Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141803

Area Forecast Discussion
National Weather Service Marquette MI
103 PM EST Sat Jan 14 2017

.SHORT TERM...(Today and tonight)
Issued at 425 AM EST SAT JAN 14 2017

Today and tonight: High pressure shifting to the east of the Upper
Great Lakes region this morning will continue eastward to the
northeasrn U.S. today as a fast moving surface trough slides across
the U.P. Moisture and forcing will both be limited with this feature,
so the main impact will be light lake effect snow developing on the
west to west- northwest wind snow belts on the back side of the
trough. Again, overall moisture will be limited across the area, but
the increased fetch across Lake Superior will allow for a bit of
added moisture for the Keweenaw Peninsula as well as areas over the
far eastern U.P. near Lake Superior. Still not expecting much more
than an inch or so of snow accumulation as moisture depth really only
reaches up to about 3kft. Blowing snow may also be an issue near Lake
Superior as winds may gust up to 25 mph through the day today before
diminishing tonight. Temperatures today will be a little warmer with
highs reaching into the upper teens to low 20s with overnight lows
cooling back down into the single digits below zero to single digits
above zero, with the coldest readings expected over the interior

.LONG TERM...(Sunday through Friday)
Issued at 458 AM EST SAT JAN 14 2017

Much warmer weather is on the way for the Great Lakes region.
Height falls that have been occurring over AK will expand and deepen
across the Gulf of AK S thru the western CONUS over the next 7 days.
The response downstream will be building heights across the E half
of N America with the positive height anomaly expanding and shifting
N from the Lower Mississippi Valley/SE CONUS now to SE Canada,
centered near James Bay, by Fri. This change in the flow will shunt
arctic air almost completely out of N America, except for the high
Canadian arctic and AK and vcnty. As a result, conditions across
Upper MI will become unseasonably warm next week as 850mb temp
anomalies increase to 1.5 to 2 standard deviations above long term
mid/late Jan climatology. Along with the warmth, it appears 2 pcpn
events over the next 7 days or so will feature at least some rain,
very atypical of January in Upper MI. The first, in the late Mon/Tue
time frame, will likely have a wintry mix for much of the area as
pcpn arrives while the cold is still giving way under the warming
trend. The second event late next week is looking a bit less likely
as the strong positive height anomaly becoming centered in the vcnty
of James Bay may force shortwaves streaming into the western CONUS
to lift n thru the Plains well w of here and/or take a southern
route across the CONUS. If any shortwaves do bring pcpn to the area,
the pcpn will be in the form of rain late week and over the weekend.
In addition, could be looking at some record warmth late week, min
and/or max temps. Looking farther ahead, it appears the warm pattern
will persist for a while as CPC and CFSv2 outlooks maintain a
positive height anomaly centered in the vcnty of Hudson Bay into
late month which would keep arctic air out of much of N America. CPC
and NAEFS outlooks for the 8-14day period (Jan21-27) indicate a very
high probability of above normal temps for Upper MI. However, it
does appear that the eastern Canada positive height anomaly will
begin shifting w and nw in the last days of the month, which would
allow for troffing to begin redeveloping in eastern Canada. So,
there should be a trend toward cooler, but probably still above
normal temps as we flip the calendar to Feb.

Beginning Sun/Sun night, fcst area will be dominated by a dry air
mass associated with high pres over the Great Lakes region. With
flow becoming more zonal across Canada, air mass will continue to
moderate with 850mb temps rising from -5 to -8C Sun morning to 0C by
Mon morning. Under sunny skies Sun, max temps should rise to the
mid/upper 20s, with some readings topping 30F over the W and N
central where sw winds downslope. Mins Sun night may slip to around
5F in the traditional interior cold spots across the S central where
winds will be lightest, closer to high pres ridge axis to the S.

Deep mid level low currently off the coast of northern Baja
California will move across far NW Mexico over the next 36hrs, then
weaken as it lifts NE, reaching the western Great Lakes on Tue.
There are still details to be worked out as this energy interacts
with another shortwave dropping out of the more zonal flow across
southern Canada. The interaction will impact how much warming occurs
into Upper MI, and thus the all important ptype fcst. While the
ECMWF had been consistent showing the interaction pulling the energy
lifting across the Plains more westward, resulting in a stronger
push of warming into Upper MI, the 00z run has trended toward the
00z GFS/CMC in showing a track displaced a bit more to the E. This
allows height falls/dynamic cooling to possibly maintain ptype as
more snow, at least across western Upper MI. Given the inherent
uncertainty involved with shortwaves interacting/phasing, expect
continued fluctuations in thermal profiles/ptypes until this event
moves into the very short term part of the fcst. For now, fcst will
reflect pcpn beginning as -sn from S to N Mon aftn/evening with a
change to a wintry mix across the central and eastern fcst area Mon
night. Fzra/ice accumulations could certainly pose a problem Mon
night, and advy headlines will likely be needed. Pcpn will likely
change to a mix of -sn/-ra everywhere on Tue as it winds down. Some
areas will see a change to just rain. Where pcpn remains mostly snow
for this event, don`t expect more than 1-3 inches.

Dry/warm weather for mid Jan will prevail for the mid week period,
or if any pcpn does occur, it would be very light. Late in the week,
trof amplification will spread across the western CONUS, resulting
in deep sw flow and unseasonable warmth into the Great Lakes.
Whether or not we`ll be talking record warmth, min temps and/or max
temps, remains to be seen, but there is good agreement for
unseasonable warmth. The last 2 runs of the ECMWF have developed a
strong mid level high with 500mb heights up to 5650m or greater over
northern Ontario/Southern Hudson Bay this weekend, a very
impressive, roughly 500m above long term climatology. There are some
CMC ensembles showing a similar pattern. This would serve to deflect
shortwaves/pcpn mostly to the W or S of the area late week and over
the weekend, more typical of a spring time pattern. So, for now, it
appears less likely that a more significant rain event would occur
at the end of the week.

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1252 PM EST SAT JAN 14 2017

Expect mainly VFR conditions at KIWD and KSAW through the TAF
period. The passage of a weak trough today has shifted winds to the
west allowing MVFR conditions to occasional IFR conditions in lake
effect clouds and snow to return to CMX. There could be some blowing
snow as well at CMX with any fresh snow and gusty west winds to 25
knots today. Approach of high pressure ridge along with moderating
airmass will end lake effect later tonight into Sunday allowing KCMX
to improve to VFR conditions. &&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 425 AM EST SAT JAN 14 2017

Tighter pressure gradient across Lake Superior this morning will
slowly relax by late afternoon. Southwest winds up to 30 kts will
shift to the west following a low pressure trough passage today.
There may even be a few gale force gusts this morning; however, the
coverage and duration of these stronger gusts are expected to be
limited. High pressure will then build back into the area this
afternoon into Sunday morning, allowing winds to diminish under 20-
25 kts. The pressure gradient will tighten once again Sunday
afternoon into Sunday night as low pressure slides across central
Canada and the high pressure ridge over the Upper Great Lakes shifts
to the east. This will allow southwest winds to increase up to 30
knots once again. The next area of low pressure will approach the
Upper Great Lakes Tuesday and move through Tuesday night; however,
the system is not expected to be overly intense; therefore, winds
are expected to remain at or below 25 knots through this time period.

Upper Michigan...
Lake Superior...
  Heavy Freezing Spray Warning until 1 PM EST /noon CST/ this
     afternoon for LSZ162-242>244-263-264.

Lake Michigan...


LONG TERM...Rolfson
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