Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250546
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
1246 AM EST Sat Feb 25 2017

.UPDATE...
Issued at 814 PM EST FRI FEB 24 2017

Aggressive dry slotting indicated on latest wv imagery that is
consistent with the vertical mstr profile shown on the 00Z GRB raob
is limiting overall pcpn coverage/intensity this evng, especially
over the central cwa. Steep mid lvl lapse rates shown on the 00Z GRB
raob has allowed for more convective elements to hit the ern cwa,
and there has even been a ltg strike or two near Newberry. As the
potent upr disturbance over Iowa this evng lifts to the ne and
becomes more negatively tilted overngt, 00Z-12Z h5 hgt falls are
fcst to reach 150-200m. So still expecting the upr lvls to become
more saturated overngt and some heavier sn to impact the area on the
cyc side of the closed upr lo. Sharpening cyc nne flow that wl dvlp
and advect colder h85 temps wl still support some lk enhancement as
well, mainly in the upslope areas near Lk Sup. So although pcpn/sn
amnts were cut back a bit over mainly the central, wl maintain going
headlines.
&&

.SHORT TERM...(This evening through Saturday)
Issued at 403 PM EST FRI FEB 24 2017

Main weather concern for the short-term continues to be the
potential for heavy snow across much of the the area through
tonight. The main areas of concern for the heaviest snowfall are
across the higher terrain north central and higher terrain over the
western U.P. Timing looks good on most of the warnings and
advisories; however, opted to extend the winter weather advisories
for the south-central portions of the U.P. through 12Z Saturday.

Tonight: The highly advertised low pressure system over central
lower Michigan this evening is expected to lift very slowly to the
northeast tonight. This low will reach southwest Quebec late tonight
into early Saturday morning. Aloft, the 700mb - 850mb low will
become nearly vertically stacked over the surface low as it passes
just east of the U.P. Just to the west of the these features, a
stronger area of FGEN is expected to set up across mainly the
central U.P. at 850mb and western U.P. at 700mb, which will increase
snowfall rates and overall snowfall totals across these areas. This
is progged to set up from late this afternoon through the early
overnight hours, which would be the main time period for hazardous
travel due to the heavy snowfall rates. In addition to the system
forcing, north to northeast winds will also be in place during this
time period allowing for both lake enchancement and upslope flow
over north-central portions of the U.P. Again, all of this points
toward a period of heavier snowfall late this afternoon through the
early overnight hours, especially for central portions of the U.P.
This would support the winter storm warnings over these areas. Over
the west, most of the heavier system snow will remain off to the
east of that area; however, the north to northeast winds will slowly
shift to the northwest overnight, allowing for steady lake
effect/enhanced snow over those areas. The main concentration of
heavier snow would likely be over the Gogebic and Ontonagon County
areas where the winter storm warnings are in place. Drier air will
filter in over the western areas late tonight, which should help to
diminish the snowfall rates. Over the east half of the U.P. a well
defined dry slot, is progged to slide across the eastern portions of
the U.P. this eveing before sliding east of the area overnight. The
main impact this will have will be the potential for a wintry mix of
freezing drizzle/rain, sleet and snow through late evening. Some
areas may even see ice accumulations around a tenth of an inch, with
the best chance of this happening over the far eastern portions of
the U.P. The overall precipitation over the east half will generally
be light through this evening. Overnight, the aforementioned FGEN
band over the central U.P. is progged to slide across the eastern
areas allowing for another quick burst of heavier snow overnight as
the snow begins to transition to mainly lake effect snow.

Saturday: The low pressure system will continue to shift north and
east of the U.P. and winds will shift to the northwest. The stronger
system forcing and deeper moisture will slowly shift out of the area
as well. This will shift the main focus to lake effect snow for
northwest wind favored snow belts as 850mb temperatures are progged
to be in the -15C to -17C range and another shortwave quickly slides
across the U.P. The heaviest snow is expected over the eastern U.P.
as that area will closer to the departing moisture and co-located
with the longer fetch across Lake Superior. Inversion heights over
the eastern U.P. are progged to be upwards of around 8kft, with much
of the moisture located directly in the DGZ through much of that
layer. This will lead to some heavier snowfall rates in the lake
effect bands through late Saturday afternoon. Most of the west half
of the U.P. will see only a couple of additional inches through the
day; however, eastern areas will likely see and additional 3 to 5
inches.

.LONG TERM...(Saturday night through Friday)
Issued at 326 PM EST FRI FEB 24 2017

Upper air pattern consists of a 500 mb trough over the northern
plains 00z Sun which heads into the upper Great Lakes on Sun. Nam
shows some 850-500 mb q-vector convergence with deeper moisture
moving through the area Sat night into Sun afternoon. GFS and ECMWF
show about the same thing as well and went with blend of the models
for this forecast. Will have some light snow move into the area late
Sat night into Sun afternoon and have some chance to likely pops in
there for this. Overall, did not make too many major changes to the
going forecast.

In the extended, GFS and ECMWF show a 500 mb trough over the Rockies
12z Tue. This upper trough moves into the upper Great Lakes 12z Wed.
An alberta clipper type system moves into the area Thu with the cold
air moving in for Fri. Temperatures cool from above normal at the
beginning of this period to near normal for most of this period.
Decent chance for mixed pcpn occurs Tue into Tue night and some
freezing rain cannot be ruled out with the snow and rain mixed in
with this system. Will continue to have to watch this system and see
if the mixed pcpn threat continues and will have plenty of
opportunity to watch this next system evolve.
&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1245 AM EST SAT FEB 25 2017

As a potent upr disturbance moves ne into the Upr Great Lks, mdt to
perhaps heavy sn wl impact the TAF sites early this mrng. Along with
the sn, blsn whipped up by some gusty nne winds wl result in
IFR/LIFR vsbys much of the time until at least 09Z. The aprch of a
high pres rdg/drier llvl air to the w shown on the 00Z INL raob wl
result in improving conditions at CMX and IWD as early as next TAF
issuance. Conditions wl continue to improve w-e on Sat and be
enhanced by a downslope wnw wind at SAW ahead of the incoming rdg
axis. With a more persistent upslope nw backing w wind, MVFR cigs wl
be most persistent at CMX and probably linger thru the end of the
TAF period. The gusty winds wl slowly diminish by later today with
the aprch of the rdg/weaker pres gradient.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 403 PM EST FRI FEB 24 2017

NE to N gales to 35-40 kts are expected over much of Lake Superior
through tonight and NW gales to 35-40 knots are expected for much of
central and eastern Lake Superior Sat into Sat evening. Some heavy
freezing spray is possible tonight into Sat, but coverage will be
limited to mainly the shoreline areas along north central Upper Mi
so no headline anticipated.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Storm Warning until 7 AM EST /6 AM CST/ this morning for
     MIZ002-004-005-009.

  Winter Weather Advisory until 7 AM EST /6 AM CST/ this morning
     for MIZ001-003-010>013-084.

  Winter Weather Advisory until 7 PM EST this evening for MIZ006-
     007-014-085.

Lake Superior...
  Gale Warning until 10 PM EST this evening for LSZ264>267.

Lake Michigan...
None.
&&

$$

UPDATE...KC
SHORT TERM...KEC
LONG TERM...07
AVIATION...KC
MARINE...KEC



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