Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 281633

Area Forecast Discussion
National Weather Service Marquette MI
1233 PM EDT SAT MAY 28 2016

.SHORT TERM...(Today and tonight)
Issued at 417 AM EDT SAT MAY 28 2016

As with the past several days, shower and storm chances continue to
hinge on the timing of subtle features rounding a mid-level ridge
over the Great Lakes region.

A weak mid-level wave brought a decent shield of rain to the central
and east early this morning before lifting across Lake Superior.
Expect a lull in precip through the remainder of the early morning
hours behind this trough as subsidence briefly takes over. Another
group of showers will then lift northward across WI and across the
west half by mid-morning. The batch of precip may diminish in
coverage while nearing the CWA as it outruns the best forcing ahead
of the trough currently exiting the central Plains.

What happens this afternoon and evening will depend largely on the
coverage of any shower activity and clouds this morning. As a subtle
shortwave ejects out ahead of the main trough axis lifting into the
Upper MS Valley, precip will expand in coverage across northern WI
and the west half of the CWA. If precip coverage remains fairly low
this morning, enough instability will be generated to produce a
decent amount of embedded thunderstorm activity late this afternoon
into the early evening. Many parameters, including mid-level lapse
rates and 1-6km shear, will be a bit low to support strong to severe
storms for most of the area. However, one or two stronger storms
will be possible on lake breeze convergence boundaries.

Another lull in precip activity is expected late this evening into
the overnight hours, though isolated to scattered showers and
possibly some storms will be possible during this time as the main
trough axis approaches.

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1227 PM EDT SAT MAY 28 2016

LIFR clouds have been stubborn to depart today with weak winds and
no dry advection. Expect improvement to low MVFR this afternoon.
Scattered showers will remain across Upper Michigan with the
greatest chances this aftn at KCMX. After the showers exit this
evening, expect BR/FG and low clouds to develop again and produce
IFR to LIFR conditions at all sites overnight. Conditions will
slowly improve by late in the TAF period.

.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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