512
FXUS63 KGRR 281952
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
352 PM EDT Sun Apr 28 2024

.KEY MESSAGES...

- Cold Front brings rain/thunder on Monday

- Multiple Chances for Showers and Storms This Week

- Warm Temperatures Through The Saturday

&&

.DISCUSSION...
Issued at 352 PM EDT Sun Apr 28 2024

- Cold Front brings rain/thunder on Monday

Extensive cloudiness into this afternoon has so far muted any
strong updrafts, although a few showers and towering cu have
managed to form in the past couple hours across the southern half
of the forecast area. Cannot rule out a few strong storms into
early evening with deep layer shear values of 25 to 30 knots.
Breaks in the clouds and surface heating could overcome the
stabilizing influence of the extensive rain showers from last
night into this morning.

For tonight, we will watch whatever showers/storms are able to
develop but they should diminish after sunset as sfc based
instability diminishes, then look for showers and storms pushing
in ahead of the advancing cold front overnight into Monday
morning. Expect the bulk of those showers to come through between
roughly 8 AM and noon on Monday with the potential for some
stronger storms across the eastern forecast area as the airmass
destabilizes. Scattered showers persist along and behind the cold
front into Monday evening before drying works in from the west.

- Multiple Chances for Showers and Storms This Week

Tuesday will be the best chance for dry weather in the long term
portion of the forecast thanks to a surface ridge and upper-level
ridging forecast to move overhead. Ensemble probabilities have
trended downward with precipitation chances for the Tuesday night
into Wednesday timeframe due to questions on low-level moisture even
with a vorticity maximum swinging through. An isolated shower can`t
be ruled out north of M20 but given low confidence will leave the
dry NBM PoPs as is.

Showers and Thunderstorms more likely Wednesday into Thursday as a
surface low to our west lifts a warm frontal boundary across Lower
Michigan. Thursday could be the most active day of the long term
period as MUCAPE values increase near to above 1000 J/kg Thursday
afternoon in both ECMWF and GFS guidance with a 30-40 knot low-level
jet. A shortwave then swings through the area Thursday night into
Friday driving a front through keeping rain chances going.

Predictability in the longwave pattern decreases notably into next
weekend. While there are signals in cluster analysis and model
guidance for a trough to setup over the central United States by
next weekend, there is considerable variation in both the positioning
and amplitude of this feature.

- Warm Temperatures Through The Saturday

Highs in the 60s are expected for Tuesday as a weak thermal trough
quickly passes through the region. Temperatures warm for the mid to
late work week into the 70s, with the 80s not out of the question,
as southwest flow brings plenty of warm air into the Central Great
Lakes.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 126 PM EDT Sun Apr 28 2024

The shield of MVFR clouds affecting all TAF sites at present will
make its way north over the next few hours bringing all sites to
at least low VFR. Tonight the I96 TAF sites drop back to MVFR with
some IFR possible at MKG (but to low confidence to include IFR in
the TAF) because of the warm frontal boundary that will remain
draped across the area. Multiple chances for showers and storms
are expected the next 24 hours including a low chance for
thunderstorms this afternoon. Enough confidence for VCTS at GRR
and MKG but all other sites did not have the confidence at this
time. Additional showers overnight will affect MKG and GRR and
bring patchy fog potential to these terminals. Moisture increases
Monday morning bringing MVFR potential back to AZO and BTL and
showers possible but just low enough confidence in affecting the
terminals to leave out at present. Winds today and tomorrow will
be 10-15 knots gusting to 20 at times and 7-12 knots overnight.

&&

.MARINE...
Issued at 352 PM EDT Sun Apr 28 2024

Webcams and satellite do not show any extensive areas of dense fog
over Lake Michigan this afternoon as winds have apparently been
able to prevent its formation. We will keep mention of patchy fog
in the marine zones for this evening.

Winds and waves increase Monday afternoon and a Small Craft
Advisory may be needed although conditions looks marginal.

&&

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

&&

$$

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