Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 192002

Area Forecast Discussion
National Weather Service Marquette MI
402 PM EDT MON SEP 19 2016

.SHORT TERM...(This evening through Tuesday)
Issued at 401 PM EDT MON SEP 19 2016

WV imagery and RAP analysis indicated a mainly zonal pattern across
the nrn CONUS with a 130-140 knots 250-300 mb jet from the nrn plains
to the Upper MS valley. Upper level div with the left exit of the
jet along with 700-300 qvector conv with a shortwave trough from
nrn Ontario, w of James Bay, to Upper Michigan supported a band of
-shra over ern Upper Michigan. MLCAPE values into the 500-1000 J/Kg
range to support TS remained just to the south and east of the cwa.
Strong subsidence/drying in the wake of the shrtwv has brought
clearing with sunny skies over the west half of Upper Michigan.

Tonight, mostly clear skies and drier air into the area with pwat
values to around 0.40 inch will result in favorable radiational
cooling conditions over inland locations where the winds will become
light. Min temps should drop into the mid 40s. However, a tighter
pressure gradient and more winds/mixing will keep temps in the upper
50s near Lake Superior.

Tuesday, a dry airmass will prevail with sfc ridging building over
the region. Under mostly sunny skies through most of the day temps
will remain above normal with forecast soundings supporting highs in
the mid 70s. Mid and high clouds will gradually spread into the area
during the afternoon with the developing waa pattern in advance of a
trough over the plains.

.LONG TERM...(Tuesday night through Monday)
Issued at 330 PM EDT MON SEP 19 2016

Zonal flow aloft the middle of this week becomes much more amplified
the upcoming weekend as sharp ridge develops mid North America btwn
upper trough over eastern Canada and trough across western Conus. At
the sfc, a low pressure system and warm front emerging onto the
Central Plains on Wed will track over the Upper Great Lakes Wed night
into Thu. This system will bring best chance of widespread rain to
the region this week. An west to east frontal boundary and pwats over
1.25 inches lifting into the boundary along with area being situated
in right entrance region of upper jet over northern Ontario suggest
could be moderate or heavy rain. Since tighter h85 temp gradient and
edge of higher instability stays south of Upper Michigan closer to
the sfc low pressure system, may also see the heavier rain remain
south. Will keep featuring highest pops over south half of cwa. Even
as sfc low and stronger instability stay to the south of cwa, there
is weak elevated CAPE and near 0c SI/s to support some rumbles of
thunder later Wed into Wed night. Best chance would be over scntrl.
Highs in the midweek period should be mainly in the 60s.

Questions remain in how strong upper trough is over eastern Canada
Thu into Fri as a stronger trough would push the sfc front far enough
south to keep conditions dry Thu night into Fri. Models are going
back and forth on this. Latest consensus suggests though there may be
some lingering showers on Thu night, most of Fri would end up dry.
Temps through this period will be at or slightly below normal. Normal
highs are in the mid-upper 60s.

Appears that high pressure will then attempt to build southward from
Manitoba and northern Ontario Fri night into Sat resulting in mostly
dry weather. However, the GFS solutions over the last couple days,
at least the ones that are reasonable in terms of the projected
upper level pattern, do indicate there still could be some rain Fri
night into Sat morning, at least for west and southwest portions of
cwa. Latest GFS has trended drier though with only far west cwa
getting clipped by additional showers. ECMWF has trended steadily to
drier weather over most of the cwa but does keep some qpf over west
cwa. Based on the trends, will keep small chances for rain Fri night
over far west and southwest cwa. Dry weather should then hold most
of Sat into Sat night as high pressure, both sfc and aloft, remains
over the Great Lakes. Highs remain in the 60s. Lows Fri night and
Sat night will dip into the low 40s inland. One of these nights may
see even lower temps perhaps as low as upper 30s, but right now not
looking for any frost.

Next chance of rain with some small chances of tsra returns Sun into
Mon. Ridging moving east and approach of at least a piece of
shortwave trough energy from the Plains will support the increasing
rain chances. Given the strength of the ridging departing and drier
air could take some time for the rain to arrive on Sun. Model
consensus works for now owing to the quicker GFS and slower
ECMWF/GEM. Latest ECMWF has edged trough aloft farther east and
would support arrival of rain earlier on Sun. Highs both days
should stay in the 60s though if the rain for later in the weekend
is delayed could see temps make run toward low 70s on Sun over parts
of the cwa.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 150 PM EDT MON SEP 19 2016

Gusty west winds are expected this afternoon behind a cold frontal
passage, especially at CMX where gusts near 35 knots are likely.
Light showers at/near SAW at the start of the period should move out
by 20z. Expect VFR conditions at taf sites through the period.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 401 PM EDT MON SEP 19 2016

West winds should generally diminish to 25 knots tonight into Tue as
the pres gradient weakens with the Canadian low lifting farther ne
across Hudson Bay. Winds will diminish to less than 20 kts Wednesday
and remain blo 20 kts into Saturday under a weak pres gradient
across the Upper Lakes.

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


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