353
FXUS63 KGRR 161737
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
137 PM EDT Thu May 16 2024

.KEY MESSAGES...

- Showers and storms late today and tonight

- Dry and very mild weekend

- Chance of showers/storms Monday through Tuesday night

&&

.UPDATE...
Issued at 1125 AM EDT Thu May 16 2024

Shower and thunderstorm threat looks quite low until tonight as
dry/stable air remains in tact into the afternoon with sfc dew pts
in the 40s. Best threat this afternoon is late / after 21Z / and
in the southwest corner of Lwr MI. This is where the higher
dewpts arrive first and a few hundred Joules of cape become
available. Otherwise main emphasis for convection holds off until
after 00Z but even then the new 12Z CAMs look a bit less ambitious
probably owing to nighttime/early morning passage of the sfc
front and shortwave.

&&

.DISCUSSION...
Issued at 327 AM EDT Thu May 16 2024

- Showers and storms late today and tonight

Mild weather is forecast today with partial sunshine and as winds
become south to southwesterly out ahead of the system approaching
from the west. High temps will reach the low to mid 70s (except
cooler near the Lake MI shoreline). Clouds will gradually
increase through the day but most of the day will be dry. Some
showers and thunderstorms will begin to develop by late this
afternoon as MUCape values reach 500-750 j/kg over our sw fcst
area by then.

A consensus of 00Z HREF svr wx parameters suggests that marginally
severe convection late this aftn/eve will stay to our west across
southern WI. That is where there is potential for stronger
instability to develop along with favorable 0-6km shear on the
order of 30-40 kts and forcing from the front.

We expect weakening convection to gradually move in ahead of the
low pressure system and upper disturbance this evening due to
relatively weak instability over our area. A few showers and
storms will linger Friday with a weak frontal boundary still in
our area.

- Dry and very mild weekend

Upper riding will build into the Great Lakes this weekend and
temperatures will respond by climbing well above normal. Highs are
going to be in the 80s Saturday and Sunday along with quite a bit of
sunshine.

- Chance of showers/storms Monday through Tuesday night

We`re still keeping an eye on a potential stormy pattern Monday
afternoon through Tuesday night. The models are quite a bit more
frisky in regard to generating instability through that period than
last night`s runs.

A northern stream low will push a cold front toward the region
Monday and bring in a strong stream of moisture with it. A minor
short wave looks to accompany the front as it moves toward Lake MI
Monday afternoon. MUCAPE rises to 1200 j/kg near the front and
showers and storms will probably develop along the boundary and clip
at least the western cwa Monday afternoon/night.

GFS and Euro show a second wave developing on the front and moving
northeastward toward Lower MI Tuesday. A stronger short wave
rotating around the low will be a catalyst for convective
development Tuesday afternoon to the west that may move across the
cwa Tuesday afternoon/evening. The LLJ looks to be stronger as does
the instability and especially the shear; we could be looking at
strong/severe storms late Tuesday.

Temperatures will cool off a bit behind the cold front
Wednesday/Thursday.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 137 PM EDT Thu May 16 2024

Conditions remain quiet this afternoon but showers and a few
storms will be possible later this evening followed by a few hours
of IFR/MVFR early Friday morning. The best chance for storms will
be in the late afternoon after 21z as a cold front moves across
lower Michigan. Deeper moisture late tonight brings lower ceilings
and reduced visibility. Conditions will begin to improve Friday
morning with ceilings back to VFR near mid-day.

&&

.MARINE...
Issued at 327 AM EDT Thu May 16 2024

Winds will gradually veer to the south and then to the southwest
to west this afternoon. Wind speeds will be fairly light at only
around 10-15 kts. Wind speeds will remain fairly minimal through
late week and this weekend and there really are no concerns for
hazardous winds/waves through then.

&&

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

&&

$$

UPDATE...Meade
DISCUSSION...Laurens/04
AVIATION...Thielke
MARINE...Laurens