Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 172356
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
656 PM EST Sat Feb 17 2018

.NEAR TERM...(Tonight through Sunday)
Issued at 349 PM EST Sat Feb 17 2018

...Periodic chances of light precip...mainly snow thru Sunday...

High Impact Weather Potential...None.

Pattern Synopsis/Forecast...Large area of strong high pressure has
pushed just off the New England coast this afternoon. Upstream cold
front extends from NW Minnesota thru South Dakota into NE Wyoming.
Southerly low level flow/WAA continues to strengthening across the
Western Great Lakes in advance of this front...drawing low/mid level
moisture into this region. Mid level returns continue to steadily
increase over our western CWA per KAPX base ref loop. Amount of
light snow reaching the ground has expanded across Wisconsin per
upstream radars and regional surface obs. ERY is has just started
reporting light snow this past hour.

Area of widespread light snow will continue to expand from west to
east across our CWA late this afternoon and into the evening hours
along and ahead of the cold front. Latest near term models still
suggest a rather low QPF event given relatively weak lift and
limited moisture along and ahead of this front. Expect only an inch
or less of new snow accumulation thru this evening...with the
highest POPs and amounts across NW Lower Michigan. Cold front will
reach the Saginaw Bay area by around midnight or so...bringing an
end to the synoptic snow. Cold air behind this front is marginally
sufficient to produce small chances of some light W/NW flow lake
effect snow showers for the snowbelt areas...with very little in the
way of additional snow accumulation. Low temps tonight will drop
back into the teens to lower 20s.

Northern Michigan will see a break in the action Sunday morning...
before a rather busy and messy weather pattern sets up for the first
part of next week. After a brief visit from a narrow ridge axis
Sunday morning...the eastern edge of a warm front along with an area
of enhanced synoptic moisture will push thru Upper Michigan Sunday
afternoon...producing an area of light snow across Eastern Upper and
far Northern Lower Michigan...mainly along and north of a line from
TVC to GLR to PZQ. Some rain will mix with the snow across portions
of Northern Lower Michigan where warmer air will be pumped into our
region south of the warm front. High temps on Sunday will range from
the upper 20s to near 30 degrees in Eastern Upper Michigan to the
upper 30s for locations along and south of M-72.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 349 PM EST Sat Feb 17 2018

...Messy wintry mix for some with potential for some significant
icing...

High Impact Weather Potential...Increasing confidence in a wintry
mix with potential for some significant icing, mainly north of M-68.

Pattern Synopsis/Forecast...Quite an impressive thermal gradient and
moisture field develops over northern Michigan during the period.
Strong high pressure off the East Coast and several waves of low
pressure ejecting out of an active western trough pattern will lead
to a rich supply of Gulf moisture being transported all the way into
the Lower Michigan Monday-Tuesday. A quasi-stationary front
initially positioned just north of eastern Upper Sunday evening will
sag a bit southward toward the Straits by Monday morning. The first
wave will depart eastern Upper by Monday morning.

A second elongated surface low will slowly ride northeast along this
front Monday into Tuesday. A robust attendant low level jet glancing
northern Lower will bring a strong push of warmer air aloft and
abundant low level moisture. PWATs will climb 3 to 5 standard
deviations above the mean across northern Lower (highest near
Saginaw Bay), with deterministic models showing potential for PWATs
around 1" or greater, especially across our southeastern counties.
For perspective, APX sounding climatology shows only one historical
instance of PWATs >= 1 inch in February, though they may not climb
quite that high over the office here. This will be a very impressive
moisture setup for mid to late February across northern Michigan.
With a strong surface high drifting across eastern Canada, low level
winds north of the boundary will become northeasterly, providing a
feed of colder air near the surface. Combined with the warm nose
aloft, this will set the stage for a very messy wintry mix of
freezing rain, sleet, and snow across mainly the northern half of
the forecast area. Icing /could/ become significant in some areas
across eastern Upper and Tip of the Mitt.

Primary Forecast Concerns...Precipitation type and amounts will be
the main concerns through the period. Also some concern over the
exact placement of the axis of heaviest precipitation.

Diminishing precip with the first departing wave Sunday night will
remain mostly snow across eastern Upper. As frontogenetic forcing
increases along the SE drifting boundary heading into Monday and the
strong LLJ lifts into the region, will see a gradual increase in
precipitation coverage and intensity...especially heading into the
afternoon. If precip manages to arrive earlier, there could be some
areas of light freezing rain Monday morning across eastern Upper and
interior northern Lower, but surface temperatures will quickly
respond to the surge of warmer air during the afternoon. This will
lead to a period of just rain across northern Lower and perhaps even
eastern Chippewa/Mackinac counties before colder air encroaches from
the north Monday night. Lots of spread among deterministic guidance
in terms of how intense the elevated warm nose will be across
northern Michigan, with the NAM/ECMWF on the warmer end of guidance
and the GFS/GEM on the cooler end. Regardless, forecast soundings
show favorable thermal profiles for freezing rain north of M-32
Monday night into Tuesday morning. Warming daytime surface
temperatures by afternoon will change precip to rain across the Tip
of the Mitt, but a cold surface layer across eastern Upper will
allow for continued freezing rain, possibly mixed with sleet at
times.

Confidence in the exact placement of the heaviest QPF axis is still
somewhat low, but trends suggest our southern counties will be right
on the northern periphery with potential for an inch or greater of
liquid precip. With plenty of QPF and thermal profile uncertainties
still lingering, it`s very tough to forecast potential ice amounts
this far out. Since yesterday, there /is/ increased confidence in
the potential for significant icing for a portion of our area, but
confidence remains low in exact icing amounts. At this time,
wouldn`t rule out 0.1 to 0.2" north of M-68, perhaps locally up to
around a quarter inch spots across eastern Upper. The good news is
winds will be fairly light, so that may limit potential damage to
trees and power lines if those ice amounts do manifest. Will closely
monitor over the next 24 hours and continue to mention in the HWO
for now.

.LONG TERM...(Tuesday night through Saturday)
Issued at 349 PM EST Sat Feb 17 2018

Rain and wintry mix chances will continue into Wednesday. With a
drying airmass and high pressure building in, the rain and mix
should wind down by Wednesday afternoon, with a period of quiet
weather following. It looks like we could be dealing with another
potentially messy system next weekend, but there is still a lot of
uncertainty with that system. Temperatures will start near normal,
slowly warming towards the 40s by the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 643 PM EST Sat Feb 17 2018

The light snow with MVFR/IFR conditions spreading across nrn
Michigan, will wane over the next 3-4 hrs. The snow is out ahead
of a cold front that will lay across nrn lower Michigan overnight,
in and around all airports. MVFR CIGS will be possible near this
front despite drier air filtering into the region. There is some
uncertainty as to exactly which airport might see BKN MVFR skies
and for how long. This front jumps north as a warm front Sunday,
with a definite trend to VFR conditions in SCT-BKN mid level
clouds. The front will be lingering just to the NW Sunday night,
and skies are expected to remain VFR, but CIGS heights expected to
start lowering.

SW winds will veer more westerly tonight but weaken Sunday, then
ramp back up Sunday night with the development of fairly strong
LLWS.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
&&

$$

NEAR TERM...MR
SHORT TERM...MK
LONG TERM...AM
AVIATION...SMD



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