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000
FXUS63 KAPX 180234
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
1034 PM EDT Sun Sep 17 2017

.UPDATE...
Issued at 1034 PM EDT Sun Sep 17 2017

Surface low pressure and cold front just exiting NE lower Michigan
into Lake Huron...with showers/storms almost out of the CWA.
Cooler air already spreading into the region behind the front
along with a brief period of low cloud cover...which should tend
to thin out overnight into Monday. No big changes needed to the
going forecast.

&&

.NEAR TERM...(Tonight through Monday)
Issued at 257 PM EDT Sun Sep 17 2017

...Showers end this evening...

High impact weather potential...A few rumbles of thunder through
early this evening.

Pattern synopsis/forecast...Cold front continues to work its way
east across the area this afternoon. Broken band of showers tied to
this passing front, with just enough instability to kick off a few
non-severe thunderstorms (latest SPC meso-anaylsis shows upwards of
500 or so J/KG of mean layer cape across portions of northern lower
Michigan). Descent clearing taking shape just to our west as weak
high pressure builds through Minnesota and into Western Wisconsin.

Above surface features expected to remain fairly transient through
the near term, with overhead cold front clearing the area fairly
quickly early this evening, allowing that upstream high to build
overhead later tonight and through the day Monday.

Timing the end of the shower threat this evening and
cloud/temperature trends through Monday are the primary forecast
concerns.

Details: Band of showers expected to exit stage right rather quickly
this evening. Still looking at a few rumbles of thunder as lingering
instability is utilized. Not expecting anything severe, but could be
looking at brief gusty winds through precip core loading and
attendant wet microbursts. Rest of the overnight looks dry as high
pressure steadily builds into the area. Core of deepest post-frontal
low level moisture pivots to our north, but may be just enough
moisture to drum up some strato-cu. Temperatures expected to tank
quite nicely where skies remain clear (into the 40s by morning),
likely allowing a bit of fog to develop in those low lying and
sheltered areas.

Although a bit cooler, expected highs in the upper 60s to lower 70s
on Monday are still near or a bit above long term normals. Only a
few cu and late day increasing high clouds are expected in an
otherwise sun-filled day.

&&

.SHORT TERM...(Monday night through Wednesday)
Issued at 257 PM EDT Sun Sep 17 2017

...Small chances of showers at times...

High Impact Weather Potential...Slight chance of thunderstorms for
parts of northern MI Wednesday afternoon.

Pattern Synopsis/Forecast...A weak shortwave will ripple across the
Upper Great Lakes region Monday night into Tuesday. Deepening
cyclonic flow over the Pacific Northwest will then lead to an
amplifying upper ridge over the Great Lakes heading into midweek.
Warm air advection will strengthen over northern Michigan on
Wednesday as southerly return flow increases ahead of an approaching
cold front. Highs Tuesday will reach the low 70s for most, climbing
through the 70s on Wednesday with some spots reaching the low 80s.

Primary Forecast Concerns...Shower chances for Monday night into
Tuesday and again on Wednesday.

Models seem to be trending towards less shower activity across
northern MI Monday night into Tuesday, largely due to limited
moisture and weak forcing associated with the passing shortwave. The
GFS and NAM both have PWATs dropping below 1 inch Tuesday morning,
keeping the better moisture downstate. They also never really have
the atmospheric column reaching full saturation, as evidenced by
forecast soundings keeping somewhat of a dry layer just above the
surface. So this forecast has lowered PoPs a bit for Monday night
into Tuesday, focusing them more south of M-32. Would not be
surprised if later forecasts continue trending towards a drier
solution.

Southerly return flow developing on Wednesday will draw increasing
moisture into northern Michigan. The question becomes whether we see
any showers or storms develop in response to the isentropic lift
that gets going over eastern Upper and northwest Lower. This would
be right on the periphery of the upper ridge, so this many days out
there is low confidence in whether showers will actually materialize
over parts of northern MI. Will keep low end PoPs going for now,
however.

.LONG TERM...(Wednesday night through Sunday)
Issued at 257 PM EDT Sun Sep 17 2017

Well above normal temperatures will be the story through the
extended period as strong ridging builds across the eastern CONUS.
Still looks like we could make a run at record highs in some
locations. The blocky downstream pattern is certainly helping this
ridging build, so an earlier than progged break in the block could
allow the troughing over the western CONUS to move in earlier than
currently expected, and bring temperatures closer to normal. But
current indications are for well above normal temperatures to
persist at least through the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 808 PM EDT Sun Sep 17 2017

Cold front has just about cleared northern lower Michigan with the
last bit of showers/storms exiting far NE lower Michigan. A brief
period of MVFR cigs will impact northern lower Michigan
tonight...behind the front. But drier air will be spreading into
the region overnight into Monday and return conditions to VFR for
Monday.


&&

.MARINE...
Issued at 257 PM EDT Sun Sep 17 2017

A cold front passing the area this afternoon and early
evening will quickly veer the winds around to north and northeast.
Winds will be a touch gusty at times tonight, and with the long
fetch, may produce borderline small craft advisory criteria waves on
Whitefish Bay. Northeast to east winds expected to continue into
Monday night. A few showers and thunderstorm are expected into this
evening, particularly across Lake Huron. Brief gusty winds may
accompany any thunderstorms.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...SMALL CRAFT ADVISORY until 5 AM EDT Monday for LSZ321.
&&

$$

UPDATE...BA
NEAR TERM...MB
SHORT TERM...MK
LONG TERM...AM
AVIATION...BA
MARINE...MB