944
FXUS63 KMQT 181843
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
243 PM EDT Tue Jun 18 2024

.KEY MESSAGES...

-Showers and thunderstorms possible tonight, particularly over
 the far west. Some severe weather is possible over the far
 west.

-Potential heavy rain event this weekend.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 242 PM EDT Tue Jun 18 2024

A scattered cu deck has formed over the western half this afternoon
whereas the eastern half is mostly cloud free as strong southerly
winds off of Lake Michigan are helping to stabilize the air a
little. Observations have already shown temperatures reaching the
80s across much of the area, with some spots such as Ontonagon and
L`Anse already getting to 90+F. Meanwhile, a shortwave low moving
through MN is continuing to lift along a cold front boundary over
the area. As the cold front continues to move eastwards into our
area tonight, expect showers and thunderstorms to move into the far
west before midnight local time. We could see some severe hail and
winds come this evening as the convection moves into our western
area, as models show MUCAPEs in the 1k-3kJ/kg range and shearing
very high in the lowest levels of the atmosphere as a low-level jet
screams across our area. In addition, the hodograph and LCL levels
are supportive of a very small chance (<5%) for an isolated tornado
late tonight. However, with CAMs showing a lot more of the
convection dying than previously anticipated, the severe weather
potential looks to be relegated to the far western U.P. as the cells
die and collapse (similar to how we saw the severe winds over the
eastern U.P. yesterday afternoon). Given the sharp drop in precip
chances as the cold front moves eastwards tonight, I`ve reduced the
chances across the central and eastern U.P. to chance wording (30-
40%). However, this may need to be lowered further as the most
recent CAMs seem to amplify the lack of rainfall late tonight.

&&

.LONG TERM /TONIGHT THROUGH MONDAY/...
Issued at 407 AM EDT Tue Jun 18 2024

The overall consensus of both ensemble and deterministic guidance
packages suggests the pattern across CONUS will continue to include
a stout mid-upper level ridge over the eastern third of CONUS while
deep and broad troughing holds fast over the western third. This
places Upper Michigan in a predominate south to southwest flow
regime and open to both Gulf of Mexico moisture and a warm/hot
airmass, and on the path for any shortwave, impulse, or MCS
developing across the Plains, at least until the weekend when a more
zonal pattern begins to emerge.


The low currently ejecting out of the central Plains early this
morning will move into Ontario tonight, slowly dragging a cold front
through Upper Michigan tonight through Wednesday. Showers and
thunderstorms begin to move into the western UP as early as this
evening, which will present another opportunity for some strong to
severe storms given impressive CAPE and sufficient shear over the
area. However, this risk remains limited and wanes further eastward
as given an unfavorable timing of the frontal passage. Will note
that most of the hi-res guidance indicates that convection will be
able to make it even as far eastward as M-95 overnight. However,
where storms can develop, heavy rain will yet again be a concern
with near 2in PWATs. As the front continues to slowly track through
during the day Wednesday, expect additional convection to develop
along it with weak daytime instability. Otherwise, expect
temperatures to come in cooler than Tuesday, with highs ranging in
the 70s behind the front and the upper 70s to lower 80s ahead of it.
Dewpoints in the 60s ahead of the front will keep things feeling
rather muggy.

The front largely clears the area Wednesday evening, with PoPs
receding southward as high pressure builds in. Thursday looks to be
mostly dry as the pattern begins to shift into something more zonal,
but some showers cannot be totally ruled out with weak impulses
rippling through. As another shortwave begins to eject out of the
Rockies, another warm front will lift into the Upper Great Lakes
Thursday night/Friday, potentially supporting showers/storms
Thursday night into early Friday. The boundary appears to stall out
Friday over the Upper Great Lakes as a surface low deepens and lifts
out of the Central Plains. The low will press through the region
Saturday night and Sunday while the shortwave aloft takes on a
negative tilt. For a few days now, guidance has been suggesting this
setup, which could lead to a potential heavy rain/flooding event in
some areas in Upper Michigan as PWATs again increase to as high as
200% of normal. Of course, this will be dependent on preceding rain,
but this system warrants monitoring.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 109 PM EDT Tue Jun 18 2024

VFR conditions are expected to continue at the TAF sites this
afternoon into very early this evening, although with a high-end
MVFR cu deck having already formed over the western half of the
U.P., we could see some BKN MVFR cigs from time to time across the
TAF sites for the afternoon hours. As the showers and storms over
Minnesota move eastwards across our area tonight, expect the
conditions at the terminals to likewise worsen from west to east
tonight to MVFR/IFR. In addition, LLWS is expected across all the
TAF sites when the gusty winds aloft from a low-level jet overhead
fail to mix to the surface. However, when those gusty winds reach
the surface from time-to-time tonight into Wednesday morning, the
LLWS will not be as much of a problem. Conditions improve Wednesday
morning behind the cold front, with the terminals eventually
becoming VFR from west to east near the end of the TAF period (save
for maybe KSAW, which could hold onto high-end MVFR cigs until after
18z).

&&

.MARINE...
Issued at 407 AM EDT Tue Jun 18 2024

A warm front lifting northward early this morning is supporting
additional showers and some thunder, but showers largely move north
of the area shortly after sunrise. Meanwhile, light winds to start
us off will keep in a potential for some patchy dense fog through
the morning.

South of the warm front, a strong low level jet will move over Lake
Superior ahead of a cold front moving eastward through Minnesota.
This low level jet will support southerly winds upwards of 30kts
across eastern Lake Superior, possibly some low end gales for higher
reporting platforms or where topography plays a local influence on
winds near the lakeshores between Marquette and Whitefish Pt. Cold
front will press through the lake tonight through Wednesday,
potentially supporting another round of strong to severe storms
across western Lake Superior and thunderstorms and showers lake-
wide. Winds slowly fall back below 20 knots while turning mainly to
the west behind the front Wednesday afternoon. High pressure appears
to try to work in Thursday but will be dependent on upstream
systems. Another front moves over the lake Friday/Saturday as a low
pressure approaches from the west, bringing with it another round of
showers/storms. Current thinking is for light winds in this system
outside of thunderstorms.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Beach Hazards Statement until 10 PM EDT this evening for
     MIZ014.

Lake Superior...
None.
Lake Michigan...
None.

&&

$$

SHORT TERM...TAP
LONG TERM...LC
AVIATION...TAP
MARINE...LC