Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 242026

Area Forecast Discussion
National Weather Service Marquette MI
326 PM EST Fri Feb 24 2017

.SHORT TERM...(Today and tonight)
Issued at 528 AM EST FRI FEB 24 2017

Has looked like a fairly complicated system all along and sure
enough that is what is looking to unfold next 24 hours. Main changes
to headlines included upgrading Gogebic, Ontonagon, Baraga and
Marquette counties to winter storm warnings for mostly the potential
for heavy lake enhanced snow and increasing blowing snow tonight.
Otherwise, going winter weather advisories still look on track for a
mess of snow, freezing drizzle/rain and sleet.

Main shortwave is pivoting ene across central Plains. Sfc low at
995mb is over northern MO and will track across lower MI this
evening (similar strength) and to east of Georgian Bay by daybreak
Sat (deepening slightly to around 992mb). Initial push of warm air
advection snow took a while to get here due to very dry low-level
air seen on 00z GRB roab, but it has arrived over scntrl cwa but not
the west cwa as dry air continues to hold heavier snow more in line
from wcntrl WI toward scntrl Upper Michigan. A mess of convection is
occurring over southern half of WI. Majority of those lightning
strikes are occuring along h85 front on northern edge of strongest
h85 warm air advection per RAP analysis. Since upper low never
really closes off and keeps on track more east than north, appears
this band of persistent heavier precip enhanced by thunder will stay
mainly south of Upper Michigan. Based on radar and short range
models, scntrl will continue to be affected by swath of moderate to
briefly heavy snow snow driven by mid-level fgen and possible
coupled jet structure next few hours. Not sure how much initlal snow
makes it toward far west and Keweenaw, so downplayed pops there for
the morning. Initial push of moderate to heavy snow will be followed
later this morning or early aftn by dry slot at h7-h6 (cutting out
moisture aloft at temps colder than -10c and warm nose to +2c at 800-
750mb. Both of these features are especially noted over east half of
cwa and both features will combine to change to snow to mainly a mix
of freezing drizzle/rain (depending on strength of lift within moist
layer) or sleet as temps blo warm nose may be cold enough to
refreeze any partially or fully melted hydrometeors. Warm nose looks
to be most emphatic at MNM and ESC. Snow amounts today will be up to
4 inches most areas, heaviest scntrl where snow is occurring now.
Ice accumulations may reach around 0.10 inch over scntrl once the
mixed precip develops. Untreated roads could become quite slippery
as temps remain blo 30 degrees.

As main shortwave and deep layer q-vector convergence arrives late
this aftn, expect focus for heavy snow to turn to the far west and
ncntrl cwa due to increasing lake enhancement. Soundings have always
been on and off for how much deep moisture occurs over far west and
it appears even the drier GFS model in mid levels leading up to this
event shows enough deep moisture for lake enhancement to be a
concern even for the far west cwa. NNE-N cyclonic northerly flow
with h85 temps as low as -16c along with favorable synoptic support
point to heavier snow for at least the evening over far west and
most of the night over the ncntrl. Both of these areas could see
snow amounts tonight checking in at the 5 to 8 inch range with
several hours of 1+ inch per hour snow rates. Blowing snow will
become bigger issue as SLRs lower, especially over the far west
where more of DGZ is in play per soundings. Thus snow will beome
more fluffy and easier to blow and drift. Heavy snow rates and
increasing blowing snow were what led to upgrading those two areas
to warnings. Elsewhere, synoptic snow with the shortwave will be
present and there may be some higher terrain lake enhancement over
even the Keweenaw, but in general the snow farther toward WI border
should not be too intense as lift overall is only moderate strength
and northerly flow is downslope to much of those areas. Where warm
layer develops today it will persist through much of night so kept
mention of freezing precip over eastern third of cwa tonight and
have higher ice amounts of perhaps over 0.10 inch in some areas.

.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 18Z TAFS through 18Z Saturday afternoon)
Issued at 113 PM EST FRI FEB 24 2017

As low pressure slides just east of the Upper Peninsula, snow,
possibly heavy at times will continue at each of the TAF sites.
Winds will also become gusty, creating areas of blowing snow. This
will allow ceilings to drop to around or just under 1kft at times
for each TAF site tonight. The best chance for each TAF site to fall
below 1 mile visibility will this evening through early Saturday
morning as snowfall intensity increases and winds become gusty.
Drier air will move in for Saturday, allowing snowfall to decrease
and visibilities to improve; however, lower ceiling will likely
remain in place.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 344 AM EST FRI FEB 24 2017

NE to N gales to 35-40 kts are expected over much of Lake Superior
this morning into 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.

Upper Michigan...
  Winter Weather Advisory until 7 AM EST Saturday for MIZ001-003-

  Winter Weather Advisory until 7 PM EST Saturday for MIZ006-007-

  Winter Storm Warning until 7 AM EST /6 AM CST/ Saturday for

  Winter Weather Advisory until 1 AM EST /midnight CST/ Saturday
     for MIZ010>013.

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

  Gale Warning until 1 AM EST /midnight CST/ Saturday for LSZ162-

Lake Michigan...
  Gale Warning until 7 PM EST this evening for LMZ248-250.



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