Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 181946

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

.SHORT TERM...(This evening through Thursday)
Issued at 246 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.

.LONG TERM...(Thursday through Tuesday)
Issued at 425 AM EST WED JAN 18 2017

Large scale pattern evolution indicated by longer range guidance for
well over a week is proceeding largely as forecasted. Negative
height anomalies over AK are expanding thru the Gulf of AK and will
expand farther s down the w coast and into Mexico by the weekend. As
this occurs, positive height anomalies currently dominating much of
the CONUS into s central/se Canada will consolidate into a strong
anomaly centered over northern Ontario/Hudson Bay. The location of
this positive height anomaly will force arctic air almost completely
out of N America, except for the high Canadian arctic and AK and
vcnty. 850mb temp anomalies are fcst to peak at 3 standard
deviations above long term late Jan climatology across northern
Ontario this Fri/Sat and 2-2.5 above climatology across Upper MI.
Thus, unseasonable warmth will continue for the remainder of this
week with the potential for some record high max and/or min temps.
Thru at least the first half of next week, the positive height
anomaly will remain intact and only shift slightly to become
centered over Hudson Bay/Quebec. This will continue to prevent any
build up of arctic air in Canada. In fact, the very cold conditions
currently over AK and far northern Canada will even moderate as
arctic air shifts farther n. As for pcpn, the strong positive height
anomaly to the n will force the strongest shortwave energy streaming
into the western states on a southern route across the southern
CONUS. Energy that does peel n will weaken as it moves toward the
positive height anomaly. Thus, the fcst area shouldn`t see any
significant pcpn thru this weekend, Despite it being late Jan, the
unseasonable warmth will mean pcpn that does occur will be liquid,
and there could be a few days when light rain and drizzle occur,
which would be very unusual for this time of year. After the
weekend, there are indications that the final batch of energy in the
series impacting the western states will make a stronger run into
the Great Lakes than its predecessors, weakening the positive height
anomaly to the n and ne, and at least bringing some potential of
accumulating snow back to the area mid week. Farther down the line,
while there are some indications of renewed troffing into eastern
Canada as we flip the calendar to Feb, there doesn`t appear to be a
strong connection to arctic air yet. So, while trending cooler next
week and into the last days of this month, temps will still remain
above normal.

Beginning Thu, NAM/GFS fcst soundings maintain a dry column under
500mb ridging over the area. The only exception is near the sfc,
roughly the lowest 1kft where saturation is indicated. At some point
during this warm spell, low clouds/stratus will become an issue, but
whether Thu is the start of the cloudy period is uncertain. For now,
will keep sky condition on the optimistic side for Thu. If the day
ends up mostly sunny, temps will easily rise into the 40s away from
any marine layer influence.

Mid level low over the central Plains Thu will open up and lift
negatively tilted up into the Great Lakes late Thu night thru Fri
night. Despite negative tilt, only modest forcing/weak isentropic
ascent is indicated by models to swing thru Upper MI. This should
lead to at least some -ra lifting across the area late Thu night and
Fri. Some of the model solutions indicate enough height
falls/evaporative cooling for a mix with snow over western Upper MI.
At this point, given the warm air dominating the area and shortwave
weakening with time, will maintain ptype as liquid. However, with
temps dropping into the upper 20s Thu night prior to pcpn arriving,
some -fzra will be possible into the morning hrs on Fri.

Would expect extensive cloudiness to then prevail thru the weekend
behind this shortwave. Along with cloud cover, precipitable water
for much of the time is in the upper portion of late Jan
climatology, so min temps which will likely stay above freezing
across the area should be in record territory. Record high min temps
at NWS Marquette are 27, 28, 31, 35 respectively from the 20th to
the 23rd. If clouds dominate, max temps won`t rise significantly
from the mins, running generally in the upper 30s/lwr 40s. Another
shortwave lifting n to the w of the area Sat into early Sun may
generate more -ra. Otherwise, there will probably be some -dz at
times thru the weekend.

A more significant shortwave/low pres system will then cut
underneath the positive height anomaly in Canada and track from TX
late Sat to the se CONUS by Monday. This system in concert with
troffing extending back nw to the northern Plains may work to bring
a better chc of pcpn, likely just -ra, to the area on Mon.

It then appears that the last significant shortwave in the series
impacting the western states will lift ne, reaching the Great Lakes
midweek. Falling heights/cooling column at that time will begin to
support ptype changing to mostly snow. Some accumulating wet snow
certainly possible Tue night/Wed.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1218 PM EST WED JAN 18 2017

Expect VFR conditions at the TAF sites into this evng with influx of
unseasonably warm and relatively dry airmass. Gusty wsw winds,
especially at the more exposed CMX location, wl lighten later in the
day as the pres gradient over the area slackens. With diminishing
winds under moclr skies tngt, some radiation fog is likely to form
mainly at SAW, where a period of IFR vsbys wl be psbl late tngt into
Thu mrng. VFR conditions wl then dominate later in the mrng after
any fog burns off.

.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...


LONG TERM...Rolfson
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