Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 150341

Area Forecast Discussion
National Weather Service Gaylord MI
1141 PM EDT Sat Oct 14 2017

Issued at 956 PM EDT Sat Oct 14 2017

Low pressure continues to deepen across northeast Iowa, and should
continue to do so as it crosses northern lower Michigan during the
early morning hours. As is often the case this far north, vigorous
convection to our south has really interfered with northward
moisture transport, keeping rainfall across our area rather light.
Not seeing much promise for heavy rain overnight given convective
trends, although do expect rain to increase in coverage as
primary forcing arrives. Still cannot rule out some elevated
thunderstorms, but any severe threat is well removed to our south.


.NEAR TERM...(Tonight through Sunday)
Issued at 258 PM EDT Sat Oct 14 2017

...Soaking Rain Tonight and Sunday Windy Sunday...

High Impact Weather Potential...Potential for flooding, mainly
near Saginaw Bay with the moderate to heavy rain. Windy with gusts
occasionally over 45 mph once the cold front moves through N
Michigan on Sunday.

Pattern Synopsis/Forecast...Deepening autumnal sfc low will track
out of the C Plains and into the Upper Great Lakes tonight and
Sunday. The low is still in the development stage in Iowa, but has
begun pushing the sfc warm front back north through the lower
peninsula. This is producing area of rain in N lower. Majority of
the lightning has been along or just north of the warm front near
the Indiana border, and around Chicagoland. Some lightning has
gotten north around GRR, but for the most part, it looks like the
best chances for thunder isn`t until later in the evening when the
Showalter indices drop to around -2c through the night. The sfc
low moves through the forecast area overnight, and is east of APN
by 12z/Sun. This allows the cold front to push through the region
quickly during the day. With the cold air moving over the warmer
lakes, the stability over the lakes, and for that matter the land
breaks down, and the tightening pressure gradient on the back side
of the low moving into the region, Winds will increase. 925 mb
and 850 mb winds on the models have 45-50 knot, so the gusts are
expected to be over 45 mph. However, once the low gets to just
north of New England around 00z/Mon, the gradient has slackened
quite a bit, and winds should begin to diminish.

Primary Forecast Concerns...Rain fall looks to remain below FFG as
the RFC maps for the 6-hour precipitation to start around 2.0" and
goes up as high as 4.0". The spread on the sref plumes shows the
majority of the members clustered between 1.00 and 2.00" over the
12 hour period. So will expect that the probability for flooding
is low, but not out of the question.

Winds on the SREF plumes for the 10m winds are between 15 and 20
knots with a few member in the 30+ kt categories. rough estimates
of this would kick out 45+ kts. So couldn`t rule out 50 mph, but
think that 40-45 mph are more likely.


.SHORT TERM...(Sunday night through Tuesday)
Issued at 258 PM EDT Sat Oct 14 2017

...Cool on Monday but much warmer Tuesday...

High impact weather potential...none.

Strong low pressure will depart eastern Canada, with a ridge of high
pressure building in Monday. Post-frontal airmass is amongst the
chilliest so far this fall, leading to cool wx into Monday. Warm
advection quickly returns behind the ridge axis Monday night, amped
by a warm front crossing from w to e toward Tuesday morning. That
will usher in what appears to be another extended stretch of very
warm weather.

Sunday night...winds will quickly diminish in the evening as the low
moves away, pressure gradient relaxes, and diurnal heating/mixing
ceases. Post-frontal nw-erly flow (gradually backing with time) and
850mb temps dipping to -3C will support some weak lake effect rain
showers in nw lower MI and western Chippewa Co (despite a generally
drying airmass). Clouds will diminish faster outside of lake effect
regimes. Min temps 40-45 near Lake MI, 30s elsewhere.

Monday...arrival of surface ridge and onset of 850mb warm advection
will erode lake effect cloud cover. Warm advection-related mid/high
clouds will replace it to some degree, especially in northern
sections. Shallower cool air will be more difficult to fully
dislodge, though there should be enough sun to push max temps past
the rather cool Nam guidance (Nam progs a high at GLR of just 48f).
Instead, a general low/mid 50s across northern MI looks fine.

Mon night/Tuesday...increase in mid/high clouds in northern sections
Monday night, associated with an incoming surface warm front, and a
shortwave crossing northern Ontario. That looks to largely depart by
dawn Tuesday, leading to plenty of sunshine and warmer temps. Onset
of warm advection and increase in cloud cover will keep min temps
higher, upper 30s to mid 40s. Highs Tuesday will be around 60 to the
mid 60s.

.LONG TERM...(Tuesday night through Saturday)
Issued at 258 PM EDT Sat Oct 14 2017

High pressure over the eastern CONUS will bring a rather quiet
extended period. Warming temperatures will once again be the main
story heading into the weekend. Normal highs this time of the year
are in the low to mid 50s, many areas could be at or near the low
70s by the weekend.


.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1139 PM EDT Sat Oct 14 2017

Strengthening low pressure expected to move across northern lower
Michigan early this morning, bringing with it a plethora of
aviation concerns. Widespread IFR producing low cigs with periods
of light to moderate rain expected to continue through the
remainder of the overnight. Wind shear will also expand across
the taf locations. Passing cold front will bring additional
showers and low clouds later this morning, with a rapid increase
in surface winds (up to 40 knots) out of the northwest after its
passage. Winds and shower/low cloud coverage looks to diminish
some by late in the day.


Issued at 258 PM EDT Sat Oct 14 2017

Tonight though Monday...Main concern is for the developing sfc low
moving out of the C Plains currently and expected to move up over
the Upper Great Lakes on Sunday. This will cause the winds to
increase out of the south to southeast tonight, getting to over
small craft conditions, then once the low is east of APN the cold
front moves through Lake Michigan, this will tighten the
gradient, and with the cold air moving over the warmer lakes, will
expect the winds gust past gale force for Sunday, first over Lakes
Michigan and Superior, then over Lake Huron. By 00z/Mon, the
gradient will have slackened enough to allow the winds to diminish
on Lakes Michigan and Superior, but the NW winds on Lake Huron
will continue gale force, mainly on the strip along the Lower
peninsula of Michigan. Eventually, the winds will diminish there
as well so that by 12z/Mon, the winds and waves should be below
small craft criteria.


MI...WIND ADVISORY from 8 AM to 8 PM EDT Sunday for MIZ008-015>036-
LH...GALE WARNING until 8 PM EDT Sunday for LHZ345-346.
     GALE WARNING until 11 PM EDT Sunday for LHZ347>349.
LM...GALE WARNING until 8 PM EDT Sunday for LMZ323-341-342-344>346.
LS...GALE WARNING until 8 PM EDT Sunday for LSZ321-322.


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