Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 230712

Area Forecast Discussion
National Weather Service Marquette MI
312 AM EDT Sun Jul 23 2017

.SHORT TERM...(This evening through Sunday)
Issued at 339 PM EDT SAT JUL 22 2017

The main impact during the short-term portion of the forecast will
be severe weather potential late this afternoon into this evening.

Tonight: A surface low and associated upper-level low is progged to
slide across Ontario tonight. This will drag a cold front across the
Upper Great Lakes region from west to east. Increased moisture ahead
of the cold front along with added forcing from the weak front and
increased instability will allow for scattered showers and
thunderstorms through late evening. Some of the storms may be strong
to severe through 03Z/23 as instability up to or around 500 to 1000
J/kg slowly diminishes this evening, the best chance for the
strong to severe storms will be along the WI border. Shear
magnitudes are expected to be in the 25 to 35 knot range along and
ahead of the front with shear vectors being orthogonal to the
cold front. The combination of the slowly diminishing instability
and the aforementioned shear will allow for the potential for a
few organized strong to maybe even severe storms. Large hail and
gusty winds will be the the main threat early this evening before
storm intensity slowly diminishes by late evening. Storm motion
will likely be from the west at or around 30 to 35 mph. By late
evening into the overnight hours the severe potential will
decrease due to loss of daytime heating; however, showers and a
few thunderstorms will still remain possible along and ahead of
the cold front.

Sunday: The surface low will slide to the east/southeast of the U.P.
as the upper-level low shifts directly overhead by Sunday morning.
The cooler air aloft along with wraparound moisture will keep rain
shower potential and cloud cover in the area through much of the
day. The combination of increased cloud cover, rain showers and
northerly flow will help keep temperatures below normal for the day
with highs only reaching into the 60s across most locations with a
few 70s expected across south central locations of the U.P.

.LONG TERM...(Monday through Saturday)
Issued at 312 AM EDT SUN JUL 23 2017

Overall, precipitation chances later this week look to be confined
to the middle of the week as a cold front pushes across the area.
Otherwise, high pressure will remain across the area and fair
weather will prevail.

Monday through Tuesday as upper-level ridging builds across the
Upper Great Lakes high pressure will linger with ample sunshine and
seasonable temperatures. By late on Tuesday afternoon and into the
overnight hours a potent shortwave trough is progged to track across
Manitoba, pushing a cold front across the Upper Great Lakes region.
This will allow showers and thunderstorms to push west to east
across Upper Michigan Tuesday night through a good portion of the
day on Wednesday. By late Wednesday, the front will push southeast
of the area and high pressure will begin to build across the region
once again. This post-frontal stable air mass will linger across the
area through the end of the week and possibly into the beginning of
the weekend.

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 137 AM EDT SUN JUL 23 2017

One area of showers and thunderstorms has exited the region while a
second continues to move through the west half of the Upper
Peninsula. This second batch of precipitation associated with better
upper level support from shortwave pushing through nrn MN at this
time. This feature continues forcing a weak front through the area
and will bring IFR/LIFR cigs with post boundary subsidence and high
low level moisture. Cigs to improve after sunrise but persistent
northeast flow should keep the cigs down at KSAW.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 339 PM EDT SAT JUL 22 2017

East to southeast winds will continue to be gusty tonight mainly
over eastern Lake Superior toward Whitefish Bay as a cold front
slowly progresses eastward through the area. A surface low will
slide over the central Great Lakes on Sunday while the cold front
continues to move southeast of Lake Superior. Expect east winds to
shift north to northeast 20 to 25 kts by Sunday morning on the back
side of the cold front. Winds will gradually diminish Sunday night
into Monday as high pressure builds across the region. A low
pressure trough moving in late Tuesday may lead to southwest winds
increasing to 25 kts late Tuesday into Tuesday night. Otherwise,
winds this week should be 20 kts or less.

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


LONG TERM...Ritzman
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