Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 160422
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1122 PM EST Fri Dec 15 2017

.UPDATE...
Issued at 1122 PM EST Fri Dec 15 2017

The pure inertia of the dominant band of snow is going to carry
higher snowfall amounts and stronger intensity snow into the
overnight hours. There will be a downtick later overnight, but had
to increase snowfall yet again and extend the advisory for
Charlevoix, Antrim and Otsego counties through 5am. Total extra
snowfall 2 to 5 inches for a good chunk of the area.

UPDATE Lake effect snows continues across a good chunk of NW
lower, especially Charlevoix, Antrim and Otsego counties where
there is definitely a dominant band. Snows have been increasing
over the last couple hours or so, right were data suggests that
there is a defined corridor of confluent flow, thus resulting in
the dominant band of snow. Snow has weakened all other areas of
the current advisory, and plan on canceling those counties.
Despite lowering inversions through the night and subsequent
drying, am thinking that the aforementioned 3 counties getting hit
hardest right now under the dominant band, may need to be
extended more into the overnight hours, as the flow is suggested
to remain steady-state. By late tonight, it`ll still be snowing,
especially with a sfc trough dropping south from eastern upper,
but lighter snows, with even lower inversion heights (3500 feet or
so). Winds become lighter and more northerly as a sfc trough
drops from eastern upper to nrn lower. This will likely keep snow
closer to the shores, and maybe with some weak returns along the
trough.

Increased snowfall within the dominant band of snow, and into the
overnight as well. Total snowfall across Charlevoix, Antrim and
Otsego for the night 2 to 5 inches. Will watch radar trends for
these areas, but will likely cancel all others.

&&

.NEAR TERM...(Tonight through Saturday)
Issued at 317 PM EST Fri Dec 15 2017

...Accumulating lake snows end tonight...

High impact weather potential...Some additional snow accumulations
expected in the traditional lake belts this evening.

Pattern synopsis/forecast: Lake effect snow showers continue early
this afternoon as passing waves within broad deep layer trough axis
continue to provide some background synoptic scale contribution.
With that said, steady drying above a slowly lowering subsidence
inversion has definitely kept overall organization of lake snows in-
check since passing of morning cold front. Still, some phenomenal
snowfall rates in the heavier showers, with up to and over 2 inches
per hour at times here at the office. Passage of that front has
targeted the traditional snowbelts of northwest lower and eastern
upper Michigan for the most persistent lake snows.

Passage of last shortwave trough this evening and attendant further
lowering of inversion heights/loss of synoptic moisture will slowly
throttle back on lake snows by later tonight. Much quieter
conditions expected to kick off the weekend as focus for lighter
snows shifts south Saturday along lingering baroclinic axis.

Primary forecast concerns/challenges: Additional snow tonight and
associated headline decisions.

Details: West/northwest flow lake effect snow showers will continue
right through the very early morning hours, although likely
decreasing in intensity as inversions further lower and transition
to a pure les environment becomes complete. Despite the lowering of
intensity, expected band organization with loss of diurnal
disruption and strong support for areas of enhanced converge north
of M-72 still supports at least a few inches of additional snow,
most of which will fall this evening. Much less favorable fetch
further south should keep accumulations minimal. Best convergence
will focus further west with time for eastern upper, but not before
numerous snow showers deposit a few more inches up near
Paradise/Whitefish Point. Wind fields becoming light northerly by
Saturday morning should end the snow shower threat for most. As for
headlines, those north of M-72 in northern lower and Chippewa county
in eastern upper will remain through their duration (midnight),
while those further south will be cancelled with the afternoon
forecast release.

Elongated weak fgen band and area of deeper moisture may bring a few
flurries/pockets of light snow Saturday morning to southern areas.
Not a big deal for sure. Continuous feed of low level dry air should
end the snow threat by afternoon, although plenty of clouds will
linger, especially south of M-72. Temperatures will remain several
degrees below normal, with highs ranging from the teens north to the
lower/middle 20s south.

&&

.SHORT TERM...(Saturday night through Monday)
Issued at 317 PM EST Fri Dec 15 2017

High Impact Weather Potential...Minimal. Some patch freezing drizzle.

Pattern Synopsis/Forecast...Strong high pressure centered just NE of
Michigan Saturday night will slide east thru southern Quebec Sunday
and Monday...as a weak area of low pressure lifts ne thru the Great
Lakes region Sunday night and Monday. This system will lack
sufficient moisture and lift to produce any measurable precip
across our area during the last half of the weekend into early next
week. But moisture cross-sections and model soundings suggest most
of our CWA will see scattered flurries/patchy freezing drizzle thru
much of this forecast period...along with persistent low clouds.

Temps will steadily moderate thru the period as dry easterly flow
shifts to the SE and eventually SW...pumping "warmer" air into the
the Great Lakes region. After a cold Saturday night with overnight
lows in the single digits above zero to teens...temps will begin to
rebound on Sunday with afternoon highs in the mid 20s to lower 30s.
Temps will cool back into the 20s Sunday night...but will rebound
even further on Monday. Afternoon highs will warm well into the 30s
across our entire CWA.

.LONG TERM...(Monday night through Friday)
Issued at 317 PM EST Fri Dec 15 2017

A bit of a mixed bag in store over the extended period. With high
temperatures getting above freezing early in the week, some areas
could see a bit of a rain/snow mix as a clipper system moves
through. A push of cold air behind it will bring another round of
lake effect Wednesday ahead of another system moving out of the
Plains bringing more widespread system snow for late week. Will have
to keep an eye on this late week system, warm air isn`t to far
removed and a more northern track with this system could bring about
some messy p-type issues. While a more southern track will keep
things cool enough for all snow.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday evening)
Issued at 1122 PM EST Fri Dec 15 2017

Lake effect snow showers have diminshed at the airports, but a
dominant band of snow was occurring between TVC/PLN. This is not
expected to impact any airport. Only isolated to scattered snow
showers anticipated at the TAF sites, as higher pressure and
drier low level air move into the region behind winds turning
light northerly. Maybe some BKN CIGS will redevelop overnight and
appear at times Saturday, especially MBL due to deeper moisture
north of a frontal boundary that sets up through srn Lake
Michigan. Maybe even a little light snow at MBL with some reduced
VSBYS. Snow to liquid ratios will remain elevated, equal to or
great than 20 to 1.


&&

.MARINE...
Issued at 317 PM EST Fri Dec 15 2017

Gusty winds will slowly subside later tonight, with sub-
advisory level winds expected for the weekend.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 5 AM EST Saturday for MIZ019-021-
     022.
LH...SMALL CRAFT ADVISORY until 5 AM EST Saturday for LHZ347>349.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...SMD
NEAR TERM...MB
SHORT TERM...MR
LONG TERM...AM
AVIATION...SMD
MARINE...MB


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