Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 230538

Area Forecast Discussion
National Weather Service Marquette MI
138 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...(Sunday through Friday)
Issued at 356 AM EDT SAT JUL 22 2017

Generally a pretty quiet stretch of weather in the long term. Strong
shortwave trough still will be over the Upper Great Lakes on Sunday.
This wave along with inverted sfc trough will support showers and
some thunderstorms mostly over the east half into early Sun aftn.
Sun will also be cooler (all but the far scntrl) with low clouds
and given the moist cyclonic upslope flow behind the departing low
there may also be drizzle in the higher terrain of the west and
north central. Low clouds and some drizzle likely will persist
well into Sun night before high pressure/drier air lead to improving
conditions through Mon morning.

The high pressure will result in quiet weather Mon into most of Tue.
Next shortwave in NW flow aloft will move through on Tue night.
Could be scattered showers and a few thunderstorms late Tue aftn
into Tue night. Appears forcing outruns greater instability which
pokes into southern U.P. Tue evening. Mismatch of these two factors
probably reduces the chances of seeing any severe storms. Once the
trough moves through, high pressure resumes dry weather for the rest
of the week.

Temperatures will generally be at or slightly above normal but we
should not be dealing with more persistent summertime humidity.
Coolest temps will be on Mon in wake of the low pressure system that
moves through this weekend. Warmest days of the week, with readings
possibly well into the 80s in parts of forecast area, will be Tue
and Wed. The humidity this weekend will be replaced by less humid
conditions on Mon with the high drifting overhead. Humidity will
increase again Tue/Wed as the sfc trough moves through. Less humid
conditions then return later this week.

.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...


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