Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 141732
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
132 PM EDT Sat Oct 14 2017

.NEAR TERM...(Today through Tonight)
Issued at 320 AM EDT Sat Oct 14 2017

High impact weather potential: Heavy rainfall. Potential flooding?
Maybe a rumble of thunder.

Pattern synopsis and forecast:

A cold front has dropped just south of nrn Michigan early this
morning with a continued corridor of deeper moisture on it`s
backside. This is still resulting in widespread clouds and pockets
of light rain and drizzle across the SE CWA. Drier air has been
trying to filter southward through eastern upper with skies already
cleared out over much of that area. The flow aloft was fast out of
the WSW with a well defined shortwave trough working through the
central Rockies. Forcing was beginning to increase out ahead of the
wave, with strengthening low to mid level WAA and right entrance
region upper divergence from 120kt jet across the central conus.
This was just ahead of developing in the lee of the Rockies.

The front will hold just south of the CWA with much of the srn areas
maybe hanging in clouds, while nrn areas will likely see some decent
sunshine for at least a good chunk of the morning. This will change
rather quickly, as the aforementioned forcing starts pushing into
nrn Michigan later today and especially tonight. Skies will become
cloudy, with rains developing along the frontal boundary, and
shifting northward with time through tonight as it turns to a warm
front. Moisture deepens incredibly to 1" PWAT in eastern upper to
1.85" near Saginaw Bay. The upper divergence and WAA continue to
strengthen as well. This all adds up to definite rains, heavy at
times, and the potential for 1.50" to 2.00" of rain across portions
of the SE CWA, especially closer to Saginaw Bay. Did think about
issuing a flood watch for Gladwin and Arenac counties, but after
discussion with GRR/DTX, will just keep an eye on things. But there
is at least some potential there. Minimal thunder threat due to lack
of instability.

Winds will be increasing through the night, but a stable BL will
prevent anything strong. The strong winds arrive tomorrow in the
cold advection. More on that below. High temps today around 60F most
areas with lows tonight ranging from the middle 40s in eastern upper
to the upper 50s near Saginaw Bay.

&&

.SHORT TERM...(Sunday through Monday)
Issued at 320 AM EDT Sat Oct 14 2017

...Rain diminishes Sunday with blustery winds and falling temps...

High Impact Weather Potential...Gusty northwest winds on Sunday with
gales likely over the Great Lakes.

Pattern Synopsis/Forecast...Strong surface low initially over
northern Lake Huron Sunday morning will depart northeast, with a
strong pressure gradient and cold air advection in its wake. Deep
cyclonic flow will result in an influx of much cooler 850mb
temperatures by midday, contributing to lake induced instability for
some lingering lake effect showers. This lingering shower potential
will diminish Sunday night as drier air quickly settles into the
region. Meanwhile, high pressure over the Southern Plains will
expand across much of the eastern CONUS, with warm air advection and
rising heights aloft developing over the Upper Great Lakes late
Sunday night into Monday.

Primary Forecast Concerns...Potential for strong winds on Sunday.

Still some timing and dynamic differences between the models with
regard to Sunday`s departing system, but enough consensus and
consistency to warrant moderate to high confidence in wind impacts
during the day, especially over the lakes. A tight pressure gradient
will develop in the wake of the departing low, with strong cold air
advection leading to efficient daytime mixing. Northwest winds at
850mb generally expected to be in the 35-45 knot range, suggesting
wind gusts in excess of 30 mph possible. Stronger winds expected
along the Great Lakes with gales likely over the nearshore waters.
Winds will quickly diminish around sunset as mixing ceases and the
pressure gradient relaxes.

The strong northwest winds and cold air advection on Sunday will
lead to falling temperatures through the day, dropping through the
50s and even 40s with Sunday night lows in the 30s. Despite warm air
advection developing on Monday, surface temperatures will be slow to
respond with highs only in the low to mid 50s.

.LONG TERM...(Monday night through Friday)
Issued at 320 AM EDT Sat Oct 14 2017

High Impact Weather Potential...None.

Rather quiet stretch of weather, likely with quite a bit of
sunshine, anticipated through the long term period. Broad surface
high will remain anchored over the Southern Plains to Mid-Atlantic
region for most of the period, keeping the weather benign even
across northern Michigan. A clipper type system will pass well to
our north Monday night, followed by weak upper ridging overhead on
Tuesday. A weak shortwave is progged to cross the region Wednesday
into Wednesday night, followed by a building upper ridge Thursday
into Friday. Temperatures will gradually moderate through the
period, rising substantially by the end of the week with highs
possibly creeping into the low 70s in some locations Friday-Saturday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 120 PM EDT Sat Oct 14 2017

The front/sfc trough is beginning to move north and showers/rain
is beginning to develop as well. This will continue to evolve as
the clouds slowly lower and thicken this afternoon with the rain
filling in over the region. As the front (a warm front actually)
moves far enough north, the frontal inversion will set up and
decouple the winds off the sfc at all of the TAF sites overnight.
We are expecting SW winds of up to 35 kts around 2000 feet with
the sfc winds S-SE around 10 kts. This will continue until the
cold front moves through the forecast area, which should be around
12z/Sun. As the inversion breaks down and the thermal profile
turns more unstable wind gusts to 35-40 kts will be possible,
mainly near PLN, TVC and MBL into the early afternoon.

&&

.MARINE...
Issued at 320 AM EDT Sat Oct 14 2017

Winds start ramping up today out of the the east with srn nearshore
waters turning out of the south, as a warm front lifts into the
region. Winds will actually lighten up some and become variable as
deep low pressure develops and crosses nrn Michigan late tonight
into Sunday, spreading moderate to heavy rains across the region.
Strong cold advection and deep overlake instability develops through
the day Sunday, which will result in widespread gales. Doesn`t look
like storm force at this point. Higher pressure and lighter winds
then gradually develop into the work week. Will go ahead with
issuing gale warnings all nearshores.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...GALE WARNING from 8 AM to 8 PM EDT Sunday for LHZ345-346.
     GALE WARNING from 8 AM to 11 PM EDT Sunday for LHZ347>349.
LM...GALE WARNING from 8 AM to 8 PM EDT Sunday for LMZ323-341-342-
     344>346.
LS...GALE WARNING from 8 AM to 8 PM EDT Sunday for LSZ321.
&&

$$

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



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