Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 140236
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1036 PM EDT Fri Oct 13 2017

.UPDATE...
Issued at 1032 PM EDT Fri Oct 13 2017

Weak cold front continues to sag slowly southeast across the area
this evening, kicking off a few light showers and plenty of low
cloud cover in the process. Sharp clearing noted to our northwest,
with this dry air expected to sweep across the northern half to
third of the area later tonight into Saturday morning. Showers
will slowly trend south in the process, perhaps exiting our area
completely for a time early Saturday morning before returning back
north through the day. Have done some minor adjustments to the
forecast to account for real-time temperature, cloud, and shower
trends.

&&

.NEAR TERM...
Issued at 749 PM EDT Fri Oct 13 2017

...Showers Tonight and into Saturday...

High Impact Weather Potential...none.

Pattern Synopsis/Forecast...The sfc trough is over the region,
running from the low in eastern Kansas, through Michigan, into
Ontario where it ends up going north to the low in Hudson Bay. There
are to highs on either side of the sfc trough. One in Minnesota, and
one off the coast of New England. This is setting up a baroclinic
zone over Michigan that will begin to sharpen up as the sfc low in
Kansas moves toward the forecast area. This is expected to bring a
new round of showers near NW Lower first, than the rest of N Lower
overnight. The Baroclinic zone is expected to move south into
downstate Michigan by 12z/Sat before it gets a surge of energy to
come back north late morning (15Z/Sat) and bring rain to the region.
There is a chance for some elevated convection late in the day as
the warm front moves north of M-55 around 00z/Sun.

Primary Forecast Concerns...Unsure of the Thunder in the late
afternoon on Saturday as the warm front moves north. Model soundings
show the lifting sfc is around 700 mb and that the CAPE is 200 J/kg
or less. Around 00z/Sun, the lifting sfc near MBL is around 850 mb
from the previous level of 700 mb at 21z/Sat, so have the chance or
slight chance for the far SW corner of forecast area.

&&

.SHORT TERM...(Saturday night through Monday)
Issued at 337 PM EDT Fri Oct 13 2017

...Rainy/blustery/cool end to the weekend...

High Impact Weather Potential: Gusty winds/gales Sunday.

Pattern Forecast: Long wave trough situated over western North
America has a pair of strong short wave troughs moving through it.
One was lifting northeast into northwest Ontario...a second was
digging southward across Washington/Oregon.  Upper ridge axis
extends from the southern Plains into New England/Quebec.  Long wave
trough will propagate en masse eastward this weekend...accompanied
by a strong southwesterly jet streak.  A second piece of energy
looks to clip the upper Great Lakes from the northwest in the
Tuesday time frame.

A cold front associated with the leading short wave trough was
moving into western Upper Michigan/Wisconsin...extending south to an
area of low pressure over Kansas.  Solidly cooler air mass behind
the cold front...while moisture gradually returns northward ahead of
the boundary across the southern/central Plains (0-1km mixing ratios
over 12g/kg into southeast Kansas/southwest Missouri). As long wave
trough shifts east this weekend...it is expected to spin up a lee
cyclone over western Kansas...with this low deepening as it tracks
across northern Michigan early Sunday.  A strong push of cooler air
will spill across the upper Lakes in the wake of this cyclone
Sunday...before high pressure ridges across the state Monday.

Primary Forecast Concerns: Potential for high winds Sunday...and QPF
on the front side of this system through Saturday night.

First dealing with winds.  More of a consensus now on a system track
across northern Lower/northern Lake Huron Sunday morning...with a
strong cyclonic gradient wrapping gusty northwest winds back across
the area.  Strong cold advection and a surface based mixed layer
with 30-40kt winds certain suggest wind gusts upwards of 35 mph and
probably stronger along the lee shores of the surrounding Great
Lakes (where Wind Advisories may be required at some point in the
future).  Building surface ridge and subsequent weakening of the
pressure gradient will allow winds to diminish starting Sunday
evening.

As far as rainfall potential...anticipating rain should be
widespread across northern Michigan by Saturday evening...with a
nice push of deep layer moisture (precipitable water values near
1.50 inches) and strong frontogenetic forcing aided by right
entrance region jet dynamics.  Rainfall amounts for the 24h period
ending Sunday morning likely to exceed an inch across much of
northern Lower.  Widespread rain should taper off for a bit (at
least across northern Lower) as we transition to showers with
moisture wrapping around the north side of the system and cold
advection increasing the lake induced contribution to instability.

While lows Sunday morning should be mild by mid October standards...
expect temperatures to drop through the day given strength of cold
advection.

.LONG TERM...(Monday night through Friday)
Issued at 337 PM EDT Fri Oct 13 2017

The Tuesday-Wednesday disturbance should be clear the area by the
start of the extended period...leaving a mainly dry Thursday.
However...a clipper will roll through the great lakes Friday,
bringing a reinforcing shot of cold air and another shot at
precipitation.  I think the story to watch will be the significantly
colder air and if it will lock in long enough to initiate some lake
processes for Friday and Saturday.  My gut feeling thinks, yes.
Temperatures will moderate on Sunday with dry conditions returning
to round out the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 749 PM EDT Fri Oct 13 2017

Cold front will slowly work its way across the area overnight,
bringing low clouds, a few light showers, and some mist along with
it. Would expect to see some lifting of the cigs from north to
south later tonight through Saturday morning. Next surge of deeper
moisture and more IFR/MVFR conditions expected to expand back
north Saturday afternoon and evening.


&&

.MARINE...
Issued at 337 PM EDT Fri Oct 13 2017

Tonight through Sunday...Winds are diminishing in the nearshore
areas as the gradient as relaxed over the last few hours. However,
as the cold front moves through tonight, and the sfc low moves up
out of Kansas and into the Mid-Mississippi Valley, the gradient will
tighten up again so that we will get small craft winds Saturday
afternoon on the Lake Michigan side, and then the Lake Huron side
and Whitefish Bay Saturday night. However, we will have Gale Watches
up on Lakes Michigan and Huron as the sfc low moves into the Upper
Great Lakes, and the winds increase to 35 knots at the least, with
40 knots possible.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...GALE WATCH from Sunday morning through Sunday evening for
     LHZ347>349.
LM...GALE WATCH from late Saturday night through Sunday evening for
     LMZ323-342-344>346.
LS...NONE.
&&

$$

UPDATE...MB
NEAR TERM...JL
SHORT TERM...JPB
LONG TERM...KB
AVIATION...MB
MARINE...JL



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