Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 100313

Area Forecast Discussion
National Weather Service Gaylord MI
1013 PM EST Sat Dec 9 2017

Issued at 1013 PM EST Sat Dec 9 2017

Updates rather insignificant tonight, consisting of increasing
coverage wording for lake effect snow showers across Chippewa
county. These snow showers will gradually lift into the far nrn
portion of the county as winds back westerly ahead of an
approaching weak low pressure and cold front. At the same time,
moisture will be thickening across the region, enhancing these
snow showers and giving their intensities a boost and helping
turn the flurries in nrn lower into bonafide snow showers later
tonight. The cold front passes eastern upper by Sunday morning in
eastern upper with winds shifting out of the north and presses
strengthening snow showers along the cold front`s sharp
convergence axis into Chippewa county. This snow band will be
capable of heavy snowfall rates before weakening as it heads
inland and off the Lake Superior moisture source. The front
crosses through nrn lower through Sunday afternoon. Westerly
enhanced snowfall will also turn out of the north. Drier air
behind this cold front will result in weaker snow intensities and
less coverage.

The advisory in Chippewa county will hold, as things haven`t even
developed yet. However, looking at the latest data that has just
rolled in, still looks like low end advisory snow amounts for
areas west of Sault Saint Marie and certainly along and north of
M-28. A localized max is centered around Paradise, with around 7
possible inches there. As for snow amounts in nrn lower, somewhat
of an uptick is also expected with the cold front, but the
convergence is weaker. Snow intensities will likely not be as
high. A lesser fetch than the one across Lake Superior will also
lead to that. Snow amounts no more than 1-2" expected, with
somewhat localized 3 inch amounts in portions of Charlevoix,
Antrim, Kalkaska and Otsego counties.


.NEAR TERM...(Tonight through Sunday)
Issued at 308 PM EST Sat Dec 9 2017

...Accumulating lake effect snow continues for some locations...

High Impact Weather Potential...Accumulating lake effect snow.

Pattern Synopsis/Forecast...Low pressure center has reached SE Lower
Michigan this afternoon...on its way southeastward toward Ohio.
Several areas of lake enhanced snow showers over Lakes Michigan and
Huron have come onshore into Northern Lower Michigan as low level
winds steadily back with the departing of the surface low. Some
locations are seeing brief heavier snow showers as a result...but
these areas of snow are rather transient as a result of the backing
low level winds.

As we head into tonight and Sunday...areas of snow showers currently
impacting our CWA will gradually diminish...with lake band
orientation eventually settling into a more NW flow this evening.
Low level winds will continue to back to the west late tonight into
early Sunday ahead of yet another short wave and surface reflection
swinging thru the Northern Great Lakes. Enhanced convergence via
this synoptic feature combined with W/NW low level flow will produce
advisory criteria snowfall across mainly northern sections of
Chippewa county tonight into Sunday. Will therefore issue an
advisory for this area with the expectation of 3 to 6 inches tonight
and another 1 to 3 inches on Sunday (mainly during the morning).
Locations targeted by W/NW flow in NW and North Central Lower
Michigan will see an inch or two tonight and another inch or two on
Sunday. Thus...will no issue a headline for this area at this time.

Expect another cold night across the Northwoods...with overnight
lows dropping into the teens. High temps Sunday afternoon will be
mainly in the 20s.


.SHORT TERM...(Sunday night through Tuesday)
Issued at 308 PM EST Sat Dec 9 2017

...A more potent clipper on Monday...

High Impact Weather Potential...It is possible that some of these
bands, as they transition from one wind flow regime to another, will
produce Higher impact weather especially on Monday as the south
winds over Lake Michigan, may enhance precipitation.

Pattern Synopsis/Forecast...Classic Ridge/Trough 500 mb flow pattern
with the trough over Hudson Bay. We will be in a bit of lull Sunday
night before the next system moves into the Upper Great Lakes
Monday. This system looks to be a little more potent than the last
few systems, but snow is still expected to generally light (1-3
inches) with lake effect snow trailing it Monday night into Tuesday

Primary Forecast concerns...Sunday night, looks to wind down as the
850-700 mb layer rh dries out, and the 1000-850 mb winds begin to
back to the southwest overnight. This will probably produce a burst
of snow as the winds push the NW bands together, in NW Lower. As the
winds continue to turn SW in the early morning hours, 850 mb
temperatures continue to remain favorable for LES (no warmer than -
8c in the southern part of the forecast area/Lake Michigan area).
Delta Ts continue to be 15 to 23c from south to north. Once the
winds are SW the issue then becomes LES in Emmet/Mackinac county as
the long fetch helps to enhance the snow fall with the clipper.
While the general amounts are 1-3, it is possible that 3-5 is
possible where ever the snow band moves onshore and can persist. By
00z/Tues (Monday evening), the trough moves through and we begin to
turn the winds back to the NW. Again the NW winds will push and SW
bands and the possibility of a some snow bursts rises. Winds
continue to veer with time from NW to NNW spreading out some of the
snow, and dropping more near TVC and points west of US-131. Models
are showing that the NNW winds will persist, and there is some
indications that with the strong Delta T (27C!) long NNW fetch
(preconditioning over Lake Superior) and synoptic moisture in the
850-700 mb layer (70-90% RH), there could be a heavy band that sets
up. This looks good through the day on Tuesday.

.LONG TERM...(Tuesday night through Saturday)
Issued at 308 PM EST Sat Dec 9 2017

High impact weather: Periodic lake effect snows with enhanced snow
from several clipper systems throughout the extended period.

The long range guidance continues to show periodic chances of lake
effect snow along with some clipper systems providing additional
chances of snow. Highs will continue to remain below normal for this
time of the year...only reaching into the 20s, with Tuesday and
Wednesday being the coldest with a push of arctic air into the
region...only reaching into the teens. Saturday will possibly be the
first day in awhile finally reaching above freezing. Lows Wednesday
morning will drop into the single digits negative and positive.


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 636 PM EST Sat Dec 9 2017

Lake effect snows will continue to impact the airports over this
TAF period, mainly TVC/PLN/MBL. Northerly winds turn more
westerly tonight ahead of weak low pressure and a cold front which
will bring an uptick in snowfall intensity late tonight through
Sunday morning. Winds turn out of the NW behind the passage of the
cold front, but snowfall intensity and coverage in the afternoon
through Sunday night is likely to be less due to the influx of
drier air. Snow ratios around 20:1 and snowfall likely no more
than an inch or two, higher in NW lower.


Issued at 308 PM EST Sat Dec 9 2017

Winds and waves will continue to reach SCA criteria tonight thru
Sunday and Sunday evening as winds gradually settle into a W/NW low
level flow in the wake of the departing low. Lake effect snow
showers will continue to impact much of our nearshore areas thru
the rest of the weekend.


LH...SMALL CRAFT ADVISORY until 5 PM EST Sunday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 PM EST Sunday for LMZ323-341-342-
LS...SMALL CRAFT ADVISORY until 5 PM EST Sunday for LSZ321-322.


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