Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 191755

Area Forecast Discussion
National Weather Service Marquette MI
155 PM EDT Mon Jun 19 2017

.SHORT TERM...(Today and tonight)
Issued at 339 AM EDT MON JUN 19 2017

Upper trough has settled across northern Ontario and Upper Great
Lakes while primary sfc low at 992mb is lifting toward James Bay.
Sheared out PV anamoly and ribbon of elevated cape extending from
stronger shortwave trough over northern Alberta/Saskatchewan to
along the base of main troughing has supported small clusters of
tsra from southern Saskatchewan to the Dakotas and Iowa while
closer to our forecast area, weaker wave aloft has resulted in a
cluster of isold shra with no thunder over western and north
central Upper Michigan early this morning.

Expect more isolated showers today as the upper trough remains
overhead. Best chances for rain will be over cntrl forecast area
late morning into aftn with peak daytime heating. Steeper lapse
rates aloft along with daytime heating will result in mlcapes up
to 500-750j/kg over scntrl and maybe as far east as ISQ this aftn
so have kept mention of thunder there. Based on h7 flow, any
storms will move from WNW to ESE at 15-20 kts. If any storms
become strong, despite minimal effective shear, low freezing
level around 8kft could allow for hail to reach severe limits near
1 inch in diameter, especially if slightly higher instability is
realized. Any storm or even heavier shower will likely produce at
least small hail and brief heavy downpours. Highs today will
mostly be in the 60s though it could stay in the 50s along Lk
Superior east of Marquette and could reach 70 over far scntrl
vcnty of MNM.

Even though loss of daytime heating will diminish shower and
thunder potential early this evening may still see isold shower
at times late evening and overnight (similar to what is occurring
early this morning) as pv anamoly and elevated cape ribbon drift
closer to Upper Great Lakes. Best chance for increase in shower
and possible thunder will occur late tonight, after 09z Tue, as
the stronger shortwave trough over western Canada this morning
drops into the Upper Great Lakes region.

.LONG TERM...(Tuesday through Sunday)
Issued at 309 AM EDT MON JUN 19 2017

Nam shows a 500 mb ridge over the western U.S. 12z Tue with a trough
over the ern half of the U.S. with a shortwave over the upper Great
Lakes. This shortwave moves through on Tue with more troughing and
shortwaves affecting the area Wed night. Nam has some 850-500 mb q-
vector convergence and deeper moisture Tue morning that moves out by
Tue evening with both returning for Wed night. Did not make too many
changes to the going forecast.

In the extended, GFS and ECMWF show a flattened and broad 500 mb
ridge over the southern half of the U.S. with a broad trough over
Canada and the northern half of the U.S. 12z Thu. Troughing remains
over the upper Great Lakes into Mon with temperatures remaining
below normal along with unsettled weather through most of this
forecast period.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 149 PM EDT MON JUN 19 2017

Cool and moist air off Lk Superior still resulting in MVFR at SAW
early this afternoon and MVFR to IFR conditions at CMX. Expect all
sites to improve to VFR by late afternoon with daytime mixing
lifting the ceilings. Scattered showers could impact SAW early to
mid afternoon. After showers die off this evening, the next best
chance of showers will be late tonight but coverage should be
spotty at best. MVFR conditions should accompany showers late
tonight into Tue.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 339 AM EDT MON JUN 19 2017

Low pressure that brought strong NW winds to gale force at times to
eastern Lk Superior on Sunday will lift toward James Bay today so
expect winds remain 20 kts or less. Winds should then remain 20 kts
or less into Wed, then may increase up to 25 kts Thu into Fri as a
low pressure system and cold front cross the Upper Great Lakes.

Built up waves over eastern Lk Superior to 5 ft per recent ship obs
will take a bit longer to subside, but should settle down to 2 ft or
less later this morning. Still some fog over parts of Lk Superior
this morning, but with cooler/less-humid air flowing over the lake,
expect the fog to dissipate today.

Issued at 559 AM EDT MON JUN 19 2017

Heavy rain of 1.25 to 1.75 inches that occurred over central Upper
Michigan on Sunday pushed the Sturgeon River near Nahma Junction in
Delta county to action/bankfull stage early this morning. Based on
current stage and trend of rise along with possible additional rain
later today due to developing showers and thunderstorms, issued a
flood advisory. Ran the advisory through late tonight, essentially
24 hours from now, to account for the additional rain that may occur
there later today.

Only other river that showed significant impact from the heavy rain
on Sunday was one of our other Sturgeon Rivers, this one in Baraga
county downstream of Prickett Dam. Releases at the dam have seemed
to have stabilized since Sunday evening and at this time that site
looks to remain below action/bankfull stage. Also any rain that could
occur at that site later today should not be near as widespread or
heavy as what could occur over south central Upper Michigan.
Therefore no advisory is needed for the Sturgeon River in Baraga
county at this time.

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


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