Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 251147

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

.SHORT TERM...(Today and tonight)
Issued at 506 AM EST SAT FEB 25 2017

Upper low became somewhat closed off and negatively tilted as it
lifted across Upper Great Lakes late last night into early this
morning. Sfc low around 993mb is currently sliding across Lk Huron
toward Georgian Bay. Despite the stronger upper level system, deep
layer of dry air aloft h7-h5 seen on 00z MPX and GRB soundings put
crimp on the deformation band of snow that tried to re form from WI
into western half of Upper Michigan in both coverage and intensity.
Based on reports received and overall look of radar loop, heaviest
snow amounts late evening into early this morning were over higher
terrain of far west and in the higher terrain of ncntrl, mainly
staying north of Michigamme to Negaunee though recently heavier snow
is spreading west to east across much of Marquette county due to mid
level fgen on northwest side of upper level low and also due to lake
enhancement off Lk Superior. Should see this area of moderate to
heavy lake enhanced snow head over eastern cwa this morning boosting
snowfall intensity there. Also seeing expansion of light to perhaps
moderate snow over scntrl as individual pv anamoly/shortwave lifts
ene over northeast WI and central Lk Michigan.

Winds to this point have been not that impressive, but due to cold
air advection and tighter pressure gradient today, expect NNW winds
to increase to 20-25 mph with gusts to 35 mph. Strongest winds will
be near Lk Superior over ncntrl Upr MI into eastern cwa where 925mb
winds of 30-35 kts are forecast and where forecast soundings show
increasingly well mixed profile. The strong winds will result in
areas of blowing snow. After the heavier lake enhanced snow this
morning, rest of day will be characterized by mainly light lake
effect with inversions up to 4kft and h85 temps -14c. Wide open lake
and ideal fetch with NW flow will help out accums, but still looking
at most of the snow (up to 3") into this morning with only minor
accums of an inch or two this aftn into this evening. Current advy
goes until 00z tonight which looks good based on the persistent lake
effect and with increased hazard from blowing/drifting as winds pick
up this morning.

Elsewhere, due to the increasing negative dynamics over west half,
already seeing synoptic snow coming to an end. NNW-NW flow and temps
at 3-5kft inversion top of -16c along with wide open waters could
result in lake effect bringing minor additional accums to far west.
Dry air upstream over MN as seen on 00z INL sounding will restrict
this potential though. Since there is still light snow ongoing along
with patchy blowing snow near the shore kept warnings and advisories
over west going until original expiration time of 12z. Same story
for WI border zones since there is still a bit of snow to go through
early this morning.

Into tonight another system currently showing up as batch of enhanced
cloud along US/Canada border MT to Manitoba and propelling a weak
sfc front along the MT/Alberta/Saskatchewan border (with a little
light snow or flurries noted) is poised to swing over western cwa
after midnight. System is lacking much moisture and warm air
advection and overall punch to lead to much snow on its own.
However, since blyr winds ahead of the system will be from the
west and it will be sufficiently cold enough for lake effect (h85
temps -12c across Lk Superior) and SLRs will be on the higher side
toward 20:1, went with a more bullish solution (in line with NCEP
WRF and NMM) for at least a couple inches of snow across
Keweenaw. Possible that if there is a direct hit from the system
even another inch or two of snow could occur though area seeing
those snow amounts should remain isolated.

.LONG TERM...(Sunday through Friday)
Issued at 511 AM EST SAT FEB 25 2017

Models suggest that a progressive pattern will prevail through
next week which will bring several rounds of precipitation into
the northern Great Lakes. Colder weather will move in toward the
end of the week as a mid/upper level trough shifts from the north
central CONUS into the Great Lakes and northeast.

Sunday into Sunday night, a mid level shortwave trough and weak sfc
front will move through Lake Superior and Upper Michigan bringing a
period of snow showers to the CWA. With only moderate 700-300 mb
qvector conv and limited moisture inflow, any accumulations will
only amount to around an inch in most locations. Expect likely POPs
into the nw CWA during the morning shifting to the east in the
afternoon. Westerly flow with 850 mb temps around -11C, the Keweenaw
should see potential for higher lake enhanced totals to near 3
inches. Some light lake effect snow showers may linger into the
evening over the Keweenaw and east of Munising.

Monday, WAA ahead of the next trough will boost temps into the mid
30s under partly to mostly cloudy skies.

Tuesday into Tuesday night, as southwest mid/upper level flow
develops ahead of a trough into the wrn CONUS, the models have been
consistent in bringing a shortwave, bands of fgen, and an
associated sfc low/wave toward the nrn Great Lakes. However, there
has been considerable variability with the strength/timing/location
of this feature. However, it should be strong enough to support
QPF at least into the 0.25 to 0.50 inch range. Precipitation type
also remains uncertain. Wet-bulb zero heights favor mainly snow
over the northwest and a mix or mainly rain changing to snow over
the southeast half as highs climb into the upper 30s in most area.
For now, both rains/snow will be mentioned. If the cooler
scenario occurs, several inches of snow will be possible.

Wednesday-Saturday, clipper shortwaves may affect the region in the
developing nw mid/upper level flow. Confidence is higher that enough
cold air will slide into the area for increasing nw flow LES from
late Thursday into Friday. A stronger Pacific shortwave and sfc
moving toward Manitoba will bring increasing WAA Saturday with a
chance of snow ahead of an advancing warm front.

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 646 AM EST SAT FEB 25 2017

As a potent upr disturbance moves across the Upr Great Lks, light
to mdt sn showers wl impact the TAF sites this morning. The
heaviest snow showers will be at SAW. Along with the sn, there
will be occasional blsn whipped up by gusty n winds, especially
into this aftn at SAW. 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 later this morning and this aftn at SAW.
The gusty winds wl slowly diminish by later today with the aprch
of the rdg/weaker pres gradient. Another system will bring in
light snow late tonight into Sunday. Have began to highlight this
system by bringing in lower vsby at CMX and IWD. Best chance of
LIFR or IFR vsby will be at CMX with w winds and lingering cold
air providing some lake enhancement. &&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 506 AM EST SAT FEB 25 2017

NW gales to 35-40 knots are expected for much of central and eastern
Lake Superior into this evening. Some heavy freezing spray is
possible as well, but coverage will be limited to mainly the
shoreline areas along north central Upper Mi so no headline
anticipated. Beyond today, winds will stay 25 kts or less through
Tue but will then become NE to 30 kts on Wed behind another low
pressure system crossing Great Lakes. Winds diminish to 25 kts or
less into Thu as the low moves toward New England and a high
pressure ridge builds from western Canada to the central Conus.

Upper Michigan...
  Winter Storm Warning until 7 AM EST /6 AM CST/ this morning for

  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-

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

Lake Michigan...


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