Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 062351
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
651 PM EST Wed Dec 6 2017

.SHORT TERM...(This evening through Thursday)
Issued at 416 PM EST WED DEC 6 2017

...Significant lake effect snow will continue into tonight as winds
gradually diminish...

Strong storm system over James Bay will continue to fill/weaken as
it moves slowly ne into northern Quebec later tonight. As a result
winds which have shifted from w to nw with a trough moving south
across Lake Superior will gradually weaken into tonight. Already
seeing signs of gradual weakening of winds over the Keweenaw and
expect further diminishment of winds across the area later tonight
as sfc ridging builds in from Ontario and the Northern Plains.

This evening into Tonight, troughing and deeper moisture along with
a shortwave moving across the Upper Great Lakes (as noted on water
vapor imagery) is supporting wnw wind flow moderate to heavy lake
effect shsn into Upper Mi. Winds continuing to veer nw into tonight
will push les bands farther inland this evening. As winds shift more
nw into this evening, best low-level wind convergence will shift
focus for heavier les bands into Gogebic-Ontonagon and Alger-Luce
and northern Schoolcraft counties as suggested by much of the high-
res model guidance.  850 mb temps close to -16C, deeper moisture
into this evening, weak enhancement by shortwave and favorable snow
growth with much of lake convective layer placed within DGZ should
result in moderate to heavy les bands through at least this evening
with typical accumulations of 3-5 inches with locally higher accums
near 8 inches over favored higher terrain areas, especially the
Porkies over the west.

As for headlines, since best les bands have for the most part
shifted south of the Keweenaw Peninsula and vsbys have improved
there due to weaker wind and less snow have decided to drop the
winter storm warning and transition to a winter weather advisory
into this evening. Advisories for Gogebic-Ontonagon and Baraga-
southern Houghton still look good through this evening for
moderate to occasionally heavy les. Also included Marquette County
in an advisory into early overnight mainly for the potential of
higher accums near 7 inches over the highlands of western
Marquette County and for areas over far eastern MQT county. The
city of Marquette will probably see closer to 3 inches total
accumulation. Not expecting much accumulation from Gwinn southward
given nw wind direction. Eastern counties will have potential for
les to last longer through night and possibly into Thu morning
with the potential for a more dominant band setting up around
Munising area as Lake Nipigon connection over Ontario lengthens
fetch across eastern Lake Superior. Kept advisory up there through
tonight and expect accums of 4 to 8 inches with locally higher
amounts of 10 inches or more into Thu morning before les
dissipates and shifts east with ridging and drier working in from
the west.

Thursday, weak sfc ridging into the nrn Great lakes will bring
backing winds and lowering inversion heights to around 3k ft even as
850 mb temps remain around -16C. With nw winds shifting to the west,
expect diminishing LES with additional accumulations of 1-3 inches
over western counties and eastern counties along shoreline east of
Munising.

.LONG TERM...(Thursday night through Wednesday)
Issued at 342 PM EST WED DEC 6 2017

Besides the deep trough parked across the Great Lakes and a strong
upstream ridge across the western CONUS, the pattern will continue
to be mainly a northwest flow. Guidance continues to indicate a weak
shortwave developing along the edge of a vort-max Fri early across
Lake Superior; however, this doesn`t appear to be too problematic to
LES. The bigger concern will end up being the next shortwave progged
for late Fri into Sat.

The next clipper will dive southeast towards Northern Minnesota late
Fri...then slide southeast through Central/Northern Wisconsin. With
this trajectory the flow should turn easterly/northeasterly off of
Lake Superior and any banded LES could impact Marquette City and
points east before flow turns northwesterly again Sat aftn/eve.

Anti-cyclonic flow will push east into the Central Plains, with the
departing clipper moisture will become less deep in its wake and
flow will turn northwesterly again. Although the thermal
differential in the lowest layers will likely still support LES
development in the main snowbelts of the U.P. into the remainder of
the weekend. Late Sun yet another fast moving shortwave will skirt
the region and could bring another round of LES, with a reinforcing
shot of cold air returning for early next week.
&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 651 PM EST WED DEC 6 2017

Passage of a disturbance and drier air following in its wake will
result in lake effect shsn diminishing from w to e later this
evening thru the overnight. At KIWD, expect prevailing LIFR
conditions for much of the evening along with ocnl IFR. Improvement
to MVFR should occur late evening with perhaps VFR developing Thu
aftn. At KCMX, IFR conditions should prevail this evening along with
ocnl MVFR. Improvement to prevailing MVFR will occur overnight.
Westerly winds and an approaching disturbance should lead to an
increase in lake effect shsn at KCMX late Thu aftn, dropping
conditions back to IFR. At KSAW, conditions should vary btwn VFR and
MVFR tonight, though MVFR conditions will probably becoming
prevailing by late evening as -shsn becoming more persistent.
Improvement to VFR expected by late Thu morning.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 416 PM EST WED DEC 6 2017

Will stay with gales into much of tonight as deep low over northern
Ontario slowly moves away from the region. Beyond tonight, winds
should stay in the 20-30 kt range into early next week. Freezing
spray is expected into Thu and again late Fri into Fri night. Air
temps staying mainly in the 20s should prohibit heavy freezing spray.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 1 AM EST Thursday for MIZ001-003.

  Winter Weather Advisory until 2 AM EST Thursday for MIZ004-005-
     084.

  Winter Weather Advisory until 7 AM EST Thursday for MIZ006-007-
     085.

  Winter Weather Advisory until midnight EST /11 PM CST/ tonight
     for MIZ002-009.

Lake Superior...
  Gale Warning until 5 AM EST Thursday for LSZ244-245-248>251-
     264>267.

  Gale Warning until 2 AM EST Thursday for LSZ263.

Lake Michigan...
None.
&&

$$

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



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