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000
FXUS63 KGRR 142330
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
730 PM EDT Sun Apr 14 2024

.KEY MESSAGES...

- Quiet Weather Through Monday Night

- Risk for Thunderstorms Remains Late Tuesday into Wednesday

- Turning Cooler Late Next Week

&&

.DISCUSSION...
Issued at 311 PM EDT Sun Apr 14 2024

- Quiet Weather Through Monday Night

A cold front will continue to press off to the south and east of
the forecast area tonight. At 19Z it was situated from portions of
Southeast Lower Michigan southwestward into Northern Indiana. Dew
points have fallen into the 30s in our northern CWA across Central
Lower Michigan behind the front. The drier air will set the stage
for temperatures to fall to near seasonal normals in the upper 30s
to middle 40s tonight. Certainly a chance to drop below those
forecast values and we will be watching conditions this evening.

High pressure will drift from west to east across the area Monday
and Monday night which will allow a warm front to approach from
the southwest heading into Tuesday morning. We will remain dry
though through Monday night. Mainly 60s for highs on Monday.

- Risk for Thunderstorms Remains Late Tuesday into Wednesday

There continues to be good agreement amongst the models and ensemble
members that rain chances will increase quickly later Tuesday and
Tuesday night. This means that there will be a decent period of dry
and mild weather before the rain moves in.

The main focus of the rain will be a 50+ knot low level jet that
will nose over the area beginning later Tuesday afternoon. Right
now, it just looks to be mainly rain showers with a small chance of
thunder. Convective instability is shown to be fairly weak to nil
with this leading edge of rain. The rain showers and isolated
thunder should taper off late Tuesday night/Wednesday morning.

We are likely to be in a relative lull for the first half of the day
on Wednesday, before additional showers and a better chance of
storms move in Wednesday afternoon and evening. The way that the sfc
front moves in, and then how another short wave aloft rotates around
the bottom of the long wave trough/low, another wave of showers/
storms will likely develop to our WSW and move in. There is a bit
better instability expected to move in ahead of the next wave as the
cold pool aloft and short wave move in. Right now, it looks like a
lot of residual cloud cover will hold in, limiting the amount of
diurnal heating that can take place.

There is still some concern that some severe weather will be
possible with this Wednesday afternoon wave. That is because it
appears based on sfc instability and temp progs that a triple point
may traverse the southern portion of the area. There looks to be a
low level jet associated with this wave that will nose up to the I-
94 corridor. Deep layer shear will be plentiful with stronger upper
level winds. Still quite a bit of uncertainty with the exact track
as it could nudge north or south. Definitely bears watching.

- Turning Cooler Late Next Week

We will definitely see this system create a pattern change to the
mild weather this weekend and expected early in the coming week. The
active southern branch of the jet sinks well south of the area. This
will lock up the good warmth and unstable conditions. We will end up
with long wave upper troughing settling in over the area from
Thursday though most of next weekend.

Rain chances are not that impressive for Thursday and beyond, but
unsettled and cool weather can be expected. The cooler air aloft and
weak impulses in the trough could bring some lower chances of a few
showers at various times. Most of the time though it will just be
cool and dry. Details are way too tough to try and pinpoint at this
juncture.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 730 PM EDT Sun Apr 14 2024

Very high confidence in VFR conditions throughout the TAF period
as SKC is expected at all TAF sites for the next 24 hours, except
for a few passing mid-level clouds that may briefly clip
terminals overnight. West- northwest winds of 10-15 knots become
north winds at or below 5 knots overnight before becoming westerly
around 8-13 knots Monday afternoon.

&&

.MARINE...
Issued at 311 PM EDT Sun Apr 14 2024

We dropped the Small Craft Advisory at midday as winds and waves
were in the process of falling below advisory criteria. All
nearshore observations (wind) and buoys (Muskegon) are all showing
conditions below criteria. Webcams also show waves have fallen
considerably. The Muskegon buoy has waves down to 2.3 feet as of
1:40pm.

With surface high pressure in the area for the rest of this
afternoon, tonight, Monday and into Monday night no headlines are
planned through Monday evening.

The next time frame of concern on the big lake is Tuesday night
through Wednesday night as low pressure approaches and moves
through the area. Initially southeast winds will be in place
shifting to the southwest and west with time. With offshore winds
initially and then along shore, it will mainly be a wind issue as
fetch will be limited. Waves come more into play Wednesday
afternoon and night as the flow becomes more onshore.

&&

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

&&

$$

DISCUSSION...Duke/NJJ
AVIATION...Thomas
MARINE...Duke