Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 160932
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
432 AM EST Thu Nov 16 2017

.SHORT TERM...(This evening through Thursday)
Issued at 259 PM EST WED NOV 15 2017

...Gusty winds into Thu morning along with some snow...

Upper level trough over Upper Great Lakes has two individual
shortwaves within it. Sfc low over eastern Lk Superior is generally
tied to first shortwave sliding across eastern WI at present. Once
this low exits eastern Lk Superior later this aftn, expect north to
northwest winds to increase to 30-45 mph on Lk Superior and adjacent
shoreline areas. Have a SPS out to highlight gusty winds and since
the stronger winds will build waves into the 14-17 ft range, have
lakeshore flood advisories out for Marquette and Alger counties.

Seond shortwave currently upstream over northern MN will result in
lake enhanced precipitation setup late aftn into early overnight
hours as it brings period of lift and deeper moisture to h7/10kft
across Lk Superior and northern to eastern U.P. As sfc-850mb low
slides east of Lk Superior, north to northwest winds along with
larger scale lift will increase precip for west and north central
this evening into early overnight. Soundings indicate rain/drizzle
this aftn will mix with/change to snow by 00z over west and through
the evening over central. Based on current obs, seems the model
guidance is running a bit fast on changeover so made appropriate
adjustments. Did just receive a call near Michigamme and Three
Lakes indicating some snow is beginning to mix in. On edge of
deeper moisture over west and southwest forecast area, could even
see drizzle/freezing drizzle at times this evening. Now, even with
the deeper moisture and lift ongoing this evening, inversion
heights remain 3-4kft and temps at inversion top only drop to
around -10c so lake enhanced precip should only be light to
moderate. SLRs will stay held down as most lift is occurring at
temps warmer than -8c.

Overall in terms of snow there could be snow amounts of 1-3 inches
tonight into Thu morning, especially for higher terrain of
west/northwest and north central U.P. If second shortwave was
stronger and it was slightly colder then the snow over all of
northern Upper Michigan would end up being more impressive. Yet,
since the snow will be wetter and near sfc temps are still cold,
will not take much snow to build up a slush/snow layer on
untreated roads later tonight as temps cool back into the 25-30F
range. Even a thin layer of slush/snow could lead to sloppy travel.
Stronger winds could also result in patchy blowing snow in exposed
areas near Lk Superior. Despite the strong winds, limited blowing
snow to patchy since sfc temps in upper 20s to near 30F are
marginal for blowing snow issues since it is a wetter snow.

With northeast to north winds on Thu morning, expect light lake
effect snow showers over north central and west. Skies will try to
clear out partially in the late morning and aftn west and scntrl
before higher clouds move in from the west. Clouds will hold down
temps northwest and north central in the upper 20s to near 30F.
Readings will be in the low to mid 30s elsewhere.

.LONG TERM...(Friday through Wednesday)
Issued at 426 AM EST THU NOV 16 2017

Models suggest that a progressive pattern will prevail over the
northern CONUS from late this week into the middle of next week with
a mid level trough and associated storm system moving through the
Great Lakes on Saturday and another significant clipper shortwave
trough moving through next Tue with an accompanying blast of cold
air and nw flow LES into Wed.

Friday-Sunday, The models have converged toward the more consistent
ECMWF but remains slower than the GEFS mean solution. So, overall
confidence in the pcpn/winds forecasts has improved.

Following closer to the 00Z/12Z ECMWF, expect widespread pcpn mainly
as rain to spread across Upper Michigan Friday into Friday evening
with fairly strong WAA and moisture advection (PWAT above 0.75 inch)
as the sfc trough moves through the Upper MS valley into the western
Great Lakes. The WAA pcpn should diminish from west to east Fri
evening as the sfc trough moves through much of the cwa.

There may be some fzra mixed with snow west and central early Fri
with an elevated warm layer developing. Any fzra/fzdz should change
over to rain midday as temps climb into the mid 30s. Fzra or ice
potential will be limited by initial dry 900-700 mb layer as noted
on fcst soundings. Dryness through DGZ could also lead to more fzdz
than fzra mixing with the snow tonight/early Fri.

CAA and nw flow LES will develop Saturday afternoon behind the
deepening low with periods of LES possible into Sat night. Some
additional enhancement to les could be provided by mid-level
trough axis rotating through the area. 850 mb temps drop down to
-8C to -10C by late Saturday and drop to near -15C Sunday morning.

Big question on Sat is with best CAA delayed until at least late
in the day and Sat night, model soundings suggest convective
layer may be too shallow and not cold enough to get much in the
way of LES during the day on Saturday over the west half. Better
chcs for accumulating les will likely be Sat night into Sun for
the nw wind snowbelts, however shallowness of convective moist
layer and increasingly anticyclonic sfc-850 mb flow from the west
will likely keep amounts on the light side.

Any lingering LES should generally diminish Sun into Sun evening as
sfc and mid level ridging builds into the area.

Monday-Wednesday, model confidence in strength/timing of a clipper
shortwave moving in Mon night/Tue is low but CAA associated with
this feature should bring LES back into the area Tue into Wed for
the nw wind snowbelts as 850 mb temps fall around -15C by Wed.
&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1154 PM EST WED NOV 15 2017

With upslope northerly winds and -shsn, expect MVFR and at times IFR
conditions at KIWD/KCMX/KSAW overnight. KIWD/KCMX are more likely to
see IFR conditions. In addition, at KCMX, stronger winds and more
persistent -shsn may lead to some LIFR conditions for the next
couple of hrs. Arrival of drier air with approaching sfc high pres
ridge will lead to improving conditions today as -shsn end. MVFR
cigs will improve to VFR at KIWD/KCMX this aftn and at KSAW this
evening.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 259 PM EST WED NOV 15 2017

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
Thu afternoon. A low pressure trough will then cross the region Fri
while deepening over the central to lower Great Lakes later in the
weekend. Expect south gales of 35-40 kts over the east half of Lk
Superior on Fri with northwest gales to 35 kts possible later Sat
into SUn morning. 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.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Lakeshore Flood Advisory until 10 AM EST this morning for MIZ005-
     006.

Lake Superior...
  Gale Watch from late tonight through Friday afternoon for LSZ244-
     245-248>251-264>267.

  Gale Warning until 10 AM EST this morning for LSZ248>251-266-267.

  Gale Warning until 8 AM EST this morning for LSZ243>245-264-265.

  Gale Warning until 5 AM EST early this morning for LSZ263.

Lake Michigan...
  Gale Warning until 10 AM EST this morning for LMZ221-248-250.

  Gale Watch from Friday morning through Friday evening for LMZ221-
     248-250.

&&

$$

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



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