Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221146

Area Forecast Discussion
National Weather Service Marquette MI
646 AM EST Thu Feb 22 2018

.SHORT TERM...(Today and tonight)
Issued at 508 AM EST THU FEB 22 2018

No hazards/concerns until late this evening through tonight when
moderate to, at times, heavy snow will move in.

A shortwave and a weak 1018mb surface low will move to just SW of
the CWA by 12Z Fri. Warm air advection out ahead of the low, along
with forcing from the shortwave and low, will lead to widespread
wet, heavy (around 12:1 snow ratios) snow. Snow moves in from the SW
around 03Z tonight and should be falling across all of the central
and W by 09Z, then across the entire area by 12Z. Fgen enhancement
looks to provide some increased rates and snow totals across the
Keweenaw. Storm total snow tonight into Fri morning is expected to
be 2 to 4 inches over much of the area, with greater amounts to
around 6 inches possible across the Keweenaw. With the timing of the
heaviest snow around the morning commute and the wet, heavy nature
of the snow, decided to issue a Winter Storm Warning for the
Keweenaw peninsula and Advisories from Marquette and Delta counties
west. The eastern counties may have to be added depending on future
model guidance, but at this time data suggests less potential for
increased amounts there.

.LONG TERM...(Friday through Wednesday)
Issued at 440 AM EST THU FEB 22 2018

Active pattern continues into this weekend. Two primary winter
weather systems affect the area first part of Fri and again Sat
night into Sun.

Bulk of snow with Fri system will be exiting northern Upper Michigan
by mid morning Fri. Mid-level shortwave and increasing moisture
advection ahead of sfc-H85 trough are main drivers for the snow.
Snow could taper off as freezing drizzle or drizzle before ending
midday Fri. Though mainly marginal snow amounts of 2-4 inches
(heavier on the Keweenaw Peninsula) are expected mainly from late
this evening through mid morning Fri, the impact could be higher due
to the timing of heaviest snow occurring just before or during the
Fri morning commute and as the snow will be wet/heavy with SLRs less
than 15:1.

Small chances for lake effect linger into Fri night as H85 temps
fall toward -10c and there is widespread low-level moisture. High
pressure builds across on Sat and with mostly sunny skies, should
see high temperatures well into the 30s. Next system will quickly
approach from the southern Plains on Sat evening. Shortwave that is
main instigator for this system currently is sliding along the
Pacific northwest coast as seen in the WV loop. As this shortwave
emerges onto the central Plains Sat, expect lee cyclogenesis to
result in 995-1000mb sfc low over IA or northern MO by Sat evening.
Shortwave becomes negatively tilted as it lifts toward Upper Great
Lakes late Sat night into Sun morning. Associated sfc low deepens to
below 990mb by Sun morning with a location somewhere over central or
eastern Upper Michigan. Given the strengthening system and mixing
ratios of 3-3.5g/kg, can see why some of the models are generating
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. GFS and tail end of
NAM indicate heaviest qpf stays over far west or more to the west of
our forecast area. GEFS probabilities of qpf over 0.50 or 1.00 inch
also tilts more to far western forecast area and on to the west.
We`ll see if these trends continue to hold up. If so, there could be
a period of very heavy snow over western U.P. 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
area. After some data issues last couple days, do have the EC back
and that also indicates best chance for heavier qpf over far western
tier. With strong sfc low, chances are winds will turn breezy Sun
aftn into Sun evening. Since snow preceeding winds will be wetter
and temps by Sun aftn will be back into the 30s, blowing snow should
be limited. Given the strong system and moisture inflow present,
this system will continue to be monitored, but before really
tackling it will first have to get through tonight into Fri system.

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.

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 642 AM EST THU FEB 22 2018

The focus for this TAF period is late this evening through tonight
when snow moves in. Snow will potentially be moderate at heavy at
times especially at KCMX. 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 508 AM EST THU FEB 22 2018

Gales are possible Sat night into Sun night as a strong low pressure
system moves through the region, but no gales are expected otherwise.

Upper Michigan...
  Winter Weather Advisory from 10 PM EST /9 PM CST/ this evening
     to 10 AM EST /9 AM CST/ Friday for MIZ002-004-005-009>013-

  Winter Storm Warning from 10 PM this evening to 10 AM EST Friday
     for MIZ001-003.

Lake Superior...
Lake Michigan...


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