Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 170008

Area Forecast Discussion
National Weather Service Marquette MI
808 PM EDT Tue Oct 16 2018

.SHORT TERM...(This evening through Wednesday)

A weak cold front continues to move eastward across the central and
eastern U.P. this afternoon, bring a shift in wind direction from SW
to W and eventually WNW, but not much else. Cloud cover has built
back in behind the front and will persist through tonight and much
of Wednesday. The main story tonight and Wednesday will be lake-
effect snow showers developing over the WNW-wind belts of the
western U.P. and Keweenaw and Superior shorelines of Alger and Luce
Counties, and down into the northern half or so of Schoolcraft
County. Moisture looks to be sufficiently deep along with sfc-850
delta T`s of 14-16 C tonight increasing to up to 17-18 C Wednesday
morning to support several robust bands. There will also be some
dendritic growth at the top of the precipitating layer, and with
high temps struggling to get above freezing away from the lake
shores, snowfall accumulations for the 24-hour period of 1 to 4
inches are expected under these bands, and perhaps up to 6 inches in
the Huron Mountains and Michigamme Highlands if a persistent strong
band sets up long enough as advertised by one or two of the CAMs.
Drier air filters in aloft and inversion heights decrease by late
afternoon, bringing snow showers to an end.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 237 PM EDT TUE OCT 16 2018

Upper air pattern will have a closed 500 mb low over UT 00z Thu with
a deep trough across the lower Great Lakes and New England with a
ridge across the sern U.S. The closed low over UT opens up and
merges into a trough that digs into the upper Great Lakes on Fri
while a rex block sets up on the west coast. Fairly quiet for this
forecast period with pcpn moving through the area on Fri. No changes
made to the going forecast.

In the extended, GFS and ECMWF show a deep 500 mb trough across the
eastern half of the U.S. 12z Sat with a rex block over the western
U.S. This rex block breaks down quickly 12z Sun with the upper
trough now in New England. A ridge builds into the Rockies 12z Mon
with a shortwave over the upper Great Lakes which moves into the
lower Great Lakes 12z Tue as the ridge moves into the central and
northern plains. Temperatures look to stay below normal for this
forecast period. Lake effect pcpn takes place for parts of this
forecast period in northwest wind lake effect pcpn belts.

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 741 PM EDT TUE OCT 16 2018

Although VFR conditions are prevailing currently, ceilings are
anticipated to drop into the MVFR category during the overnight
hours as low-level stratus persists. Along with the stratus deck,
lake-effect showers will be possible, as is already evident in
area obs. These showers though are not currently forecast to be
robust enough to reduce visbys, but will of course be monitored
closely. Look for NW winds to remain elevated and gusty into


.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 330 PM EDT TUE OCT 16 2018

Northwesterlies will decrease to around 25 knots this evening,
allowing the Gale Warning for eastern Superior to expire, but will
then persist at around 20 knots across all of Superior through
midday Wednesday as a deepening low in northern Ontario departs to
the east, and through Wednesday evening for the eastern half of
the lake. Winds become southwesterly and pick back up to 20 knots
over the western lake by sunrise Thursday and over the eastern
lake by early Thursday afternoon and stay at around 20-25 knots
through midday Friday. After a brief lull of about 15 knots, winds
shift to northwesterly Friday evening with the next shot of cold
air and increase back to 20-25 knots for Saturday and Sunday, and
occasionally to 30 knots over eastern Superior late Saturday
afternoon into Sunday evening.

Upper Michigan...
Lake Superior...
  Gale Warning until midnight EDT tonight for LSZ265>267.

Lake Michigan...


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