Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221144

Area Forecast Discussion
National Weather Service Marquette MI
744 AM EDT Thu Jun 22 2017

.SHORT TERM...(Today and tonight)
Issued at 442 AM EDT THU JUN 22 2017

The upstream shortwave over northern MN and associated lift is
supporting showers and isolated t-storms from central and northeast
MN into Lake Superior and portions of Upper Mi early this morning.
Strong 850 mb warm advection and moisture transport at the nose of
40-50 kt low-level jet and along 850 mb warm front was also
supporting strong to severe convection over se MN and central WI in
environment of 2000-3000 j/kg MUCAPE and effective shear of 50-60
kts where SPC has highlighted a slight risk for day 1.

Latest RAP shows increasing instability into Upper Mi in the next
several hours fm 08-13Z mainly over the west and south central
portions where MUCAPE values climb to 500-1000 j/kg. Effective deep
layer shear also increases to 25-40 kts over these areas which could
lead to a few of the developing storms becoming strong to possibly
severe through 13-14z.

After the initial shortwave moves east of Lake Superior and q-vector
divergence spreads in from the west, expect a drier period later
this morning into early afternoon.  Models then indicate another
shortwave riding along stalled out frontal boundary developing more
convection into mainly the se half of Upper Mi late this afternoon
and evening. Again, RAP fcst MUCAPE values 500-1200 j/kg and
effective shear near 50 knots would indicate a risk of possible
severe storms into south central Upper Mi late this afternoon
and evening mainly effecting Menominee and Delta counties.

Shortwave moving east will push frontal boundary east and move any
remaining convection east of the fcst area late tonight. Another
shortwave approaching from Manitoba/northern Ontario could bring in
a few showers into the west late.

Expect highs temps today mainly in the 70s under partly to mostly
cloudy skies with lows mainly in the 50s tonight.

.LONG TERM...(Friday through Wednesday)
Issued at 355 AM EDT THU JUN 22 2017

Upper level troughing and resulting cool weather pattern still on
track to begin to settle across Upper Great Lakes on Fri. Main sfc
low near 1000mb starts day over northern Ontario with lead cold
front already east of the forecast area by daybreak on Fri. Weaker
front may slide across through the day but deep drying should result
in mainly dry conditions. Suppose with pooling of 50-55F dwpnts off
northern Lk Michigan and Green Bay and temps into the 70s could see
up to 250j/kg of sbcape and potential for isolated showers over the
southeast especially if there is any type of additional forcing from
shortwave trough working through. With upper level jet axis still
overhead into the aftn ahead of upper troughing, could also be
pockets of upper level divergence to help convection along. Limited
moisture will keep chances very low.

Upper trough expands over the Great Lakes this weekend into early
next week. Daytime highs will stay below normal. Coolest days will
be Sat and Sun as stronger shortwave trough and enhanced rain
chances affect area (Sat) and with lowest temps aloft rotating
across (Sun). Readings both of these days will be in the upper 50s
near Lk Superior and into the upper 60s far south central. Steep mid
level lapse rates up to 6.5-7c/km at times with several shortwaves
and pockets of enhanced moisture and sfc troughs wrapping through
the region within the large scale trough will lead to daily chances
for showers and some thunderstorms Sat through at least Mon, with
maximum coverage occurring during peak heating late morning through
aftn into early evening and/or when stronger shortwaves come across.
On days the thunderstorms are stronger, at least small hail would
occur. Could also see some more cold air funnel episodes (similar to
what occurred Mon of this week). As water temps warm up on Great
Lakes, getting to the point where this type of upper trouging/cold
air advection regime could even lead to waterspouts, though waters
may be just cool enough to not support that at this time.

Troughing begins to break down by middle of next week. Temperatures
should warm back toward normal levels and the periodic chances of
rain should end at least for a day or two. By late next week should
see rain chances increase yet again as strong low crossing central
Canada and cold front extending south across the plains allows warm
and humid air to stream north into the Upper Great Lakes.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 738 AM EDT THU JUN 22 2017

Expect MVFR conditions to develop this morning as moisture with
plenty of low-level moisture ahead of trough. Look for the most
persistent MVFR cigs at SAW and CMX where upslope flow prevails.
Conditions should improve to VFR by afternoon with drier air
moving in behind the trough. SAW may be edge of showers which
develop over the se half of Upper Mi later this afternoon and
evening so included a VCSH to account for this possibility.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 442 AM EDT THU JUN 22 2017

Some patchy fog is possible today with rain sliding over the lake.
Some patchy fog could linger into tonight. Winds will remain
generally below 20kts today; however, there could be a brief
increase in wind gusts with any thunderstorms that move over the
marine environment. Winds should remain blo 20 knots into early next

Upper Michigan...
Lake Superior...
Lake Michigan...


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