Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 222109

Area Forecast Discussion
National Weather Service Marquette MI
409 PM EST Mon Jan 22 2018

.SHORT TERM...(Today and tonight)
Issued at 526 AM EST MON JAN 22 2018

...Winter storm to impact Upper Michigan mainly later this afternoon
into tonight...

Potent storm system centered over nw MO/sw IA as noted on satellite
imagery and sfc analysis supporting convection into eastern MO and
western IL and north into IA and southern WI early this morning as
noted on radar and satellite imagery. As this system lifts slowly
northeast today and tonight, swath of pcpn on its northern and
western flank is expected to move across mainly central and eastern
Upper Mi this afternoon into tonight.

Since consensus of high-res models have bulk of pcpn with system
delayed until late afternoon into tonight for most locations, had to
trim back QPF and POPs this morning into early afternoon stressing
fzdz as main hazard, especially for e-ne upslope facing terrain from
the Keweenaw through Baraga and western Marquette counties. Best
forcing (deep layer q-vector convergence) and deep moisture for pcpn
will move in later this afternoon into tonight, but despite delay,
it still appears that warning snowfall amounts will be on track for
most areas. Model consensus total qpf for system around .5 inch with
expected SLRs around 12/1 would equate to warning amounts of 6 or
more inches of wet snow over 12 hours.  Looks like far western
counties will be on western edge of better pcpn/forcing and thus may
have hardest time reaching warning criteria snowfall. Included a
wider range of snowfall amounts over Gogebic/Ontonagon with the
lowest accumulation of 2-3 inches west and a greater chance of a
tenth of an inch of ice accumulation. Expect best chance for warning
snowfall over Gogebic-Ontonagon from Watersmeet to Trout Creek where
localized amounts of 6-8 inches could still be possible. The highest
snow totals during the event are still expected over Baraga and
Marquette counties where a widespread 6-10 inches looks likely, with
localized amounts exceeding a foot over the higher terrain of Baraga
into western Marquette counties where upslope ne flow and lake
enhancement off Lake Superior will provide added boost to totals.

Dry slot with system moving into south central and western counties
will end snowfall there later tonight with any remaining pcpn likely
in the form of fzdz. Snow and lake effect snow will last longest
into eastern and north central counties tonight with n-ne flow off
Lake Superior.

Northeast winds gusting near 30 mph late today into tonight especially
along Lake Superior could also cause areas of blowing and
drifting snow further helping to reduce visibilities.

.LONG TERM...(Tuesday night through Monday)
Issued at 405 PM EST MON JAN 22 2018

Models suggest that a progressive pattern will prevail through next
weekend. Mid/upper level ridging will advance through the cntrl
CONUS to the Great Lakes from Wed into Fri as a trough moves through
the wrn CONUS. Temps will climb well above normal from Thursday into
Friday and then drop closer to normal for Sunday and Monday.

Tuesday night, shallow cold air with 900 mb temps to around -14C
below the 3k-4k ft inversion should provide enough instability to
maintain light LES for northerly flow favored locations. However,
the shallow instability will limited any additional accumulations to
less than an inch.

Wednesday, a weak clipper shortwave trough may support some
additional light snow showers or flurries, but with winds becoming
light or offshore, only slight chance POPs were included during the
morning with little or no accumulation is expected.

Wednesday night into Thursday, WAA will increase as the mid level
ridge move eastward and low pressure develops into the plains. With
a dry airmass upstream, no pcpn is expected as most of the WAA will
result in layer warming rather than net isentropic lift.

Friday-Saturday, a vigorous shrtwv and associated low is expected to
lift into nw Ontario which will draw unseasonably warm air into the
region and push highs to around 40 Fri. The GFS/GEM remain faster
with the cold fropa compared to the ECMWF moving through either
Friday evening or early Saturday with temps possibly remaining
above freezing most of Friday night. There may be some light rain
showers changing to snow but with limited moisture
inflow/availability, any pcpn will be minimal with only chance
POPs mentioned.

Saturday night through Monday, a period of nw to n flow LES will be
possible as 850 mb temps drop into the -15C to -18C range. Any LES
should taper off toward Monday as sfc and mid level ridging build
into the region.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 106 PM EST MON JAN 22 2018

SAW: VLIFR to LIFR conditions expected through tonight at SAW before
slow improvement late tonight into Tuesday morning. IFR vsby
expected with LIFR vsby at times where heavier snow is expected to
occur. Northeast winds gusting to 25-30 knots later tonight may also
result in blowing snow/further reduced vsby.

IWD and CMX: LIFR to IFR conditions will be more common at KIWD and
KCMX in freezing drizzle/light snow. Mostly vsby should be IFR.

Expect gradually improving conditions to MVFR late tonight into
Tuesday at all the terminals. Vsby could even rise to VFR late
tonight into Tuesday at IWD and CMX.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 500 AM EST MON JAN 22 2018

With high pres to the ne of the Upper Great Lakes and low pres
tracking ne, passing across Lower MI Tue morning, expect increasing
winds across Lake Superior, reaching gale force 35-40kt across much
of the lake today and tonight, probably lingering into Tue morning
across the e half of the lake. With these stronger winds, expect
heavy freezing spray at times tonight into Tue. High pres ridge
arrives on Wed, providing a period of light winds under 15kt. Winds
will then increase Thu/Fri as the high shifts e and a cold front
approaches. Southerly winds may reach gale force over the e half of
Lake Superior Fri aftn/night. Westerly gales will probably occur in
the wake of the cold front passing late Friday night/Sat morning.

Upper Michigan...
  Winter Storm Warning until 1 AM EST /midnight CST/ Tuesday for

  Winter Storm Warning until 6 AM EST Tuesday for MIZ006-007-013-

  Winter Weather Advisory until 6 AM EST Tuesday for MIZ001-003.

  Winter Storm Warning until 1 PM EST Tuesday for MIZ004-005.

Lake Superior...
  Heavy Freezing Spray Warning from 4 AM to 6 PM EST Tuesday for

  Gale Warning until 10 AM EST Tuesday for LSZ264>267.

  Heavy Freezing Spray Warning from 10 PM this evening to 4 PM EST
     Tuesday for LSZ263-264.

  Gale Warning until 10 AM EST Tuesday for LSZ263.

  Gale Warning until 1 AM EST /midnight CST/ Tuesday for LSZ162.

Lake Michigan...
  Gale Warning until 1 PM EST Tuesday for LMZ248-250.



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