Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 280800

Area Forecast Discussion
National Weather Service Marquette MI
400 AM EDT SAT MAY 28 2016

.SHORT TERM...(This evening through Saturday)
Issued at 345 PM EDT FRI MAY 27 2016

SW flow aloft bringing multiple minor shortwaves across Upper Great
Lakes. Leftover weak shortwave has helped drive cluster of shra
and isold thunderstorms as far north as Menominee county and Bay
of Green Bay. Pocket of mucapes over 500j/kg also supporting these
showers and storms which should lift into central cwa next few
hours. Additional scattered showers are streaming north across WI
and western Upr Michigan. Not much thunder seen though as sfc based
or elevated CAPES are fairly meager, generally less than 500j/kg.
Scattered showers and an isold thunderstorm expected early this
evening based on radar trends over Upper Great Lakes. As another
shortwave and sfc front/weak low pressure wave lift toward Upr
Michigan later this evening, expect another round of widespread
showers with at least a slight chance of thunderstorms as elevated
cape remains less than 250j/kg. Another mild night with temps mainly
in the 50s and fog should develop again, though probably
later as the rain moves through initially.

Chances for showers and thunderstorms continues on Sat. Put a lull
in during the morning as subsidence behind the wave that moves
through tonight will probably lead to a min in coverage. Models
are in agreement with that idea, though with this type of pattern
near term convection will depend on individual shortwaves that are
hard to determine at this point. Daytime heating should increase
coverage of showers and thunderstorms in the aftn. Will depend on
how much instability is realized. Some hint that low clouds may
hang around til midday, so that would alter forecast of sfc based
CAPEs up to around 1000j/kg. Also think there will be better chances
in afternoon as upper level trough and sfc trough are closer to the
region attm. High temps should reach at least low 70s and could
reach upper 70s if there is enough sunshine.

.LONG TERM...(Sunday through Friday)
Issued at 359 AM EDT SAT MAY 28 2016

Main fcst concerns in the medium/extended range wl focus on pops for
Sun and then Tue into Thu. Interaction btwn shrtwv lifting NEwd out
of deamplifying central CONUS trof on Sun and deep mstr over sfc lo
pres trof drifting acrs Upr MI may result in some heavy showers/TS
especially over the central counties in the aftn. After a drying
trend on Memorial Day behind departing shrtwv and ahead of trailing
shrtwv rdg axis, models have trended faster on bringing more
showers/some TS back into the area on Tue/Wed ahead of another
disturbance aprchg fm the W.

Sun...The approach of a shrtwv lifting NEwd out of deamplifying
central CONUS upr trof and accompanying DPVA/Deep lyr qvector cnvgc
over lo pres trof/cool fnt/axis of deeper mstr moving E on the srn
flank of lo pres lifting NEwd thru Ontario wl trigger numerous
showers/TS in the presence of daytime heating. The 00z GFS shows
MUCAPE as hi as 2200 j/kg, but prefer the lower 00z NAM fcst up to
near 1500 j/kg given expected cld cover and relatively modest mid
lvl lapse rates not much hier than 6C/km. 0-6km wind shear no more
than about 20-25 kts and deep mstr suggest heavy ra wl be the main
threat fm rather slow moving TS under weakening winds alf. Expect
the hier pops over the central cwa, where the arrival of the fnt/lo
pres trof wl coincide better with the diurnal heating cycle.

Sun ngt...With DNVA/deep lyr qvector dvgc and mid lvl drying in the
wake of passing shrtwv and ahead of aprchg shrtwv rdg axis as well
as nocturnal cooling, lingering showers/TS over the E in the evng wl
diminish. Since the llvl drying does not appear to be as sgnft as in
the mid lvls, concerned some lo clds could linger especially in
areas that experience upslope flow with the fcst WNW llvl wind. Mon
mrng wl be cooler than recent mrngs

Mon/Mon ngt...Aprchg shrtwv rdg axis/mid lvl dry air/sfc hi pres rdg
axis extending S fm larger hi pres center moving toward Hudson Bay
should bring a pcpn-free fcst, but some of the models do generate
some lgt pcpn over mainly the scentral at diurnal peak heating time
on Mon aftn on what appears to be focused llvl cnvgc along a Lk MI
lake breeze bndry. Considering the very dry mid lvls shown by many
of the models associated with the aprchg shrtwv rdg, opted to retain
a dry fcst despite concerns about slower llvl dry advctn. With h85
temps fcst to peak arnd 10C, expect max temps to peak arnd 75 away
fm lk moderation. Even drier llvl air is fcst to arrive on Mon ngt
with lgt winds under sfc rdg axis, so expect lo temps to fall into
the 40s at the cool spots.

Tue thru Fri...Medium range guidance has trended faster on moving
next fairly vigorous shrtwv to the E thru the nrn plains and into
the NW Great Lks on Wed. Most of the models now generate some pcpn
over at least the wrn CWA on Tue. The 00Z ECMWF is fastest by
showing pcpn even reaching the ern zns by 00z Wed. So pops wl be
hier than on previous fcst for Tue. Although the bulk of the warm
conveyor belt pcpn may end on Wed as the deeper mstr pushes to the
E, deep cyc flow associated with the passing shrtwv indicates some
light showers may linger into Thu. Closer aprch of trailing sfc hi
pres on Fri wl bring a drying trend. Temps should average AOA normal
on Tue/Wed but then fall blo normal later in the week with arrival
of h85 thermal trof/temps arnd 5C in the cooler NW flow behind the
departing shrtwv.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 135 AM EDT SAT MAY 28 2016

An area of showers will lift northward across the eastern half of
the UP through the early morning hours. Moist easterly flow off fog
covered Lake Superior has already lowered cigs/vsbys at CMX into LIFR
range and that should persist through the overnight hours. As has
happened the last couple of nights cigs/vsbys will also lower into
the IFR range at IWD and SAW with the moist airmass in place.
Daytime heating will allow scattered showers to develop almost
anywhere over the western half of the UP during the day on Saturday
but there will be some improvement in cigs/vsbys by mid morning.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 359 AM EDT SAT MAY 28 2016

A relatively weak pres gradient/hi stability will dominate the Upper
Great Lakes this forecast period, so expect winds at or below 20kts.
Since moist air will linger over the chilly lake waters, dense fog
will persist into at least Sun. Will continue going Dense Fog
Advisory thru the day on Sun. The fog should begin to diminish Sun
night/Mon as drier air arrives from the NW.

Upper Michigan...
Lake Superior...
  Dense Fog Advisory until 6 PM EDT /5 PM CDT/ Sunday for LSZ162-

Lake Michigan...
  Dense Fog Advisory until 4 PM EDT this afternoon for LMZ221-248-



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