Area Forecast Discussion
Issued by NWS Gaylord, MI

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082
FXUS63 KAPX 131531
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1131 AM EDT Fri Oct 13 2017

.UPDATE...
Issued at 1130 AM EDT Fri Oct 13 2017

Didn`t have to do much in the near term. Did start to tweak the
forecast for Saturday, with the morning being a little drier
before the front moves back north. will be diving into that with
the new model runs.

&&

.NEAR TERM...(Today through Tonight)
Issued at 304 AM EDT Fri Oct 13 2017

High impact weather potential: None.

Pattern synopsis and forecast:

Upper ridging was in place over the eastern conus early this
morning, with troughing across the west. Nrn Michigan was within
increasing SW mid level flow between these two features, with warm
air aloft continuing to support an inversion aloft. S/SE winds which
advected low level moisture/clouds northward yesterday, was stuck
underneath this inversion, resulting in areas of drizzle. The low
clouds were rather widespread, seen all over the western Great Lakes
and even back through Wisconsin and eastern MN, just ahead of a cold
front. Temperatures around nrn Michigan were in the 50s, rather mild
underneath the veil of low clouds.

Low level moisture remains locked underneath the inversion through
the day, with what appears to be little in the way of anything
helping to mix things out for any appreciable sun. Cloudy skies
expected on the whole with temperatures only rising into the lower
half of the 60s for most areas. Areas of drizzle/light rain are also
expected through mainly this morning. The upstream cold front will
gradually make it`s way into the region late this afternoon and this
evening. Winds will be fairly light and still see no reason for much
mixing to help scour out clouds. Forcing will be rather weak, with
only some increased DPVA and WAA through the night, with the thought
that maybe it`ll be more so late tonight. Will bring more bona fide
shower chances accordingly, but wouldn`t surprised if precip was
still more light rain/drizzly. Lows tonight still remaining rather
mild along and south of the front for the SE CWA, with readings in
the lower half of the 50s. Cooler behind it, with the lower half of
the 40s across eastern upper.

&&

.SHORT TERM...(Saturday through Sunday)
Issued at 304 AM EDT Fri Oct 13 2017

...Wet weekend on tap; windy and cooler on Sunday...

High Impact Weather Potential...Periods of heavy rain likely
Saturday night along with a chance of thunderstorms. Gale force wind
gusts likely over the Great Lakes on Sunday.

Pattern Synopsis/Forecast...Cold front initially stalled downstate
Saturday morning will lift back through northern Michigan as a warm
front during the day. This will occur in tandem with a cyclone over
the Central Plains rapidly deepening as it ejects toward Wisconsin.
By the time the low tracks into northern Michigan late Saturday
night, it`s central pressure is progged to drop to 2 to 3 standard
deviations below the mean for mid-October, continuing to drop as the
system passes into Ontario and Quebec on Sunday. Most of northern
Lower should lie within the warm sector for a time Saturday night,
resulting in rising nocturnal temperatures. At the same time, an
intense low level jet will nose into northern Lower, leading to very
strong moisture transport and PWATs climbing above 1.6 inches across
much of the area (+3 to 4 standard deviations).

A cold front will then sweep through northern Michigan shortly after
daybreak Sunday with gusty NW winds leading to strong cold air
advection and steadily falling temperatures through the rest of the
day. Precipitation will transition from synoptic rainfall to lake
effect showers by afternoon.

Primary Forecast Concerns...Rainfall, thunder, and wind potential
with Saturday night into Sunday`s system.

With strong signals continuing to show up in deterministic and
ensemble guidance, confidence is increasing in a very wet Saturday
night into Sunday morning with periods of heavy rain. However,
important details such as exact location of heaviest rainfall axis
and timing still remains somewhat murky given continuing model
fluctuations in the system`s intensity and track. The 00Z GFS/ECMWF
show a slight southward shift, while the Canadian has a dramatic
southward shift and the NAM takes it a bit farther north into the
U.P. The 00Z NAM also shows somewhat explosive deepening over Lake
Superior on Sunday, whereas the other models remain more progressive.

Regardless, guidance is in good agreement with a substantial
increase in moisture late Saturday into Saturday night.
Strengthening isentropic lift and fgen along the warm front will
lead to increasing rain chances through the day Saturday from south
to north. Additional forcing will come from a strong 60+ knot 850mb
jet Saturday night. Ingredients coming together for a widespread
rain event with periods of heavy rainfall overnight. Pretty good
likelihood for some embedded elevated convection as well with a few
hundred J/kg of MUCAPE coming into play. Looks like the bulk of the
heaviest rain will depart shortly after daybreak Sunday as a
significantly drier air sweeps in behind the cold front. Current
expected axis of heaviest QPF lies south of M-32 where 1.5 to 2
inches is forecast.

A tight pressure gradient over northern MI on Sunday with 850mb
winds of 40-50 knots combined with strong CAA will lead to effective
downward momentum transfer. Thus, a windy day is on tap, especially
over the Great Lakes where gale force gusts are looking increasingly
likely. Inland gusts of 30-40 mph are expected.

.LONG TERM...(Sunday night through Thursday)
Issued at 304 AM EDT Fri Oct 13 2017

Shot of colder air behind Sunday`s cold front doesn`t stick around
for long, as 850mb temps already start to jump again by Monday
afternoon. This along with steady influx of drier air will bring a
fairly quick end to any lingering light lake effect rain showers.
The rest of the period looking pretty quiet as a broad surface high
initially over the midsection of the country slides toward the Mid-
Atlantic and a subtle upper ridge drifts across the Great Lakes.
Some hints at a possible system for Wednesday night into Thursday,
but models differ in regard to intensity of upper trough possibly
dropping through the Great Lakes. Temperatures will gradually
moderate through the week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 646 AM EDT Fri Oct 13 2017

MVFR and occasional IFR ceilings are expected to continue through
much of the day, as abundant low level moisture will continue to
remain stuck underneath an inversion, aiding in low clouds and
areas of light rain/drizzle. While the prevailing condition is
expected to be MVFR, there will be short-lived periods of VFR.
S/SE winds will remain rather light while shifting more SW, then
more W/NW tonight behind a passing cold front. Maybe a few gusts
into the teens this afternoon and early evening ahead and with the
front. Much drier air bleeds southward late tonight, with skies
clearing out at PLN, possibly APN/TVC at the end of the TAF
period.


&&

.MARINE...
Issued at 304 AM EDT Fri Oct 13 2017

Low end advisory level gusts still expected through today with
overlake instability, especially over Lake Michigan. An upstream
cold front will approach late this afternoon and evening, with a
weaker gradient/light winds. Winds shift from southerly to light NW
tonight, before turning easterly and increasing ahead of low
pressure that arrives with showers a possibly some rumbles of
thunder Saturday into Sunday. Winds are expected to be highly
variable over the weekend, shifting from easterly to strong out of
the W/NW Sunday. Gales and maybe even storm force winds are expected
over this time, mainly Sunday.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 7 PM EDT this evening for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 7 PM EDT this evening for LMZ323-341-
     342-344>346.
LS...SMALL CRAFT ADVISORY until 7 PM EDT this evening for LSZ321-322.
&&

$$

UPDATE...JL
NEAR TERM...SMD
SHORT TERM...MK
LONG TERM...MK
AVIATION...SMD
MARINE...SMD



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