FXUS63 KAPX 300207

Area Forecast Discussion
National Weather Service Gaylord MI
907 PM EST Tue Nov 29 2022

Issued at 906 PM EST Tue Nov 29 2022

Steadily deepening low pressure (~990mb`s) making quick progress
northeast across central upper Michigan this evening. Cold front
extending south from this low, cutting rapidly east across eastern
Wisconsin. Sustained pre-frontal moisture advection/convergence
within deepening deep layer forcing helping kick off an area of
expanding showers across northern Michigan. Mild conditions out
ahead of this front, with temperatures still well up into the 40s.

Low pressure continues to deepen, reaching well below 990mb levels
as it exits the north shore of Lake Superior early this morning,
reaching central Ontario by sunrise Wednesday. Cold front races east
in the process, reaching Lake Huron before sunrise Wednesday.
Showers will continue to percolate along and ahead of this front.
Brief dry slot follows in its wake, with the return of deeper
moisture tied to primary mid level wave arriving during the early
morning hours. Combine this with a growing lake response within
rather intense post-frontal cold air advection regime, and the stage
is set for showers to again expand into northwest lower and eastern
upper Michigan. Rapidly shrinking melting layer supports showers
mixing with snow, with a full changeover to snow by morning. Snow
accumulations will be minor tonight, likely well under an inch.
Despite this, those rapidly falling temperatures and very gusty
winds will result in a flash-freeze scenario, supporting the
development of hazardous driving conditions in those inherited
advisory areas. Speaking of those winds, strong downward momentum in
that cold air advection will bring gusts in excess of 30 mph.
Perusal of latest real-time trends and incoming guidance continues
to support hazardous driving conditions Wednesday with lake snows
and areas of blowing snow within very gusty west/southwest winds
(over 40 mph). Inherited headlines already have these impacts well
handled, with no changes needed.


.NEAR TERM...(Through Tonight)
Issued at 324 PM EST Tue Nov 29 2022

High Impact Weather Potential...Moderate, esp. tonight

Pattern Synopsis/Forecast:

Upstream shortwave trough approaching...with difluent flow over the
Upper Great Lakes attm...as Michigan lingers in the warm sector
ahead of a strong cold front poised to our west from a triple point
over western Ontario...down through the tip of the western UP, to a
second low over extreme northeast KS. Warm advection continues this
afternoon...with deeper moisture overspreading the area. That band
of radar returns finally started hitting the ground late
morning...with some -RA recently showing up at KERY. Radar returns
continuing to spread northeastward over Lake Michigan attm as well.
Temps already surging into the low and mid 40s as of 19z. A little
bit of clearing developing over SW Lower Michigan attm which will
try to spread northward too...with temps surging into the upper 50s
over parts of SW Lower.

Primary Forecast Concerns: Winds tonight...precip tonight...

Strengthening SW LLJ moving into the region this afternoon...with
winds likely to ramp up above 40+kts this evening ahead of the
front...with up to 35kts just off the deck around 1kft. Anticipate
any mechanical mixing will lead to some periodic stronger gusts even
in the more stable warm sector ahead of the cold front. If any of
that clearing to our south makes it in here...we could see some very
strong winds in short order. Already note it`s gusted to 37mph at
KGLR just before 19z today...ahead of the stronger winds aloft.
Noting strong isallobaric gradient with this system as it pushes
through...I anticipate there will be a window a few hours either
side of fropa tonight where we could see gusts higher than currently
expected...though how strong is unknown. Meridional front should
come through between about 7z and 12z from west to east...with winds
shifting to more of a W to WSW flow behind the front. Winds aloft
attm do not look as strong behind the cold front as ahead of
it...though it will still be in the realm of 30+kts...but CAA should
more efficiently bring those stronger winds to the surface for the
latter half of the night and beyond.

Precip should continue to overspread the region this afternoon into
this evening ahead of the cold front...mainly in the form of
rain...noting temps in the 40s and that WAA. Anticipate some less
stable conditions in the mid-levels which could support better
rainfall rates at times...and with some signals for low-level CAPE
right along the front...along with some fgen...suspect some areas
will see some decent rainfall ahead of the front. Also anticipate it
will be in the form of showers...with some potential for convective
instability along the front ahead of a mid-level dry
slot...supportive of thunder potential, particularly across NW
Lower. Boundary layer stays moist behind the front...and delta Ts
rapidly increase behind the cold front...supportive of a transition
to lake effect with time overnight...and those crashing temps will
support a quick transition to snow. For now...anticipate this should
transition right from rain over to snow as temps cool quickly to ice
nuclei activation temps. Additionally...do have concerns for a flash
freeze with the rapid temperature drop late tonight/early Tuesday
morning behind the front...though whether the winds will be able to
dry things up is uncertain, as again...the post-frontal air mass
remains on the moist side. Inversion heights rise toward morning,
further supporting the LES idea. Suspect that the Tuesday morning
commute will be messy...noting it will be tricky to treat roads with
the quick switchover from rain to snow...and then the strong winds
and transition to snow, too. Slick, icy roads are likely...with
reduced visibilities running hand in hand with those stronger
winds...though the bulk of the impacts fall in the short term
section (see below).


.SHORT TERM...(Wednesday through Friday)
Issued at 324 PM EST Tue Nov 29 2022

...Whiplash of Winds, Snow, and Potential Flash Freeze on

High Impact Weather Potential...Moderate...Dicey travel to develop
in places Wednesday morning into the afternoon. Lake effect snow and
very gusty winds may create a myriad of hazards, including downed
trees / power lines and possible whiteout conditions.

Pattern Synopsis... Cyclogenesis currently ongoing over Great Plains
in conjunction with divergence aloft owing to favorable jet
dynamics. The aforementioned cyclone is expected to continue
deepening as it moves into the northern Great Lakes and undergoes
the process of phasing with a broad upper level low that moves in
from Manitoba. The associated cold front passes through the CWA by
14z Wednesday at the latest, and ushers in a colder airmass. High
pressure moving into the central Plains in the wake of this system,
combined with the aforementioned phasing...will lead to enhanced
flow on the backside of the low pressure as the cyclone begins the
process of occluding while it approaches Hudson Bay. Temperatures
aloft will cool considerably and allow for the development of lake
effect instability on Wednesday, as W to WSW flow becomes the
dominant direction to advect instability over land. This process
will continue into Wednesday night before flow tapers and subsidence
associated with high pressure largely ceases any lake effect
instability through the day on Thursday. Ridging will begin to
develop on the heels of this system as a lingering baroclinic zone
begins to develop. Flow then turns more southerly Thursday night
into Friday, drawing in another mild airmass to the region ahead of
another emerging shortwave in the central Plains.

Primary Forecast Concerns...Winds will be the most impactful from
this system, which can easily produce downed trees/limbs and power
outages. Travel issues may quickly develop through the day on
Wednesday owing to falling temps leading to a possible flash freeze,
gusty winds, and areas of lake effect snow, but some uncertainty
remains how widespread impacts from lake effect snow would be.

Wind...Surface temperatures will be plummeting by 12z Wednesday
across the CWA in conjunction with the passing cold front. The result
will be a much colder airmass being drawn into the region. In
addition, a pinched pressure gradient will lead to very strong
return flow on the backside of the low pressure. 925mb winds will
generally be in the vicinity of or exceeding 40kts for much of the
day, which, coupled with steepening low level lapse rates, will
allow for mixing to easily carry this flow to the surface. Frequent
gales are expected to spread across the open waters of the northern
Great Lakes on Wednesday, with the strongest gusts likely felt in
the vicinity of the Straits, along with Whitefish Bay...which may
see scattered gusts approaching 55kts. Over land, the wind will also
play a major role, particularly in areas along the immediate
lakeshores of NW lower and across Chippewa County in the vicinity of
Whitefish Bay. Wind gusts of 45-55mph will be frequent in these
locales (and may peak as high as 60mph) , while most other spots see
gusts in the range of 40-50mph. This is not to take away from
impacts that the wind will be able to bring across inland locations.
Gusts of this magnitude, which will be relatively frequent, can
easily lead to downed limbs and powerlines, along with unsecured
objects flowing freely across the landscape. In general, winds will
begin to taper late Wednesday night, with less frequent gusts as we
continue through Thursday morning. In the wake of the system, winds
will still be briefly gusty, but largely less extreme than what we
expect to see on Wednesday...as high pressure moves into the
southern Great Lakes by Thursday, eventually leading to the
suppression of strong flow just above the surface, and therefore
will lead to lower wind gust speeds as we progress through the day.

Snow...As colder air sweeps in on the heels of the cold front, low
level lapse rates will increase significantly through the morning as
upper levels cool, and air flowing over the lakes contributes to the
development of instability. Flow will turn predominantly W to WSW,
and given the strength of the flow, will lead to lake effect snow
being carried pretty far inland through the day Wednesday.
Initially, there may be a brief lull around sunrise for spots east
of I-75...but deteriorating conditions will already be ongoing or
imminent across NW lower and the eastern Yoop, as lake effect
instability really kicks into overdrive.

850mb temps will be in the range of -12 to -16 degrees Celsius
across the CWA by noon at the latest, with deteriorating travel
conditions spreading west to east in conjunction with snowfall.
While profiles may be favorable for the development of lake effect
snow through the morning and into the afternoon, there is some
possibility that subsidence in the mid levels tries to sneak in and
suppress heavier lake effect snow south of Grand Traverse Bay.

For spots north of there, the profile looks quite favorable through
the day and early overnight for lake effect snows. The greatest
areas of concern with accumulations will generally be around Antrim,
Otsego, Charlevoix, Emmet, and Cheboygan County. Given W to WSW
flow, there is potential for the largest band to favor the Little
Traverse Bay area, which would likely lead to heaviest localized
shows favoring southern Emmet and Cheboygan Counties, and
potentially as far east as portions of Presque Isle
County...potentially coinciding with the evening commute. Areas that
see the steadiest snows across northern lower will see a general 3-
6" of snow, with some localized areas certainly able to see upwards
of 8" of snow, though measuring may be quite difficult. For this
reason, I decided to roll with a strongly worded Winter Weather
Advisory...but given the potential for impacts, it is not impossible
to see a few warnings put out where heaviest snows will fall.

Lake effect will not be limited to the lower peninsula either, as
bands are expected to develop off of Lake Superior and Whitefish
Bay, and impact Chippewa County. This will be where the heaviest
accumulation will occur. Snow will be steadiest later in the day on
Wednesday, tapering some later Wednesday night before ceasing
Thursday morning. With W to WNW flow expected here, areas along and
N of M-28 will see a general 3-6" of snow, with localized spots of
8"+ possible near Whitefish Point and Sault Ste. Marie. It is
possible for some banding to briefly impact western Mackinac
County as well. Going with a Winter Storm Warning for western and
central Chippewa, with Winter Weather Advisories elsewhere across
the eastern Yoop.

The Bottom Line...These two hazards (snow and wind) will create a
double edged sword of impacts across the region. Preceding warmth
and rainfall will lead to wet roads across the area while
temperatures are falling to or below freezing. This can lead to a
flash freeze in the morning and early afternoon hours owing to a
very narrow window to get treatment down on area roadways following
preceding rainfall. This, combined with near-zero visibilities from
any snowfall or blowing snow (which won`t require a lot of
accumulation given the wind speeds), can give way to dangerous
commuting conditions building through the afternoon and into the
evening. Furthermore, regardless as to whether it is snowing or not
at any given location, wind will drive impacts through the day on
Wednesday, with the potential for downed trees/limbs and power

Thursday and Friday... High pressure returns for Thursday, shutting
down lake effect processes and easing winds across the region.
Temperatures will be rather chilly through the day, with highs
expected to peak in the upper 20s to low 30s. By Friday, a shortwave
will be emerging into the central Plains, and will tap into
divergence aloft from favorable jet dynamics, and lead to ascent
building back into the Great Lakes, bringing a return of southerly
flow and milder air as the day holds dry. Temperatures are expected
to peak in the upper 30s to mid 40s.

.LONG TERM...(Friday night through Tuesday)
Issued at 324 PM EST Tue Nov 29 2022

High Impact Weather Potential...Moderate...another system expected
this weekend

Yes, just as we get away from the midweek system, another shortwave
emerges from the lee of the Rockies and sets its eyes on northern
Michigan. Some uncertainty remains as to how amped this system will
get, but given favorable jet dynamics and a baroclinic zone, it is
hard to imagine this system not deepening and organizing further as
we get into the weekend. Furthermore, there is growing concern with
wind potential from this system, as high pressure sinks out of
western Canada into the Plains, which may potentially result in
another pinched pressure gradient right over the Great Lakes. In
general, the timing of this system would favor Friday night into
Saturday, with high pressure likely returning rather quickly for
Sunday. This system also appears to feature a rain-to-snow
precipitation type across northern lower Michigan, with an outside
chance that parts of the eastern U.P. remain all snow for the
duration of the event. Advancing into next week, it looks like the
baroclinic zone will hold east of the Rockies with Greenland
blocking. There is the possibility of additional shortwaves emerging
into the Plains by early next week, but exact movement and behavior
of these systems is rather uncertain at this time. In general,
temperatures are expected to linger in the upper 30s to low 40s
early next week, which would be slightly above normal for this time
of year.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 601 PM EST Tue Nov 29 2022

Period of rather high impact weather expected across the taf
locations through this period. Expect primarily MVFR conditions
under period of showers this evening, with passing cold front
bringing a rain/snow mix later tonight. Lake snows take center stage
Wednesday, likely producing brief periods of IFR conditions. Snow
amounts shouldn`t be too extreme, likely on the order of an inch or
two. Gusty southeast winds this evening will steadily veer overnight
into Wednesday, with very gusty west/southwest winds on Wednesday.
Expect wind gusts in excess of 35 knots on Wednesday, producing
areas of blowing and drifting snow. Per the usual with lake effect,
expect the worst conditions across eastern upper and northwest lower


Issued at 324 PM EST Tue Nov 29 2022

Gales to continue on the nearshores into Wednesday night for most
areas...with storm force winds expected over Whitefish Bay Wednesday
afternoon. Southeasterly winds this afternoon will continue to
increase through the remainder of the day...and shift to west and
westsouthwest as a strong cold front crosses the area
tonight...likely entering the Lake Michigan nearshores around
midnight...crossing through Whitefish Bay closer to 2am...and Lake
Huron zones between 2-7am tonight. Anticipate some gusts could be
stronger than currently expected within a few hours of the frontal
passage. Winds will remain strong and largely westerly through the
remainder of the nearshore period...through Wednesday night...though
diminishing some with time going into Thursday.


MI...Winter Weather Advisory from 5 AM Wednesday to 7 AM EST Thursday
     for MIZ016-017-021-022-027-099.
     Winter Weather Advisory from 7 AM Wednesday to 7 AM EST Thursday
     for MIZ018-023-028-029-033-034-088-095>097.
     Winter Weather Advisory from 4 AM Wednesday to 7 AM EST Thursday
     for MIZ020-025-026-031-032.
     Wind Advisory from 4 AM to 10 PM EST Wednesday for MIZ024-030-
     Winter Storm Warning from 7 AM Wednesday to 7 AM EST Thursday
     for MIZ086-087.
     Wind Advisory until midnight EST Wednesday night for MIZ098.
LH...Gale Warning until 4 PM EST Thursday for LHZ345>349.
LM...Gale Warning until 4 AM EST Thursday for LMZ323-341-342-344>346.
LS...Storm Warning from 1 PM Wednesday to 4 AM EST Thursday for
     Gale Warning from 7 AM Wednesday to 7 AM EST Thursday for LSZ322.



NWS APX Office Area Forecast Discussion