Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141926

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

.SHORT TERM...(This evening through Sunday)
Issued at 225 PM EST SAT JAN 14 2017

Tonight and Sunday: Broad surface high pressure shifts east across
the Upper Great Lakes region tonight and will persist into Sunday
ensuring dry conditions across much of Upper Mi through the period.
Lingering light lake effect snow over the Keweenaw Peninsula and the
far ne cwa will gradually diminish or end later this
evening/overnight as building high pressure from the west continues
to moderate the airmass while lowering subsidence inversions to 2-3
kft as noted on model forecast soundings. Diminishing wind and
proximity to high pressure area moving just to the south will allow
western interior locations especially near the Wi border to dip into
the single digits blo zero again tonight. Min temps will stay warmer
(generally in the single digits above zero) near Lake Superior with
expected onshore wnw flow through much of the night.

Warm advection under sunny skies should allow max temps to rise into
the mid/upper 20s on Sunday, with some readings topping 30F over the
W and N central where sw winds downslope.

.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 PM Lake Superior forecast issuance)
Issued at 225 PM EST SAT JAN 14 2017

Pressure gradient will continue to weaken across Lake Superior this
evening as high pressure builds back into the area tonight, allowing
winds to diminish under 20-25 kts late tonight. The pressure
gradient will tighten once again Sunday 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. There could
even be a brief period of gales to 35 knots between Isle Royale and
the Keweenaw Peninsula late Sun afternoon/early evening. 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 as winds should remain at or below 25 knots
through this time period. High pressure dominating the last half of
next week will continue to keep winds generally light (blo 20 knots)
thru much of the period.

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


LONG TERM...Rolfson
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