Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 132045
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
345 PM EST Sat Jan 13 2018

.NEAR TERM...(Tonight through Sunday)
Issued at 345 PM EST Sat Jan 13 2018

...Lake effect snow lingers...

High Impact Weather Potential...reduced visibilities in lingering
lake snows tonight. Flow backs SW with some heavier snow showers
pushing into Upper Michigan Sunday.

Pattern Synopsis/Forecast...Afternoon surface analysis reveals
1042MB high pressure over the upper Midwest still centered over
the South Dakota/Minnesota border but slowly edging into the
western Great Lakes. Primarily N/NNW flow remains established
across the state although pressure pattern remains muddied by
lake aggregate troughing stretching from eastern Lake Superior
down through the NE lower Michigan coastline. N/NNW lake snow
showers have continued to impact both coasts especially the Grand
Traverse Bay region where briefly heavier snow showers have
reduced VSBYs to 1/2SM at TVC with snowfall rates up to one inch
per hour. Snow showers have also persisted across Presque Isle
county into the Alpena area also with some lower VSBYS.

However...winds are in the process of backing at this juncture
with snow shower activity beginning to push back inland (and out
of the APN area) while becoming a little more disorganized. There
is also a daytime heating component evident...with inland STCU
cloud bands showing up on satellite and heating induced snow
shower pockets streaming down through southern lower Michigan.
Heating induced snow shower component will diminish quickly this
evening.

Primary Forecast Concerns...evolution of lake effect snow through
Sunday.

Low level mean flow will back to southwest by Sunday morning and
south through the day Sunday...as high pressure migrates down and
through the Ohio Valley and low pressure edges into the upper
Midwest by Sunday evening. Ongoing lake effect snows will of
course follow suite and spread back inland and eventually up the
Michigan coastline through the course of the night. We may see a
bit of an uptick in lake effect snow intensities this evening
(particularly across eastern upper MI) as smaller pocket of
deeper moisture (evident on satellite imagery) rotates down
through far northern Michigan. But overall...anticipate relatively
minor accumulations through tonight...on the order of one to
three inches where snow showers persist.

Winds backing south on Sunday will shift focus of Lake Michigan
snow showers up into parts of eastern upper Michigan...west of
I-75. Still anticipate minor accumulations through the day
anyway...until the next synoptic system arrives Sunday night (see
below). So at this juncture...plan on no winter weather headlines
through the near term. We may need something for Sunday going into
Monday with the next system but will defer that to later shifts.

&&

.SHORT TERM...(Sunday night through Tuesday)
Issued at 345 PM EST Sat Jan 13 2018

...Snow Sunday Night into Monday...

High Impact Weather Potential...Moderate to heavy snow amounts
possible in the western part of Mackinac county Sunday night into
Monday.

Pattern Synopsis/Forecast...500 mb shortwave trough drops into the
Upper Great Lakes trough in the evening, which has already spun up a
clipper sfc low. The southerly flow and the -16c or colder 850 mb
temperatures will produce lake enhanced snow bands along in N Lake
Michigan on the south shore of the UP. Temperatures on all of the
models look to remain consistent through 12z/Mon. Looks like, from
the model precipitation it will be just west of the
Mackinac/Schoolcraft county border. As the sfc low continues into
the Upper Great Lakes, the winds continue to back to the SE and
shift the threat more to the west. By 00z/Tue the winds are east
with some enhancement possible along the northern Lake Huron shores
along in E Upper and in NE Lower. The main sfc low is east of the
state, by 12z/Tue, and backing the winds to the NE. This would end
the threat to most of the region, but for down the Lake Huron Shore,
where a band impacting the region from APN down to OSC, is possible,
and another possibly along NW Lower shores from CVX to Sleeping Bear
Dunes. By 21z/Tue, we are on the back side of the upper low (500 mb)
with the heights rapidly rising.

Primary Forecast concerns...All of the lake enhancement/effect snow
bands will be dependent on the wind directions and the residence
times over the the lake, and where they come ashore. After some
discussions with MQT, agree that the most likely placement Sunday
night will be in their area, in southern Schoolcraft county. Looks
like moderate amounts of snow in Western Mackinac county adjacent.
There is a small chance for the flow to go east, but think, based on
the storm system moving in, that the flow will set up to the west of
the forecast area.

There is uncertainty on the Lake Huron band later on Monday
night/Tuesday. will have to look at subsequent model runs to see
where that will end up. It too, could be significant.


&&

.LONG TERM...(Tuesday night through Saturday)
Issued at 235 PM EST Sat Jan 13 2018

After some lingering north flow lake effect Wednesday morning,
temperatures will begin to moderate through the weekend, with
temperatures above freezing for most by Friday. Weather is
expected to remain quiet for the most part, but can`t completely
rule out an occasional shortwave kicking off some light showers.
This could come in the form of rain or rain/snow mix with the
warmer weekend temperatures.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 111 PM EST Sat Jan 13 2018

NNW flow lake effect clouds/snow showers will continue to impact
TVC/MBL and APN this afternoon. Minor snow accumulations with
lower snow ratios...however smaller flake sizes are very effective
at reducing VSBYS. As a result...flight categories keep bouncing
from MVFR to LIFR as the bands move through...difficult to
forecast in the context of a terminal forecast. Lake clouds and
snow showers should move out of the APN area by the end of the
afternoon and tonight...but will continue to impact TVC/MBL for
through the night into Sunday.

PLN remains VFR this afternoon and much of tonight. Winds backing
SW by Sunday morning will eventually push lower clouds and snow
showers into that terminal site for a time early Sunday morning.


&&

.MARINE...
Issued at 345 PM EST Sat Jan 13 2018

Northerly flow this afternoon backs southwesterly tonight and
south on Sunday. Winds/waves will remain below headline criteria
through tonight. But increasing wind/waves Sunday may require a
small craft advisory on the Lake Michigan nearshore areas later
Sunday into Monday.

&&

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

$$

NEAR TERM...BA
SHORT TERM...JL
LONG TERM...AM
AVIATION...BA
MARINE...BA



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