Area Forecast Discussion
Issued by NWS Gaylord, MI

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077
FXUS63 KAPX 051821
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
121 PM EST Mon Dec 5 2016

.UPDATE...
Issued at 115 AM EST Mon Dec 5 2016

Westerly flow lake effect has ended across far nrn lower and over
Whitefish Bay as WAA ate away at the deeper overlake instability.
Issues in the update revolve around sky cover. Decent clearing
had developed across M-32 south, as well as in western chip/Mack.
Trends will lead to clearing across the region, but there is some
uncertainty as to how much moisture is in the BL for diurnal
development. Fcst soundings showing that skies will just be mostly
cloudy/cloudy this afternoon with low level moisture trapped under
a subsidence inversion and continued shallow overlake instability.
Maybe some possible clearing later this afternoon as data suggests
the subsidence inversion squashes through the BL. Knowledge of
these scenarios leans in the direction of at least sct-bkn strato-
cu cloud deck in the westerly flow regimes and with diurnal
heating. There is some deeper low level moisture seen developing
and expanding north and to some extent east toward nrn Michigan.
These low clouds will build into nrn Michigan from SW to NE later
this afternoon and tonight.

&&

.NEAR TERM...(Today and tonight)
Issued at 236 AM EST Mon Dec 5 2016

...Lingering rain and snow showers quickly come to an end...

High Impact Weather Potential: Lingering snow covered roads this
morning.

Pattern Synopsis/Forecast: Negative tilt wave/associated band of
deep QG support and enhanced moisture quickly pulling off into
Canada, rapidly ending the widespread accumulating snow. Trailing
compact vort and just enough cold air to begin to entice some west
flow lake response off northern Lake Michigan. Lake modified
boundary layer quickly moving inland, resulting in a rain/snow mix,
with even some hints of drizzle as deeper synoptic moisture has
departed. While low clouds remain rather stubborn as far west as
western Wisconsin, clear skies rotating east across Iowa and
southern Minnesota show the rapid drying that is occurring upstream.
This aggressive drying is occurring under building mid level
heights, themselves driven by strong shortwave trough diving through
Montana.

Whole pattern will continue to evolve today and tonight, with mid
level ridging building and pushing east into our area as that
Montana shortwave digs and deepens into the Northern Plains. This
sets the stage for a relatively quiet stretch of weather for the
next few days, waiting until the arrival of much colder air later
this week to ramp up the lake effect machine (that great information
can be found in the long term section below).

Primary Forecast Concerns: Ending of lake processes this
morning. Cloud and temperature trends today and tonight.

Details: Drying will win out today, and when combined with rapid waa
processes, should end any remaining lake effect rather quickly this
morning. As mentioned above, even hints drying will be aggressive
enough to allow some sunshine, although up-top waa processes may
bring some increasing high and mid level clouds later this
afternoon. All in all, not to shabby of a early December day, as
despite fresh snow cover, should easily see afternoon temperatures
reach well into the 30s.

That band of isentropic driven mid level clouds may bring a few
flurries to northern areas tonight. Otherwise, more quiet conditions
as mid level ridging remains in control. Temperatures do not drop
too much with maintenance of light south to southeast winds, with
lows by morning in the mid 20s to lower 30s.

&&

.SHORT TERM...(Tuesday through Wednesday night)
Issued at 236 AM EST Mon Dec 5 2016

...Cold front ushers in a more active winter pattern...

High Impact Weather Potential...Lake effect snow showers will
develop on Wednesday, but accumulations will be minor with any
impacts expected to be minimal through Wednesday night.

Pattern Synopsis/Forecast...A strong cold front associated with a
slow-moving occluded low over southern Ontario will push through the
Great Lakes on Tuesday. This will usher in a much colder airmass for
the latter half of the week and activate a period of lake effect
snow.

Primary Forecast Concerns...Return flow will allow for ongoing weak
warm air advection for much of Tuesday as a cold front approaches
from the west. Highs across northern Michigan will be several
degrees above normal, topping out around 40 degrees. The system
moving through the Ohio Valley should stay far enough south to not
have an impact on the APX forecast area, so the cold front will be
the main weather maker for the day. Precip chances will increase
through the afternoon and evening hours, with PoPs and precip
amounts higher across eastern Upper where mid level forcing will be
stronger, adding to the frontogenetic lift. Rain will be favored
initially due to the mild temperatures, transitioning to snow
Tuesday evening as the front passes through and strong cold air
advection takes effect. Tuesday night lows will range from the mid
to upper 20s across northern MI.

Winds veering to the WSW and 850 mb temps plummeting to around -10C
or lower will allow lake effect snow showers to develop Tuesday
night into Wednesday, mainly across northern Lower and far eastern
Upper. Models differ with time of onset of LES and its southward
extent along Lake Michigan shoreline, so confidence in Tuesday night
is not particularly high. Meanwhile, the cutoff upper low will
wobble eastward across southern Ontario on Wednesday, providing some
synoptic lift for snow showers across the eastern Upper as several
lobes of vorticity rotate around it. Forecast soundings show more
favorable thermodynamics and deeper instability for LES arriving
Wednesday night, and PoPs will correspondingly increase going into
Thursday.

.LONG TERM...(Thursday through Sunday)
Issued at 236 AM EST Mon Dec 5 2016

High impact weather potential: Accumulating lake effect snow
Thursday through Friday night.

The main concern throughout the extended revolves around potentially
significant lake effect snow in the typical snowbelts of NW Lower
and eastern Upper. Broad troughing is expected to be anchored over
the midsection of the country come Thursday morning with broad
cyclonic flow aiding to filter in much colder temperatures locally.
As was mentioned yesterday morning, there remains disagreement
between global model solutions as to any synoptic system brushing
northern Michigan during the day Thursday, although that may be
fairly inconsequential as lake effect will really be the main focus
during the extended. H8 temps of roughly -12 C Thursday morning
continue to cool toward -15 C by Friday night. Forecast soundings
continue to be favorable for potentially significant LES Thursday
through Friday night with steepening low-level lapse rates,
increasing subsidence inversion heights, and negative omega pegged
in the DGZ at various times through the period. While there`s high
confidence in lake effect occurring, much colder temperatures, and
our first extended look at winter so far this season, confidence in
exact locations and amounts is lower at this juncture due to subtle
differences in wind direction. Will wait for more run-to-run
consistency to begin detailing the highest threat locations. Toward
the very tail end of the period, trends suggest a more vigorous
northern stream wave crossing the Midwest/Great lakes...potentially
brining more widespread, synoptically driven precip to the region.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1243 PM EST Mon Dec 5 2016

Remnant westerly flow lake effect will keep clouds in across PLN
for a few more hours, while skies have been thinning with more
holes for sunshine across much of nrn lower. Maybe there can be a
handful of hours of VFR, but looking upstream across Wisconsin and
srn Lake Michigan, more widespread stratus was seen. The nrn edge
of this clouds was also thinning due to a bit of afternoon mixing,
but can foresee these clouds expanding north and east into tonight
as night falls and the BL cools with the presence of an inversion
just above the ground. This would lead to IFR/MVFR CIGS.
Confidence is not too high right now with the whole cloud scenario
though.

Winds will back around to out of the south, then SE and increase
into Tuesday.

&&

.MARINE...
Issued at 236 AM EST Mon Dec 5 2016

Gusty southwest winds will continue this morning, particularly on
northern Lake Michigan. Winds turn back southerly later today and
tonight as low pressure lifts into srn Canada, with additional
advisories likely for Whitefish Bay and parts of Lake Michigan.
More widespread headlines expected for the remainder of the week
as increasingly cold air increases over-water instability.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 PM EST this afternoon for
     LHZ345>347.
LM...SMALL CRAFT ADVISORY until 1 PM EST this afternoon for LMZ323-
     344>346.
     SMALL CRAFT ADVISORY until 5 PM EST this afternoon for LMZ341-
     342.
LS...NONE.
&&

$$

UPDATE...SMD
NEAR TERM...MSB
SHORT TERM...MEK
LONG TERM...MJG
AVIATION...SMD
MARINE...MSB



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