711 
FXUS63 KMQT 131755
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
1255 PM EST Mon Dec 13 2021

.SHORT TERM...(Today and tonight)
Issued at 311 AM EST MON DEC 13 2021

Strong zonal flow in the upper levels will persist across the 
eastern two-thirds of the CONUS throughout the short term period as 
a deep low pressure system pushes into the Pacific Northwest.  As 
that low tracks farther inland, will even see that zonal flow 
transition into some ridging late in the period further enhancing 
the subsidence over Upper MI.  At the surface, west/southwesterly 
flow around the southeast U.S. surface high will advect warmer 
temperatures into the Upper Peninsula today, pushing daytime highs 
into the low 40s.  Late in the day, a dry cold front is progged to 
drift southward through the forecast area, but the main impact will 
just be a wind shift to the northwest with FROPA.   

Tonight, time cross sections are hinting at some high cirrus 
drifting through the region after Tue 06Z.  But otherwise, it will 
be a quiet night with overnight lows trending above normal.  Expect 
lows generally in the low to mid 20s with some upper 20s along the 
lakeshore.

.LONG TERM...(Tuesday through Sunday)
Issued at 348 AM EST MON DEC 13 2021

On Tuesday, the large-scale upper-level pattern will be dominated by 
a deep trough moving into the West Coast and anomalously strong 
ridging downstream across the eastern half of the CONUS. On 
Wednesday, a shortwave embedded within the longwave trough will take 
on a negative tilt as it rounds the base of the longwave trough over 
the Southwest, and then eject northeastward across the Plains, 
reaching the Upper Great Lakes by Thursday morning. The resultant 
surface cyclone spun up by this wave will be the main story of the 
long term period. Seasonably cold air advects in behind that system 
for the end of the week, bringing lake effect snow chances with it, 
especially Friday night and Saturday.

Tuesday morning, a strong surface high around 1036 mb is expected to 
be centered east of Lake Superior. SE flow on the western periphery 
of the high will advect moisture from Lake Michigan onshore and 
upslope into the U.P., leading to partly to mostly cloudy skies for 
much of the area. This cloud cover will counteract warm temps aloft 
and keep highs in the mid to upper 30s. Tuesday night, WAA, and more 
importantly moisture advection, will continue through the night as 
the southeasterly flow continues. As dew points climb above 
freezing, the continued onshore/upslope flow will make for more low 
clouds as well as areas of fog developing. Models continue to show 
around 3-5 kft of surface-based saturation over much of the area 
Tuesday night and into Wednesday, meaning drizzle as well. With this 
cloud cover and drizzle continuing Wednesday, we'll miss out on what 
could have otherwise been a very pleasantly mild day. Still, it will 
feel mild with highs in the 40s.

Temps will remain mild Wednesday night as the U.P. ends up in the
warm sector of a rapidly developing surface cyclone over the 
Upper Midwest associated with the aforementioned shortwave. By 06z
Thursday, there is a strong consensus in the models for a surface
low in the 975-980 mb range to be located over northern Minnesota
or western Lake Superior. The 00z GEFS mean low is at 980 mb at 
that time, and yesterday's 12z EPS mean low was around 980 mb as 
well. In fact, the EPS mean low is so strong that it is outside of
the CFSR climo for this time of year. In other words, models are 
forecasting an unprecedentedly strong low pressure. The result of 
this will be stiff southerly winds Wednesday evening ahead of the 
system's cold front, followed by strong (perhaps very strong) 
southwest to west winds behind the cold front later Wednesday 
night and into Thursday. The signal for strong, possibly damaging 
winds continues to be impressive. Yesterday's 12z EPS showed a 
large portion of the U.P. with an EFI >0.9 for wind gust and an 
SoT >1, indicating a high likelihood of wind gusts that would be 
extreme relative to climatology. BUFKIT profiles continue to show 
a 2-4 hour period immediately behind the FROPA with PBL mean winds
of 40 kts or more and PBL-top winds of 50-60 kts, or in some 
cases even more than 60 kts. The strongest winds will likely be in
the Copper Country, but all of the area should see a period of 
strong winds gusts late Wednesday night into Thursday morning. Do 
not want to advertise any specific wind speed numbers yet, but if 
current indicators hold, there is a good chance of some very 
strong gusts for the entire area with wind damage definitely not 
out of the question. 

The good news is that with the pattern being so progressive, that 
low lifts off to the northeast quickly Thursday night and winds drop 
off substantially Thursday evening. Colder air advecting in behind 
the system will make for some lake effect snow showers in the west 
wind snow belts, but not much since moisture will be lacking. Temps 
will fall through the day Thursday behind the front, reaching the 
low 20s west and upper 20s east by sunset. This cold air will remain 
in place Friday and Saturday. Another mid-level shortwave is progged 
to cross the Upper Great Lakes Friday night and Saturday bringing 
with it an uptick in moisture and increased lake effect snow chances 
for the typical northwest wind snow belts.
&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1255 PM EST MON DEC 13 2021

VFR conditions are expected at all TAF sites through the TAF period. 
Low-level moisture trapped beneath an inversion tonight, as well as 
light upslope flow from Lake Superior may bring IFR conditions to 
CMX and SAW late tonight/early tomorrow morning. Confidence is low 
at this time so have opted to place as a 6SM BR with SCT010 at this 
time.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 422 AM EST MON DEC 13 2021

West winds 20-30 kts continue across the lake today, veering around 
to NW this afternoon. Winds will become light across the lake from 
west to east this evening and overnight as high pressure scoots by 
to the north, then become SE on Tuesday as the high continues moving 
eastward away from the lake. There will be about a 6-hour period of 
marginal SE gales on the east half Tuesday evening. Decided not to 
issue a Gale Watch yet since gusts look marginal (mostly 35 kts with 
a few 40 kts at times) and it looks like a relatively short period. 
However, one may be needed with future forecast packages. Winds will 
subside below gale force early Wednesday morning but remain in the 
20-25 kt range on the east half through the day Wednesday.

The big story continues to be the increasing likelihood of a very 
strong system Wednesday night and Thursday. Southerly gales are 
possible on the east half of the lake ahead of the system's cold 
front, but winds will really start cranking behind the front when 
they veer around to westerly early Thursday morning. Have introduced 
storms to the forecast for Thursday with this forecast package 
which, still being more than 3 days out, is an indication of how 
high confidence is that this will be a very strong system. If the 
strongest model solutions verified, there could even be an isolated 
hurricane-force gust or two. All marine interests across Lake 
Superior should prepare to be in safe harbor by late Wednesday 
night. Winds will quickly subside below gale force Thursday night as 
the system pulls away to the northeast, with lighter winds expected 
across the lake Friday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&

$$

SHORT TERM...TDUD
LONG TERM...RJC
AVIATION...JAW
MARINE...RJC