Area Forecast Discussion
Issued by NWS Gaylord, MI

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882
FXUS63 KAPX 080440
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1140 PM EST Thu Dec 7 2017

.UPDATE...
Issued at 820 PM EST Thu Dec 7 2017

Main update tonight is obviously the new winter weather advisory
headlines for Chippewa county and portions of NW lower (more may
be needed later).

First Chippewa county, an impressive west flow lake effect
dominant band of snow was pounding eastern Lake superior attm. A
strong shortwave dives SE into the region late tonight into Friday
morning that will result in winds shifting more WNW and dropping
that heavy band of snow with high snowfall rates, into areas
mainly along and north of M-28. Additional lake effect to continue
into the afternoon. Snowfall there north of M-28 3 to 5 inches
but locally higher amounts to maybe 9 inches in and around
Paradise.

For portions of NW lower, WSW snowbelts are expected to see lake
effect snows intensify after midnight into Friday morning due to
enhancements from the same shortwave. Emmet, Cheboygan and even
western Presque Isle will see snows taper off by afternoon as
winds shift more WNW, while Antrim, Kalkaska and Otsego counties
see decent accumulating snow into the afternoon. Not blockbuster
snow totals, but 3 to 5 inches in these areas is decent enough for
an Advisory issuance. Winds not expected to be a real concern.

Inversion heights for these areas rise to greater (much greater?)
than 7800 feet with the shortwave, which is impressive. All of
this comes focused around the morning commute for a greater
impact.

Additional lake enhanced snows are expected across the GTV Bay
region Friday night into Saturday morning, as an even stronger
shortwave arrives with enhanced low level convergence lining up
along the Lake Michigan shoreline from Leelanau county south.
Maybe advisories will be needed here, but the overnight shift can
look at that one.

&&

.NEAR TERM...(Tonight through Friday)
Issued at 316 PM EST Thu Dec 7 2017

...Accumulating lake effect snow continues...

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

Pattern Synopsis/Forecast...Deep cyclonic flow...modest synoptic
moisture and over-lake instability continues to produce lake effect
snow showers impacting much of our CWA this afternoon. NW flow...
multi-banded structure continues to target the NW half of our CWA
for the greatest chance of snow showers as well as highest snow
accumulations. Nature of the convection has become more cellular as
is a typical daytime evolution of lake effect snow. Discrete bands
are still definable despite cellular nature...with the heaviest
snow still impacting NW sections of our CWA. Overall intensity has
diminish throughout the day. Latest regional obs and radar suggest
that low level winds have begun to back to the west ahead of an
approaching short wave.

As we head into tonight...low level winds will continue to gradually
back to a more westerly component this evening...and eventually to a
W/SW trajectory later tonight. Diurnal impact to nature of lake
banding will begin to wane with sunset...but shifting winds will
produce additional disruption of band organization. Thus...expect
continued snowfall should be more evenly distributed across
locations impacted by NW and westerly flow. Greatest snowfall shift
shift northward to far NW Lower Michigan and the tip of the Mitt
tonight where new snow amounts should be 1 to 3 inches (generally
below advisory criteria). Far northern Chippewa county will see
another in or two tonight. Thus...will let all remaining warning and
advisory headlines across NW Lower Michigan expire on time at 21Z
this afternoon...and will not issue any additional headlines for
tonight at this time.

W/SW winds Friday morning will shift to the W/NW Friday afternoon
with the passage of the short wave...shifting lake snow bands
southward again. Locations targeted for highest snowfall on Friday
will be far Northern Lower Michigan and areas along and west of I-75
under the direction of westerly flow. Expect another 2 to 4 inches
of new snow on Friday (i.e. low end advisory criteria). Also expect
some blowing/drifting snow on Friday as winds strengthen to 15 to 25
mph in the wake of the short wave.

Expect a cold night across the Northwoods with overnight lows
falling mainly into the teens. High temps on Friday will warm back
into the mid to upper 20s.

&&

.SHORT TERM...(Friday night through Sunday)
Issued at 316 PM EST Thu Dec 7 2017

...An extended period of wintry weather and below normal
temperatures...

High Impact Weather Potential: Additional snowfall during the period
with winds increasing on the backside of an exiting clipper
Saturday.

Primary Forecast Concerns/Challenges: Headline concerns along with
the location and amounts of additional snowfall during the period.

Pattern Synopsis/Forecast...Upper level trough in place over the
Great Lakes will remain anchored through the weekend, with a
reinforcing shot of cold air dropping into the region Saturday.
850mb temps in this pattern, will fall from around -13c Friday night
to around -18c Saturday night, as the second shot of cold air
plunges into the base of the 500mb trough. At the surface, a very
active pattern is setting up this weekend as two clipper systems
sweep over the region Friday night and Sunday.

Overall, snow will continue across northern Michigan and the Great
Lakes Friday night through Sunday, as lake influences and sfc
features combine over the state. Highest pops and snowfall will be
confined to Lake Michigan snowbelt regions. Widespread snow is
expected across the entire cwa Friday night and Saturday with
850/700mb qvectors showing strong forcing over the cwa with
approaching clipper, while model soundings show significant moisture
from the sfc through 500mb. Some significant snows, possible
advisory amounts, are possible over the srn cwa and between Tvc to
Cad as clipper forcing and lake influences combine. Model soundings
showing strong lake bands to setup between Tvc and MBL Saturday, as
925/850mb southwest winds from Friday night trend north and
inversion heights deepen to over 9kft. Snowfall will diminish over
the cwa Saturday evening as model soundings show mid and upper lvl
moisture drying quickly behind exiting clipper. Dry mid and upper
lvls lingering over the region Sunday, which will limit snowfall
early. However model soundings show mid lvl mstr increasing quickly
by the afternoon in advance of second clipper. Lake effect potential
will increase through the afternoon and become better organized by
Sunday evening, as winds shift early and trend northwest while low
level inversions increase to over 5k ft.

.LONG TERM...(Sunday night through Thursday)
Issued at 316 PM EST Thu Dec 7 2017

High impact weather potential: Continued cold with snow.

Upper lvl trough which has been anchored over the Great Lakes since
earlier in the week, will remain centered over the Great Lakes
through the forecast period. 850mb temps in this pattern will linger
around -16c which will maintain below normal afternoon high temps in
mid 20s through much of next week. Several chances for snow
continues through next week as a clipper drops into the state
Tuesday while a mid Atlantic storm lifts into Quebec.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1138 PM EST Thu Dec 7 2017

Periods of lake effect snow will continue through Friday night
with more synoptically enhanced lake effect snow anticipated this
morning and Friday evening. Three separate disturbances aloft
will allow for prevailing MVFR CIGS at various times for the
airports, mostly the NW lower airports. One is crossing the region
now, then another late tonight into Friday morning, which is also
the one looking to bring the best lake effect snows to mainly
PLN, but also TVC to some degree. The lake effect bands will also
be capable of snowfall rates of over an inch per hour, with 1 to 2
inches accumulation in NW lower and as much as 4 inches or so
nearer to PLN. The enhanced snows Friday evening are looking to
impact mainly TVC and MBL, and these snows could be rather
vigorous as well.

Westerly winds a tad gusty at times through Friday, going lighter
and more variable Friday evening.

&&

.MARINE...
Issued at 316 PM EST Thu Dec 7 2017

Winds and waves will continue to reach SCA criteria tonight thru
Friday and Friday evening as westerly winds continue to gust to 15
to 25 kts. Lake effect snow showers will continue to impact much of
our nearshore areas thru the weekend.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until midnight EST Friday night for
     MIZ008-019-021-022.
     WINTER WEATHER ADVISORY until noon EST Friday for MIZ016>018.
LH...SMALL CRAFT ADVISORY until 5 PM EST Friday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 PM EST Friday for LMZ323-341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 5 PM EST Friday for LSZ321-322.
&&

$$

UPDATE...SMD
NEAR TERM...MR
SHORT TERM...SR
LONG TERM...SR
AVIATION...SMD
MARINE...MR



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