Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 231013

Area Forecast Discussion
National Weather Service Marquette MI
513 AM EST Fri Feb 23 2018

.SHORT TERM...(Today and tonight)
Issued at 513 AM EST FRI FEB 23 2018

Forecast and ongoing headlines still look on track this morning with
WAA snow moving across the Upper Lakes and ahead of 850 mb low
centered over central MN.  Isentropic ascent on the 290-295K sfcs
and up to 4g/kg mixing ratios advecting across the area with up to 6-
8 hours of best lift along with 850-700 mb fgen forcing will
continue to support high-end advisory to marginal warning snowfall
amounts of 4 to locally 7 inches over the western counties of the
U.P. Easterly flow of low-level dry air has initially limited snow
amounts to an inch or two into central counties. Drier air aloft
working from the sw has also contibuted to fzdz reports for
locations along the WI border in past hour. However, another wave of
pcpn will be moving in from north central WI in the next hour or two
ahead of a shortwave moving up from the sw. This could add another
quick inch or two of wet snow especially into central counties
before snow tapers off to light fzdz or ends by late morning. As a
result will keep advisories going into the morning hours for the
central counties of U.P. With consensus high res model QPF showing
.2-.3 inches into central counties and .3-.5 inches in the western
counties and with SLRs around 12/1 expect total snow amounts close
to fcst values of 4 to locally 7 inches west and 2 to locally 4
inches into central counties.

Fcst soundings indicate mid-level drying this afternoon in the wake
of the mornings shortwave trough which will continue into tonight as
ridging builds into the area. As result expect mainly dry conditions
this afternoon into tonight. Expect highs today ranging from the mid
30s to the lower 40s, warmest south central. Lows tonight will
generally be in the teens with partial clearing expected over the

.LONG TERM...(Saturday through Thursday)
Issued at 457 AM EST FRI FEB 23 2018

...More wintry precipitation expected Sat night into Sun...

Shortwave that will bring another wave of wintry precipitation to
our forecast area (now in a suddenly active pattern), is currently
over northern California digging toward Arizona and New Mexico later
today. As this shortwave emerges onto the central Plains Sat, expect
lee cyclogenesis to result in 995-1000mb sfc low over southern IA or
northern MO by Sat evening. Shortwave still looks to become
negatively tilted as it lifts toward Upper Great Lakes late Sat
night into Sun morning. Sfc low deepens to below 990mb by Sun
morning (GFS seems on the lower side, showing MSLP to around 980mb)
with a location somewhere over central or eastern Upper Michigan.
Last couple runs of NAM point to sfc low farther west, over western
Lk Superior, though that breaks with overall clustering from SREF so
think the NAM idea may be too far west.

Given the strengthening upper system and deepening sfc-H85 lows
with H7 mixing ratios of 3-3.5g/kg, a band of heavier qpf/snow
seems realistic. System moving through fast though so it should be
a quick hitter for when heaviest snow falls. 12 hour qpf either
from 00z-12z Sun or 06z-18z Sun over 1 inch to the west of sfc low
lifting through the region. Overall pretty good model consensus
and agreement from SREF and GEFS members that heaviest qpf/snow
occurs over far western U.P. and on to the west. This also lines
up well where GEFS indicates best link up of mid-level deformation
and moisture influx (sharp negative U component to H85 winds with
sharply positive V component to H85 winds). QPF and expected
dynamic forcing indicate far west sees best chance of seeing
warning criteria snow (6+ inches in 12 hours) Sat night into Sun
morning with moderate snow changing to a wintry mix of snow/sleet
and freezing rain/freezing drizzle over central and eastern forecast

With strong/deepening sfc low, winds will be breezy ahead of the low
Sat night into Sun morning (east to southeast winds) and also in
cold air advection region behind the low (west winds late Sun
morning into Sun afternoon). Wind gusts could reach 40-45 mph later
Sun, especially on more exposed Keweenaw Peninsula. Snow will be
wetter type and temps will be around freezing or above later on Sun
so not sure extent of blowing snow. Kind of getting concerned about
possible power outages with lower SLRs and expected winds,
especially if end up seeing very heavy snow in parts of our forecast
area before the winds hit. Will be something to keep eye on. Overall
we will need a headline for this event unless something drastically
changes in the persistent guidance/ensembles. Not sure if all of
forecast area will need a headline but there is time to sort that
out. Impact will be lower compared to a weekday morning as heaviest
snow occurs late Sat night into Sun morning (though those attending
church services on Sun will certainly be affected). Stronger winds
and possible freezing rain/icing could be nudging factors though in
possible headline issuance.

Light LES possible in wake of the Sun system Sun night into Mon.
Marginal temps and decreasing low-level moisture as main system
quickly lifts into northern Quebec should limit extent of LES. Rest
of extended looks generally quiet at this time. No real cold air
intrusions with daytime highs most days in the 30s.

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1138 PM EST THU FEB 22 2018

Overnight periods continue to be greatest concern for reduced CIGs
and VSBYs, possibly trending towards IFR conds for several hours
between 7-12z at TAF sites. Snow will potentially be moderate at
heavy at times especially at KCMX and KIWD. Exact timing of
snowfall is the greatest uncertainty, but confidence in the
forecast is otherwise good.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 457 AM EST FRI FEB 23 2018

Next period of gale force winds arrives Sat night as strong
deepening low pressure system lifts across Upper Great Lakes
region into Sun. East gales expected Sat night, then west gales
(higher end possible) expected later Sun. Gale watches have been

Upper Michigan...
  Winter Storm Warning until 10 AM EST this morning for MIZ001-003.

  Winter Weather Advisory until 10 AM EST /9 AM CST/ this morning
     for MIZ002-004-005-009>013-084.

  Winter Weather Advisory until 1 PM EST this afternoon for MIZ006-

Lake Superior...
  Gale Watch from late Saturday night through Sunday evening for

  Gale Watch from Sunday morning through Sunday evening for LSZ162-

Lake Michigan...


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