Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 260743

Area Forecast Discussion
National Weather Service Marquette MI
343 AM EDT FRI AUG 26 2016

.SHORT TERM...(Today and tonight)
Issued at 340 AM EDT FRI AUG 26 2016

A surface cold front trailing a shortwave trough crossing Northern
Ontario into Quebec has crossed the Keweenaw Peninsula early this
morning. Slowly seeing expansion of low clouds as cooler air works
across Lk Superior behind the front. 00z KINL sounding showed h85
temps down to +7c and with water temps on Lk Superior in mid to
upper 60s (18-20c) we are coming close to meeing threshold for lake
effect rain showers. Airmass along and ahead of the sfc front fairly
dry so thus far the increase of clouds has been slow. Expect clouds
to continue to expand as h9-h8 moist layer just behind front settles
over Lk Superior. Before daybreak expect lake effect showers to
begin to form in wnw low-level flow over the west cwa. Additional
lift for showers will also come in this morning as shortwave over
eastern ND crosses western and northern cwa and Lk Superior. Cverall
the sufficient over-water instability along with lift fm the
shortwave and additional convergence along the sfc front moving
through will combine to produce isolated to scattered showers from
western cwa into central cwa through the morning. Not expecting a
lot of rain as deeper moisture is limited with this system but could
see up to a tenth of an inch of rain in areas that see the more
persistent showers.

Cold front settles over eastern cwa this aftn and with 925mb winds
more westerly, the low-level convergence near the front along with
daytime heating should be enough to develop additional showers near
the front over the east, especially mid to late aftn. Recent runs of
the HRRR show good continuity here and even suggest a few showers
may linger near Lk Michigan into early this evening as the front
slowly moves through. Highs today will remain in the 60s behind the
front especially near Lk Superior. Temps could reach low 70s over
scntrl with later arrival of cold front. High pressure is overhead
most of the night so interior cool spots may see temps as low as mid
to upper 40s. Return flow warm air and moisture advection kicks in
late tonight as upper trough deepens over the Northern Plains. High
clouds should increase but attm it appears bulk of any rain will
hold off til after daybreak on Sat morning.

.LONG TERM...(Friday night through Thursday)
Issued at 315 PM EDT THU AUG 25 2016

Recent model runs have trended faster at brining a return of deeper
mstr/pcpn to the area late Fri ngt/Sat ahead of a shrtwv aprchg thru
MN on Sat. With this faster trend, Sun now looks to be the drier day
of the upcoming weekend. A WNW flow aloft to the E of a bldg upr rdg
in the Plains will dominate the wx pattern next week. A disturbance
embedded in this flow wl track fm Scentral Canada into Quebec early
next week and drag a cool fnt across the cwa Mon ngt/early Tue. More
sgnft extended model differences are then the rule the second half
of next week.

Fri ngt...Although the night wl start off on the tranquil side with
sfc hi pres rdg/mid lvl dry air in place, a SW flow aloft ahead of
an aprchg shrtwv in the Nrn Plains is fcst to draw more moisture
into the Upper Lks later at ngt. The result wl be incrsg clds, and
perhaps some showers near the WI border toward 12Z.

Sat/Sat ngt...Arrival of dpva/isentropic ascent on the 305K sfc/deep
lyr qvector cnvgc/deep mstr ahead of aprchg shrtwv wl cause an area
of more nmrs/wdsprd showers to move into the Upper Lks. There are
still some inconsistencies among the guidance on the strength/track
of accompanying sfc lo pres and location of greater qpf, so tended
toward a consensus of the guidance. While there are differences on
the track/qpf, models have overall trended toward a faster solution.
So tended to bring pops in faster on Sat and then dry out the fcst
quicker on Sat ngt. Plenty of clds on Sat and h85 temps not far fm
12C to the N of sfc warm fnt wl greatly hold down max temps on Sat.

Sun...There could be some lingering mrng lo clds, but arrival of
dnva/deep lyr qvector dvgc/larger scale drying/sfc hi pres during
daytime warming ahead of trailing shrtwv rdg wl bring a return of
some sunshine during the day. H85 temps in the 12-14C range wl allow
for max temps into the 75-80 range away fm some cooling downwind of
mainly Lk Sup with WNW h925 winds. The hiest temps wl be over the
Scentral, where this WNW flow wl downslope.

Early next week...The medium/extended range guidance advertises a
WNW flow aloft over the Great Lks to the E of a bldg upr rdg in the
Plains wl dominate the wx pattern. There is decent agreement a
shrtwv/sfc lo wl tracking thru Scentral Canada on Mon will drift
across nrn Ontario and into Quebec on Mon ngt/Tue. Although there
could be some showers/TS as early as Sun ngt in the WAA ahead of
this feature and as the attendant cold fnt drifts thru the Upr Lks
on late Mon/early Tue, passage of the stronger dynamic forcing to
the N should limit pops over Upr MI. Temps early next week should
average aoa normal.

Extended...Although the longer range guidance points toward a bldg
mean upr rdg in the Plains, there are some sgnft differences among
the explicit longe range models on how far to the S a Canadian hi
pres wl settle in the more or less NW wind component to the E of the
upr rdg axis. While the 00Z ECMWF showed a hier amplitude trof over
ern Canada/a sharper NW flow into the Great Lks/farther S track of
the sfc hi pres into NW Ontario late in the week, recent GFS runs
indicate a more WNW flow wl prevail in Ontario to the E of the upr
rdg axis and allow a warm/humid SW flow arnd sfc hi pres over the SE
Conus to dominate the Upr Lks just to the S of a W-E oriented stnry
fnt just N of Lk Sup. The GFS fcst scenario would support above
normal temps/chcs for showers and TS while the ECWMF fcst would
result in aob normal temps/mainly dry wx except when that model
shows another shrtwv digging thru the Upr Lks on Thu. Considering
the sharp differences/plausible outcomes, wl maintain the consensus
fcst for now.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1224 AM EDT FRI AUG 26 2016

A trough will drop through the area later on tonight. Behind it,
MVFR cigs should develop at all TAF sites late tonight into Friday
morning. Conditions will begin to improve Friday afternoon.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 340 AM EDT FRI AUG 26 2016

Lingering high waves are gradually coming down along the west shore
of the Keweenaw Peninsula early this morning. Otherwise, despite the
passage of a cold front today, expect winds into this weekend and
early next week to remain at 20 kts or less as the overall pressure
gradient will remain weak.

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


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