Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 210752
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
252 AM EST Tue Nov 21 2017

.SHORT TERM...(Today and tonight)
Issued at 252 AM EST TUE NOV 21 2017

Upper air pattern consists of a 500 mb ridge on the west coast, a
trough on the Gulf Coast, a trough dropping into the upper Great
Lakes this morning. This trough digs into the lower Great Lakes
tonight. Moisture quickly moves through the area today along with
some lake effect pcpn. Basically, going forecast has things well in
hand and did not make too many changes to the going forecast.

.LONG TERM...(Tuesday night through Monday)
Issued at 302 PM EST MON NOV 20 2017

The mid-upper level pattern will remain fairly progressive into
early next week across the northern CONUS between mean troughing
over the Gulf of Alaska/NE Pacific and troughing over eastern Canada
and the NE CONUS.

Tue night into Wed, nw gradient flow should be gradually weakening
as a shortwave trough pushes e and strong ridging builds in from the
w. 850 mb temps near -15c should equate to a lake-h85 delta-t of
around 20C. Dry air should limit nw flow LES accumulation from 2 to
5 inches Tue night into Wed with the greatest amounts east. A few
spots could reach borderline advisory criteria during the event.
Warming temps and winds becoming w to sw should end any lingering
LES Wed afternoon over the far eastern shoreline.

Another clipper shortwave is progged by models to move from northern
Manitoba into northern Ontario Wed night and Thu bringing another
cold front and quick shot of colder air across the Upper Great Lakes
on Thu. Models differ on how cold the airmass will be with the 12Z
GFS and NAM coming in about 5 degree Celsius colder than either the
12Z Canadian or the 00z ECMWF. Even with the colder GFS/NAM
solutions not expecting much more than 2-3" of nw flow LES
accumulation Thu into Thu evening as again large scale anticyclonic
flow and dry air will limit accumulations.  Backing flow and
moderating temperatures will end any lingering LES Thu night.

Friday into Sunday, both the GFS and ECMWF advertise another strong
shortwave moving across the Upper Great Lakes with a 982 mb sfc low
tracking e through northern Ontario just north of Lake Superior Fri
afternoon and evening. Elevated warm layer in strong warm air
advection ahead of this low pressure system could lead to some mixed
precipitation late Thu night/early Fri in form of light snow/light
fzra before pcpn changes over to mostly rain late Fri morning.
Bigger story with this system will be the wind as ssw wind gusts
ahead of the system could approach advisory criteria over a few of
the eastern counties on Fri. Behind the cold front as winds shift w-
nw, gusts could reach advisory criteria at a few of the more exposed
spots along Lake Superior Fri night into Sat. Looks like a decent
shot of cold air moving in behind the system coincident with the
main shortwave trough and secondary cold front as 850 mb temps drop
near -16c per 12z GFS by late Sat into Sat night. With colder air,
expect light to moderate LES in the NW wind snowbelts. Accumulation
will be likely be limited by dry air beneath lowering subsidence
inversion in large scale anticyclonic flow. LES will taper off from
w to e on Sun as sfc high pres builds in from the w and temps slowly
moderate.

Model uncertainty increases out to next Mon but the 12z ECMWF and to
a lesser extent the 12z Canadian show another shortwave and
associated sfc low moving through Ontario and glancing northern Lake
Superior. This could bring some light mixed pcpn to the area.
&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1151 PM EST MON NOV 20 2017

Cold front passing across the area overnight will be followed by the
development of strong w to nw winds, -shsn and MVFR conditions. At
KCMX, winds are likely to gust in excess of 40kt into the morning
hrs. Winds will gust upwards of 35kt at KIWD and 30kt at KSAW. The
gusty winds will also lead to some blsn at KIWD/KCMX. While MVFR
conditions should prevail, will probably see some brief periods of
IFR at KIWD and especially at KCMX where winds will be strongest,
kicking up more blsn. Winds will diminish during the late aftn and
evening. Conditions will improve to VFR at KSAW in the evening.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 252 AM EST TUE NOV 21 2017

A strong low pressure system will track eastward just north of Lake
Superior this morning. NW gales of 35 to 45 knots across much of
Lake Superior will continue today. Winds will diminish to under 25
knots while becoming westerly through Wednesday morning, before
backing to SW winds of 20 to 30 knots Wednesday night. Westerly
winds of 20 to 30 knots Thursday will back to the south on Friday.
Another strong low pressure system will then bring the potential for
northwest gales of 35 to 40 knots Friday night into Saturday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Wind Advisory until 1 PM EST this afternoon for MIZ001-003.

  Lakeshore Flood Advisory from 11 AM this morning to 9 PM EST
     this evening for MIZ006.

  Wind Advisory until 10 AM EST this morning for MIZ002.

Lake Superior...
  Gale Warning from 6 AM this morning to 10 PM EST this evening
     for LSZ248>251-267.

  Gale Warning until 10 PM EST this evening for LSZ265-266.

  Gale Warning until 10 PM EST this evening for LSZ243>245-264.

  Gale Warning until 4 PM EST this afternoon for LSZ246-247.

  Gale Warning until 5 PM EST /4 PM CST/ this afternoon for LSZ162-
     240>242-263.

Lake Michigan...
  Gale Warning until 6 AM EST early this morning for LMZ248-250.

&&

$$

SHORT TERM...07
LONG TERM...Voss
AVIATION...Rolfson
MARINE...07



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