Area Forecast Discussion

FXUS63 KMQT 201751

Area Forecast Discussion
National Weather Service Marquette MI
1251 PM EST Wed Jan 20 2021

.SHORT TERM...(Today and tonight)
Issued at 427 AM EST WED JAN 20 2021

Busy short term period today. With the northern stream of split flow 
at the mid-upper levels positioned across the northern conus, a 
robust shortwave will dig southeast into our neck of the woods this 
evening. At the moment, ridging building across the central plains 
is helping to increase subsidence and introduce some drier air into 
the west. This has cleared out skies and allowed surface temps to 
drop below zero in the interior west. Where the cloud cover and 
continued LES off Lake Superior have persited through the night, 
temps have remained largely in the teens.

Looking upstream, GOES East water vapor imagery positions the 
shortwave moving into northern Montana and North Dakota, with 
southerly and southwesterly winds gusting ~35 mph along the 
isallobaric maxima. MSAS analysis has the 3 hour pressure change 
between -6 and -8mb in these locations. This maxima is progged to 
dip into our region this afternoon as the shortwave inches closer 
and the surface cold front moves into the west. There is a 
consistent signal in the 0z guidance of this maxima will maintain 
itself as the front moves through, perhaps being even a little 
stronger. Coupled with some low level instability and an expansive 
area of 35kts at 925mb, strong winds mixing down to the surface 
should make for a blustery day. CAMS are really hitting hard on 
strong winds along the Lake Superior shoreline in the east and 
downslope areas along the LLJ core axis. I incorportated some of 
that into this package. Overall, I'm expecting wind gusts 
approaching 30 mph across the entire forecast area this 
afternoon/evening. Terrain may help create some localized higher 
amounts, specifically downslope of the Michigamme Highlands into 
Marquette, Goegebic Range and the along the immediate lakeshores of 
Alger and Luce counties. Along these lakeshore locations, stronger 
40-50mph winds are expected. Combined with the recent snow and 
potential additional light snow developing off Lake Michigan this 
evening, area's of blowing snow look likely. Elected to issue a 
winter weather advisory for these counties, including northern 
Schoolcraft, as lower visibilties and some drifting snow in exposed 
roadways appears likely. I also opted to issue a lakeshore flood 
advisory for Schoolcraft, as the strong southerly to southwesterly 
winds will help build waves 8-10 feet. Some areas, particlarly east 
of Manitsique could see some beach erosion or lakeshore flooding.

This evening, winds will veer westerly as the surface low moves to 
just north of Lake Superior. With the strong pressure gradient 
lingering, stronger winds are expected in the Keweenaw. At the 
moment, some 35 mph gusts look possible, particiarly along the 
lakeshores. Ended up issuing another lakeshore flood advisory for 
Northern Houghton and the Keweenaw, as waves along the western 
lakeshore could build to 12 to 15ft. Elsewhere, the winds will 
slowly let off through the evening but still remain blustery along 
the lakeshores. 

In terms of precip, some lingering LES are expected in the east this 
morning. Through this evening, radar has observed these slowly 
shifting eastward as ridging builds into the region and winds become 
westerly and southwesterly. The airmass building in is pretty dry 
out and any forcings along the system's cold front will need to 
overcome this in order for any snow to occur. The exception is just 
upstream of Lake Michigan, where moisture flux from the lake 
combined with the theta-e and fgen should be enough to help squeek 
out some light snow. Some additional snow may linger after the front 
as 850mb temps remain near -10C. Another area that could see some 
snowfall is in the Keweenaw. There CAA this afternoon and evening 
will help sink 850mb temps back down to -10C. A combination of 
upslope enhancement and surface convergence could produce some snow 
showers in the west wind belts this afternoon and evening.

Under this WAA regime, daytime temps will quickly warm up this 
morning, reaching the upper 20s to perhaps some low 30s being 
possible. Tonight temps won't fall to much and I'm expecting 
widespread 20s.

.LONG TERM...(Thursday through Tuesday)
Issued at 147 AM EST WED JAN 20 2021

Upper air pattern consists of a 500 mb trough over the upper Great 
Lakes 12z Thu. This trough remains into Friday and broadens. 
Troughing then drops into the northern plains by 12z Sat. Lake 
effect snow will continue to slowly wind down for this forecast 
period and this is already covered in the going forecast. Had to 
bump pops up to account for lake effect and this is the major change 
to this forecast. 

In the extended, the GFS and ECMWF show a 500 mb trough over CA and 
a trough across the Canadian Prairies 12z Sat. This Canadian trough 
heads into the northern plains 12z Sun. Troughing remains in the 
western U.S. 12z Mon and then heads into the Rockies on Tue and into 
the central plains on Wed. Temperatures warm to near normal for this 
forecast period with the storm track well to the south of the area. 
There is an Alberta clipper type system that quickly moves through 
on Sun and weakens.

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1251 PM EST WED JAN 20 2021

Strong clipper-type low pressure system moving through Manitoba and 
Ontario will push a strong 50-60 kt LLJ across the area this 
afternoon leading to a period of LLWS at all terminals - worst at 
IWD. Gusts mixing down to the surface could lead to some blowing 
snow as well, but don't think there will be any significant vis 
reductions from BLSN this afternoon. 

Cold front moves through later this afternoon/early this evening 
with MVFR cigs moving in behind it at IWD and CMX. Strong gusty 
winds are expected overnight and tomorrow at CMX behind the front 
with 45 kt gusts possible. These stronger winds will also lead to an 
increase in BLSN so have dropped vis lower during this period at 
CMX. Second period of more marginal LLWS is expected at SAW behind 
the front as well. MVFR cigs reach SAW tomorrow morning and remain 
in place at all terminals through the end of the TAF period.

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 427 AM EST WED JAN 20 2021

Southerly gales are expected to develop this morning in the west 
half ahead of a robust shortwave and surface low thats moving into 
Ontario. These gales will spread into the east this afternoon. Gales 
of 40 to 45 kts are expected, and it should be noted that some 
higher storm force gusts are possible, particlarly offshore of the 
southern Lake Superior shoreline east of Marquette this afternoon 
and evening. Freezing spray will also be possible today lakewide. 
Winds will let off some and become westerly tonight behind the low's 
cold front and then become northwesterly Thursday morning. Gale 
force gusts to 35kts look to stay possible through Thursday. An 
arctic front is progged to dip into the region late Thursday. The 
colder air will once again make for freeing spray conditions with 
some heavy freezing spray is looking possible across the north 
central part of Lake Superior. Winds look to lighten to near 20kts 
Friday night through Saturday before increasing to 25kts in the east 
on Sunday.

Upper Michigan...
  Winter Weather Advisory until 1 AM EST Thursday for MIZ006-007-

  Lakeshore Flood Advisory from 9 PM this evening to 5 AM EST 
     Thursday for MIZ001-003.

  Lakeshore Flood Advisory from 4 PM this afternoon to 1 AM EST 
     Thursday for MIZ014.

Lake Superior...
  Gale Warning until 10 AM EST Thursday for LSZ245>251-265>267.

  Gale Warning until 7 AM EST /6 AM CST/ Thursday for LSZ162-

Lake Michigan...
  Gale Warning until 1 AM EST Thursday for LMZ221-248-250.