Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 180808
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
408 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
temps.

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
end.

.LONG TERM...(Sunday through Friday)
Issued at 408 AM EDT SAT MAR 18 2017

Nam shows a 500 mb ridge over the upper Great Lakes 12z Sun with a
shortwave over south central Canada that passes by to the north Sun
night into Mon. Another shortwave near Lake Winnipeg 00z Tue will
move through the area Mon night. Nam shows some 850-500 mb q-vector
convergence and deeper moisture moving through the area Sun night.
Temperatures look to be warm enough for the pcpn to be mostly rain
Sun night. Lake effect snow showers get going late Mon night.
Overall, did not make too many changes to the going forecast.

In the extended, GFS and ECMWF show a cold 500 mb trough over south
central Canada 12z Tue with manual progs showing a sfc cold front
moving through the area. 850 mb temperatures at 12z are from -16C to
-18C over Lake Superior at that time. The core of the cold air moves
into Quebec on Wed as a ridge moves into the plains. This ridge then
moves into the upper Great Lakes 12z Thu. A 500 mb trough moves into
the Rockies on Fri with a shortwave moving through the northern
plains. This trough moves east into the Mississippi River Valley 12z
Sat. Temperatures go below normal starting Tue and lasting into Thu
before warming back to near normal. Fri morning there looks to be a
nose of warm air that moves through and with temperatures below
freezing early, cannot rule out mixed pcpn of some freezing rain,
sleet, snow and rain and have that in there for a few hours early
Fri morning.
&&

.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
closer.
&&

.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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...JLA
LONG TERM...07
AVIATION...KC
MARINE...Titus



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