Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 160915

Area Forecast Discussion
National Weather Service Marquette MI
415 AM EST Fri Feb 16 2018

.SHORT TERM...(Today and tonight)
Issued at 415 AM EST FRI FEB 16 2018

Light to at times moderate lake effect snow may make for slippery
travel this morning; however, the snow will diminish throughout the
day from the west.

A quick moving shortwave, sliding across the U.P., has helped to
steepin lapse rates and create more favorable conditions for lake
effect snow across the area, especially from near Marquette
eastward. Overall not expecting accumulations to be too impressive;
however, there could be a couple inches wherever the bands end up
sitting for a while. By mid morning and through much of the evening
hours, dry high pressure will build into the Upper Great Lakes
allowing the lake effect snow potential to end and skies to steadily
clear from the west. Highs today will be mainly in the 20s. A cold
front will approach the far western U.P. late tonight, which may
allow some very light snow to slide in near Ironwood. Again this
would be very light snow as there will be some dry air that lingers
into the overnight hours. The rest of the U.P. will remain dry.
Overnight lows will mainly be in the single digits above zero,
coldest inland west.

.LONG TERM...(Friday night through Thursday)
Issued at 342 PM EST THU FEB 15 2018

...Active winter weather returns to Upper Michigan starting Sunday...

Still on track for a rather active period of winter weather starting
up on Sunday and lasting through Tuesday. After quiet weather,
especially in terms of system snow for much of the winter thus far
and certainly first half of February, this will be quite a change.
Multiple waves of light to moderate snow could affect the area first
on Sunday/Sunday night, then later Monday into Monday night and now
it looks like another wave of snow moves across Tuesday into Tuesday
evening. Temps start out chilly Friday night but will mainly be at
or above normal into Monday. Temps should cool back some by mid week
before bouncing back above normal, but overall temps through the
next week will not feature any significant warm ups or cool downs.

High pressure will bring dry weather on Friday night. Though temps
will be cool they should not bottom out below zero as southwest
winds increase in gradient between high pressure moving to Mid
Atlantic states and low pressure sliding over northern Ontario.
Could be a 3-6 hour period of light snow (well under an inch) on
Saturday pretty much everywhere mainly due to forcing aloft. Low-
level dry air will limit amounts and keep pops only in low chance
range. Best chance for seeing an inch or two of snow will be over
east with flow off open waters of northern Lk Michigan. Cold front
tied to sfc low slides through Saturday evening. Cold enough (H85
temps -15c) and moist enough (moisture up to 3-4kft AGL) in wake of
the front for light lake effect for mainly west wind snow belts.
Recent openings/leads developing in ice field over south central and
eastern Lk Superior point to some light snow accumulations east of

Active weather pattern ramps up Sunday as attn turns to incoming
area of H85-H7 moisture advection ahead of H85 low developing over
northern Plains and sfc low tracking across southern MN and WI.
Divergence aloft from right entrance region of upper jet along with
Upper Michigan located to north of H85 baroclinic zone will focus
area of light to moderate snow spreading across Upper Great Lakes
Sunday morning through Sunday evening. Still some small differences
on latitude of axis of heavier snow but model agreement has become
better than recent days. Based on blend of model qpf and GEFS and
SREF ensembles, looking at 1-3"/2-4" amounts, heaviest west half.
Possible that could see enhanced snow amounts due to banded snow
with negative EPV occurring atop H85-H7 fgen present. Pinning this
type of detail down will be a nowcast issue later in the weekend.
Good agreement that snow diminishes late Sunday night then another
system(s) affects area with more snow Monday and Monday night and
maybe into Tuesday.

Pretty certain it will snow Monday into Monday night but exactly how
the system(s) evolve is still highly uncertain. Upper level system
that will lead to these snow chances still traces back to northern
Pacific at this time, so details will likely change over the next
few days. GFS broke from continuity with what it was showing by now
having a couple separate waves of snow Monday/Monday night and again
on Tuesday. ECMWF/GEM focus on one primary system lifting through on
Monday/Monday night with high pressure bringing in drier air on
Tuesday. Slug of moisture advection and increasing forcing from
deformation and divergence aloft to north of sfc-H85 lows should
support widespread moderate snow which could impact parts of Upper
Michigan. Only negative continues to be that the sfc low is forecast
to weaken as it moves toward Upper Michigan. One concerning item of
note is also more of a warm layer aloft (H85 temps up to +3c) now
showing up on ECMWF and GEM. If either of these models would verify
as forecast attm, would be looking at freezing rain over eastern
forecast area. In terms of snow, based on forecast mixing ratios,
model qpf and GEFS probabilities still looks like at least advisory
level snow amounts (2-4"/3-5" in 12 hours) are on track Monday into
Monday night. If qpf and/or SLRs end up even higher, could see
warning amounts (6" or more in 12 hours).

As mentioned earlier, latest GFS shows another system moving through
on Tuesday. Looks like GEFS supports that idea somewhat too with
some members showing stripe of light to moderate snow affecting much
of Upper Michigan. Pops will stay in the high chance to likely
range. ECMWF/GEM and even the slower GFS would support mainly dry
weather moving in mid to late next week as high pressure becomes
main weather feature.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1155 PM EST THU FEB 15 2018

Much colder air driving se into the Upper Great Lakes will likely
support MVFR cigs overnight at KIWD/KCMX as lake effect clouds
expand. Considerable ice coverage on western Lake Superior will keep
developing lake effect shsn light and sct, so not expecting any
significant vis reductions. NW wind will not be favorable for KSAW
to be affected by shsn, and cloud bases will probably stay above
3000ft, though some periods of bkn MVFR cigs are possible. As winds
back, MVFR cigs should clear out at KIWD early this morning and at
KCMX a short time later. VFR conditions will then prevail at all
terminals into the evening.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 415 AM EST FRI FEB 16 2018

A few southwest gale force gusts are possible on Saturday and north
to northeast gale force gusts Monday and Monday night, otherwise
winds will be below gales through the forecast period.

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


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