Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 130828
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
328 AM EST Sat Jan 13 2018

.NEAR TERM...(Today through Tonight)
Issued at 300 AM EST Sat Jan 13 2018

...Cold with lake effect...

High Impact Weather Potential...Low wind chills, especially this
morning.

Primary Forecast Concerns...Low wind chills and snowfall amounts.

Arctic air remains across the region through the period. Lake
effect snow has pushed a little farther inland than originally
anticipated early this morning. However, it`s rather light (closer
to just flurries) so it`s really not a big deal. Land breeze
development from cold air drainage should tend to push activity a
little farther west over the next few hours. Lake effect snow
showers will continue today into tonight, especially near the
Lake Michigan shoreline counties and near Whitefish Point.
Activity will try to push inland some later today into tonight as
mean winds slowly back into the northwest this afternoon and the
west southwest early Sunday. However, wind fields are rather light
(around 10 knots) so activity will have a hard time moving too
far inland and likely hang closer to the lake shore despite the
backing winds. Low level moisture increases today with mean
850-700 mb rh going from about 50 percent at 12z to near 70
percent at 14/00z...then holds at near 70 percent tonight.
Inversion heights grow a bit today to around 5000 feet or so.
Generally speaking an inch or two of accumulation expected today
in favored locations (surrounding GT Bay and Whitefish Point) with
locally up to around three inches possible. Another inch with
locally up to two possible tonight. Highs today ranging from the
upper single digits north to the middle teens southwest. Lows
tonight ranging from the single digits below zero north to around
10 above southwest. Wind chill readings in the teens below zero
eastern upper to the single digits below zero northern lower this
morning, the single digits above zero this afternoon and the
single digits below zero tonight.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 300 AM EST Sat Jan 13 2018

...Snow threat increases...

High impact weather potential: Growing concern for an accumulating
lake enhanced snow event for small portions of the area Sunday night
into Monday evening.

Pattern synopsis/forecast: Pattern set to get a bit more amplified
as we head into early next week, setting the stage for a strong
shortwave to dig southeast into our area on downstream side of sharp
western ridge axis. Although this system will be largely moisture
starved, favorable over-water thermodynamics and simple pattern
recognition supports the potential for significant lake enhanced
snow...first in favored south flow areas Sunday night, transitioning
to the rare southeast/east flow areas Monday.

Primary forecast concerns/challenges: While widespread light snow is
expected Sunday night and Monday, primary forecast emphasis is on
those favored lake enhanced snow threat areas mentioned above.

Details: Biggest story for Sunday is the continuation of well below
normal temperatures, with afternoon highs expected to largely remain
in the teens. Developing southerly winds on backside of retreating
high pressure will keep wind chill readings in the single digits.
Simple inertia and air/water thermal gradient will keep lake snows
going, transitioning from west flow areas to start the day to south
favored areas by evening. Lack of any synoptic support/moisture will
keep snow showers disorganized and only capable of producing minimal
accumulations.

Sharp shortwave trough and attendant weak surface reflection will be
diving southeast into the western Lakes Sunday evening, looking to
slide into lower Michigan by Monday evening. This will spread a
large, although likely disorganized, area of light snow into our area
overnight Sunday, lasting through the day Monday. Precipitable water
values remaining under a quarter of an inch and southward passing
best upper jet support should keep snow amounts minimal
overall...generally looking at one to two inches. However, that will
likely not be the case in those favored lake enhanced areas as
synoptic moisture contribution and increasing inversion heights
(bufkit has lake induced convective layer pushing 8kft) really look
to ramp-up and organize the lake processes. "Warming" H8
temperatures right into the prime dendritic growth zone and enhanced
omega within this thermal regime should only help the snow-producing
cause. Question becomes one of wind direction, and that remains a
bit more formidable question to answer. Latest guidance progs have
best snows straddling the Mackinac/Schoolcraft county line, give or
take a few miles. Not completely sold on this idea just yet, and
fully expect some changes to this better band placement as the event
draws nearer. Gotta believe those impacted will see several inches
of snow, with some headlines possible needed. Flow backs southeast,
and eventually easterly, late Sunday night into Monday. While this
will punt Lake Michigan snow contribution out of our area, Lake
Huron induced snows take center stage into far eastern upper
Michigan and parts of northeast lower Michigan. Always a less
confident endeavor when forecasting snow off Lake Huron, but once
again pattern recognition supports good to excellent lake
enhancement processes. Shifting winds will likely limit duration of
heaviest snows, but would expect to see inch per hour or greater
snows punch into areas near Drummond Island at some point Monday,
and then rapidly transition west into the rest of east/southeast
Mackinac/Chippewa Counties, and then eventually into northeast lower
Michigan. While totals may not be too impressive, simply because of
lack of duration, snow intensity will likely result in some travel
impacts.

&&

.LONG TERM...(Monday night through Friday)
Issued at 300 AM EST Sat Jan 13 2018

High impact weather potential: Lingering lake enhanced snow threat
Monday night into Tuesday.

Details: Low pressure departs off to the east Monday night into
Tuesday, ending the threat for widespread light snow in the process.
Northeast flow lake enhancement expected Monday night into northeast
lower Michigan, likely bringing some additional snow accumulation
along with it. Flow goes north and eventually northwest Tuesday and
Tuesday night, bringing lake effect snow showers back off Lake
Michigan. Support will be weakening with time, which will likely
help keep snow shower intensity in-check some. Rest of the extended
looks to feature moderation as longwave trough gets the boot east,
replaced by more of a zonal upper level flow regime across the
northern Conus. If things work out as currently planned, we way see
readings top freezing for parts of northern lower Michigan by
Friday. No big systems expected, although cannot rule out a some
additional light snow activity with any passing waves.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1045 PM EST Fri Jan 12 2018

Arctic air parked over the Great Lakes region will continue to
produce light northerly flow lake effect snow showers overnight
thru Saturday. Locations targeted for these snow showers will
remain along the Lake Michigan shoreline around TVC and MBL.
Conditions will drop to MVFR/possibly IFR within some of these
snow showers. Northerly winds gusting to 15 to 25 kts will
gradually diminish thru Saturday as the strong high pressure
center begins to build into the Western Great Lakes region.


&&

.MARINE...
Issued at 300 AM EST Sat Jan 13 2018

Gusty northerly winds through much of this morning. Winds will
then gradually decrease this afternoon while backing a little
more northwest. Winds continue to back tonight into Sunday into
the south. Lake effect snow showers will continue through the
period, becoming enhanced Sunday night from a wave approaching
from the northwest.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY until 11 AM EST this morning for LMZ323-342-
     344>346.
LS...NONE.
&&

$$

NEAR TERM...AS
SHORT TERM...MB
LONG TERM...MB
AVIATION...MR
MARINE...AS



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