Area Forecast Discussion
Issued by NWS Gaylord, MI

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039
FXUS63 KAPX 232103
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
403 PM EST Thu Feb 23 2017

.NEAR TERM...(Tonight and Friday)
Issued at 350 PM EST Thu Feb 23 2017

High impact weather potential: Accumulating snow and freezing rain.
Possible thunderstorms.

Pattern synopsis and forecast:

Sfc low pressure was deepening in the central plains this afternoon,
out ahead of broad upper troughing across the western conus. Nice
potent vorticity maximum and DPVA is working with strong warm
advection and upper divergence in left exit region 120+ knot jet to
produce the beginnings of a solid winter storm for the nrn plains
and Great Lakes, as well as, a potential severe weather threat for
areas downstate and in the Ohio river valley. Across our neck of the
woods, low level moisture remains stuck under an inversion, and thus
clouds were quite stubborn to erode in most areas. Mid and upper
level clouds out ahead of the developing low in the plains was
rapidly advancing toward us, so for those that have seen clearing
this afternoon, it will not last long.

Heading into tonight, those mid and upper level clouds will thicken
and bring back cloudy skies everywhere. The main impact will be with
the approach of the low pressure, which will work into SW lower
Michigan by Friday afternoon. There remains a decent amount of
uncertainty, still, in how things will evolve, particularly
precipitation type. That said, moisture will deepen and lift
northeast through the night, north of an elevated warm front that
will eventually lay out near the SE CWA. The aforementioned forcing
starts moving in close to midnight but really settles in late
tonight and into Friday. Some additional FGEN mesoscale banding is
possible across the far NW CWA of western Chip/Mack counties late in
the afternoon as the systems parent shortwave tries to phase with
another shortwave dropping south out of Manitoba. The way this
system is now playing out, is for warm advection snows to start
breaking out around/after midnight across areas south of M-32,
before spreading up into eastern upper Friday. The warm conveyor
belt and elevated warm nose wraps in across much of nrn Michigan and
rain develops across NE lower, while freezing rain is more dominant
across NW lower and much of eastern upper. Am only going with
general light amounts of snow through Friday with an inch or less
across the SE CWA, to as much as 2-3 inches in far NW lower and
eastern upper. Have opted to not go with too much snow since the
system is not exactly working with real deep moisture, plus fcst
soundings really show periods of drizzle (little QPF). Finally, the
air mass is quite unstable above 850mb, leading to the potential for
convection which could provide for heavier bursts of snows/rain
(which could offset periods of drizzle/little QPF). Factor in
strengthening easterly winds, and we got a pretty good little winter
storm.

Ice accumulations are not expected across a good chunk of the SE
CWA where it`ll be too warm. However they do look potentially
impressive further west across NW lower and eastern upper, with a
tenth to two tenths of an inch ice. This would be quite treacherous
for driving, but hopefully the intial snow will offset the impacts
of ice.

&&

.SHORT TERM...(Friday night and Sunday)
Issued at 350 PM EST Thu Feb 23 2017

...Wintry weather this weekend...

High impact weather potential: Wintry mix continues Friday night,
primarily across the Tip of the Mitt/Eastern Upper. Lake effect snow
returns Saturday...diminishing Saturday evening.

Pattern Forecast: By Friday evening, well-defined cutoff upper-level
low is progged to be spinning across the mid-Mississippi Valley. Upper
levels gradually become negatively tilted by Saturday morning along
with corresponding surface low pressure deepening as it crosses
through central Lower Michigan. This will ultimately drag a cold
front across the region Friday night, reinvigorating cold air aloft
and lake effect snow chances during the day Saturday. Upper-level
flow turns more zonal Saturday night with a weak disturbance
bringing additional snow shower chances to the area on Sunday.

Primary Forecast Concerns: Primary forecast concerns and challenges
revolve around lingering wintry mix Friday night prior to post cold
frontal surge of cooler air allowing for lake process to get
underway along with p-type becoming all snow. As was mentioned by
the prior shift, the overall low-level thermal regime stays fairly
stagnant Friday evening, perhaps even rising a degree or two, before
the front pushes through and CAA takes over by Saturday morning.
Fully expect a messy wintry mix of snow, sleet, freezing rain/rain
to continue Friday night, especially across the higher terrain north
of M-72, Tip of the Mitt, and into eastern Upper where the coldest
thermal profiles are expected to continue. With a cool low-level
northeasterly wind and based on forecast model soundings, the threat
may take shape more as freezing drizzle, rather than a pure freezing
rain or snow threat, as dry slotting continues to work its way
overhead and deep layer moisture scours out...leaving saturation
confined to sub-875 mb. An additional 0.05-0.15 inches of ice isn`t
out of the question for those in the higher terrain north of M-32/
Tip of the Mitt Friday evening.

Much colder air continues to spill into northern Michigan from west
to east Saturday morning as winds shift northwesterly. H8 temps
progged to vary from -13 to -16 C by mid-late Saturday morning
across northwest Lower/eastern Upper...thus activating lake effect
snow processes. Subsidence inversion heights lying steady throughout
much of the day in the 5-6 kft range aren`t necessarily something to
write home about, but nothing to scoff at either. Early indications
suggest 1-3 inches (perhaps locally higher) of snow in WNW/NW flow
targeted lake belts during the day Saturday before any lingering
synoptic moisture/support departs off to the east, and low-level
ridging impedes on the area from the south Saturday evening. Fairly
quiet weather is expected Saturday night with the exception of
lingering light lake effect snow showers across far northern
Chippewa County...limited to just flurries south of the bridge.
Zonal upper-level flow prevails by Sunday morning, although another
weak ripple in the flow is expected to spark off snow showers across
a good chunk of the CWA as early as mid-morning Sunday continuing
into Sunday afternoon.

&&

.LONG TERM...(Sunday night through Thursday)
Issued at 350 PM EST Thu Feb 23 2017

The extended period continues to host a rapidly morphing 500mb
pattern...which efficiently pushes troughs across the conus and
quickly returns to zonal. So we start our period with the Friday
night storm exiting to the east...and flow flattening rapidly
behind. This will allow enough CAA to set up a lake effect regime
for Saturday night through Sunday night. We quickly lose our wind
profile and colder air aloft into Monday, but not before most NW-W
flow snow belts should pick up some accumulating LES.

Things quiet down for Monday (and I think into Tuesday). However,
blended solutions show moisture will increase into Tuesday in
advance of the next weather maker. The latest model runs are getting
excited about a rapidly deepening closed low once again lifting from
the plains over the northern lakes for Wednesday and Thursday. That
said...there are a couple thoughts on this. 1) That`s day 7 and
beyond. 2) The last 2 or 3 storms that showed impressive
cyclogenesis a week out ended up being less than advertised. 3)
Despite one and two...the euro and GFS are already in pretty good
agreement (relatively speaking for a week out), so it`ll certainly
be something to keep an eye on.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday morning)
Issued at 355 PM EST Thu Feb 23 2017

MVFR CIGS have been very stubborn to erode this afternoon, with
low level moisture stuck under an inversion. Latest satellite
imagery is showing clearing moving into all airports. and am still
looking for things to go VFR for awhile into this evening and part
of the overnight. Then, deepening low pressure will be approaching
from the west, with winds starting to turn out of the east while
increasing. Also, snow and periods of drizzle will break out late
this evening and overnight, while also transitioning to more of a
mix with freezing drizzle/freezing rains, then just rain for
TVC/MBL/APN. Total ice accumulations of under a tenth of an inch
for TVC and MBL (hardly any for APN), with upwards of two tenths
for PLN.

&&

.MARINE...
Issued at 350 PM EST Thu Feb 23 2017

Low pressure will track from the central plains through lower
Michigan by Saturday morning, and will bring a wintry mix of
precipitation and gale force winds to most of the nearshores. The
gales will occur Friday through Friday evening as winds shift out of
the east ahead of the sfc low. These gales may need to be extended
into Saturday and Saturday night for numerous nearshores as colder
air arrives under NW winds.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY from 11 PM this evening to noon EST
     Friday for MIZ020-021-025>028-031>034.
     WINTER WEATHER ADVISORY from 11 PM this evening to 1 AM EST
     Saturday for MIZ016>019-022-023.
     WINTER WEATHER ADVISORY from 7 PM Friday to 1 AM EST Saturday
     for MIZ008-015.
LH...SMALL CRAFT ADVISORY from 1 AM to 7 PM EST Friday for LHZ349.
     GALE WARNING from 7 AM Friday to 1 AM EST Saturday for
     LHZ345>348.
LM...SMALL CRAFT ADVISORY from 1 AM to 7 PM EST Friday for LMZ323.
     GALE WARNING from 7 AM Friday to 1 AM EST Saturday for LMZ341-
     342.
     GALE WARNING from 7 AM to 7 PM EST Friday for LMZ344>346.
LS...NONE.
&&

$$

NEAR TERM...SMD
SHORT TERM...MJG
LONG TERM...KAB
AVIATION...JZ
MARINE...SMD



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