Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 301935

Area Forecast Discussion
National Weather Service Marquette MI
335 PM EDT Fri Sep 30 2016

.SHORT TERM...(Today and tonight)
Issued at 438 AM EDT FRI SEP 30 2016

Upper low and sfc low spinning over Ohio Valley vcnty of northern KY
this morning while high pressure ridge is stationed north of Lk
Superior. NE winds btwn these features and nighttime cooling and
lingering low-level moisture is supporting low clouds and patchy fog
over parts of western and north central Upper Michigan. Low-level
winds change little into tonight and there is minimal dry air
advection occurring so expect sct-bkn low clouds to persist over
western Upper Michigan through tonight. Elsewhere should see
generally partly cloudy skies as h85-h7 moisture on north edge of
upper low drifts across. May be enough saturation and weak lift to
help develop a few showers late today far scntrl. Not a great chance
of rain by any stretch though.

The Upper low and sfc low drift slowly back to the north later
tonight toward the Lower Great Lakes, but model trends and forecast
soundings indicate that even though clouds will steadily increase
from se to nw through the night, chances of rain will be confined to
scntrl and east cwa and those will be late at night aft 09z Sat.
Since upper low will be still south of lower Michigan through
daybreak, any rain that occurs this far north will be very light or
probably just a few sprinkles. Lowest temps tonight in the mid to
upper 40s over interior west while temps elsewhere will stay in the
low or even mid 50s with increasing and thickening cloud cover.

.LONG TERM...(Saturday night through Friday)
Issued at 334 PM EDT FRI SEP 30 2016

Deep mstr arnd a slow moving closed lo pres in the Lower Lks could
cause some showers over the se half of Upr MI on Sat ngt into Sun,
but then an upr rdg shifting into the area wl bring dry wx into at
least Wed. The biggest uncertainty wl be on sky cover/potential for
lo clds during this time. As the cold fnt ahead of a deep, slow
moving wrn trof moves toward the area, shower chcs wl return later
in the week. Unseasonably warm air wl dominate the Upr Lks until
late next week, bringing continued above normal temps to Upr MI.

Sat ngt/Sun...Closed upr lo over far srn Lower MI on Sat evng is
fcst to lift slowly to the ne and thru far se Ontario on Sun.
Although the models are consistent showing a good deal of mstr
extending into the Upr Lks within the deep cyc ne flow on the nw
flank of this disturbance, the bulk of the larger scale deep lyr
cnvgc is progged to remain mostly to the se closer to the track of
the closed lo and impact only the ern portion of the cwa. Even this
forcing is progged to exit to the e on Sun as the closed lo drifts
in that direction away fm Upr MI. So the fcst wl continue to show no
more than chc pops over the se half, hiest on Sat ngt toward the
LOT/APX cwas and diminishing on Sun. Expect temps thru the weekend
to remain above normal, especially on Sat ngt with lots of clds in
the presence of h85 temps arnd 9C. The best chc for more sunshine on
Sun wl be over the w closer to slowly aprchg hi pres rdg axis if lo
clds associated with persistent near sfc mstr in that area do not
linger. Max temps on Sun should run mainly in the 60s even though
more persistent clds toward the e wl limit insolation.

Sun ngt into Wed...As the upr rdg to the e of a deep wrn trof shifts
into the wrn Great Lks early next week, a sfc rdg axis extending
swwd fm a hi pres center drifting fm over Hudson Bay into Quebec wl
dominate the Upr Lks. On Tue and Wed, this rdg wl shift the e,
causing a tightening pres gradient/strengthening sly flow over the
cwa to the e of falling mslp in the Plains associated with the
slowly progressive wrn upr trof.  While dry wx wl prevail during
this time with larger scale subsidence under the upr rdg, some of
the medium range models have hinted at some lo clds/fog under
strengthening subsidence invrn with lgt ne winds off Lk Sup on Mon
and then the sly flow off Lk MI on Tue/Wed at a time of the year
dominated by lowering sun angle/diminished daytime mixing/longer
nocturnal cooling. The potential for this lo cld cover is the
biggest uncertainty during this period. Fcst h85 temps arnd 9C
rising toward 12C on Wed wl ensure temps run abv normal during this
time, but the presence or not of lo clds would alter the min/max
temp anomalies and diurnal ranges. Best chc for anomalously warm
daytime max temps wl be on Tue/Wed in the downslope areas near Lk
Sup, where the prospect for more sunshine wl be greatest and
could lift daytime max temps aoa 70.

Wed thru Fri...Although there remain some timing differences on how
quickly the wrn trof and cold fnt attendant to associated lo pres
lifting into scntrl Canada wl move toward the cwa, shower chcs wl be
on the incrs on Wed/Thu as this fnt/warm conveyor belt mstr ribbon
aprch. Some of the longer term guidance generates a good deal of
pcpn over the area, not out of the question considering pwats fcst
to rise as hi as about 1.50 inches under the warm conveyor belt and
relatively slow ewd progression of the features that would extend
residence time of the stronger sly flow/deeper mstr. On the other
hand, some of the models show the more sgnft hgt falls passing to
the nw with lighter pcpn over the wrn Great Lks. Considering these
important differences, ll not deviate fm the consensus fcst.
Following the eventual cold fropa, looks like much cooler air wl
invade the area late in the week. The 00Z ECMWF shows one of the
coolest scenarios with h85 temps dipping blo 0C by late Fri and
supporting some lk enhanced pcpn under lingering moist cyc nw flow.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 151 PM EDT FRI SEP 30 2016

Expect VFR conditions will continue to prevail through this evening
under the influence of dry high pres over nrn Ontario. Some
radiationa fog will be possible late tonight at IWD.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 438 AM EDT FRI SEP 30 2016

Weak pressure gradient across Lake Superior through the weekend and
early next week will keep east to northeast winds at 20 kts or less.
South-southeast winds may increase over 20 kts Tue into Wed ahead of
front moving out the Northern Plains. Strongest winds would be over
north central and eastern Lk Superior.

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


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