Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 152047

Area Forecast Discussion
National Weather Service Marquette MI
347 PM EST Wed Feb 15 2017

.SHORT TERM...(Today and tonight)
Issued at 415 AM EST WED FEB 15 2017

The main weather impacts in the short-term will be the slowly
diminishing lake effect snow along with slowly decreasing winds
throughout the day. The winter weather advisory will continue
through 7 am due to the combination of gusty winds and continued,
mainly light snow. The wind gusts will steadily diminish along with
snowfall intensity; therefore, there is no reason to extend the

Today: Surface low pressure will continue to shift to the east and
southeast of the area today, which will keep northwesterly flow over
much of the area. Overall, the deeper moisture will exit with the
departing low; however, the  flow across the longer fetch of eastern
Lake Superior will allow lake effect snow to continue as 850mb
temperature only modify to around -15C over the eastern portions of
the U.P. Inversion heights are expected to slow trend downward
throughout the day, to around 3 to 4kft by late this afternoon.
850mb temperatures over the western portions of the U.P. will warm
to around -10C, which will allow any lake effect snow to diminish to
very light snow or flurries at best. Generally expecting only a
couple additional inches for areas from Munising and east near Lake
Superior. Blowing snow will also be an issue near Lake Superior
through early afternoon as the pressure gradient slowly relaxes
across the area. Otherwise, clouds will likely linger over most
areas along Lake Superior, while south central locations may see
some sunshine breaking out on downsloping winds. This will also help
temperatures to remain a bit warmer in the clearing areas as well,
probably in the mid to upper 20s, while other locations will be in
the upper teens to low 20s.

Tonight: 850mb temperatures are progged to remain around -13C to -
15C over the eastern portions of the U.P. tonight, which will help
to keep continued, very light lake effect snow going across the
eastern U.P. The chilly 850mb temperatures in place will be
partially in response to another quick moving shortwave progged to
slide through during the evening hours over the east. Western
portions of the U.P. will be influenced by approaching high
pressure, which will allow the lake effect to completely end over
the western half of the area. Not really expecting much more than an
inch or so of accumulation over the east as inversion heights
continue to decrease to around 3kft. Again, there will probably
continue to be lake effect cloud cover along Lake Superior, with
clearing possible over the south central locations. Where skies
clear, temperatures will likely fall into the single digits above
zero, while the cloudy locations will only fall into the low to mid

.LONG TERM...(Thursday night through Wednesday)
Issued at 249 PM EST WED FEB 15 2017

Real good agreement in the models and GEFS ensemble that upper ridge
over the western Conus builds across central Plains and Great Lakes
Fri into Fri night. Shortwave trough crossing northern Ontario on
Sat will flattern ridge slightly but it should build again Sun into
Mon with GEFS h5 heights and h85 temps both 2-3 standard deviations
above normal. Ridge will result in dry weather this weekend. Main
question will be how warm it will get Fri through Sun.

Latest NAM indicates increasing moisture 950-900mb (500ft-1500ft
agl) as early as Fri and certainly by Sat. Just not sure if this is
realistic or an artifact of models trying to generate too much low-
level moisture due to warming temps and expected melting snow.
Previous GFS runs were showing similar idea with low-level moisture
but 12z run looks more realistic with minimal moisture. With ridge
overhead, main low and cyclonic flow well to the north across
northern Ontario and sfc dwpnts Fri into Sat staying mainly below
freezing, have doubts that either day will have bkn-ovc low clouds
as NAM would indiate. Could see sct cumulus clouds though. Mixing to
925mb as soundings (even from the drier GFS) show seems too low with
upper ridge overhead and plenty of dry air in mid-upper levels. For
the warm Monday we saw earlier this week (set record high at NWS MQT
that day of 44F) the forecast soundings leading up to that day were
indicating similar scenario as NAM indicates on Fri and Sat (low
clouds and limited mixing height). Instead INL and GRB RAOBs at 00z
Tue indicated a mixing depth to 875mb to 850mb was achieved. Skies
were mostly sunny.

Though there was stronger mixing on Mon in lowest 5kft compared to
what should occur on Sat, think it could end up just as warm if not
warmer since h85 temps are much warmer (-2c on Mon and at least +8c
on Sat). Will continue to use 900mb temps as gage for high temps
which supports highs Fri mainly in the 40s and mainly in the upper
40s to middle 50s Sat and Sun. Since is it forecast to be drier in
low-levels on Sun that day may end up the warmer day. Lake breezes
are possible either day which would result in falling temps in the
aftn locally near the Great Lakes. Overall this weekend will feel
more like spring instead of winter. Record highs this weekend are
mostly in the 50s to low 60s. Here is a sampling of the record highs
for Fri 2/17 through Sun 2/19. Record highs seem possible.

Ironwood: 2/17 is 60 (2011), 2/18 is 58 (1981) and 2/19 is 60 (1930)
 Irn Mtn: 2/17 is 58 (1981), 2/18 is 51 (1930) and 2/19 is 62 (1930)
 NWS MQT: 2/17 is 61 (1981), 2/18 is 52 (1997) and 2/19 is 46 (1988)
Mqt city: 2/17 is 55 (2011), 2/18 is 52 (1954) and 2/19 is 62 (1930)
Newberry: 2/17 is 47 (1954), 2/18 is 46 (1997) and 2/19 is 47 (1994)

Shortwave trough moving over the Pacific Northwest later this
weekend deepens as it tracks across the northern Plains on Mon and
over the Great Lakes Mon night into Tue. Sfc trough over the plains
on Mon deepens to 995-1000mb low while lifting across northern
Ontario by Tue morning. With enough morning sunshine on Monday could
see temps again rise well into the 40s if not reach the 50s. Clouds
should thicken later in the day though as shortwave comes closer.
Upper Great Lakes will be well within warm sector of this system on
Mon night with h85 temps up to +10c and sfc dwpnts rising toward
40F. SW H85 winds over 50 kts will pump PWATs over 1 inch or roughly
4-5 standard deviations above normal. The abundant deep moisture
should help to develop rain showers over Upper Michigan late Mon
into Mon night. Timing still varies, though would expect a period of
rain sometime from late Mon aftn through daybreak on Tue. Given
strength of theta-e ridge just upstream and moisture advection
suppose there could also be thunder. Sfc dwpnts over 40F advecting
over the melting snowpack could result in areas of fog Mon night.
Sfc trough crossing the area on Tue morning will shift winds to the
W or NW pushing a drier and cooler airmass across Upper Michigan
through the day.

Tue into Wed the shortwave trough will head east across Quebec and
New England while weakening. Upper flow will become more zonal again
which casts doubt on the cold air that was showing up for mid to
late next week in model runs 24 hour ago. GFS remains cooler than
ECMWF and GEM especially for middle of the week, but consistency in
the ECMWF and GFS runs is lacking. Will leave consensus for now
given the poor run to run continuity, but overall think models are
heading toward zonal pacific flow pattern with temps at least
slightly above normal.

Beyond the end of the long term, recent runs of GFS and ECMWF
including latest runs hint at stronger storm system over ncntrl
Conus late next week (24-25 Feb). That system could bring snow to
portions of northern Plains and snow and/or mixed precipitation
across Upper Great Lakes.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 346 PM EST WED FEB 15 2017

Cold air flowing across Lake Superior will result in MVFR ceilings
at KIWD/KCMX/KSAW through this afternoon. However, an influx of
drier air will result in diminishing -shsn that will be affecting
mainly KIWD/KCNX. Visibility will mainly be in the MVFR range in the
snow showers that do impact the TAF sites. While KIWD should break
out to VFR this evening through Thursday morning, MVFR or near MVFR
cigs will likely persist at KCMX/KSAW through much of the TAF period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 415 AM EST WED FEB 15 2017

Gales to 35 knots will continue over the eastern half of Lake
Superior through much of the morning hours before the pressure
gradient decreases through the afternoon as low pressure slides
farther away from the area. Since colder air will continue to filter
into the area, heavy freezing spray warnings will continue through
late this afternoon for central and eastern Lake Superior. Winds
will remain below. Winds through the weekend will remain at or less
than 20 knots as the pressure gradient remains week across the area
in the absence of any major pressure systems.

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


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