Severe Thunderstorm Warning 20, NWS Marquette, MI

Area Forecast Discussion
National Weather Service Marquette MI
625 PM EDT Wed Jul 8 2020

.SHORT TERM...(This evening through Thursday)
Issued at 356 PM EDT WED JUL 8 2020

Well, so far not quite as warm as was forecast thanks to some cirrus
convective contamination from storms across MN this morning. Didn't
cut them back too much, but took a couple degrees off across the
board to go with the trend through the day. A few thunderstorms made
their way into western UP this afternoon, but diminished quite
quickly as they propagated into an unfavorable convective
environment. Through the rest of the afternoon and into the evening,
temps may climb a few more degrees, but otherwise expecting more of
a filtered sun through the cirrostratus across the west and central
and status quo across the east.

Tonight, things become interesting fairly early on this evening as
CAMs suggest thunderstorms to develop across central MN and
propagate eastward. CAMs suggest upscale growth to occur earlyish on
as any isolated storms congeal into a MCS as they move over Lake
Superior into the UP circa 00UTC. Latest HRRR is suggesting a little
later closer to 02-04UTC. Either way, models suggest upwards of 2500
to 3000 J/kg of sfc CAPE, with bulk shear near 30kts and 0-3km
200m2/s2 helicity. The better shear remains just behind the CAPE
gradient, which should help keep the svr threat lower, but there is
some potential for strong to svr winds across western UP as the
storms move into the CWA. AS they continue to propagate eastward,
they move into a less favorable environment and as such, the CAMs
show a diminishing trend rather quickly, struggling to make it any
further than Marquette/Menominee counties.

Tomorrow, residual low-level moisture may lead to some morning fog
for some before skies become partly cloudy by mid morning/early
afternoon. Another hot and muggy day expected with highs a little
cooler in the west(mid to upper 80s), but near 90 across the central
and east where a little more sunshine is possible. With Tds in the
mid to upper 60s, the "feels like" temperatures will push in to the
low 90s for most. As a shortwave lifts north through WI tomorrow,
CAMs suggest another round of developing thunderstorms in the
afternoon/evening across the central, but better forcing remains
behind the instability and have cut back and slowed PoPs from the
going forecast. Seems like ARW core models are much faster to bring
these storms in with NMMB models keeping conv tightly tied to the
shortwave and developing weak sfc low.

.LONG TERM...(Thursday night through Wednesday)
Issued at 310 PM EDT WED JUL 8 2020

Generally progressive pattern will persist across the northern Lakes
through next week. Upper low moving into far northwestern Ontario
will push a weak cold front through the Upper Great Lakes and U.P.
Thursday night into Friday. Well defined MCV will eject out of the
Plains into the lower Lakes later Thursday into Friday.  The end
result will be better upper forcing passing to the north and south
of the U.P. with the weak front the main forcing mechanism for
scattered showers and thunderstorms lingering across the area
Thursday night and moving eastward through Friday morning.

Dewpoints behind the front will fall off into the 50s especially
across the west by Friday afternoon. 85H temps will fall back into
the 10-12C range for the weekend allowing for more seasonable
temperatures through the weekend. 2 weak shortwaves in the west
northwesterly upper flow passing through later Saturday and on
Sunday may be enough to trigger a diurnal shower or tsra but
coverage of any precipitation will be small.

With ridging overhead on Monday expect a dry, seasonable day. Beyond
Monday the Upper Great Lakes will be on the northern fringe of a
nearly 600dam 500H ridge across the Ohio Valley. Shortwaves embedded
in the westerly flow may trigger some more organized shower and
thunderstorm activity by later next Tuesday into Wednesday.
Temperatures will return to their significantly above normal levels
by that time.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 625 PM EDT WED JUL 8 2020

VFR conditions are expected to continue through at least tonight
before a line of thunderstorms develops this evening across north-
central MN and propagates eastward. The best chance of thunderstorms
look to impact IWD and CMX before they begin to diminish on their
way to SAW. With these thunderstorms, MVFR to potentially IFR vsbys
are expected in the heaviest rain axis. Have kept TSRA in for SAW as
there is still a decent chance they persist this far eastward.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 356 PM EDT WED JUL 8 2020

Patchy fog, locally dense at times, will continue through this
forecast period given the warm and moist airmass over the region.
This evening, thunderstorms are expected to move into the western
portions of Lake Superior. Some storms could be strong, capable of
producing gusty winds and heavy rain fall, capable of reducing
visibilities quickly. Expect fog to develop in locations that
receive the rainfall. Another small chance of thunderstorms are
possible across the east half tomorrow night. With the exception of
any gusty winds in these storms, winds are expected to be below 20
knots through the forecast period.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

SHORT TERM...JAW
LONG TERM...MZ
AVIATION...07
MARINE...JAW

Hazardous Weather Outlook
National Weather Service Marquette MI
314 PM EDT Wed Jul 8 2020

MIZ001>007-009>014-084-085-091200-
Keweenaw-Ontonagon-Northern Houghton-Baraga-Marquette-Alger-Luce-
Gogebic-Iron-Dickinson-Menominee-Delta-Southern Schoolcraft-
Southern Houghton-Northern Schoolcraft-
314 PM EDT Wed Jul 8 2020 /214 PM CDT Wed Jul 8 2020/

This Hazardous Weather Outlook is for portions of western Upper
Michigan and central Upper Michigan.

.DAY ONE...Tonight

Thunderstorms are possible in the far west. A few of the storms
could be strong. The storms will weaken as they move further east.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Thunderstorms are possible again Thursday afternoon into Thursday
night mainly across the south central. A few of those storms
could be strong.

Hot and humid conditions will make Thursday feel like
it will be in the mid to upper 90s in some Upper Michigan
communities. Everyone is reminded to limit time outdoors during
peak heating, make sure you and your pets stay hydrated, and never
leave pets or passengers unattended in hot vehicles!

.SPOTTER INFORMATION STATEMENT...

The need for weather spotter reports is not anticipated at this
time.

LSZ162-240>251-263>267-091200-
Lake Superior west of a line from Saxon Harbor WI to Grand
Portage MN beyond 5NM-Saxon Harbor WI to Black River MI-
Black River to Ontonagon MI-
Ontonagon to Upper Entrance of Portage Canal MI-
Upper Entrance of Portage Canal to Eagle River MI-
Eagle River to Manitou Island MI-
Manitou Island to Point Isabelle MI-
Point Isabelle to Lower Entrance of Portage Canal MI-
Lower Entrance of Portage Canal To Huron Islands MI Including
Keweenaw and Huron Bays-Huron Islands to Marquette MI-
Marquette to Munising MI-Munising to Grand Marais MI-
Grand Marais to Whitefish Point MI-
Lake Superior from Saxon Harbor WI to Upper Entrance to Portage
Canal MI 5NM off shore to the US/Canadian border including Isle
Royale National Park-
Lake Superior from Upper Entrance to Portage Canal to Manitou
Island MI 5NM off shore to the US/Canadian Border-
Lake Superior West of Line from Manitou Island to Marquette MI
Beyond 5NM from shore-
Lake Superior East of a line from Manitou Island to Marquette MI
and West of a line from Grand Marais MI to the US/Canadian Border
Beyond 5NM from shore-
Lake Superior from Grand Marais MI to Whitefish Point MI 5NM off
shore to the US/Canadian border-
314 PM EDT Wed Jul 8 2020 /214 PM CDT Wed Jul 8 2020/

This Hazardous Weather Outlook is for portions of Eastern Lake
Superior...Central Lake Superior and Western Lake Superior.

.DAY ONE...Tonight

Thunderstorms are possible over the western Lake tonight. A few of
the storms could be strong.

Areas of fog are expected tonight. Some locally dense areas will
be possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Thunderstorms are possible over much of Lake Superior Thursday
through Thursday night.

.SPOTTER INFORMATION STATEMENT...

The need for weather spotter reports is not anticipated at this
time.

LMZ221-248-250-091200-
Green Bay North of line from Cedar River MI to Rock Island
Passage-Seul Choix Point to Point Detour MI-
5NM East of a line from Fairport MI to Rock Island Passage-
314 PM EDT Wed Jul 8 2020

This Hazardous Weather Outlook is for portions of Northern Lake
Michigan.

.DAY ONE...Tonight

Thunderstorms are possible late tonight.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Thunderstorms are possible Thursday into Friday. A few of the storms
could be strong.

.SPOTTER INFORMATION STATEMENT...

The need for weather spotter reports is not anticipated at this
time.

MZ

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