Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 281854

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

.SHORT TERM...(This evening through Sunday)
Issued at 245 PM EDT SAT MAY 28 2016

SSW upper flow still in place. Primary upper low is centered over
eastern SD with 1007mb sfc low over far northwest IA. Subtle warm
front arcs ahead of the sfc low, but it remains humid even north of
warm front with dwpnts in the low to mid 60s over Upr Michigan. Weak
shortwave and slight elevated instability with mucape up to 500j/kg
is supporting scattered showers over west cwa. Additional isolated
showers are affecting the far eastern cwa. Min in showers is noted
over central U.P. thus far. Radar trends and HRRR and RAP suggest
current pattern should hold for most part into the evening. There
has been no tsra yet as clouds have held down temps and instability.
Cannot count it out as there are tsra now forming upstream in WI.
Will keep isolated mention of tsra. Seems greatest chances for rain
and thunder into early evening will be over western Upper Michigan.

On a side note, latest flash flood guidance over western U.P. is
lower than points over central and eastern cwa - around 1.5-2.0
inches for 1 or 3 hours as there has been greater coverage to rain
there last few days. Any stronger storms could produce heavy rain
with 12z GRB sounding showing PWATS over 1.50 inches or over 200 pct
of normal. K-index was 34. Will be something to keep eye on as the
aftn goes into the evening.

Another mild night with lows in the upr 50s to low 60s. No need to
alter current persistent pattern with fog/stratus forming late
tonight and lingering into Sunday morning. Could see increase in
showers late tonight over sw as upper trough over SD moves to MN/WI.
Sfc low will be sliding over western U.P. during that time. Better
chances of showers and some thunderstorms will be later Sun morning
through Sun aftn with upper trough axis moving overhead and as
sfc-h85 trough axis crosses. Since low clouds should be around to
start day, could again see situation like last couple days where
instability forecast by models may be held down which will lead to
less chance of tsra. Proximity of mid level trough axis may lead to
higher lapse rates though since dry slot on leading edge of trough
(which has helped form tsra this afternoon over southern MN into
northern IA) will be pretty much east of cwa by aftn think that may
be where greater tsra chances will reside. Overall will keep thunder
chances low. Finally, once the sfc low and sfc-H85 trough pass by
expect strong/gusty west winds to develop over Lk Superior and
Keweenaw Peninsula. As the winds shift west and bring in slightly
drier air, should finally begin to scour out the fog over Lk
Superior. High temps on Sunday with plenty of clouds should reach
upper 60s to low-mid 70s with warmest readings south central and east
away from Great Lakes.

.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 PM Lake Superior forecast issuance)
Issued at 245 PM 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 Sunday for LSZ243>246-264>267.

  Dense Fog Advisory until 2 PM EDT /1 PM CDT/ Sunday for LSZ162-

Lake Michigan...


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