443
FXUS63 KGRR 201152
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
752 AM EDT Mon May 20 2024

.KEY MESSAGES...

- Marginal Risk for Severe Thunderstorms Today

- Warm and Humid Tuesday

- Severe Weather Risk Tuesday Night

- Dry and Pleasant Late Week Period

&&

.DISCUSSION...
Issued at 330 AM EDT Mon May 20 2024

- Marginal Risk for Severe Thunderstorms Today

A fairly complex mesoscale pattern will evolve across our area
today as a warm front just south of our area early this morning
moves slowly north. Meanwhile well off to our west convection
across eastern IA early this morning will continue moving ene. A
consensus blend of latest CAMs and 00Z HREF suggest that this
convection will reach our west to northwestern fcst area by mid to
late morning.

Severe wx is unlikely with this first round of rain and embedded
convection given limited instability and fairly weak shear as
well as unfavorable timing. However this complex of rain and
convection may inhibit the warm front from moving much further
north then perhaps the I-96 corridor.

Our main risk for marginally severe wx then comes for this
afternoon and evening as instability builds in the warm sector.
SB/MU cape values should reach around 1500 j/kg near to south of
I-96 by mid to late aftn with potential for convective development
with relatively strong updrafts by then as suggested by the 00Z
HREF.

Localized damaging wind gusts are the primary svr wx threat from
mid aftn through the evening as fcst soundings show potential for
dry adiabatic low level lapse rates and dcapes to reach 1000 j/kg.
Localized large hail is also possible looking at fcst soundings
and we also can`t rule out potential for an isolated weak spinup
in the vicinity of the warm front where enhanced updraft helicity
is expected. A diurnally driven gradual decrease in convection is
fcst late this evening and overnight.

- Warm and Humid Tuesday

It will be warm and quite humid Tuesday and most of the day will
be dry. We do expect some scattered showers and thunderstorms to
begin to develop from mid to late afternoon coincident with the
peak in diurnally driven instability (sb/mu capes potentially
reaching close to 2k j/kg).

However convective potential is somewhat mitigated by the lack of
a stronger focusing mechanism for convective development to occur.
An upper shortwave moving in from the wsw could focus some convective
initiation from mid to late afternoon before we get back into
some mid to upper level nva.

- Severe Weather Risk Tuesday Night

A QLCS emanating from the upstream SPC Day2 ENH risk area is
expected to make a run at wrn Lwr MI on Tuesday night with the main
threat being damaging wind gusts. The severe weather risk should
gradually wane overnight as this feature eventually loses steam with
eastward extent due to declining instability.

Some question as to the areal extent of convection on Wednesday
since the sfc boundary may slip south of the area, but best pops
will be focused south and east of GRR and especially near JXN. It`s
possible much of the area dries out with stable low level westerly
flow becoming established.

- Dry and Pleasant Late Week Period

A period of dry and pleasant weather looks likely for the end of the
week as sfc ridging takes over and a drier air mass with dew pts in
the 40s arrives. Also an amplifying upper level ridge is shown to
be overhead by Friday.

Pops appear to ramp up again over the holiday weekend as the ridge
moves east and warm front returns, although confidence regarding
the timing and coverage of convective events is low at this time.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 752 AM EDT Mon May 20 2024

Line of storms moving northeast from MKE will impact the MKG and
GRR terminals for a couple hours roughly 14-16Z, but the other
terminals south and east of GRR likely will not be impacted. While
a few random/pop-up storms cannot be ruled out this afternoon,
The next good chance of storms will be after this evening after
22-23Z when the MCV currently in ern IA will be tracking through
the area. Late tonight there is a risk of some fog/stratus which
could create IFR conditions, with the primary threat of that
being at MKG/GRR, and possibly LAN.



&&

.MARINE...
Issued at 330 AM EDT Mon May 20 2024

Winds and waves will remain rather minimal and below Small Craft
Advisory levels early this week. However locally higher winds and
waves are possible in thunderstorms today through Tuesday night.

&&

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

&&

$$

DISCUSSION...Meade/Laurens
AVIATION...Meade
MARINE...Laurens