Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 171753

Area Forecast Discussion
National Weather Service Marquette MI
153 PM EDT Fri Mar 17 2017

.SHORT TERM...(Today and tonight)
Issued at 558 AM EDT FRI MAR 17 2017

A shortwave and SFC low over southern Manitoba will drive conditions
in the short term. The shortwave and low will move across the CWA
from the NW this evening and early tonight.

Isentropic ascent ahead of the system has led to a band of mixed
precip moving in from the SW. At the moment, only precip in the CWA
is over portions of Gogebic County and W Lake Superior. The dry air
out ahead of the system (28/12 at IMT, 32/25 after some saturation
at IWD) is holding precip off for a while, but once rain does
saturate the temps are being cooled below freezing. Freezing rain
and ice covered roads has been reported near IWD, so decided to
issue a Winter Weather Advisory over western Upper MI. Not looking
at significantly measurable ice accumulations, but enough for
treacherous travel. The freezing rain will turn to snow in the next 1-
3 hours as the overall airmass dynamically cools and the precip
moves across the rest of the area. SFC temps will then warm enough
to bring rain or rain/snow mix this afternoon. Along and behind the
system late this evening and tonight, cooler air moves in and
upslope W-NW flow will lead to snow mainly W and E, but at least
isolated snow everywhere. Could see 1-2" of snow today and another 1-
2" tonight, greatest in the upslope areas near Lake Superior.

.LONG TERM...(Saturday through Thursday)
Issued at 412 AM EDT FRI MAR 17 2017

Nam shows a 500 mb closed low over Lower MI 12z Sat with an upper
ridge over the Rockies. This ridge moves into the plains late Sat
and into the upper Great Lakes on Sun. Another shortwave drops into
south central Canada Sun night. Nam does bring in some 850-500 mb q-
vector convergence and deeper moisture through the area Sun night.
GFS and ECMWF show about the same thing as well and will use a blend
of the models for this forecast. Overall, did not make too many
changes to the going forecast. Kept in a mix of freezing drizzle,
drizzle and snow for Sat morning for the area as the system pulls
out. QPF amounts do not look like very much on Sat morning. Could
see some rain again for Sun night.

In the extended, GFS and ECMWF show a 500 mb broad ridge across the
southern U.S. 12z Mon with a trough over the northern plains and
southern Canada with some colder air in Canada at that time. This
cold air heads south into the area on Tue with 850 mb temperatures
falling to -13C from the ECMWF on Lake Superior to -19C from the
GFS. The core of the cold air drops into New England by Wed with a
slow modification to the airmass as a ridge builds into the Rockies
and western high plains 12z Wed. This ridge builds into the upper
Great Lakes 12z Thu. A closed 500 mb low will move into the central
plains 12z Fri. Temperatures fall to below normal starting Mon night
and then warm back to near normal by Wed into Thu. Will have to
watch the storm coming out of the wsw on Friday as that could
produce some mixed pcpn.

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 152 PM EDT FRI MAR 17 2017

Ceilings lower to LIFR/IFR rest of aftn into this evening and should
remain that low into Sat morning. Heaviest snow will be at CMX this
aftn with vsby down to LIFR at times. Steady mixed rain/snow at SAW
will gradaully give way to some very light snow/drizzle late aftn
into the evening. Later tonight into Sat, expect steadier snow to be
at CMX with upslope NW flow developing. Otherwise, should be light
snow and/or drizzle at IWD and SAW. All the sites should see
prevailing IFR vsby due to the precipitation or even some fog.
Expect conditions to improve later on Sat with arriving high
pressure ridge/drier air.


.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 558 AM 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...
  Winter Weather Advisory until 2 PM EDT /1 PM CDT/ this afternoon
     for MIZ002-004-009-010-084.

  Winter Weather Advisory until 7 PM EDT this evening for MIZ001-

Lake Superior...
Lake Michigan...


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