Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 161956

Area Forecast Discussion
National Weather Service Marquette MI
256 PM EST Thu Nov 16 2017

.SHORT TERM...(This evening through Friday)
Issued at 255 PM EST THU NOV 16 2017

...Wintry mix leads to slippery travel at times through Fri...

WV loop and 12z ROABS indicate deep trough over Pacific Northwest
with 130-140kt jet rounding base of trough from CA to northern U.S.
Rockies. As trough shifts east through Fri toward central Conus, jet
splits with northern branch surging toward northern Ontario while
southern branch jet moves toward Middle Mississippi River Valley and
eventually the Ohio River Valley. As stronger shortwave in the
trough over southern Alberta and Saskatchewan moves to northern
Ontario on Fri morning, a 992-996mb sfc low will track over Manitoba
and Hudson Bay/northern Ontario. Thus late tonight through Fri
morning expect heavier precip to remain to north of Lk Superior.
Model soundings indicate increase in mid level moisture tied to warm
air advection aloft with the shortwave to the north. Any precip
tonight that occurs due to this moisture advection would be light
the form of snow. However we will also have a continued risk of
freezing drizzle/flurries over higher terrain of central due to
upslope flow, this evening from northeast winds and overnight from
south to southeast winds as return flow develops.

Later Fri morning, diffluence from upper jet streaks along with
increasing moisture advection ahead of sfc trough tied to low over
northern Ontario will spread light to moderate precip over much of
Upper Michigan. Still could see risk of freezing precipitation late
morning or even into early aftn as temps stay near freezing over
inland west. Most areas by early to mid aftn should see precip
change to rain as temps warm into the mid 30s with warmer air moving
in behind the warm front. There may be enough cold air for snow to
mix with the rain over far west in the aftn and also in the far east
forecast area.

Overall it looks like we`ll be dealing with a messy mix of wintry
precip late tonight through much of Fri. At this point since the
heavier precip is expected to fall during the aftn when most areas
will see only rain will handle light wintry precip in the morning
with an SPS. Evening or mid shift can issue winter weather advisory
if it appears there will be more precip around late tonight into Fri
morning when ptype will be bigger issue. The SPS will mention the
possible slippery travel and also strong/gusty south winds expected
as the warm front moves through.

.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 18Z TAFS through 18Z Friday afternoon)
Issued at 102 PM EST THU NOV 16 2017

Clouds will persist through the night at all the terminals but
should see cigs rise from MVFR to VFR by this evening. Next low
pressure system and warm front will bring light precipitation and
MVFR cigs to the area late tonight and Fri. Best chance for steadier
precip will be at KCMX. Warm layer aloft may result in mixed drizzle
and snow. Some light icing is possible Fri morning as sfc temps will
be around freezing. South winds will also become strong with gusts
over 30 kts possible Fri morning at KIWD and KSAW.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 255 PM EST THU NOV 16 2017

Brief lull in winds into this evening then south to southeast winds
increase late tonight into Fri as low pressure crosses northern
Ontario. Gales are expected over central and eastern Lk Superior and
a gale warning has been posted. Cold front to the south of the low
moves through Fri night with winds diminishing blo gales. However,
northwest winds increase to gales again late Sat into Sat night.
Winds diminish to 30 kts Sun-Mon but more gales are possible Tue
into Wed as active pattern continues.

Upper Michigan...
Lake Superior...
  Gale Warning from 5 AM to 4 PM EST Friday for LSZ244-245-248>251-

Lake Michigan...
  Gale Warning from 10 AM to 7 PM EST Friday for LMZ221-248-250.



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