Area Forecast Discussion
Issued by NWS Gaylord, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KAPX 040754
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
254 AM EST Sun Dec 4 2016

.NEAR TERM...(Today and tonight)
Issued at 251 AM EST Sun Dec 4 2016

...Accumulating snow later today and tonight...

High Impact Weather Potential: Light snow accumulation to bring
periods of slick travel, especially this afternoon into this
evening.

Pattern Synopsis/Forecast: Hard to believe (typed sarcastically of
course), but still some weak lake showers coming off northern Lake
Michigan, this despite light and disorganized winds under overhead
ridging. Light southerly return flow focusing these showers/snow
showers more so into western Mackinac County and the tip of the
mitt. General light nature of these showers and marginal surface
temperatures have resulted in minimal accumulations and impacts.
Apex of overhead mid level ridging is pushing east of the area at
this early hour, with deep layer return flow surging north into the
Corn Belt between it and fast approaching central plains shortwave
trough. Already an area of mixed rain and snow tied to this
northward surging moisture plume, with this area expected to
continue to expand as it heads northeast through this morning as
forcing does the same. This area of forcing/precipitation will make
a run into and through our area this afternoon and evening,
essentially bringing the first widespread accumulating snow event of
the season to all of northern Michigan.

Primary Forecast Concerns: Timing of snowfall and total snow
accumulation. Possible headline considerations.

Details: Other than some of those lingering very light lake induced
showers, the morning should start out a quiet one as high pressure
and upper level ridging slowly depart. Weather definitely turns more
active this afternoon and evening as upstream shortwave trough races
northeast, becoming negative tilt in the process. Attendant strong
surge of QG forcing collocated nicely with plume of deeper moisture
(precipitable water values up near half an inch), both of which are
set to slide through our area later today. Thermal progs are
marginal to begin the event, so initially expecting a rain/snow mix
as precipitation arrives later this morning into early this
afternoon. Magnitude of lift and cooling through melting should
transition all areas over to snow rather quickly during the
afternoon, although lake modification may keep areas right along
Lake Huron mixy for a bit longer. System is a quick mover, but given
forcing and available moisture, hard to argue with guidance blend
QPF totals around a quarter of an inch...give or take a few
hundredths. To complicate matters, low level thermal environment
remains cold enough for some potential lake enhancement off both
northern Lake Huron and northern Lake Michigan. With Convective
boundary layer winds going southerly, appears best Lake Michigan
contribution will remain just west of Mackinac County. Lake Huron
impacts a little more problematic, with at least some hints of lake
enhancement running right up the St. Marys river into eastern
Chippewa County (including Sault Ste Marie). Cooling thermal
profiles and strong support for periods of enhanced lift in the
dendritic growth layer suggests snow-to-liquid ratios pushing
respectable 12-14:1 values early this evening, especially away from
the big waters. All told, inherited 1 to 3 inch snow totals still
expected, with the highest amounts centered across interior sections
of eastern upper (where local amounts pushing 4 inches is possible
along the St. Marys River) and northern lower Michigan. Snow winds
down quickly by later this evening and overnight as forcing races
off to the northeast. May see a brief period of drizzle/freezing
drizzle as mid level moisture departs. Post-system airmass remains
cold enough for some continued lake contribution as winds turn
southwest later tonight. Convective boundary layer remains awfully
shallow, suggesting any lake effect snow showers will remain light
at best.

Headline consideration: Do not expect widespread total snow
accumulations to approach advisory levels, and winds do not appear
strong enough to support much blowing and drifting. Do believe
there will be some travel impacts, especially later today when
snowfall rates overcome initial warm road conditions. After
collaboration with surrounding offices, have decided to forgo
specific headlines, using the special weather statement to
highlight expected travel impacts.

&&

.SHORT TERM...(Monday through Tuesday night)
Issued at 251 AM EST Sun Dec 4 2016

...Drying out Monday followed by a few showers on Tuesday...

High Impact Weather Potential...Minimal.

Pattern Synopsis/Forecast...Weak upper ridge and surface high will
build over the region on Monday with low level subsidence leading to
drying out above the boundary layer. An occluded low over southwest
Ontario will push a front through the western Great Lakes on
Tuesday. Another low with more significant moisture will largely
stay south of the area as it tracks through the Ohio Valley on
Tuesday.

Primary Forecast Concerns...Several SREF members as well as the NAM,
ECMWF, NMM, and ARW show a few lake effect showers lingering into
Monday morning over the tip the mitt and eastern Upper before weak
WAA takes effect and winds back from west to southwest. The rest of
the day and Monday night will be dry as weak upper ridging and drier
air aloft settle over the region. This will allow for a decrease in
middle/high clouds, but a steepening low level inversion will trap
boundary layer moisture and prevent much net loss in low level cloud
cover, particularly Monday night as weak isentropic lift develops.

By Tuesday the upper ridging and surface high will have moved off to
the east as a cold front lifts northeast into the area. Moisture
associated with this front will be limited with PWATs under a half
inch, but have gone with 20 to 30 percent PoPs. The better moisture
will be associated with a stronger system to our south traveling
through the Ohio Valley. Recent model runs have been fairly
consistent with this low tracking just far enough south to keep the
bulk of its precipitation out of the APX forecast area. At this
time, however, cannot entirely rule out our southeast counties
seeing some precip from this system. Thermal profiles would support
just rain during the day, changing over to snow Tuesday evening. As
southerly winds veer to the southwest and temperatures fall behind
the front, lake effect snow showers may develop off Lake Superior
and northern Lake Michigan.

Temperatures Monday and Tuesday will be above normal with highs
around 40, which is close to MOS guidance. Normal highs for this
time of year are in the low to mid 30s.

&&

.LONG TERM...(Wednesday through Saturday)
Issued at 251 AM EST Sun Dec 4 2016

Active weather returns to the area for the middle and end of next
week as vertically stacked low pressure spins near Hudson Bay with
broad troughing centering itself over the midsection of the country.
There continues to be a lack of guidance consistency with its handle
on several pieces of energy expected to pinwheel around the southern
periphery of aforementioned troughing and their direct impact (if
any) locally. Worth watching for any shift in guidance over the next
several days in terms of any synoptically driven precip brushing the
forecast area during the Wednesday-Thursday timeframe. One thing of
more certainty and clearly the greatest potential impact is the
arrival of cold air and lake effect snow. H8 temps begin to cool
Wednesday continuing through the end of the week with LES expected
to ramp up significantly. Forecast soundings become very favorable
for efficient lake effect snow processes Thursday into Friday (aided
by a weak shortwave invigorating the chilly air and providing an
uptick in deep layer moisture/synoptic support) as H8 temps fall to
-10 to -15 C, low-level lapse rates steepen, and max negative omega
values peg directly in the DGZ at various times. Still a few days
out from detailing potential snow amounts and possible impacts, but
it`ll suffice to say that this will be our first extended bout of
winter this season.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1152 PM EST Sat Dec 3 2016

Overcast skies tonight with a mix of mostly VFR and some MVFR ceilings.
Flight conditions expected to deteriorate Sunday afternoon as rain/snow
move in from the southwest...eventually changing over to all snow.
IFR ceilings visibilities expected to develop after 18z.

&&

.MARINE...
Issued at 251 AM EST Sun Dec 4 2016

Southeast winds will be on the increase today, with winds
becoming south and southwest heading through tonight and Monday. It
appears conditions will remain just below SCA criteria most waters,
although marginal advisory conditions may occur on Whitefish bay
given enhancement experienced in a southeast wind regime. More
significant marine concerns arrive later this week as a surge of
much colder air drops across the region.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...SMALL CRAFT ADVISORY from 7 AM this morning to 7 PM EST this
     evening for LSZ321.
&&

$$

NEAR TERM...MSB
SHORT TERM...MEK
LONG TERM...MJG
AVIATION...JPB
MARINE...MSB


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.