Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 192025

Area Forecast Discussion
National Weather Service Marquette MI
325 PM EST Sun Nov 19 2017

.SHORT TERM...(This evening through Monday)
Issued at 324 PM EST SUN NOV 19 2017

The main forecast concerns through the short-term forecast is the
potential for continued mainly light lake effect snow for west to
west-northwest wind favored snow belts through late this evening.

Tonight: A surface high pressure system to the south of the area
will shift very slowly to the east through the overnight hours. The
main impact this will have on the U.P. weather will be to shift the
winds to the west-northwest or west through late evening then to the
southwest overnight. This will effectively shift the lake effect
snow to the Keweenaw Peninsula and over the far eastern U.P., closer
to the shoreline east of Munising through the evening hours.
Overnight, the lake effect snow will shift over Lake Superior and
slowly diminish as drier air moves into the area. To start the
evening, 850mb temperatures are progged to be around -10C to -12C;
however, as winds become southerly and WAA increases across the
area, 850mb temperatures are expected to warm to around -6C to -8C
by 06Z/09Z Monday. This along with drier air moving into the area,
would all point to the diminishing lake effect snow trend tonight.
An addition 2 to 4 inches can be expected closer to the shoreline
over the eastern U.P. In fact, a mesolow over north-central Lake
Superior will potentially help support the higher end of these
totals over easter Alger County and northern Luce County. The
mesolow will likely have some gustier winds with it during the
evening hours; therefore, issued a SPS for lower visibility and
heavier snowfall rates. The Keweenaw Peninsula may see up to an
inch; however, the drier air and decreasing inversion heights will
help to limit totals.

Monday: As the aforementioned high pressure system slides to the
east, south winds will increase, allowing for more WAA into the
area. Temperatures aloft will steadily warm and the lake effect snow
potential will be gone by early Monday morning for all of the U.P.
Many areas may actually see some sunshine sneaking out by Monday
afternoon as drier air continues to filter into the U.P. Also, with
the warm air advection, temperatures are expected to warmer, with
highs reaching into the upper 30s to around 40 degrees in most

.LONG TERM...(Monday through Saturday)
Issued at 446 AM EST SUN NOV 19 2017

Mainly focused on late Mon night into early Wed when moderate LES
and gusty winds will be possible. A couple shortwaves move through
the region, which will usher in colder air down to -15C at 850mb and
NW winds gusting to 30-40mph along the Lake Superior shore. LES will
begin late Mon night and taper off on Wed. Dry low levels may limit
accumulations some, but generally expect a few inches of snow in the
NW wind snowbelts. Looks like maybe an advisory level event if
anything. No significant impacts expected for Wed travels, since LES
will be lighter by then and only impacting a small portion of the
CWA as winds turn more westerly.

Potential exists for a more significant winter system and following
moderate LES Fri into the weekend, but there still plenty of
uncertainty with the track/strength of the low. Confidence in
trailing cold air putting LES into NW wind snowbelts later Sat into
early next week is higher. Stayed with consensus blend output for
this time period until the predictability horizon is more within
sight on the system.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1228 PM EST SUN NOV 19 2017

Cold air flowing across Lake Superior on northwest to west
northwesterly flow will allow lake effect snow showers to continue
into this evening. The primary focus will be at KCMX; however, a few
flurries or very light snow showers are still possible at KIWD and
KSAW. Otherwise, winds will become more westerly, then southwesterly
tonight into Monday, allowing the lake effect potential to diminish
by late tonight into early Monday morning. This will allow for
steadily improving conditions at each TAF site tonight into Monday.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 324 PM EST SUN NOV 19 2017

West to west-northwest winds of 20 to 30 knots are expected through
this evening as pressure gradient remains fairly tight ahead of high
pressures building into the area. An area of low pressure will
approach, then move through the area Monday night through Tuesday
giving a period of south gales Monday night before shifting to
northwest gales Tuesday into Tuesday night. The next chance of
seeing near-gale winds will be Friday into Saturday; otherwise,
winds are generally expected to be in the 15 to 25 knot range.

Upper Michigan...
Lake Superior...
  Gale Watch from Tuesday morning through Tuesday evening for

  Gale Watch from Tuesday morning through Tuesday evening for

  Gale Watch from Monday evening through Tuesday afternoon for

Lake Michigan...
  Gale Watch from Monday evening through late Monday night for



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