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FXUS63 KMQT 222125

Area Forecast Discussion
National Weather Service Marquette MI
425 PM EST Thu Dec 22 2022

.SHORT TERM...(Through Tonight) 
Issued at 220 PM EST THU DEC 22 2022

Key Messages:
-Lake-enhanced system snow bringing 2-5 inches of snow through 
-Road conditions are slick, but still driveable if absolutely 

Winter Weather Advisory-level snow continues for the Upper Peninsula 
as a weak, broad surface low passes through the region ahead of a 
deepening, negatively tilting 500mb trough. 850 mb warm advection 
will decrease through the day as the low passes and winds aloft 
begin turning to be out of the north. Snow today is mostly system 
snow however it is lake enhanced from Lake Michigan with southerlies 
ahead of the low and Lake Superior with northerlies behind the low. 
The 850mb temperatures ahead of the low are in the 
-8 to -10 C range while behind the low the temps aloft are easily 
into the negative teens and 20s C. As far as the snow:liquid 
forecast, a fairly deep dendritic growth zone will support higher 
ratios but those will be kept in check by strong winds and wind 
shear tearing apart some flakes, so mostly forecasting around 15:1, 
though 10:1 was been observed at the office in Negaunee Township 
this morning and that has increased throughout the day. With those 
snow ratios in mind, most of the UP will see an additional 3 inches 
(give or take an inch or 2) leading up to the warnings late tonight. 
With multiple observations and reports of slick roads thus far, 
travel is not necessarily advised, but it is still possible for now.

.LONG TERM...(Friday night through Thursday)
Issued at 422 PM EST THU DEC 22 2022

Increasingly negative-tilt mid-level trough now moving into the 
central CONUS as noted on the latest water vapor imagery and its 
associated 160+ kt upper-level jet rounding the base of the trough 
will cause rapid deepening of the storm system over the central 
Great Lakes over the next 24-48 hours. With incredible 24-hr 500 mb 
height falls of 350-400m forecast to occur over the Ohio River 
Valley by Friday morning the resulting "bomb cyclone" which forms 
over Lake Huron by Friday morning will likely yield storm force 
winds over much of Lake Superior and blizzard conditions over the 
northwest snow belts Friday into Saturday.  

Beginning Tonight, as the negative-tilt mid-level trough and the 
upper level jet max rounding its base deepens the closed low over 
the Ohio Valley the sfc low is expected to rapidly deepen near Lake 
Huron late tonight into Friday morning. The inverted sfc trough into 
the eastern portion of the U.P. will be the focus for synoptic snow 
over the east half tonight of 1 to maybe 3 locally 3 inches. 
Meanwhile CAA in a developing northwest flow on the backside of this 
sfc trough will result in LES into the western U.P. tonight. A very 
cold airmass as noted on fcst soundings will confine the DGZ near 
the sfc which will likely limit snow accumulation, but the finer 
flakes will be more efficient at reducing vsby. 

Friday into Saturday, as the sfc low deepens near 970 mb just east 
of Lake Huron on Friday and then slowly lifts north toward vicinity 
of James Bay on Saturday and strong CAA northwest flow on the 
backside of the low will be in full force across the cwa. Model 
soundings and ensemble guidance support the potential for very 
strong northwest winds into the east half of Upper Mi both days with 
gusts maybe reaching as high as 70 mph at some locations. Over the 
west, gusts as high 55 to 60 mph certainly seem possible. Very 
deep moist cyclonic northwest flow and unstable conditions under 
this CAA regime will result in a long-duration moderate to heavy 
snow event for the northwest wind snow belts of Upper Mi. The 
moderate to heavy snow combined with the strong winds will also 
result in widespread blizzard conditions over this same time for 
the northwest snow belts so will maintain the Blizzard Warning 
headlines for these counties late tonight through Saturday. For 
the rest of the counties, will keep Winter Storm Warnings in place
for late tonight into Saturday. Model consensus QPF amounts along
with SLRs generallly in the mid to high teens to one will likely 
yield two-day snow totals Friday into Saturday of 12 to 24 inches 
over the northwest wind snowbelts, greatest over the higher 
terrain near Lake Superior. Snow amounts will gradually taper to 
lesser amounts the farther inland you get from Lake Superior, 
although keep in mind the strong winds during this event will 
allow LES bands to carry much farther inland than what typically 
occurs. The look off the fcst soundings over the western UP Friday
into Saturday with the DGZ getting squashed near the sfc could 
limit LES accumulation due to finer flakes, but at the same time 
being more effective at lowering vbsys and enhancing blizzard 

By Sunday, northwest winds will be quickly winding down as the sfc 
low weakens near James Bay and although there will still be 
lingering LES ridging and drier air/subsidence will begin to 
taper off the LES from west to east.   

Ridging building across the area later Monday should finally put an 
end to the LES. Models and ensembles then trend toward a less 
amplified quasi-zonal flow pattern for the middle to latter portion 
of next week which looks like it will bring in milder Pacific air to 
the region and a trend toward above normal temps. Models hint at a 
shortwave or two moving through this flow which could bring some 
opportunities for mixed pcpn.

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 104 PM EST THU DEC 22 2022

IFR conditions will be the dominant category at all TAF sites for 
this TAF period minus IWD, which has been VFR in a dry slot all 
morning and will start the TAF period MVFR. Eventually, lake effect 
snow, gusty NW winds, and blowing snow will drive the aviation 
impacts in the forecast at all sites. With all 3 TAF sites within a 
Blizzard Warning after 06Z tonight, occasional whiteout conditions 
are possible, though exact periods of airport minimums will be 
difficult to pinpoint until it happens in real time. Some wind shear 
is also present in the SAW TAF as rapidly changing wind speeds with 
height in the vicinity of the TAF do reach LLWS criteria.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 422 PM EST THU DEC 22 2022

Winds of 25 knots or less over Lake Superior this evening with a 
trough hanging over the region will transition to a major storm 
force wind event on Lake Superior beginning later tonight and 
continuing into Saturday. Winds quickly ramp up later tonight into 
Friday in response to the deepening storm center taking shape near 
Lake Huron by Friday morning. Although winds don't actually reach 
storm force until later Friday morning the storm warning headline 
will start at 06Z Friday to account for the start of the the gales 
late tonight. Fairly solid storm force winds to 50 knots are 
expected from late Friday morning through Saturday across much of 
the lake with a possible brief period of high-end storms of 55-60 
knots over the eastern half of the lake on Saturday. Storms will 
begin to fall off to gales west half by Saturday afternoon and by 
Saturday evening east half with further diminishment of winds blo 
gales later on Sunday as the surface low slowly weakens near James 
Bay. The strong northwest winds will also usher in cold air 
resulting in a heavy freezing spray hazard as wind-driven waves 
could reach near 25 knots over the eastern half late Friday into 

Marine interests with passage plans through Lake Superior tonight 
through Monday should make the appropriate plans now to avoid these 

Upper Michigan...
  Winter Weather Advisory until 1 AM EST Friday for MIZ001>007-

  Blizzard Warning from 1 AM Friday to 7 PM EST Saturday for 

  Lakeshore Flood Warning from 7 AM Friday to 7 PM EST Saturday 
     for MIZ001-006-007.

  Lakeshore Flood Advisory from 4 PM Friday to 7 PM EST Saturday 
     for MIZ002-003.

  Winter Storm Warning from 1 AM Friday to 7 PM EST Saturday for 

  Lakeshore Flood Advisory from 1 PM Friday to 7 PM EST Saturday 
     for MIZ005.

Lake Superior...
  Storm Warning from 1 AM Friday to 1 AM EST Sunday for LSZ162-

  Heavy Freezing Spray Warning from 1 AM Friday to 1 AM EST Sunday 
     for LSZ162-240>251-263>267.

Lake Michigan...
  Storm Warning from 1 AM to 7 PM EST Friday for LMZ221-248-250.

  Heavy Freezing Spray Warning from 1 AM Friday to 7 AM EST 
     Saturday for LMZ221-248-250.