Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 150925

Area Forecast Discussion
National Weather Service Marquette MI
425 AM EST Wed Nov 15 2017

.SHORT TERM...(Today and tonight)
Issued at 420 AM EST WED NOV 15 2017

Early this morning, water vapor imagery shows broad troughing
tracking across the northern and central Plains, with a few embedded
shortwave features, and the associated low pressure system moving
across the Upper Mississippi Valley. Ahead of this trough,
widespread rain has developed across the warm sector, which
continues to lift northeast across central and eastern Upper
Michigan. The main forecast concern over the next 24 hours is the
transition from rain to snow later today and tonight and the onset
of strong and gusty northerly winds, especially near the shore of
Lake Superior.

The above mentioned low pressure system will track eastward across
Upper Michigan today and slightly strengthen across eastern Upper
Michigan as the southern and northern streams phase later
today/tonight. As the surface low tracks east across the area today,
rain will eventually transition over to patchy drizzle as the deeper
moisture and better large-scale lift slowly shift eastward with the
warm sector. Across the west, wrap around precipitation will lift
across the area later today. Initially this precipitation will start
off as rain, but through the late afternoon/evening and into the
overnight hours increasing cold air advection behind the exiting
system will strengthen and allow rain to transition over to snow.

As the main 850mb low slowly traverses the region winds will become
northerly through the overnight hours, favoring lake effect snow
showers in the north wind snow belts. While accumulating snow is
expected, the cold air advection will be on the weaker end of the
spectrum, with reduced lake-induced CAPE values and inversion
heights. These factors coupled with strong winds through the
convective layer should work together to keep snowfall totals
between 1 to 3 inches. The bigger issue tonight may very well be the
reduced visibilities and blowing snow due to strong northerly winds.
Contemplated issuing a wind advisory for tonight for areas
susceptible to the northerly, onshore flow from Lake Superior.
However, there is some uncertainty in how strong the wind gusts will
get over land, so opted to issue an SPS for now. These strong
onshore winds will however lead to beach erosion and the possibility
of lakeshore flooding mainly across Alger County; therefore, have
issued a Lakeshore Flood Advisory mainly for tonight.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 432 PM EST TUE NOV 14 2017

Models suggest that a progressive pattern will prevail through this
weekend with a couple of mid level troughs and sfc lows moving
through the region bringing rain followed by colder air and LES.

Wednesday night, a shortwave trough will slide to the southeast
with the strongest 700-300 qvector conv through northern and
eastern Lake Superior. The combination of deep moisture and 850 mb
temps to around -10C (over water temps around 6C) with cyclonic
low level winds veering from nw to n will bring LES through the
nrn cwa. With the steadily shifting winds and marginal
instability, snow totals should remain in the 1 to 3 inch range.
In addition the colder air will arrive overnight, after the
stronger low level conv moves through during the evening.

Thursday, dropping inversion heights to 3k ft as high pres builds
into the area will bring diminishing LES with some clearing in the
afternoon along with diminishing winds.

Friday-Sunday, The GFS/GEFS/GEM have trended weaker and faster
toward the previous ECMWF runs as the nrn and srn streams phase
slightly later as the low moves away from the central Great Lakes.
Expect widespread pcpn mainly as rain to spread across Upper
Michigan Friday into Friday night with strong WAA and moisture
advection (PWAT above 0.75 inch) as the sfc trough moves through the
Upper MS valley into the wrn Great Lakes. There may be some isold
fzra cntrl early Friday before sfc temps climb by midday. Fzra or
ice potential will be limited by initial dry 900-700 mb layer.
Although strong CAA and nw flow LES will develop Saturday behind the
deepening low, confidence in wind strength is still low given models
variability. Moderate LES with with some heavier bands will be
possible with considerable blsn. Lingering LES will diminish Sunday
as sfc and mid level ridging build into the area.

Monday-Tuesday, confidence in details regarding a clipper shortwave
depicted by the GFS/ECMWF/GEM is low but this feature could bring
additional light sn/LES ino the area. &&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1111 PM EST TUE NOV 14 2017

LIFR/VLIFR conditions will continue for most of the period with slow
improvement starting Wed afternoon at all sites.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 420 AM EST WED NOV 15 2017

Winds will be less than 20 knots through much of today as a surface
low tracks across the area. However, north-northwest winds behind
the exiting surface low will ramp up across the lake later this
afternoon/evening through the overnight hours, with gale force winds
of 35 to 40 knots expected across much of the lake. Winds will
diminish to around or less than 20 knots by Thursday afternoon.
Friday through Saturday, confidence is not high in regards to how
winds will evolve across Lake Superior. Right now it looks like
southerly gales will still be possible ahead of the system on
Friday, and then northwesterly gales behind the system by late
Saturday into Sunday. In between the two possible gale events, winds
should drop down to between 15 to 25 knots as the surface pressure
gradient is relaxed along the surface trough axis.

Upper Michigan...
  Lakeshore Flood Advisory from 1 AM to 10 AM EST Thursday for

Lake Superior...
  Gale Warning from 6 PM this evening to 10 AM EST Thursday for

  Gale Warning from 4 PM this afternoon to 7 AM EST Thursday for

  Gale Warning from 4 PM this afternoon to 4 AM EST Thursday for

Lake Michigan...
  Gale Warning from 7 PM this evening to 7 AM EST Thursday for



SHORT TERM...Ritzman
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