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108
FXUS63 KGRR 270027
AFDGRR

Area Forecast Discussion
National Weather Service Grand Rapids MI
827 PM EDT Sun May 26 2024

.KEY MESSAGES...

- Risk for Storms into Tonight

- A few Thunderstorms possible Memorial Day, especially in the
evening

- Cool and unsettled weather continues Tuesday

- Dry weather with increasingly warmer temperatures Wed through Fri

- Rain chances return for next weekend

&&

.UPDATE...
-- Changed Discussion --
Issued at 819 PM EDT Sun May 26 2024

We`re watching radar trends this evening and specifically the band
of strong/severe storms moving off of northeast IL just ahead of
the cold front. Mesoanalysis indicates 1k j/kg SBCAPE over the
far southwest cwa west of US-131 and as far north as northern
Ottawa County. However, progs are for this SBCAPE to diminish to
500 j/kg or less by 10 pm. Bulk shear, however, remains aoa 35kts
for the next several hours. Thus, the stronger storms that make it
across the lake will likely be along the I-94 corridor. The
threat for strong storms will diminish overnight once the cold
front moves through.
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&&

.DISCUSSION...
Issued at 252 PM EDT Sun May 26 2024

- Risk for Storms into Tonight

One line of showers/thunderstorms will be pushing northeastward
through the CWA now through 7 or 8pm.  With a narrow corridor of
elevated DCAPE values out ahead of it, gusty winds appear to the be
main risk.  Upstream in northern IN there were some weather stations
that recorded gusts in the 20 to 30 knots range, KVPZ and KMGC.  The
latest HRRR suggests we will see some wind gusts similar to those in
IN across our CWA, especially south.  Isolated higher values are
possible.  It`s worth noting that higher surface dewpoints were
being reported at a several sites downwind of Lake Erie with KTOL
showing 66 degrees. Thus there are elevated values of instability
and effective deep layer shear reaching now towards Jackson
County. That could be one area to monitor for possible enhanced
winds/convection.

By 8 pm the bulk of the activity should be moving northeast of KLAN
and KMOP. Additional storms are possible during the evening hours
but the coverage is expected to be scattered. However after midnight
the instability builds again with an increased potential for MU CAPE
values to make a run at 1000 J/kg ahead of the cold front. Thus,
the convection could increase once again. Deep layer shear is
forecast to diminish as the instability builds overnight so the
risk for organized convection will be limited.

- A few Thunderstorms possible Memorial Day, especially in the
evening

The atmosphere destabilizes as we go through the afternoon and into
the evening.  With a cold pool overhead, scattered showers and a few
thunderstorm are expected to develop.  A digging mid level vort max
arrives from the west northwest 02z to 06z and that will likely lead
to an increase in the activity, especially for the western zones.
Ensemble 6hr qpf values remain fairly low with most areas seeing
under a tenth of an inch and trends don`t really show much
increase/decrease.

- Cool and unsettled weather continues Tuesday

We will see more of the same weather from Monday, on Tuesday and
Tuesday night once again. This holds true as the broad upper
cyclonic flow and cold pool aloft remains entrenched over the upper
Great Lakes. The models are indicating that at least 3 to 4 short
waves will be rotating around the upper low and across Southern
Lower. This will ensure that cool weather prevails, and occasional
showers will remain possible at times. Tuesday afternoon/evening
will see a chance of some thunder as diurnal instability combined
with the cold pool aloft will provide sufficient instability for
some thunder.

- Dry weather with increasingly warmer temperatures Wed through Fri

There has been better agreement that the rain chances from early in
the week should pretty much move out of the area by Wednesday
morning. The final short wave in the series looks to pass through
late Tuesday night, before the upper ridge axis will move close
enough to keep the area dry Wednesday. This cooler air holding in
for Wednesday, combined with high pressure at the sfc will allow for
a fairly cool night Wednesday night/Thursday morning. It does look
like there is a chance of some frost across Central Lower.

Otherwise the upper ridge slowly building toward the area will bring
plenty of subsidence with it over the area, will keep the area dry
for at least a couple of more days through Friday. We will see max
temperatures warm from the 60s on Wednesday, to approaching 80 by
Friday as warm return flow sets up in the lower levels.

- Rain chances return for next weekend

We continue to watch for the potential for a period of rain sometime
next weekend, however the timing remains a bit uncertain. The key
factor in this scenario and the eventual timing of the rain will be
mostly based on the evolution of the upper low off of the New
England coast. This low is expected to close off a bit more, and
will hold up the weather pattern across the CONUS to some degree.
The stronger and more closed off it is, the more likely the pattern
will hold upstream. Rain could start moving in as early as by
Saturday afternoon, or as late as holding off until Sunday or beyond.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 733 PM EDT Sun May 26 2024

As the earlier round of thunderstorms exits the area, all sites
will be initially VFR. After 02z, scattered showers and
thunderstorms will enter West Michigan and expand east over the
next few hours. Do not currently have confidence in TSRA directly
impacting the terminals to support TAF inclusion due to widely
scattered nature of TSRA but will reassess and amend as needed.
Locally gusty winds and IFR conditions are possible in any storms.
With the showers come lower cigs, initially MVFR before becoming
IFR at all sites after 05z (MKG may briefly go LIFR). Low cigs
remain through much of the day before lifting to MVFR for the I94
TAF sites Monday afternoon, and Monday Evening LAN becomes MVFR
while MKG/GRR become VFR. Scattered showers will continue through
the day Monday. South- Southeasterly winds tonight veer to
westerly Monday with 10-15 knot winds, gusting to 25 knots Monday.

&&

.MARINE...
Issued at 252 PM EDT Sun May 26 2024

Earlier we did issue a Small Craft Advisory and Beach Hazards for
Memorial Day. High confidence exists for winds to increase to 20
knots or higher and waves to reach 4 feet for much of the area.
North of Whitehall there may be a delay in the onset of hazardous
conditions as the surface low will be in that region 12z Monday,
however by noon conditions will deteriorate in that region.

&&

.GRR WATCHES/WARNINGS/ADVISORIES...
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MI...Beach Hazards Statement from 8 AM EDT Monday through Monday
     evening for MIZ037-043-050-056-064-071.
MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Monday for LMZ844>849.
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&&

$$

UPDATE...04
DISCUSSION...MJS/NJJ
AVIATION...Thomas
MARINE...MJS/Hoving