860
FXUS63 KMQT 112331
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
731 PM EDT Sat May 11 2024

.KEY MESSAGES...

- A few rumbles of thunder possible late tonight west, then
  scattered thunderstorms to develop Sunday afternoon into early
  evening, especially south central. There is a marginal risk
  (5%) of large hail and/or damaging wind south central.

- Dry weather returns by Monday, continuing through Wednesday
  afternoon.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 424 PM EDT Sat May 11 2024

Water vapor imagery and RAP analysis show nw flow from western
Canada to the Great Lakes region. The vigorous shortwave that
brought shra to Upper MI last night is now tracking into southern
Ontario. A much weaker shortwave is currently over central Lake
Superior/central Upper MI. Upstream, the next vigorous shortwave is
dropping se into northern Manitoba. Shortwave currently over the
area combined along with MLCAPE increasing to 100-300j/kg per latest
RAP has supported isold/sct shra development across central Upper MI
this aftn. A few rumbles of thunder have occurred from around
Escanaba into Menominee County where MLCAPE is maximized. To the e,
low stratus is noted along Pictured Rocks extending e and ne over
the lake. Current temps range from the 40s e along Lake Superior to
the lower 60s F well inland over western Upper MI.

Ongoing isold/sct shra over central Upper MI will end over the next
few hrs. Attention then turns to the shortwave currently over
northern Manitoba. It will reach northern Ontario Sun morning. In
response, a 35-45kt low-level jet develops into Upper MI late
tonight/Sun morning, leading to a good push of waa/isentropic ascent
and rather sharp theta-e advection. As a result, sct -shra should
develop into roughly the w half of Upper MI overnight, spreading
eastward Sun morning. Initial surge of theta-e advection may support
some -shra into western Upper MI this evening, but there is a good
layer of dry air from around 800mb to the sfc. Might be a few
sprinkles. Expect min temps tonight ranging from the low/mid 30s e
where skies will be mainly clear longest to the mid/upper 40s far w
where clouds increase before sunset.

After the initial waa/isentropic ascent pcpn moves across the area,
attention on Sun aftn turns to lake breeze aided cold front that
moves across the area. Timing of this feature will be coincident
with peak heating across the central, s central in particular.
Consensus model guidance has MLCAPE increasing to around 400-700
j/kg Sun aftn though NAM/RAP are up to 1000j/kg. Deep layer shear of
30-40kt will support storm organization and an isolated svr risk for
large hail and damaging winds. Wetbulb zero heights at 7-9kft are
supportive of a large hail risk while dry subcloud air/inverted v
profile will enhance potential of strong winds. Expect highs on Sun
in the 60s along Lake Superior w and also across the e into the mid
70s F interior west half.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 331 PM EDT Sat May 11 2024

A couple cold fronts will press through the Upper Great Lakes Sunday
evening, allowing a cool to seasonable airmass to break into the
region through at least mid-week. Ahead of the initial cold front on
Sunday, afternoon shower and thunderstorm development may occur if
we`re able to destabilize enough following the Sunday morning
isentropically/warm frontally forced showers. By 0z Sunday and the
start of this forecast period, the cold front looks to be draped
across the central UP with the aforementioned shower/thunderstorm
region out ahead stretching from Menominee County northeastward
into the eastern UP. The environment at this point should be less
conducive for any new convective development given the quickly
waning influence of the day`s diurnal heating. However, if a strong
or severe storm does develop earlier, guidance suggests enough deep
layer shear could sustain updrafts into the evening hours. However,
the window will be short lived given the cold front`s fast eastward
progression. By 3z, CAMS all suggest convective activity should be
outside of the forecast area.

Behind the cold front, a dry airmass will press into the region
while a secondary cold front moves through after midnight Sunday
night. This, in addition to surface ridging building over the area,
will sustain a dry couple of days for the forecast area. The daytime
high temperature gradient Monday and Tuesday should stretch from
near 50F by Lake Superior to the low-mid 60s across the south-
central. On Wednesday, more widespread 60s are expected, with most
areas outside of the immediate lakeshores and Keweenaw looking to
climb into the low-mid 60s. Overnight lows should be mostly in the
30s, with chances for sub-freezing temperatures in the interior-
central spots (20-30% chance). Fire weather concerns should be
mitigated by the near to slightly cooler then normal conditions and
light winds these days. But daytime mixing into a dry airmass aloft
may support RH values nearing 30% for some interior central and west
locations.

Mid-level ridging shifts through the region on Wednesday followed by
a shortwave pressing through Minnesota/western Ontario Wednesday
night. Consensus among the 12z deterministic guidance suite has this
pressing into our forecast area Thursday, supporting another round
of showers through the day. This contrasts some with the GEFS, EC,
and GEPS ensemble systems, where some members suggest precip could
start Wednesday night.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 729 PM EDT Sat May 11 2024

VFR conditions will prevail thru this fcst period at IWD/CMX/SAW. As
low pres drops into far northern Ontario tonight, a low-level jet
will develop into Upper MI late tonight into Sun morning, resulting
in 2-6hrs of LLWS at all terminals, lasting longest at IWD. The low-
level jet will also generate sct showers, but confidence in a
shower passing over any of the terminals is low. Not expecting
conditions to drop out of VFR if a shower does occur. More
showers/possible t-storm will develop Sun afternoon across
central Upper MI, possibly affecting SAW.

&&

.MARINE...
Issued at 331 PM EDT Sat May 11 2024

Winds are mainly expected to remain below 20 kts through the
entire forecast period, with some exceptions.

A warm front will lift through the lake late tonight and early
Sunday. Ahead of and behind the front, some isolated 20-25 kt wind
gusts will be possible. The stronger pressure gradient will be
Sunday across the east half and behind the warm front; however, the
increasingly stable airmass over the lake should work against mixing
the stronger southerly winds to the surface. Given the environment,
higher reporting platforms would be more likely to observed these
stronger winds then the surface buoys. A cold front will press from
west to east through Lake Superior through the day as well. A shower
or thunderstorm can`t be ruled out by afternoon across the east
half, but with the focus for convection being over Upper Michigan
and not Minnesota, the probability is low (20-30%). Behind the
front, high pressure will settle over the lake, supporting a few
days of mostly 20kts or less over the lake through at least midweek.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
  Small Craft Advisory from 2 PM to 11 PM EDT Sunday for LMZ248-
     250.

&&

$$

SHORT TERM...Rolfson
LONG TERM...JTP
AVIATION...Voss
MARINE...JTP