206
FXUS63 KAPX 220603
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
203 AM EDT Wed May 22 2024

.KEY MESSAGES...

- A strong to severe line of storms is possible late this
evening/tonight. The primary threat is damaging winds, with large
hail and a tornado or two also possible.

- Pleasant temperatures but with occasional rain chances for the
Memorial Day weekend.

&&

.UPDATE...
Issued at 916 PM EDT Tue May 21 2024

Mature convective complex well underway across western WI and
eastern IA/MN this evening. A few stray isolated cells developing
near GRB out ahead of the main line(s) of storms. Latest expectation
is for this activity to continue to trek east-northeastward across
eastern WI and the central U.P. through the evening, albeit in a
somewhat weakening fashion.

Locally, instability will be diminishing with time and eastward
extent with elevated CAPE progged up to 1,000 J/kg west of I-75 by
midnight as convection begins to make a run across northern Lake
Michigan. Have major doubts on just how much survives that march
across the lake, but there remains enough support to continue the
mention of isolated to scattered severe storms during the overnight
hours with the primary threat continuing to be damaging winds. This
threat aided by impressive wind fields progged to increase to 40-50+
kts just off the deck, strong low level shear (35-45 kts 0-1 km
shear / 40+ kts 0-3 km shear) and relatively steep low-mid level
lapse rates. Primary severe risk area still appears to be maximized
west of Interstate 75, and even more so west of US-131...coinciding
well with where MCS maintenance probabilities are highest. This area
also where ~500 J/kg surface based CAPE may linger and the low
potential for a tornado. The overall severe threat is fairly short-
lived... largely ending by 3-4 AM.  No changes to the SPC 01z Day
outlook with the highest severe probabilities over western
areas of the APX footprint.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 326 PM EDT Tue May 21 2024

Pattern/synopsis: Surface low pressure (currently 995 mb across
western Iowa) is shown to deepen to 981 mb by Wednesday morning
while tracking well northwest of the region.

Forecast: Tonight...As the deepening area of low pressure tracks
from the central Plains into the northern Mississippi Valley, a line
of strong to severe thunderstorms is expected to march across
Wisconsin this evening, possibly reaching far western zones of
northern lower just before midnight. Strong winds aloft (0-6 km bulk
shear 50 to 60 knots) will likely accompany the line as well as the
potential for large hail and perhaps even a tornado or two given the
strong speed and directional shear. The latest SPC outlook continues
the enhanced risk for severe storms near Manistee with a slight risk
across much of the remainder of northern lower. However, the
combination of the loss of daytime heating and the relatively cold
waters of Lake Michigan will make it tough for any line of strong to
severe storms to hold together this far east. A vast majority of
model guidance is on board with this thinking and has the line
weakening/splitting/falling apart as it progresses across the big
lake. Although it looks doubtful, there is still a small chance
chance that it could still impact parts of the region, especially
along and near Lake Michigan. Most guidance doesn`t give the line
much of a chance of holding together east of I-75 on toward Lake
Huron. Time will tell on this one and this will be monitored by the
evening shift for current trends. Muggy tonight with lows only in
the upper 50s to mid 60s.

Wednesday...Subsidence behind the departing system is expected to
lead to at least partly sunny skies. Downsloping east of I-75 is
expected to lead to highs of well into the 70s to around 80. Highs
to the west in the low and mid 70s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 326 PM EDT Tue May 21 2024

PATTERN SYNOPSIS/FORECAST:

A closed low will slowly track eastward as shortwave ridging builds
across the Midwest in response to troughing digging across the
Plains, and eventually towards Lake Superior. SW winds will turn W
for Thursday and then slowly turn more N for Friday in response to
the aformentioned features influencing the forecast area. Ridging
and high pressure will provide moderating temperatures into the
weekend, with highs more seasonable in the 60s and 70s for Memorial
Day weekend as flow turns more zonal. For Thursday, areas along the
Lake Huron side could reach the 80s as W flow downslopes. Long term
guidance suggests energy quickly tracking overhead through Friday
night, bringing about the next appreciable shower chances to the
region. The aforementioned trough will also bring more shower
chances to the region for the holiday weekend.

PRIMARY FORECAST CONCERNS:

- Holiday weekend: Looks like an exceptional holiday weekend with
moderating seasonal temperatures and mostly clear to sunny skies
with some chances for showers at times. Daytime highs look to be in
the 60s/70s for most, and potentially in the 80s for those in the
southern-most locations of the forecast area. Friday night into
Saturday continues to be the most likely timeframe for rain
showers, and potentially a rumble of thunder or two. Looking at
Sunday night into Monday, chances for showers pop up again as a
trough and its associated low pressure tracks to Lake Superior.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 202 AM EDT Wed May 22 2024

Thunderstorms will work across areas near the Lake Michigan
shoreline and eastern upper over the next several hours, and
continue to push inland. Strong wind gusts of 40-50+ kts and small
hail will be possible with these storms. Storms look to diminish
later Wednesday morning. LLWS is also expected at TAF sites into
this morning with winds quickly increasing in magnitude just off the
surface. MVFR CIGS look to set in for a time across most TAF sites
this morning into early afternoon. Southwest winds of 10-15 kts will
gust to 20-30 kts at times through this afternoon before diminishing
this evening. A return to VFR conditions is anticipated this
afternoon through the end of the issuance period.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ323-
     341-342-344>346.
     Small Craft Advisory until 8 PM EDT this evening for LSZ321-
     322.

&&

$$

UPDATE...MJG
SHORT TERM...AJS
LONG TERM...NSC
AVIATION...DJC