Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 062353
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
653 PM EST Wed Dec 6 2017

.NEAR TERM...(Tonight through Thursday)
Issued at 300 PM EST Wed Dec 6 2017

...Accumulating lake snows to continue...

High impact weather potential...Lake effect snow showers, locally
quite heavy, to continue right into Thursday.

Pattern synopsis/forecast: Winter has most definitely arrived, with
deep overhead troughing opening a nice pipeline to cold Canadian
air. Fixed forcing of the Great Lakes doing their job, with multi-
band lake snows propagating off both Lake Superior and Lake Michigan
into the traditional west and northwest flow snow belts. Despite not
terribly impressive inversion levels (up around 6kft on local 12z
sounding), nice synoptic moisture plume above inversion level and
omega pegged within prime dendritic growth layer has resulted in
some rather intense snow showers, with visibilities frequently
falling below one quarter mile and estimated snowfall rates pushing
2 inches per hour. A bit of disruption noted after passage of
morning shortwave, although still decent speed shear within the lake
induced convective boundary layer has kept some respectable band
organization. Not a ton of reports so far, but based off radar, do
believe some areas of northwest lower and across the snow belts of
Chippewa County have received several inches of snow just today.

Pattern remains largely unchanged right through the start of
Thursday, with synoptic scale moisture and passing waves only
helping the lake generating snow cause. Atmosphere begins to dry out
a bit Thursday afternoon, but by no means enough to end the lake
processes.

Primary forecast concerns/challenges: Snow band morphology and
attendant placement of heavier snow amounts. Headline management
concerns.

Details: Simply following the slowly veering wind fields tonight for
better snow accumulations as essentially all other lake parameters
remain steady-state. Per the usual, overnight trends should be for
more defined band organization as any diurnal disruption is quickly
lost. Combine that organization with an increasing Lake Superior
connection, and would expect snow intensity to trend upward into
parts of northwest lower. Pattern recognition supports hi-res
guidance trends of the most intense band orienting west with time
into Antrim and Kalkaska counties, where snowfall rates by later
tonight may exceed an inch per hour. Transition of other bands to a
northwest/southeast direction will fan out accumulating snows to
the other warned and advisory areas, with additional accumulations
in these areas of at least a couple more inches (locally higher of
course under band pivot points and where multiple bands traverse the
same area). This veering wind field will eventually push best Lake
Superior activity into Luce county and points west, but not before
depositing a few more inches. Lighter snows/flurries with minimal
accumulations expected outside the favored lake areas.

Northwest flow lake effect continues unabated into Thursday morning,
bringing more accumulating snow to the traditional lake belts.
Departure of passing shortwave trough by later in the morning scours
out much of the synoptic moisture help and helps lower inversion
levels. Would expect this to result in less organized and intense
lake snows during the afternoon. Winds will also be backing more
west during those afternoon hours, fanning the snow out more.

Headline management: Given trends and expected evolution of lake
snow placement/intensity, see no reason to deviate from current
type/placement/or end times of inherited winter weather headlines.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 300 PM EST Wed Dec 6 2017

...Lake effect snow leading to hazardous travel continues...

High Impact Weather Potential: Additional accumulating lake effect
snow expected across parts of northwest lower and eastern upper
Michigan with hazardous travel likely.

Pattern Forecast: Anomalously deep troughing continues across the
midsection of the country through the forecast period. Slightly
below normal temperatures and continued lake effect snow is expected
with occasional upticks in intensity as a couple weak waves of
energy/clippers quickly dives from Manitoba into the western great
Lakes Thursday night and again late Friday-Saturday.

Primary Forecast Concerns/Challenges: Lake effect snow through the
remainder of the week, perhaps enhanced with synoptic support/
moisture at various times.

Slow reorientation of the low level flow is expected to be ongoing
Thursday evening into Thursday night as winds gradually back from
WNW to more westerly...and eventually west-southwesterly by Friday
morning. Uptick in LES parameters are progged on nearly all guidance
after midnight Thursday through at least Friday morning. Uptick in
deep layer moisture (coinciding with a subtle shortwave dropping
from western Ontario to the far northern reaches of the Great
Lakes), along with rising inversion heights to nearly 10kft, lift
pegged in the DGZ and the result could be easily another several
inches of fresh snow across W/WSW flow locales (including some of
the harder hit areas over the past 18 hours - Emmet, Cheboygan,
Charlevoix, northern Otsego) before flow once again wobbles back to
more westerly/west-northwesterly during the day Friday. Considered
issuing a new winter storm watch for the Tip of the Mitt for the
Thursday evening-Friday morning timeframe, but opted not to cause
complication with the current set of ongoing headlines across the
bulk of NW lower/E upper.

By Friday night, guidance is in fairly good agreement with respect
to a clipper quickly dropping southward from Manitoba into the
western Great Lakes. However, the strength, track and resultant
increase in synoptic support/moisture remain somewhat uncertain. The
NAM remains slightly further north than its counterparts. Either
way, an increase in snow coverage/intensity certainly seems like a
good possibility Friday evening into Friday night...perhaps with
lake enhanced snow across sections of northeast lower on Saturday as
east/northeast winds are expected for a period of time on the north
and west side of the departing clipper.

High temperatures throughout the forecast period remain several
degrees below normal...ranging from the mid-20s across eastern upper
and the higher terrain of northern lower to the mid-20s near the
lake shores. Overnight wind chill values in the single digits each
night, despite a lack of overly gusty winds.

.LONG TERM...(Saturday night through Wednesday)
Issued at 300 PM EST Wed Dec 6 2017

High impact weather potential: Periods of lake effect snow, enhanced
by occasional clipper systems, are expected to continue through the
forecast period...and likely beyond.

More of the same for the foreseeable future as deep troughing
remains anchored across the Great Lakes providing plenty of cold
air/over-lake instability for lake effect processes to continue.
Brief "moderation" late this weekend as H8 temps rise to -7 to -10
C...only to be quickly replaced by a reinforcing shot of cold air
dropping into the region on Tuesday (H8 temps progged at -17 to -20
C) by Tuesday night. Snow may be enhanced at times through the
period with additional weak perturbations dropping across the
northern Great Lakes...most likely to occur during the later Monday-
Tuesday timeframe and again late next Wednesday-Thursday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 653 PM EST Wed Dec 6 2017

Lake effect clouds and snow continues, with variable conditions.

Lake effect snow showers will continue through the TAF period,
but will focus the better snows south of PLN, closer to TVC later
tonight, as winds veer more out of the NW behind a sfc trough.
Snowfall rates of greater than an inch per hour expected late
tonight into Thursday morning with a general 3 to 6 inches in
and around the GTV Bay region, lesser elsewhere.

Gusty winds at times through the TAF period.

&&

.MARINE...
Issued at 300 PM EST Wed Dec 6 2017

Winds continue to slowly subside, but still remain well
within small craft advisory criteria into much of Thursday.
West/southwest winds veer more west to northwest tonight and
Thursday. Winds become west to southwest once again Thursday night
into Friday, increasing in speed once again in the process. Think
winds will remain below gale criteria however.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 4 PM EST Thursday for MIZ020-025-
     026-028-031>033.
     WINTER STORM WARNING until 4 PM EST Thursday for MIZ019-021-022-
     027.
     WINTER WEATHER ADVISORY until 5 AM EST Thursday for MIZ008.
     WINTER STORM WARNING until 7 PM EST this evening for MIZ016-017.
LH...SMALL CRAFT ADVISORY until 5 PM EST Thursday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 PM EST Thursday for LMZ323-341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 5 PM EST Thursday for LSZ321-322.
&&

$$

NEAR TERM...MB
SHORT TERM...MG
LONG TERM...MG
AVIATION...SMD
MARINE...MB



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