnier skies and warmer high temps in the mid 50s are
anticipated which should lower afternoon minimum relative
humidities down to 25-30 percent. This will place much of the
area in an elevated fire danger, particularly across mid-michigan
where the strongest winds are expected.

Another frost/freeze threat may exist on Sunday night with
lighter winds and less clouds expected, although guidance temps
still marginal like tonight.


- A Couple Rounds of Precipitation Expected Next Week

We have two good chances for precipitation next week. The first
will come Monday night through Tuesday night and the second will
occur Friday night into Saturday. The early week event is
associated with an upper low digging our direction from the
Northern Plains. The upper wave will push a cold front through the
area on Tuesday which is when we have our highest chances for
precipitation (80 percent). There is just enough instability
(850mb LIs around -1 and several hundred j/kg of MUCAPE) present
to carry some thunder in the forecast. Rainfall amounts do not
look to be significant...in the quarter to half inch range.

The late week system is a southern stream upper wave that quickly
slides through the Great Lakes region Friday night and Saturday.
This system looks to be a warm frontal precipitation event for the
most part. Being a southern stream system more moisture is available
and present indications are that a half to maybe one inch of rain is
possible. As expected with more moisture this time of year more
instability is also in the models. The ECMWF has 1000-2000 j/kg of
MUCAPE available for the system to work with. Obviously we have
thunder in the forecast.

- Typical Spring Rollercoaster Temperatures

Temperatures will very much be up and down during the Monday through
Saturday time frame. A thermal ridge is in place on Tuesday ahead of
the front and another on Saturday with the low moving through.
Tuesday (around 60) and Saturday (around 70 in the south) are the
warmest days of the 7 day forecast. The coolest day of the upcoming
work week will likely be Wednesday with the thermal trough overhead.
Highs Wednesday will range from the upper 40s to lower 50s.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 203 PM EDT Sat Apr 20 2024

Widespread diurnal stratocumulus has developed today with cold
temperatures and troughing aloft. Bases in general are VFR, but
there is some MVFR ceilings near Lake Michigan at times early this
afternoon. We feel VFR will be the dominant category the next 24
hours. Clouds will be fairly widespread the rest of this afternoon
and most of tonight. Clouds will initially be stratocumulus but
will be aided and backfilled by clouds moving in from Wisconsin.
All of these clouds will have bases in the 3500 feet to 5000 feet.
We expect at least partial if not complete clearing late tonight
after 10Z to 12Z.

Winds will be gusty through sunset from the west at 10 to 20
knots. Speeds will become light around 5 knots overnight before
increasing again on Sunday after 14Z.

&&

.MARINE...
Issued at 331 PM EDT Sat Apr 20 2024

Recently deployed buoys at Port Sheldon and South Haven indicate
4-5 foot waves currently, but trend should be for quickly
subsiding winds and waves this evening so the 6 PM ending time of
the Small Craft Advisory still looks okay.

Only marginal advisory conditions for Sunday since strongest
winds are shown to occur inland from the Lk MI shoreline but 2-4
ft waves still a good bet.

Marine headlines appear likely Monday, Tuesday, and Wednesday as
frontal system passes through. Initially the winds will be strong
from the south/southwest ahead of the front Monday into the first
half of Tuesday, then out of the north on Wednesday behind the
front.



&&

.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for LMZ844>849.

&&

$$

DISCUSSION...Meade/Duke
AVIATION...Duke
MARINE...Meade