Area Forecast Discussion
Issued by NWS Gaylord, MI

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000
FXUS63 KAPX 170422
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1122 PM EST Sat Dec 16 2017

.UPDATE...
Issued at 951 PM EST Sat Dec 16 2017

Sfc high pressure was in Ontario this evening, with weak low
pressure in eastern Iowa and a frontal boundary stretched out
eastward through the srn lower Michigan border. A corridor of
deeper lower level moisture was within the tight baroclinic zone
north of the front. This was resulting in low stratus in and
around Manistee. but also in the higher interior terrain aided by
upslope, and in much of NW lower where weak easterly winds were
coming in off Lake Huron. Otherwise, mid and upper level clouds
were common. Made things more cloudy in the update, and will keep
the scattered/chance of light snow showers/flurries across NE
lower. All-in-all, a much quieter night in nrn Michigan.

Difficult low temp forecast. If higher cloud thins out in the nrn
half of the CWA...could get quite chilly. Single digits in far nrn
lower and negative single digits in eastern upper. Fairly steady
in the stratus areas.

&&

.NEAR TERM...(Tonight through Sunday)
Issued at 237 PM EST Sat Dec 16 2017

...Relatively quiet with moderating temps...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...Strong high pressure remains centered
north of Lake Superior this afternoon...with ridging and drier air
continuing to build southward thru Northern Michigan. Early morning
light synoptic snow has pushed well SE of our CWA...replaced by some
light NE flow light lake effect snow showers streaming off of Lake
Huron into portions of NE and North Central Lower Michigan. Temps
remain rather cold across our CWA...ranging from the single digits
in Eastern Upper Michigan to the low to mid 20s across our far
southern CWA.

As we head into tonight and Sunday...persistent easterly flow...
sufficient over-lake instability and shallow low level moisture will
continue to lend to the production of light lake-induced snow
showers...mainly across the NE half of Northern Lower Michigan. Some
patchy light freezing drizzle may periodically mix with the light
snow showers...but this will certainly not be the rule.

Expect another cold night across the Northwoods...with overnight
lows dropping into the single digits to teens. Our "warming" trend
will begin on Sunday as winds begin to shift to the SE and WAA
commences. High temps Sunday afternoon will warm mainly into the mid
20s to around 30 degrees.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 237 PM EST Sat Dec 16 2017

High Impact Weather Potential: Patchy light mixed precipitation
potential Sunday night-Monday night.  Lake effect snow developing
Tuesday with blowing snow possible.

Primary Forecast Concerns/Challenges: Weak forcing and marginal
thermal profiles resulting in questionable p-type issues Sunday
night through Monday night.

A weak shortwave will dampen out as it pushes across the northern
lakes Sunday night.  Moisture profiles on forecast soundings
increase, although most of the moisture generally remains warmer
than -10C.  This raises some concerns for freezing drizzle (or maybe
snizzle?).  Forcing is weak and think anything that falls will be
quite light. Will include patchy freezing drizzle/light snow mix in
the forecast for some areas.  Low temperatures in the 20s.

Minimal forcing and diminishing moisture on Monday likely results in
a fairly quiet weather day with little if any precipitation.  Milder
temperatures as 850mb thermal ridge slides across the area. This
will push temperatures into the middle and upper 30s in some areas.
Upstream upper trough and surface cold front push toward western
parts of the area Monday night with moisture profiles once again
showing increasing moisture depth.  Still plenty of questions about
p-types with light snow, freezing rain or rain possible across the
area.  Best chances of precipitation may be across parts of eastern
upper Michigan (where moisture will be deeper).

Colder air sweeps in behind the front on Tuesday transitioning
lingering precipitation back to snow.  After initial
subsidence/drying following fropa, the lake effect machine should
begin to ramp up during the mid-late afternoon as H8 temperatures
fall toward -10c with 70%+ moisture in the H8-H7 layer.  It will be
windy on Tuesday with mean boundary layer winds around 30kts. The
combination of wind and some developing lake effect snow could
impact travel with reduced visibilities - stay tuned.

.LONG TERM...(Tuesday night through Saturday)
Issued at 237 PM EST Sat Dec 16 2017

Much more progressive flow regime expected, at least to start the
extended period. Core of coldest temperature anomalies will retreat
north, waiting toward renewed pattern amplification toward the end
of the week to be forced back south. However, well agreed upon
detachment of strong southwest mid level low may force greater
downstream heights and locking the core of the coldest temperature
just to our northwest with time, but plenty of time to work those
details out in the coming days. Area gets clipped by a brief bout of
renewed cold air advection through mid-week as trough axis races
across southern Canada. This will, of course, reinvigorate the lake
processes. However, trends support very marginal parameters as core
of synoptic support and coldest temperatures pass well to our north.
Suppose some accumulations are possible Tuesday night into Wednesday
morning in the traditional northwest flow belts, but unless
parameters change, definitely does not look like anything too
significant.

Attention then turns to the potential for much more widespread
accumulating snow event later Wednesday night into Friday morning
(exact timing subject to change of course). Dprog/dt`s of all mid-
range guidance progs support a weaker and further south track to low
pressure, which makes complete sense as most substantial "piece" of
mid level support gets left behind in the southwest Conus.
Uncertainty is high, but with current trends, support is definitely
there for a long duration light to moderate snow event with several
inches of snow possible. Given pattern, would not be at all
surprised to see a weaker and further south adjustment with time.
Will continue to highlight this potential in our latest hazardous
weather products. Colder weather returns with perhaps some light
lake effect snows to start next weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1122 PM EST Sat Dec 16 2017

A corridor of deeper moisture and MVFR CIGS was over MBL and
across much of NE lower, including APN, due to weak easterly winds
off Lake Huron. The stratus expands back down into srn lower,
north of a frontal boundary stretched out across the lower
Michigan border. In weak easterly winds, doubt MVFR CIGS will do
much more expanding tonight, but working through the day Sunday,
winds do turn more southerly which ought to eventually draw all
that stratus from downstate into all the airports. Could be a
little light snow/flurries crossing mainly PLN/APN late tomorrow
afternoon and evening, associated with a disturbance aloft and
sfc troughing. Certainly no accumulation expected at this point.

&&

.MARINE...
Issued at 237 PM EST Sat Dec 16 2017

Winds and waves will remain below SCA criteria thru Sunday night as
high pressure and subsidence remain the rule. Conditions will
approach SCA criteria on Monday as the low level pressure gradient
tightens ahead of an approaching front. Wx will remain rather quiet
for the remainder of the weekend and Monday.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

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


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