Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 180531

Area Forecast Discussion
National Weather Service Marquette MI
131 AM EDT Sat Mar 18 2017

.SHORT TERM...(This evening through Saturday)
Issued at 405 PM EDT FRI MAR 17 2017

Shortwave trough continues to deepen across Upper Great Lakes. Sfc
low at 1008mb north of KINL supported arc of warm air advection
precip across Upper Michigan through the day. Ptype has been mainly
rain or snow dictated by near sfc temps, though fzra and sleet have
also been observed. Fzra was mostly over far west cwa early this
morning when there was elevated warm layer up to +1c. As upper low
deepens, still looks like the main shortwave is going to dig over
northern IL into southern lower MI. Arc of precip should clear
Keweenaw by 00z (when the advy that was issued earlier will
finish up) and slowly move over eastern cwa into this evening.
Ptype over the east probably will end up rain/snow though as dry
slot aloft (shows up nicely on experimental GOES low-level wv
channel) moves in later this evening, precip could transition to
more of a dz/fzdz. Have opted to issue a Special Weather Statement
into the evening as thin layer of slush may form on untreated roads.
Evening shift can evaluate if any additional advy will be needed
over the east this evening based on expected ptype and near sfc

Farther west for western and north central cwa, deeper moisture
currently moving across North Dakota into northwest MN should slide
back overhead btwn 03z-06z and change any dz/fzdz back to mainly
snow as moisture is forecast to extend to temps of at least -8c.
Usually getting moisture up to -8c is good enough for flurries/light
snow especially as winds turn NW off Lk Superior with terrain also
providing some additional lift. SLRs with any snow will be hard
pressed to be around 10:1. Expect maybe a couple inches of wet snow
for favored higher terrain areas of the west and north central.
Could see more snow if it was colder aloft but with h85 temps only
around -5c tonight setup is very marginal for an already weak lake
enhanced regime. Late tonight into Sat, most areas near Lk Superior
should see enough moistening for snow, especially in the areas
favored by N to NW winds off Lk Superior. As day progresses and near
sfc temps warm, could see snow turn to mixed drizzle and snow or
even turn to mainly rain in the aftn. Deeper moisture above h9
begins to diminish in the aftn which should diminish precip chances.
Do expect plenty of clouds to stick around though with moisture at
h9 persisting and flow coming off Lk Superior. Snow accums on Sat
will be light, maybe reaching 1 inch but that would be on the high

.LONG TERM...(Saturday night through Friday)
Issued at 451 PM EDT FRI MAR 17 2017

Models suggest that a progressive pattern will prevail through next
week with a warmup from Sunday into Monday, a brief bout of cold air
and LES Tuesday into Wednesday, and the moderating conditions toward
the end of the week with a larger low pressure system bringing
snow and mixed precipitation changing to rain.

Saturday night into Sunday, shallow cold moist air with 900 mb temps
around -9C will still be enough to support light LES chances for nw
flow favored areas in the evening. Otherwise, sfc and mid level
ridging moving into the region will bring dry weather overnight.
WAA and mid level isentropic lift will bring increasing clouds
Sunday as temps climb above normal into the 40s.

Sunday night and Monday, a shortwave trough will track well to the
north through nw Ontario into nrn Quebec. Models consensus suggests
A band of WAA ahead of the associated sfc trough trailing to the
south should be strong enough to support some light rain showers
into the central and east portions of the cwa Sunday evening that
may linger overnight as the sfc trough/front moves through. Even
with CAA Monday behind the trough/front dropping 850 mb temps to
around -6C, sunshine and deeper mixing will still push sfc temps
well into the mid to upper 40s over most of the area.

Tuesday-Wednesday, much colder air behind a secondary cold front
with 850 mb temps to around -18C will bring LES for nw flow LES snow
belts, mainly from late Tuesday into Tuesday night. Expect the LES
to end Wednesday with high pres building into the region.

Thursday-Friday, confidence in any details is low but there was
reasonable agreement that a vigorous shortwave will emerge from the
plains with a strong low pressure system lifting toward the upper MS
valley or western Great Lakes. Precipitation beginning as snow would
likely change to a wintry mix and then to rain per GFS/GEFS/ECMWF
thermal field and low track near Upper Michigan.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 127 AM EDT SAT MAR 18 2017

As winds shift to the wnw and turn gusty in the wake of a passing
sfc lo pres and attendant cold fropa, the arrival of a bit drier
llvl air wl allow current IFR/LIFR conditions to improve into the
MVFR range by about sunrise. There will be a further improvement to
VFR later in the period as a trailing hi pres/more acyc flow move

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 405 PM EDT FRI MAR 17 2017

W-NW gales are possible Mon and Mon night. Otherwise, no gales or
heavy freezing spray is expected.

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


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