689
FXUS63 KGRR 191048
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
648 AM EDT Sun May 19 2024

.KEY MESSAGES...

- Very warm and mainly dry today

- Continued warm and more humid with scattered storms Monday

- Stormy Monday night through Wednesday

- Hot Tuesday, then cooler

&&

.DISCUSSION...
Issued at 330 AM EDT Sun May 19 2024

- Very warm and mainly dry today

It will be very warm again today with high temps reaching the low
to mid 80s. The exception to this will be near the Lake MI
shoreline where winds becoming onshore will keep it cooler. A weak
cold front will bring isolated showers early this morning nw of
KGRR.

Dry wx is expected for the majority of our area today. However a
few showers and storms will redevelop along and just ahead of the
weak cold front this aftn over our se fcst area where sb cape
values will potentially reach around 2k j/kg as suggested by the
00Z HREF.

Svr wx is not expected given weak sfc convergence/forcing
from the front and weak shear. However an isolated stronger pulse
type storm in the vicinity of KJXN seems possible by late aftn
coincident with peak diurnal heating and instability. This notion
is supported by a consensus of 00Z HREF convective parameters.

- Continued warm and more humid with some showers/storms Monday

It will become increasingly warm and noticeably more humid Monday
as winds become south to southwesterly and waa/moisture advection
occurs. SB cape values will build through the day and reach
around 1k-2k j/kg. Some stronger to marginally severe convective
development is expected in the afternoon and evening in an
increasingly humid and unstable airmass with deep ssw flow and as
the llj ramps up to around 35 kts late in the day.

- Stormy Monday night through Wednesday

Several rounds of showers and thunderstorms are expected through mid
week. The first round arrives Monday night when a short wave tracks
across northern Lower. There will likely be storms ongoing Monday
evening north of the cwa. However, convection earlier in the day may
leave some unattended boundaries that may interact with convection
that could fire along the trailing cold front; NAMNest shows a
flareup of convection after midnight Monday night over the central
cwa where it may take advantage of MUCAPE around 600-700 j/kg. Shear
values less than 20 knots suggest severe storms won`t be a player
Monday night.

That could change Tuesday. A much stronger storm will emerge from
the Plains and push a warm front north through the cwa late in the
day. We could see some activity along the warm front Tuesday
afternoon when SBCAPE climbs to 2k+ j/kg, but the higher likelihood
is Tuesday night and Wednesday along the trailing cold front. Model
trends have slowed the advancement of the front and if trends
continue, early Wednesday could be a favored time to see storms
develop. If that occurs, the southeast cwa would realize the most
instability Wednesday morning as the front arrives.

Bulk shear climbs to 45-50kts Wednesday ahead of the front and so
given the instability already in place, we could see strong/severe
storms develop, especially over the southeast cwa. This bears
watching.

Once the front clears later Wednesday, we`ll see several days of dry
weather at the end of the week.

- Hot Tuesday, then cooler

Highs in the lower to mid 80s are expected Tuesday with temperatures
falling into the 70s Wednesday with clouds and precipitation along
the frontal boundary. Thursday will be the coolest day with highs
from the upper 60s north to lower 70s elsewhere. Highs in the lower
to mid 70s are expected next weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 645 AM EDT Sun May 19 2024

IR loop shows scattered mid clouds over the western portion of
Lower MI where a cold front is crossing the lake. Expect VFR
conditions through the period. However, from roughly 21z-02z there
may be a shower or storm that develops near LAN/JXN.



&&

.MARINE...
Issued at 330 AM EDT Sun May 19 2024

Winds and waves will remain well below sca criteria through the
rest of the weekend into early next week. Potential for marine fog
looks minimal today but may increase again a bit on Monday as a
more humid airmass begins to move in. Thunderstorms will pose a
hazard to mariners early to midweek.

&&

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

&&

$$

DISCUSSION...Laurens/04
AVIATION...04
MARINE...Laurens