Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 221752

Area Forecast Discussion
National Weather Service Marquette MI
Issued by National Weather Service GAYLORD MI
1252 PM EST Thu Feb 22 2018

Issued at 1135 AM EST THU FEB 22 2018

13z surface/composite analysis shows a 1041mb surface ridge axis
extending from southern Quebec west into the upper Great Lakes/upper
Midwest. Southwesterly upper jet axis cuts across Michigan with a
200kt jet streak over Quebec...entrance region of this jet streak
helping drive an area of precipitation across the upper Ohio
Valley/ Pennsylvania/New York. Broad area of low level isentropic
ascent also spreading some radar returns northeast across
Wisconsin into Lower Michigan...12z APX/GRB/MPX soundings are
quite dry below not much in the way of anything
reaching the ground at this point until you get back into Iowa
where precipitation being aided by some low level frontogenesis
and along the leading edge of higher precipitable water values.
Just some Ci/Ac floating overhead at late morning across the Upper
Peninsula with thicker cloud cover to the east.

The afternoon is expected to remain dry with an increase in mid
cloud over time.  Not expecting precipitation to arrive until later
this evening.  After a chilly start...temperatures expected to
rebound to within a couple degrees either side of 30 degrees.

.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 18Z TAFS through 18Z Friday afternoon)
Issued at 1248 PM EST THU FEB 22 2018

VFR conditions this afternoon with increasing mid cloud...but am
anticipating worsening flight conditions as the evening
progresses as ceiling heights fall and eventually snow overspreads
the western and central U.P. after 03z. LIFR conditions expected
overnight and into the first part of Friday morning at
IWD/CMX/SAW...visibilities expected to improve as the morning
progresses and snow winds down.


.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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