Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 231022

Area Forecast Discussion
National Weather Service Marquette MI
522 AM EST Thu Feb 23 2017

.SHORT TERM...(Today and tonight)
Issued at 522 AM EST THU FEB 23 2017

Received right around 3 inches of snow overnight at NWS MQT with the
shortwave and FGen forcing. Presently, rain and snow showers
associated with the shortwave are over the eastern CWA, with light
upslope snow in N wind upslope areas of the central and west. Expect
precip to continue rapidly diminishing, ending completely around 18Z
today. Attention then turns to the incoming storm system, but most
of that system is in the long term time range, so see that
discussion for more details. Could see up to 2 inches of new snow
over the far south tonight by 12Z Fri.

.LONG TERM...(Friday through Wednesday)
Issued at 522 AM EST THU FEB 23 2017

Positive height anomalies that have dominated the Great Lakes n thru
Hudson Bay in recent days, bringing unseasonable/record breaking
warmth to the area, have been shifting e and se over the last 24-
36hrs and will shift e more quickly this weekend. This will occur in
response to building heights over the ne Pacific/AK/nw Canada that
will support a trof shifting from the western CONUS to central N
America this weekend. These changes aloft will bring colder, more
typical late Feb conditions this weekend following a Plains to Great
Lakes winter storm that will lead the troffing into central N
America. Next week, the positive height anomaly over the ne Pacific
will retrograde a bit, and broad troffing will set up across much of
Canada. This will allow a good supply of arctic air to build up to
the n with bitterly cold air, the coldest air in the northern
hemisphere, eventually developing across central/northern Canada.
With that large scale trof having varying amplitude into the CONUS
as shortwaves swing around it, temps next week may be quite variable
btwn blo and above normal across the Upper Lakes, though
normal/above normal may be the more common outcome on most days.
Whether or not the bitter cold air building to the n will be able to
make a surge to the s beyond next week remains to be seen, but right
now there are no strong signals for that to occur.

Beginning Fri, energy that is now over the western CONUS will have
shifted out into the central Plains by 12z and will close off a mid-
level low over IA during the day with associated sfc low tracking
toward northern IL/southern Lake MI. Overall thinking from yesterday
hasn`t changed too much as the mid-level low is still fcst to open
back up as it shifts across the western Great Lakes region Fri
night/Sat, though model trends indicate a slower opening up of the
low. This still suggests that the deformation hvy snow shield that
develops on the nw side of the system will peak to the sw of here
and then tend to weaken as it lifts into the Upper Lakes.

Waa/isentropic ascent will quickly translate ne thru the Upper Lakes
Fri morning downstream of the deepening system over the Plains.
Additional forcing will be provided by the right entrance of a 100kt
upper jet lifting n across the Upper Lakes to northern Ontario. The
NAM, which had been a notable outlier in bringing a heavy swath of
pcpn s to n across the area Fri morning under a strong isentropic
ascent regime has pulled back and is now more inline with most other
guidance. This surge of pcpn will be all snow with all fcst
soundings across the area showing column temps blo 0C. With mixing
ratios around 3g/kg avbl in the 700-750mb layer, should see a
general 2-4in snowfall with this initial batch of snowfall on Fri.
Do have some concern across the s central/se fcst area where a
number of models show higher qpf under a bit more focused isentropic
ascent as well as some elevated instability which may yield some
convectively enhanced pcpn. Whether or not this occurs will be more
of a near term fcst problem as the event unfolds. Snowfall on Fri
will be wet/hvy making plowing/shoveling more difficult than normal.
The wet snow will also make roads especially slippery.

Fri aftn/night, there is uncertainty in whether sufficient mid level
drying will surge n into at least the eastern fcst area to cut off
ice nucleation as moisture above the sub -10C isotherm cuts out.
Local procedures suggest that will occur, but there are concerns
since not all models are aggressive with the drying. For now, fcst
reflects some mix with -fzra, more likely just -fzdz, which cuts
down snow accumulations over the e half to just 1-3 inches Fri
night. If the mid level moisture does not cut out, snow
accumulations will be higher than currently fcst Fri night. To the n
central and especially w, air mass will be more than cold enough to
support lake enhancement as winds back more directly onshore.
However, the w will be very near the edge of deep layer moisture,
making for a challenging fcst that could range from 6-12hrs of hvy
snow to just light snow. Fcst for the n central and w leans toward
the more conservative side with snow accumulations Fri night in the
3-6 inch range. System will exit on Sat with a transition to light
LES from w to e. Finally, gusty winds up to 30mph, higher at times
in exposed areas near Lake Superior, will lead to blsn, mainly Fri
night into Sat morning.

The only other fcst item of note this morning occurs during the
midweek period next week. Shortwave dropping down the W Coast
Sun/Mon is fcst to shift e and ne to the Great Lakes midweek. GFS
still remains weaker with this wave, but is trending a little more
amplified. As has been the case over the last 24hrs, the CMC/ECMWF
remain more amplified and stronger with sfc low that will lift into
the Great Lakes, and suggest a low track far enough n for mixed pcpn
or even just rain for a time for at least parts of the fcst area.
Majority of CMC ensembles favor a warmer look, and fcst will
continue to include mixed pcpn. A few ensembles wrap up a strong
system, but the majority don`t. Will be a system to monitor next

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1232 AM EST THU FEB 23 2017

A strong upr disturbance wl bring a period of sn to the TAF sites
early this mrng, resulting in some IFR/LIFR vsbys at times, mainly
at IWD and SAW where the llvl nly flow wl upslope.  Llvl dry air is
closer to CMX and wl limit the potential for persistent lower vsbys.
Once the disturbance/accompanying forcing shift to the e, expect
conditions to improve w-e, but persistent upslope nly flow wl
maintain some MVFR cigs, especially at IWD/SAW. The arrival of drier
air/an acyc llvl flow wl bring a return of VFR conditions by
early/mid aftn, and these wl linger into the evng. Some lo clds in
advance of a deeper lo pres aprchg fm the sw may arrive late in the
TAF period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 522 AM EST THU FEB 23 2017

NE to N gales to 35-40 kts are expected over much of Lake Superior
Fri morning into Fri night. NW gale force gusts to 35 knots are then
possible over south central and eastern Lake Superior Sat into Sat
night. Some heavy freezing spray is possible Fri night into Sat
night, but coverage will be limited.

Upper Michigan...
Lake Superior...
  Gale Warning from noon Friday to 1 AM EST Saturday for

  Gale Warning from 7 AM EST /6 AM CST/ Friday to 1 AM EST
     /midnight CST/ Saturday for LSZ162-263.

Lake Michigan...
  Gale Warning from 7 AM to 7 PM EST Friday for LMZ248-250.



LONG TERM...Rolfson
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