Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 240558

Area Forecast Discussion
National Weather Service Marquette MI
1258 AM EST Tue Jan 24 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 232 PM EST MON JAN 23 2017

Broad upper trough from western Canada to the Upper Great Lakes
becomes more influenced by deepening trough from western Conus to
the central Plains through Tue. At the sfc, weak trough from
Manitoba to the Great Lakes dissipates as strong low pressure system
emerges over the central Plains and noreaster low pressure system
continues its trek along the coast of the Mid Atlantic and New
England states. Weak pressure pattern tonight through Tue will keep
light winds and moisture in place from higher dwpnts and melting
snow and that spells more areas of dense fog.

Within the broad trough aloft, shortwave lifting northeast across
Upper Great Lakes combined with increasing deeper moisture above h9
and up to h7-h6 should bring an area of steadier precipitation over
far eastern cwa (likely pops only over Luce county with only small
chances farther west of that area) mainly this evening. Soundings
show it will be close call whether saturation occurs high enough to
bring ice crystals into play. If ice crystals are introduced then
could see snow mix in with the rain. Otherwise, just looking at
rain/drizzle with no snow. Will continue with mix of rain/snow over
far east but otherwise will just have drizzle or freezing drizzle
based on low level temps. Seems better chance of drizzle would be
over east closer to the deeper moisture and also late tonight into
Tue morning over the western higher terrain where NW winds provide
upslope lift. Soundings show some weak lift in low-level moist layer
over west so that would also support possible drizzle. Joined WFO
GRB and increased temps slightly so now have most areas staying just
above freezing into the mid 30s tonight. Therefore not expecting
much icing even as temps are in the lower 30s.

Later Tue morning into the aftn the shortwave and deeper moisture
gradually depart leaving mainly drizzle if anything with best
chances over far east. Kept some fog going especially during the
morning when low-level saturation will be maximized. Central plains
system will continue to organize on Tue aftn but expect stronger
forcing and deeper moisture from that system will not arrive until
after 00z Wed.

.LONG TERM...(Tuesday night through Monday)
Issued at 246 PM EST MON JAN 23 2017

Nam shows a closed 500 mb low over Nebraska 00z Wed. This closed low
moves east into lower MI on Wed. More troughing is in the northern
plains Wed that moves into the upper Great Lakes on Thu. Nam brings
in some deeper moisture and 850-500 mb q-vector convergence Tue
night through Thu. Looks like pcpn will be rain and snow for this
forecast period as temperatures aloft stay below zero and freezing
rain looks to be such a very low probability that it was not worth
putting into the forecast. Overall, did not make too many changes to
the going forecast.

In the extended, the GFS and ECMWF show a 500 mb trough over the
central Rockies and also the Great Lakes region 12z Fri with colder
air over Lake Superior with 850 mb temperatures ranging from -11C to
-14C. The GFS and ECMWF show 850 mb temperatures dropping down to
-14C to -16C 12z Sat. Troughing digs down into the upper Great Lakes
12z Sun with a modification of temperatures starting Mon as the cold
air and trough moves east into New England. Lake effect snow showers
will continue through the period as it stays cold enough.
Temperatures will stay near normal for this forecast period.

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1258 AM EST TUE JAN 24 2017

With lingering llvl mstr over slowly melting snow pack and lgt winds
in the presence of nocturnal cooling, expect lo clds with LIFR cigs
and vsbys falling at least near landing mins in dense fog at times
into mid mrng. There wl be a slow improvement during the day on Tue
with some daytime heating, but cigs are likely to remain in the IFR
range. Conditions wl likely deteriorate again in the evng,
especially at SAW where a llvl ne wind ahead of a lo pres aprchg fm
the sw wl present an upslope component.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 232 PM EST MON JAN 23 2017

A relatively weak pressure gradient over the Upper Great Lakes in
the absence of any strong weather systems will continue to result in
winds under 20 kts over Lake Superior early this week. As a low
pressure system moves from the central Plains to eastern Canada mid
to late week expect NE winds to 25 kts Tue night then N-NW winds to
25 kts Wed into Fri.

Upper Michigan...
Lake Superior...
Lake Michigan...
  Dense Fog Advisory until 10 AM EST this morning for LMZ248-250.



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