Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 271641

Area Forecast Discussion
National Weather Service Marquette MI
1141 AM EST Mon Feb 27 2017

.SHORT TERM...(Today and tonight)
Issued at 459 AM EST MON FEB 27 2017

WV imagery and RAP analysis indicated a mainly zonal pattern across
the nrn CONUS with a mid/upper level trough moving into the west. At
the surface, a weak ridge extended from Upper Michigan into nrn
Ontario. A warm front was developing from nrn South Dakota into
central MN ahead of a low pressure over nrn Wyoming. Radars
indicated light snow from ne MN into nw WI associated with an area
of 280K isentropic lift but with only a few reports of flurries.
Otherwise, mostly clear skies prevailed over Upper Michigan where
radiational cooling has allowed temps to drop into the -5 to -10
range near IWD/LNL.

Today, mid clouds will quickly spread across the cwa as the area of
isentropic ascent slides to the northeast. Since the low levels are
very dry, no more than a few flurries are expected. Otherwise,
increasing southerly flow WAA will help push temps into the mid to
upper 30s.

Tonight, as the mid/upper level trough deepens over the wrn CONUS
the sw flow out of the plains will continue to bring warmer air into
the region. A band of 285K-295K isentropic lift moving into the west
after 06z will bring an increasing chance of light precipitation.
However, no more than 30-50 POPs were mentioned given the very dry
900-700mb layer. Forecast soundings suggest that there will be
enough of a 925-850mb warm layer to support a mix of freezing rain
and possibly sleet where pcpn does develop. With climbing temps
overnight, even just rain will be possible over the far west.
However, with ground temps below freezing, there will be a risk of
light icing in roads where the pcpn occurs. If any pcpn moves into
the far south near MNM, mainly rain would be expected.

.LONG TERM...(Tuesday through Sunday)
Issued at 451 AM EST MON FEB 27 2017

Pattern looks active through the week. Strong split flow across
northern Pacific comes together over the western Conus, carving out
deep trough over central to eastern Conus Wed into Thu. Shortwave
energy in a couple pieces on the leading edge of trough will support
stronger sfc low across Great Lakes Tue into Wed. Mixed precip will
occur over Upper Michigan Tue into Tue night with this system. This
low will move to eastern Canada by Thu which will help drag down
seasonably chilly airmass from northern Canada across the Great
Lakes and northeast Conus late in the week. Troughing and cold air
is brief though as strong jet stream flattens heights by the weekend
with Pacific airmass sweeping from northern Plains to the Great
Lakes. Since the cold air will not be too far to the north, a decent
low-level temperature gradient should be in place by late in the
weekend which may help fuel stronger storm as first full week of
March begins.

Lead shortwave and more so the warm air advection with the wave will
support widespread precip across Upper Michigan. Forecast soundings
indicate quickly advancing warm layer sfc-h85 to switch precip to
liquid across all but far west and northwest Upper Michigan.
Lingering cold air at the sfc Tue morning may lead to freezing rain
over central and east interior. may be situation where ground temps
lag air temps by a few hours which would lead to more icing in the
morning. Even so, by late morning or noontime, air temps will be
into the mid or upper 30s where rain is occurring so icing potential
should diminish. Over far west and northwest, soundings indicate a
rain/snow mix through late aftn with a likely quick changeover to
snow in the evening there once sfc winds becoming northeast in
response to sfc low crossing the southern portions of the western
Great Lakes. Elsewhere, dry air aloft will result in mainly drizzle
into the evening. Some of that drizzle could turn to freezing
drizzle as cold air advects back in the later evening and overnight
assuming there is not enough sub cloud drying to diminish precip
chances all together. Freezing drizzle potential would especially be
higher where north winds provide upslope lifting over cntral cwa.

Enough cold air advection works in through the blyr to result in
ptype switching to snow or snow showers late Tue night into Wed
morning all areas. Since main shortwave will be heading east of Lk
Superior providing overall drying and subsidence and h85 temps in
wake of the shortwave/sfc low are only -12c or so, pops will be low
for snow showers and snow accumulations should be on the light side.
Bigger story will be gusty north winds over 30 mph with higher gusts
near Lk Superior in the morning as the system departs. Those winds
along with temps in the low 20s will put a bite in the air compared
to the warmer conditions on Tue as wind chill readings stay in the 5
to 10 above range during the morning. Looks generally quiet later
Wed into Wed Night and possibly Thu morning as though it is becoming
colder with h85 temps falling to -16c on 12z Thu, very dry air as
low as h85 should put crimp on any lake effect as inversions stay
3kft feet even at end of fetch over eastern Lk Superior.

Later Thu into Thu night, models hint at reinforcing cold front with
h85 temps dropping blo -20c by 12z Fri. Also looks to be a bit more
low-level moisture as well. GFS soundings look favorable for at
least moderate snow for a time late Thu into Thu evening as the
front moves through with inversions rising to 6-8kft in the wake of
the front. Spike up in the lake effect likely should begin
diminishing on Fri as high pressure quickly slides across the
region. High slides east late Fri into Fri evening as flow aloft
flattens out. Next shortwave and associated warm air advection will
bring swath of light to moderate snow across Upper Michigan Fri
night over west cwa and late Fri night into Sat morning for east
cwa. As enough warming occurs in the low-levels precip may end as
mix of rain/snow but switch over may be inconsequential as there
does not look to be much precip left by that point later on Sat
morning into rest of Sat.

Active but a muddled picture for Sun into early next week. Possible
fgen rain/snow Sun along tight baroclinic zone over the Upper Great
Lakes though model consistency is poor at best. Also could be
stronger low pressure system over the Great Lakes. Last three runs
of the GFS show potential for higher impact system with rain/snow
turning to heavy snow while ECMWF shows mainly snow but also keeps
it progressive enough to limit heavy snow potenital. Canadian also
shows mainly snow system around early next week, just slower.
Overall all the operational models seem latched on to something for
that time range. We will see if this continues with later model runs.

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1141 AM EST MON FEB 27 2017

Although some low clouds that are MVFR are at all sites, they will
quickly move out early this forecast. Conditions will deteriorate
late tonight at all sites as some mixed pcpn moves in late tonight.
IFR conditions set in Tue morning at all sites.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 459 AM EST MON FEB 27 2017

Winds will remain 30 kts or less through mid Tue afternoon. There
will be a period of northeast gales late Tue afternoon and Tue night
as the pressure gradient strengthens between high pressure over nrn
Ontario and a trough into the central Great Lakes. Winds will then
remain below 30 knots through the rest of the forecast period.

Upper Michigan...
Lake Superior...
Lake Michigan...


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