Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 220255
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
955 PM EST Sat Jan 21 2017

.UPDATE...
Issued at 955 PM EST Sat Jan 21 2017

Scattered rain showers continue to develop across much of our CWA
late this evening along and ahead of a trough axis associated with
low pressure over the Upper Mississippi Valley...NW Wisconsin and
Western Upper Michigan. Entire CWA remains above freezing...and
will likely remain so even overnight...although some low level
cooling will take place. Main forecast issue thru Sunday morning
remains the persistence of widespread dense fog. Still expect
dense fog will continue to expand throughout our entire CWA
overnight as the boundary layer continues to cool...ample low
level moisture remains in place enhanced by a melting snowpack and
winds remain light/calm. Will certainly maintain the Dense Fog
Advisory for all counties overnight into Sunday morning. Also
expect scattered showers will remain possible thru the night...
remaining all liquid as temps hold above freezing.

&&

.NEAR TERM...(Tonight)
Issued at 309 PM EST Sat Jan 21 2017

...More fog...

High Impact Weather Potential...dense fog continues into Sunday.

Shortwave trough is currently swinging northward through the
upper Midwest/western Great Lakes, pronounced circulation clearly
evident on water vapor imagery advancing through Wisconsin into
northern Michigan. Baggy surface low pressure analyzed over the
upper Midwest with a warm front stretching eastward through the
lower lakes region. Lots of stratus/fog north of the warm front
across most of Michigan, although warm front has been making a
northward push with drier and warmer air lifting through lower
Michigan. It has largely cleared out along the I-94 and I-96
corridors and temperatures are near 60F along the Michigan
southern border.

Up this way, still some very spotty showers moving through the
northern half of the CWA along advancing theta-e gradient into
northern Michigan. But otherwise, widespread stratus and still
quite a bit fog out there this afternoon with no real big
improvement noted today.

Shortwave trough will slowly rotate up into southern Ontario
through the day Sunday. Additional showers will remain a
possibility along the north/eastern edge of this feature tonight
into Sunday. But bigger issue continues to be fog. As mentioned,
already quite a bit of fog heading into the evening. And with
light winds, cooling boundary layer...fog is likely to remain or
become dense once again. Thus, will hoist yet another dense fog
advisory for tonight through Sunday morning, in collaboration with
surrounding WFOs.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 309 PM EST Sat Jan 21 2017

...Light rain Sunday night and Monday transitions to light snow
Monday night...

High Impact Weather Potential...Minimal, but a brief wintry mix will
be possible Monday night as rain transitions to snow.

Pattern Synopsis/Forecast...Michigan will lie within an area of
split weak flow aloft Sunday night and Monday as a deep cutoff low
wobbles from the Tennessee Valley into the Mid-Atlantic and a
developing shortwave trough pivots across the Upper Midwest. At the
surface, an inverted trough will linger over northern Michigan
Sunday night through Monday, giving way to persistent easterly flow.
A tightening temperature gradient will develop west of I-75 Sunday
evening, but the easterly low level flow will push the best
frontogenetic forcing west of Lake Michigan by Monday morning. A
decent plume of moisture will come into play Sunday night and Monday
with PWATs climbing to around 0.7 inches. The flow pattern changes
Monday night into Tuesday as upper level ridging develops behind a
passing shortwave trough. This will also usher in some cooler 850mb
temperatures.

Primary Forecast Concerns...Ptypes Monday night into Tuesday will be
the main forecast challenge as somewhat colder air comes into play.
There looks to be a very small chance for spotty freezing rain
across parts of eastern Upper late Sunday night into Monday morning
as surface temperatures there get close to freezing, but most
deterministic models and ensembles suggest lows Sunday night will be
about 33F or warmer there. Wouldn`t completely rule out the
possibility of some icy patches on less-traveled roads that still
have a bit of lingering snowpack, but overall potential looks low so
have left out of the forecast. Chance PoPs will spread westward
overnight into Monday, and as colder air spills in Monday night
there will be a better chance for rain briefly transitioning to
mixed wintry precip before changing over to light snow. The NAM
still shows a more favorable mixed precip sounding than the GFS, and
the GFS itself has more colder air at 850mb than the NAM, ECMWF, and
Canadian Monday night. Thus, would not discount the possibility for
a brief wintry mix, but impacts are expected to be minimal...perhaps
a trace of ice across mainly eastern Upper. Warming temperatures
Tuesday morning will cause the snow to transition back to rain with
another very brief wintry mix transition possible in between. All
told, snow accumulations of less than an inch are expected through
Tuesday morning.

.LONG TERM...(Tuesday night through Saturday)
Issued at 309 PM EST Sat Jan 21 2017

The big picture in the extended period will be unsettled weather
with a general cooling trend from Wednesday to Saturday.  The 500mb
pattern shows the conus dominated by broad troughing that slowly
shifts east...with ridging building on the west coast by
Saturday.

A closed low develops in the central plains and sets it sites on the
great lakes...with an ETA of Wednesday.  It`s track will dictate
exactly how Northern Michigan is effected...with most solutions
agreeing (for today) of a track across the midsection of the lower
peninsula....which is a bit of a southern shift from yesterday. This
can still and likely will, change by midweek...but will remain the
main forecast challenge in the long term. The temperature regime and
this storm track would indicate we`ll be dealing with P-type issues,
at least across the lower peninsula...while the Eastern Upper may be
looking at all snow (and maybe some decent accumulations at that).

Colder air begins to infiltrate on Thursday...the question will be
if it will be cold enough to generate good enough over-lake
instability to get the LES machine cranking. Moisture will be
abundant and wind fields will line up for a good period...all we
need is for temperatures to cooperate. It is still too far off to be
confident in this call...but certainly warrants chance pops at least.

Berger

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 600 PM EST Sat Jan 21 2017

IFR/LIFR conditions are expected at all Northern Lower Michigan
TAF sites tonight and Sunday as ample low level moisture...light
winds and a melting snowpack continue to produce widespread
stratus and dense fog across all of Michigan.

&&

.MARINE...
Issued at 309 PM EST Sat Jan 21 2017

Light winds/waves will persist through the weekend and into early
next

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...DENSE FOG ADVISORY until 1 PM EST Sunday for MIZ008-015>036-041-
     042.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...MLR
NEAR TERM...TBA
SHORT TERM...MEK
LONG TERM...KAB
AVIATION...MLR
MARINE...TBA


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