Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181158

Area Forecast Discussion
National Weather Service Marquette MI
658 AM EST Sat Feb 18 2017

.SHORT TERM...(Today and tonight)
Issued at 332 AM EST SAT FEB 18 2017

Nothing tricky in the short term, just fine-tuning temps and winds.

W winds will keep the Keweenaw and shoreline areas exposed to W
winds cooler today, with the warmest temps expected over the central
U.P.. Should see temps up to 58F over the south central today, which
should be enough to break a couple or more high temperature records.
Lows tonight will be in the uppers 20s to low 30s.

.LONG TERM...(Sunday through Friday)
Issued at 422 AM EST SAT FEB 18 2017

Positive 500mb height anomalies currently extending from the Upper
Mississippi Valley/Great Lakes n across Hudson Bay will persist thru
roughly the middle of next week. The anomaly will peak over the
Upper Great Lakes on Mon at 2.5 standard deviations above the long
term mid/late Feb avg. As a result, unseasonably warm conditions
will continue thru the middle of next week. With 850mb temps during
this period running 1.5 to 2.5 standard deviations above the long
term mid/late Feb avg, record high max and min temps may be set on
some days. As for pcpn, dry weather will prevail until late Mon into
Tue morning when a shortwave trof lifting out of the western CONUS
passes across the Upper Great Lakes. Given the unseasonable warmth,
this wave will produce shra only... no frozen pcpn. That should be
the only meaningful pcpn until late next week. Late next week,
positive height anomalies over the area will weaken in response to
building heights over the ne Pacific into western Canada. As this
occurs, attention will turn to trof bringing yet another round of
hvy pcpn to the W Coast during the first half of next week. This
trof is fcst to reach the Plains Fri with energy closing off into a
mid level low by the time it reaches the mid/upper Mississippi
Valley. Compared to 24hrs ago, more CMC/GFS ensembles are supporting
the overall consensus of operational CMC/GFS/ECMWF runs in depicting
the energy organizing a strong storm system over the Plains Thu
night that will then lift into the Upper Great Lakes late Fri into
Sat. More on this later. Farther down the line, CMC ensembles point
toward a cooler pattern heading thru the last days of this month and
into the first days of Mar with this cooler pattern resulting from
building heights over the ne Pacific. The colder regime here will be
initiated by the aforementioned storm system passing late next week.
Latest CPC week 3-4 fcst has fairly high probabilities for overall
blo normal temps during the Mar 4-17 period.

Beginning Sun, mid level ridge amplifying over the Mississippi
Valley ahead of a trof swinging thru the western CONUS will
support a sfc high pres ridge that will move across the fcst area.
Resulting light wind regime will allow lake breeze cooling.
Combined with the southern edge of colder air mass brushing the
area later today/tonight, expect an overall cooler day for most
locations on Sun compared to today. While the interior w should
still see temps rise to around 50F, expect low/mid 40s in general
elsewhere, ranging down to the mid/upper 30s lakeside. Will
continue to downplay potential of low clouds which continues to be
most aggressively suggested by the NAM. Expect a partly cloudy
day with sct/bkn high clouds.

Sfc high pres ridge shifts e Sun night as western trof moves to the
western Plains. Temps will only fall back to the mid 20s/lower 30s,
more inline with normal high temps at this time of year. Downsloping
se wind over the far w should hold temps to the mid 30s. There could
be some fog over mainly the e half with light winds under the slowly
passing sfc ridge axis.

Trof swinging thru the western CONUS on Sun will weaken as it lifts
ene into the ridge/positive height anomaly across the western Great
Lakes region Mon night/Tue morning. Precipitable water is still fcst
to increase to a little over 1 inch which would be record territory
as sounding climatology for Green Bay shows that a precipitable
water value over 1 inch has never been recorded in Feb. Warm
conveyor moisture ribbon/trof/deep layer forcing will yield a band
of shra that will spread across the area w to e Mon aftn/evening,
then end w to e late Mon night/Tue morning. Could be some hvy
downpours given the unusually high precipitable water. Also, even
though showalter index never falls blo 0C and there is essentially
no elevated instability, not out of the question that there could be
a rumble of thunder with 50kt low-level jet shifting across the area.

Tue could end up quite warm as there is little caa in the wake of
the shortwave, and with rather sharp drying, skies should trend
toward mostly sunny from w to e during the day. With westerly winds,
downslope locations across central Upper MI could see temps rise
well into the 50s.

A shortwave ejecting from the next western trof will track ene
across the Upper Great Lakes midweek. ECMWF/CMC/UKMET are slower
than the GFS and show wave arriving Wed night as opposed to the GFS
idea of Wed morning. The slower solutions would support a very warm
day on Wed as ECMWF/CMC show 850mb temps rising to at least 10C.
Hedged fcst toward the slower idea and raised temps into the low/mid
50s for areas not affected by w to sw winds off the Great Lakes. If
slow timing does work out, would not be surprised to see temps rise
above 60F over a large part of the w and central fcst area on Wed.
Track of shortwave across the area suggests best chc of pcpn would
be n of Upper MI. For now, only schc/chc pops were included across
northern Upper MI Wed aftn/night. Cooler air will follow for Thu as
850mb temps fall back to the 0 to -5C range. Max temps Thu should be
in the mid 30s to lwr 40s.

Attention at the end of the week will be on the evolution of a trof
pushing onshore along the W Coast midweek. Latest medium range model
runs continue to be consistent with previous days runs, indicating
that this energy will close off a mid level low over the central
Plains late week, supporting a vigorous low pres system that will
track ne into the western Great Lakes. An overall trend from the 00z
operational runs and GFS/CMC ensembles is for a slight se shift in
the sfc low track. This increases the potential for a significant
snow event for at least nw Upper MI. A mix of pcpn will remain in
the fcst for scntrl into the eastern fcst area. Right now, Fri
appears to be the target day for heaviest synoptic pcpn, which will
be followed by lake enhancement transitioning to LES off Lake
Superior Fri night/Sat. Obviously, with system still 6 days out from
affecting the area, a lot can change, but it will be something to
monitor in the coming days.

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
Issued at 655 AM EST SAT FEB 18 2017

Pretty basic TAFs. Most uncertainty is with timing of fog
diminishing off at KSAW, which is starting already. Otherwise, a
breezy day across the Keweenaw.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 332 AM EST SAT FEB 18 2017

No gales or heavy freezing spray is expected in the forecast period.

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


LONG TERM...Rolfson
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