Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 011813

Area Forecast Discussion
National Weather Service Gaylord MI
113 PM EST Thu Dec 1 2016

Issued at 1046 AM EST Thu Dec 1 2016

Mid level vorticity center and associated batch of overnight widespread
light precip has exited through central Lake Huron. Next low-mid level
trough axis seen on satellite imagery and radar precip pattern in
the process of swinging down through central/eastern upper Michigan
into northern Lake Michigan. Several lake enhanced precip bands
have formed out ahead of the trough and are now sliding through NW
lower Michigan. Mainly rain, with just a hint of "mixiness" here
in the high terrain. This next batch of enhancement/modest forcing
will slide through northern Michigan through the afternoon
bringing a combination of light synoptic precip (mostly rain) and
lake enhancement, with the highest precip chances anticipated
across NW lower Michigan and parts of eastern upper.

Lake effect parameters improve tonight with arrival of yet another
short wave and pocket of upstream colder air...seen over SW
Ontario this morning. Will see some light accumulating snow across
the inland higher terrain tonight.


.NEAR TERM...(Today and Tonight)
Issued at 223 AM EST Thu Dec 1 2016

...Breezy with lake-enhanced precip...

High Impact Weather Potential...Low. Mixed rain and snow showers

Pattern Synopsis/Forecast...Nearly vertically-stacked low pressure
centered over SE Ontario will very slowly push eastward into Quebec
thru tonight. Deep cyclonic flow will linger over the Great Lakes
region in the wake of this deep low pressure system thru tonight (at
least). Short wave and surface reflection/trough will rotate around
the base of the upper trough today and thru Northern Michigan. This
feature will increase areal coverage and (to a lessor extent )
intensity of ongoing lake-enhanced precip...especially during the
afternoon as the trough axis swings thru our CWA. Another wave and
surface trough will begin to drop southward thru Northern Michigan
later tonight...providing another enhancing shot of upper support
and thus some enhancement to ongoing lake precip.

Primary Forecast Concerns...In coordination with surrounding
offices...have increased POPs to categorical this morning...and then
likely for this afternoon thru tonight for locations targeted by
W/NW low level flow for highest lake-enhanced POPs. Certainly precip
type is a concern. Model soundings still suggest the potential for
mixed rain and snow showers this morning...becoming all rain this
afternoon and then mixed rain and snow again tonight (after 22Z).
Best chance for snow mixing with the rain will be across inland
higher terrain areas based on temp profiles. Snow accumulations will
be minor (likely well under an inch) given mixed nature of precip
and overnight low temps barely reaching the freezing mark for inland


.SHORT TERM...(Friday through Saturday)
Issued at 223 AM EST Thu Dec 1 2016

...Cooler, but near-normal temperatures return...

High Impact Weather Potential: Mixed rain and snow showers expected
into the weekend.

Pattern Forecast: By Friday morning, a 160+ kt jet streak is
expected to be racing into the Pac NW with a large buckle in the jet
stream evident across the desert southwest.  Low pressure over
Quebec will help to dampen heights across the eastern two-thirds of
the CONUS with a 120+ kt jet stream embedded across the Mid-MS
Valley. Cyclonic flow across the Great Lakes is expected to persist
through the day Friday into early Saturday before winds back
southwesterly with return flow expected to prevail ahead of a wave
set to cross the region Sunday-Sunday night.

Primary Forecast Concerns: The main forecast concerns and challenges
for Friday into Saturday revolve around lingering lake induced
rain/snow shower activity. Pockets of deeper moisture will continue
to pinwheel around the western periphery of aforementioned low
pressure (centered over Quebec by Friday morning) with the best
threat for shower activity to continue through Saturday morning.
Little change in thinking from the prior shift in terms of this
period with any lingering synoptic support aided by favorable delta
T`s as cooler temps continue across the Great Lakes as the system
slides east.

Delta T`s, while sufficient to continue lake processes (13-15 C),
are far from outstanding. Limiting factors also continue to include
lowering inversion heights (dropping to 2,700 - 3,300 ft), little
moisture above the -10 C isotherm per model soundings, and a lack of
overwhelming forcing for ascent. While I`ve increased PoPs Friday
through Friday night in NW flow favored locales as lake processes
should certainly be underway, the aforementioned variables should
limit overall intensity and accumulation. Best chance for additional
minor accumulation up to half an inch or so will be early Friday
morning and again after sunset Friday evening into Friday night as
temps flirt with the freezing mark during the windows (and p-type
remains mainly snow), especially across the higher terrain of
northern Lower/eastern Upper. Little to no accumulation as you head
into the lakeside counties.  Winds begin to back by midday Saturday
(shutting off the majority of any lingering lake effect) as return
flow ramps up ahead of a wave expected to eject out of the
Intermountain West and quickly race toward the Great Lakes Sunday
into Sunday night.

.LONG TERM...(Saturday night through Wednesday)
Issued at 223 AM EST Thu Dec 1 2016

An active pattern continues through the extended with several
systems to pique ones interest. The first is expected to arrive
Sunday with p-type once again prevailing to be the main challenge.
As precip begins during the daylight hours, expecting rain to be the
primary type with snowflakes mixing in across the higher terrain. As
the sun sets, would expect snow to become the dominant p-type as
temps in the lowest 1-2 kft sufficiently cool to allow for such.
Wouldn`t be shocked if there wound up being a sneaky accumulation of
a couple of inches in spots by the time precip winds down Sunday
night/early Monday morning.

Several additional systems look possible, one Tuesday-Wednesday and
another just beyond the fcst period late Wednesday-Thursday with a
robust lake effect setup possible beyond that. As one would expect,
the lack of run-to-run guidance consistency provides little in the
way of confidence on the details, but worth monitoring over the
course of the next week as one, if not two, impactful systems may
affect portions of the Great Lakes.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 101 PM EST Thu Dec 1 2016

Lake enhanced/effect rain and snow will persist throughout much
of the TAF period. Tonight will see the mainly rain, especially
along the shorelines, to mix over and possibly completely change
over to snow. MVFR ceilings will accompany the showers. West-
Northwest winds will increase this afternoon, with gusts of 20-25
kts possible.


Issued at 223 AM EST Thu Dec 1 2016

Winds and waves will strengthen to SCA criteria today...with SCA
conditions continuing tonight and into Friday as the low level
pressure gradient tightens on the backside of the departing low.
Deep cyclonic flow...wrap-around moisture and CAA will continue to
produce lake-enhanced precip thru Friday...targeting mainly NW Lower
Michigan for highest POPs under the direction of W/NW low level flow.


LH...SMALL CRAFT ADVISORY until 7 PM EST Friday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 7 PM EST Friday for LMZ323-341-342-
LS...SMALL CRAFT ADVISORY until 7 PM EST Friday for LSZ321-322.


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