Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 121952
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
352 PM EDT Thu Oct 12 2017

.NEAR TERM...(Tonight through Friday)
Issued at 350 PM EDT Thu Oct 12 2017

...Becoming Damp and Drizzly...

High Impact Weather Potential...none.

Pattern Synopsis/Forecast...Low-level moisture has been moving into
the region through the day, and has nearly covered the forecast
area. Models have the moisture increasing from around 850 mb down to
the sfc, and with the moisture increasing with height and some wind
shear at the top of the layer, will expect that during the early
evening will see some drizzle, mainly in NE Lower, where the
moisture is deeper first. Overnight, the moisture associated with
the cold front to the west will move into the region and sets up
some more drizzle/light rain, for the early morning hours in NW
Lower. It looks like there is a brief period when the drizzle ends
as well as the rain as temperatures warm and the low level air dries
out enough to stop the precipitation through 21z. After 21z, it
looks like the moisture begins to increase again, especially with
the sfc trough having stalled over N lower. Will expect the chances
of precipitation to begin to ramp up, as the sfc low moves toward
the Upper Great Lakes.

Primary Forecast Concerns...The drizzle could be rather patchy,
especially on the Lake Michigan shore, until the cold front
approaches from the west. With the SE wind, there will be
downsloping in NW Lower. As the cold front/sfc trough approaches,
the winds turn south and allows NW Lower to moisten up.

&&

.SHORT TERM...(Friday night through Sunday)
Issued at 350 PM EDT Thu Oct 12 2017

...Unsettled weather for the weekend/Cooler and windy for Sunday...

High Impact Weather Potential: High winds Sunday...with gale force
winds expected within surrounding Great Lakes waters.

Pattern Forecast: Fairly amplified but progressive western trough/
eastern ridge pattern across North America this afternoon. Short
wave energy over the central Rockies will eject out of this trough
to the northeast and pass north of the Upper Lakes Friday...though
axis of a fairly substantial jet streak (140+kt) will cut across
Upper Michigan.  Long wave ridge axis will then shift east this
weekend...and bring unsettled (and eventually cooler) weather to
Michigan.

Surface analysis features high pressure over Quebec ridging west
into the Great Lakes...low pressure over Saskatchewan/Manitoba with
a trailing cold front across the Dakotas and back into Wyoming/Utah.
Air mass ahead of this front is pretty bereft of moisture...as deep
layer moisture has been shoved into the mid-Atlantic and
southeastern states.  Although bulk of the height falls associated
with its parent short wave trough will lift into Ontario...there
will be enough of an impetus to push the cold front across northern
Michigan Friday night before stalling across southern Lower Michigan
Saturday as a new cyclone spins up over the central High Plains and
races northeast into the Upper Midwest Saturday night.  This low
should spin up rapidly Sunday as upper dynamics catch up with the
system...though timing of how quickly this system crosses the region
Sunday is still in doubt and will probably be tied somewhat to its
intensity.

Primary Forecast Concerns: System for Saturday night/Sunday is going
to the be main forecast problem.  Initial cold front passage Friday
night will be accompanied by low clouds...not a ton of moisture with
the front as mentioned earlier but there will be some return given a
fairly long period of southerly flow ahead of this front before it
arrives across Lower Michigan.  Initial precipitation may be more
spotty/drizzly as the front arrives...but as front slows down across
central/southern Lower Michigan indications are that precipitation
coverage will expand along the boundary.  This would most likely
impact areas south of the M-32 corridor into Saturday morning.  As
low pressure develops upstream on Saturday...southerly flow/
isentropic ascent increases above the boundary and precipitable
water values eventually increasing above 1.50 inches (a solid 2-3
standard deviations above the mean for mid October).  So anticipate
that rain will expand north later Saturday and should be widespread
Saturday night.

Deepening surface low will be tracking northeast out of Wisconsin
Saturday night...and across northern Lake Michigan and probably into
central/eastern Upper.  Transition to cold advection expected with
cold front passage Saturday night...not certain about the strength
of the surface low depicted by the GFS by 12z Sunday (986mb)...but
it`s a pretty dynamic setup so won`t totally discount the
possibility.  It will become windy with the cold front passage
Sunday morning...gusts at least 30-40mph expected (and more if the
GFS system strength comes to pass).  Widespread rain to continue
into Saturday night...then transition to more convective showers
Sunday as the colder air arrives.  Given such a dynamic system some
thunder threat also in the cards for Saturday night...looks like a
good setup for a windy squall line to our southwest...but don`t
think at this point that threat will reach into northern Lower.
Event total QPF expected to be over an inch across northern Lower
through Sunday afternoon...with some two inch amounts across
southern portions of the forecast area possible.  Expect
temperatures to fall during the day Sunday and will reflect that in
the temperature forecast grids.

&&

.LONG TERM...(Sunday night through Thursday)
Issued at 350 PM EDT Thu Oct 12 2017

High impact weather potential: Minimal.

Cold air behind Sunday`s departing system is rather fleeting as
heights aloft begin to rise during the day Monday. Any lingering
light/scattered lake effect rain activity is expected to come to an
end during the day Monday. Another system early next week is
expected to pass by just to our north; however, high pressure over
the midsection of the CONUS should provide mainly dry conditions
locally with gradually moderating temperatures.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 146 PM EDT Thu Oct 12 2017

Clouds are moving into the forecast area, and will cover all of
the TAF sites in the next hour or two. CIGS have been MVFR to IFR
with lower heights expected later this evening as the drizzle
begins to develop. The drizzle/light rain will expand over most of
the forecast area, overnight. The rain/drizzle will taper off
during the morning on Friday so that cigs should start to improve
by the afternoon.


&&

.MARINE...
Issued at 350 PM EDT Thu Oct 12 2017

Tonight through Saturday...Winds will remain around small craft
criteria through the night as the pressure gradient continues to
remain tight. By Friday morning the gradient begins to relax as the
next system approaches. The sfc trough stalls over the Upper Great
Lakes, and keep the weak gradient through Friday, then Saturday, as
the low moves east, the gradient tightens up, and the winds begin to
gust to 25 knots, once again.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY until 5 AM EDT Friday for LHZ345>349.
LM...SMALL CRAFT ADVISORY until 5 AM EDT Friday for LMZ341-342-
     344>346.
LS...SMALL CRAFT ADVISORY until 5 AM EDT Friday for LSZ321.
&&

$$

NEAR TERM...JL
SHORT TERM...JPB
LONG TERM...MG
AVIATION...JL
MARINE...JL



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