Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 240448

Area Forecast Discussion
National Weather Service Gaylord MI
1148 PM EST Thu Feb 23 2017

Issued at 1043 PM EST Thu Feb 23 2017

...Wintry mess on the way...

Overview: Potent surface low is located over the Oklahoma/Kansas
border this evening, ahead of a low amplitude short wave over
Nebraska and strong upper jet core punching across the SW states
into the lower Mississippi River Valley. Tight thermal gradient is
unfolding from the central plains into lower Michigan with axis
of warm advection and deformation forced precip stretching along
that gradient from lower Michigan into Nebraska, eastern edge just
getting into northern lower Michigan in the last few hours.
Precip runs the gamut from snow north to rain south along the
precip shield with mainly snow reported in the SW counties
(MBL/CAD) thus far.

Rest of tonight through Friday morning...surface low will advance
to near chicago by midday Friday pushing tight thermal gradient
and axis of precip up through northern lower Michigan. Precip
type remains the biggest forecast headache.

Most recent operational and blended model guidance has trended
maybe just a tad colder in thermal profiles across this CWA
through Friday morning, suggesting a bit longer period of snow for
areas north of M-72. Always a tough call when dealing with such a
tight thermal gradient. But given the surface low track through
southern lower Michigan, a bit longer period of snow and higher
snow accumulations may be the way to go, again particularly for
areas north of M-72. Warm nose and a wintry mix (sleet/freezing to
rain) of precip will eventually get into northern Michigan late
overnight and heading through the day Friday.

One item of note...12Z Hires ARW east paints a narrow swath of
three quarter of an inch QPF across northern lower Michigan
through Friday morning (mesoscale banded precip perhaps?). If
true, parts of northern lower Michigan north of M-72 could end up
with with much more than the 2-4 inches we have in the forecast.


.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

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 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 06Z TAFS through 06Z Friday night)
Issued at 1148 PM EST Thu Feb 23 2017

Storm system in the central plains will track up through lower
Michigan through the day Friday. This will bring a wintry mess of
precipitation (snow/sleet/freezing rain) up into northern lower
Michigan overnight through the Day Friday. Precip will eventually
transition to mainly rain across most of northern lower Michigan
on Friday. Expect IFR conditions to develop later tonight and
remain IFR through Friday.


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.


MI...WINTER WEATHER ADVISORY until noon EST Friday for MIZ020-021-
     WINTER WEATHER ADVISORY until 1 AM EST Saturday for MIZ016>019-
     WINTER WEATHER ADVISORY from 7 AM Friday to 1 AM EST Saturday
     for MIZ008-015.
LH...SMALL CRAFT ADVISORY until 7 PM EST Friday for LHZ349.
     GALE WARNING from 7 AM Friday to 1 AM EST Saturday for
LM...SMALL CRAFT ADVISORY until 7 PM EST Friday for LMZ323.
     GALE WARNING from 7 AM Friday to 1 AM EST Saturday for LMZ341-
     GALE WARNING from 7 AM to 7 PM EST Friday for LMZ344>346.


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