Area Forecast Discussion
Issued by NWS Gaylord, MI

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927
FXUS63 KAPX 230345
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1045 PM EST Wed Nov 22 2017

.UPDATE...
Issued at 939 PM EST Wed Nov 22 2017

Evening surface analysis reveals elongated ridge axis stretching
from Texas into the lower Great Lakes region...keeping things on
the quiet side for the moment. Upstream...modest mid level short
wave trough is making it`s way through the far western Great Lakes
with a weak surface reflection over the eastern Dakotas. Thicker
mid and high cloud cover ahead of this feature has already made
it`s way into Michigan and there is some light precip making it`s
way across Wisconsin heading down into the lower lakes.

Here at home...not much happening aside from this persistent lake
STCU deck blanketing most of the area. Per APX radar...there were
some hints of light lake effect precip streaming off northern
Lake Michigan into the Straits earlier in the evening...but not at
the moment.

Rest of tonight into Thanksgiving morning...short wave and
associated QG-forcing for ascent will slide through the region
particularly late overnight through Thursday morning. Overall lake
effect parameters are not terribly impressive...inversion heights
under 5K feet and lake induced CAPE values <400 J/KG. But enough
to bring an uptick in SW flow lake induced/enhanced snow showers
impacting the tip the mitt/straits region and the potential for
some areas across Emmet/Cheboygan/Mackinac and Chippewa counties
to get an inch or two of snow.

&&

.NEAR TERM...(Tonight through Thursday)
Issued at 304 PM EST Wed Nov 22 2017

High impact weather potential: Minimal.

Pattern synopsis and forecast:

A ridge of sfc high pressure extended from Texas into the Great
Lakes this afternoon, with an overall dry air mass in place in nrn
Michigan. Of course we still have overlake instability and moisture
flux in westerly flow off the Great Lakes to bring in moisture
underneath a lowering inversion. This has resulted in mostly cloudy
skies and continued light lake effect snows. The moisture was
shallowing out through the day and winds were backing with time.
This was allowing for lighter and lighter snows that were gradually
shifting north. No significant accumulations under this scenario.
Upstream, a weakish shortwave and cold front were seen in south
central Canada and the Dakotas. DPVA and low to mid level warm
advection ahead of these features were producing light snow and
flurries into MN.

Overlake instability remains sufficient to continue producing light
lake effect snow and flurries that will gradually orient themselves
in SW flow from Lake Michigan through the Straits and Drummond
Island. Little to no accumulation for awhile into the night. Late
tonight into Thanksgiving day, the aforementioned shortwave dives
into nrn Michigan while the associated cold front sort of washes out
over us. Despite warm advection ahead of this system, we never lose
the overlake instability while deeper moisture arrives and gives the
lake effect a little boost in activity. Can see a corridor of 1 to
maybe 3 inches from far nrn lower, through the Straits and to
Drummond Island. The action tapers off Thanksgiving afternoon as
stronger low pressure starts developing into central Canada. Warm
advection will already be kicking in ahead of this feature, and that
is when we will be on our way to begin eliminating the deeper
overlake instability (which really occurs Thanksgiving night). Only
very minimal afternoon accumulations.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 304 PM EST Wed Nov 22 2017

...Temperatures going up then coming down...

The extremely changeable pattern continues with the next in the
series of low pressure systems affecting the region during this time
period. The main player this go around will be a deepening area of
low pressure which will track by to our north across southern
Ontario Friday into Friday night then depart into southern Quebec
Saturday. Very mild air in advance of this system will stream in on
Friday (along with gusty southerly winds) and lead to highs of well
into the 40s and perhaps even a few 50s. This will be followed by a
period of rain Friday evening into the first half of Friday night.
Colder air will once again advect in behind the departing area of
low pressure yielding another round of fairly short lived lake
effect snow showers Saturday (along with steady to slowly falling
daytime temperatures). Moisture is lacking and fairly shallow
(inversion heights only about 5,000 feet) so accumulations should
generally be limited to an inch or two. It will be a little windy on
the backside of the system so there could be some minor blowing snow
as well.

.LONG TERM...(Saturday night through Wednesday)
Issued at 304 PM EST Wed Nov 22 2017

Still some lake effect chances as we head into the overnight hours
Saturday as cold H8 air remains overhead. Height rises will be
building into the region through the day Sunday as flow backs
southerly on the back side of high pressure sliding through the Ohio
Valley. This should bring a quiet start to the week, with well above
normal temperatures. The pattern does remain progressive, as it has
been over the past few days, and another system will bring precip
chances around mid-week. Not much agreement on weather this is a
clipper moving overhead, or passing more to our north but dragging
on a stronger cold front through. We could see another brief period
of lake effect if the cold airmass gets far enough south.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1045 PM EST Wed Nov 22 2017

Fairly solid deck of MVFR-low VFR lake induced stratus remains
shrouded across northern lower Michigan. Thicker deck of mid and
high cloud cover has spread across much of the state...associated
with a modest short wave sliding through the far western Great
Lakes. This feature will bring an uptick to lake effect snow
showers overnight into Thursday morning...primarily impacting the
tip of the mitt (KPLN) area.

Lake induced precip diminishes through the day Thursday and we
should see an eventual return to VFR cigs as we go through the
day.

&&

.MARINE...
Issued at 1115 AM EST Wed Nov 22 2017

Wind speeds have diminished over the Great Lakes as a ridge of
sfc high pressure extended from north Texas into the western Great
Lakes. This ridge will slide southeast tonight, allowing for weak
low pressure and a cold front to approach tonight. Winds will
increase to lower end advisory levels over Lakes Michigan and
Huron into Thursday. Winds really ramp up Late Thursday night and
especially into Friday ahead of stronger low pressure developing
in central Canada. Gales are looking likely on at least Lake
Michigan.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 PM EST Thursday for LHZ347>349.
     SMALL CRAFT ADVISORY until 6 AM EST Thursday for LHZ345-346.
LM...GALE WATCH from late Thursday night through Friday evening for
     LMZ323-342-344>346.
     SMALL CRAFT ADVISORY until 5 AM EST Friday for LMZ323-342-
     344>346.
     SMALL CRAFT ADVISORY until 6 AM EST Thursday for LMZ341.
LS...NONE.
&&

$$

UPDATE...BA
NEAR TERM...SMD
SHORT TERM...AS
LONG TERM...AM
AVIATION...BA
MARINE...SMD



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