Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 182327

Area Forecast Discussion
National Weather Service Marquette MI
627 PM EST Wed Jan 18 2017

.SHORT TERM...(This evening through Thursday)
Issued at 312 PM EST WED JAN 18 2017

12Z raobs/latest wv imagery and RAP analysis show a split flow with
polar branch upr rdg over central Canada into the nrn Plains to the
n of a closed lo in the subtropical jet over the srn Rockies into
the srn Plains. Unseasonably warm Pacific air has flooded into srn
Canada and the nrn CONUS to the s of the polar branch jet stream.
12Z h85 temps were as hi as 6C over scentral Canada at The Pas
Manitoba and YPL to aoa 10C over the nrn Plains, including 13C at
Glasgow MT. The 12Z INL/MPX/GRB raobs also show a very dry mid lvl
airmass under the upr rdging, so skies are generally mosunny, which
has allowed temps to rise aoa 40 at some places. There is a shrtwv
sliding esewd thru NW Ontario, but with the mid lvl dry air in
place, only some hi clds are brushing nrn Lk Sup. The exception is
over the ern cwa, where a ssw flow off Lk MI is resulting in a good
deal of lo clds/some fog that has restricted the diurnal temp rise.

Main fcst concerns in the short term are fog/lo cld trends as bldg
upr rdg/mid lvl dry air dominate the wx pattern.

Tngt...As the Ontario shrtwv moves quickly to the e and the pres
gradient weakens under slowly rising upr hgts/lingering mid lvl dry
air and sfc rdg axis, expect fog/lo clds to dvlp over the melting sn
pack. While a wshft more to the w behind passing shrtwv to the n wl
cause the lo clds near Lk MI to at least briefly break up into this
evng, a backing llvl flow to the sw later tngt suggests the lo clds
and fog wl be more focused in this area again. With the lighter
winds and dry mid lvl air, lo temps at the colder interior central
locations wl dip into the teens.

Thu...Morning fog/lo clds wl grdly dissipate but be most persistent
again near Lk MI, especially to the e of Escanaba with a llvl sw
flow off the water. Many of the models do show the sw flow wl tap
more llvl mstr and some lo clds now present to the sw over se MN/sw
WI and advect these into the Upr Lks. But with at least partial
sunshine and the unseasonably warm airmass lingering, expect hi
temps to rise aoa 40 again away fm Lk MI. If the hi temp at the
Marquette NWS reaches at least 40 again, Thu wl be the 4th day in a
row when the mercury has at least reached that mark at this office.
This streak will tie the record consecutive days with a max of 40 or
better that was established fm 1/11 thru 1/14 in 1987 at the
Marquette NWS.

.LONG TERM...(Thursday night through Wednesday)
Issued at 311 PM EST WED JAN 18 2017

January thaw with well above normal temperatures continues into
early next week. Mid to late next week upper level troughing is
expected to settle from western Canada into central portion of the
Conus which should bring colder pattern back to Upper Great Lakes.
As the pattern begins to shift back to colder conditions there is
potential for a storm system to affect the Great Lakes. Would be
cold enough to see some system snow late Tue into Wed.

Main issue later this week will be increasing low-level moisture blo
1km/3kft/900mb as high pressure ridge over Ohio Valley moves east
and positive tilted upper level trough and associated sfc trough
lifts across the Upper Great Lakes. Deeper moisture and stronger h7-
h5 q-vector convergence/lift arrives late Thu night into Fri
morning. ESE winds later Thu aftn into Thu night and the low-level
moisture could support light drizzle for upslope areas of central
Upper Michigan. Temps either side of 32F will be on the edge for
drizzle/freezing drizzle. As deeper moisture and stronger lift
arrives could see freezing rain late Thu night into Fri morning,
especially in the scntrl cwa where the most qpf occurs when temps
are forecast to be blo freezing. Will continue to mention the icing
potential in the Hazardous Weather Outlook (HWO).

Shortwave and stronger forcing continues lifting north on Fri and
there may be a lull in rain (or at the least steadier rain may
diminish to drizzle for a time) later Fri into Fri night. Another
shortwave and area of forcing lifts across Upper Great Lakes on Sat
so expect another period of steadier light rain to affect Upper
Michigan. Most of the deeper moisture is blo h7/8-10kft so qpf
should stay well blo 0.25 inch. However, even light rain will lead
to saturated low-levels and increase drizzle potential over cntrl
cwa and across the Keweenaw. Melting snowpack, ongoing drizzle and
sfc dwpnts rising above freezing will also lead to fog potential.
Unlike the warm conditions ongoing, it appears that conditions this
weekend will be more murky featuring more in way of rain/clouds and

Sun into Mon strongest shortwave energy over the central Conus will
be tracking from southern Plains to the Tennessee River Valley.
Expect fairly strong sfc low Tennessee River Valley into the Ohio
Valley while a weak trough extends northwest across the western
Great Lakes region. Majority of heavier qpf should be tied into the
system to the southeast of here, but weaker shortwave energy lifting
across the Great Lakes may bring some light rain to parts of Upper
Great Lakes on Mon. Best chances would be eastern cwa closer to
stronger jet forcing. As alluded to earlier, deep troughing is
forecast to develop across western half of the Conus Tue into Wed
which results in strong lee side low pressure forming over the
middle Conus on Tue and lifting toward Great Lakes late Tue into
Wed. Gulf moisture will be available for this system with mixing
ratios over 3g/kg shown by ECMWF. Seems likely there could be
stronger system affecting middle Conus into the Great Lakes, though
energy may remain tied into stronger storm system affecting east
coast early in the week. Both of these solutions are feasible. If
there is a stronger storm system in the middle Conus, one of the
main issues would be how far west the wrapped up low would track and
ultimately what will be extent of warm air/mixed precip with the
system. Plenty of time to sort out those details.

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 627 PM EST WED JAN 18 2017

With some low level dry air in place over the nw half of Upr MI,
vfr conditions to prevail into at least this evng. Not out of the
question there could be some mvfr cigs at CMX this evng with a
strengthening upslope w wind component and them some lo clds/fog at
SAW overngt with a period of lighter winds under passing sfc hi
pres, but maintained previous vfr fcst as confidence is lo on these
outcomes. The strengthening wsw wind above nocturnal invrn wl result
in some llws at IWD late tngt into Wed mrng.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 246 PM EST WED JAN 18 2017

A relatively weak pres gradient over the Upper Great Lakes in the
absence of any strong weather systems will result in winds under 20
kts over Lake Superior most of the time into early next week.

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


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