Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 170256

Area Forecast Discussion
National Weather Service Gaylord MI
1056 PM EDT Sat Sep 16 2017

Issued at 1017 PM EDT Sat Sep 16 2017

Deepening short wave trough clearly evident on water vapor
imagery advancing through the plains and into the upper Midwest
this evening. Associated surface low is centered over far western
Lake Superior with a cold front and several lines of
showers/storms stretching down to another area of low pressure
over Oklahoma and Texas. Warm front extends eastward through SE
Ontario. Much of northern Michigan remains precip-free...on the
eastern fringe of the moisture/instability channel although there
are some showers/storms heading for the western U.P...and a few
showers that have popped up over the eastern U.P.

Rest of tonight...mainly quiet. A few showers will continue to
threaten eastern upper MI through the night...with dry weather and
clear/partly cloudy skies elsewhere. Very mild...nearly
summerlike temperatures with lows spanning the 60s.


.NEAR TERM...(Tonight through Sunday)
Issued at 303 PM EDT Sat Sep 16 2017

High Impact Weather Potential: Chance of a few thunderstorms
Sunday afternoon.

Upstream front gets a kick eastward late tonight as a piece of mid
level energy moves races across the Northern Plains. Deep layer
moisture channel tied to this front will be thinning with time, and
what is left of it is not slated to arrive into our area until
Sunday. May see some increasing mid-high clouds as initial stages of
top-down saturation begin, but still expecting mostly clear to
partly cloudy skies overnight.  The exception may be northwest
Chippewa County where things will moisten up a bit more by 12z and
an isolated shower could work into that area.  Light southerly winds
will keep it very mild, with overnight lows ranging from the
upper 50s to upper 60s (is this September?).

Primary Forecast Concerns/Challenges: Primary focus through this
period revolves around PoPs/thunder chances associated with Sunday`s
cold front, along with high temperatures pre-FROPA near Saginaw Bay
Sunday afternoon.

Deep southerly flow will continue early Sunday morning helping to
increase temperatures to the mid-upper 70s across the majority of
the area by late morning. Narrow enhanced ribbon of moisture and
forcing are expected along and just ahead of the approaching cold
front, likely keeping the most numerous shower activity confined to
the afternoon hours associated with FROPA. Guidance continues to
show MLCAPE values between 500-1000 J/kg, sufficient to continue
the mention of thunder. Increased cloud cover and the threat for
showers will keep high temps a few degrees cooler than Saturday.
But still the potential for another well above normal day exists
as you head toward Saginaw Bay...last to see effects from the
approaching frontal boundary.


.SHORT TERM...(Sunday night through Tuesday)
Issued at 303 PM EDT Sat Sep 16 2017

...A couple small chances for showers...

High Impact Weather Potential...A few lingering thunderstorms
possible Sunday evening.

Pattern Synopsis/Forecast...A cold front and upper level shortwave
will be exiting northeast Lower Michigan late Sunday evening.
Surface high pressure will build into the Upper Great Lakes on
Monday, followed by another shortwave late Monday night into
Tuesday. Temperatures will be noticeably cooler on Monday behind the
front (highs: mid 60s north to low 70s south), rising a little bit
heading into Tuesday (upper 60s north to low-mid 70s south).

Primary Forecast Concerns...Exiting showers/storms Sunday night and
pinpointing shower chances again late Monday night into Tuesday.

A narrow ribbon of higher moisture will still be found across
northeast Lower Michigan Sunday evening until the cold front pushes
through. Instability will be waning quickly, but it looks like still
perhaps a few hundred J/kg of MUCAPE near Lake Huron through late
evening. So may still see a few thunderstorms over northeast Lower
Sunday evening, with FROPA bringing and end to rainfall chances by
around midnight.

A significantly drier airmass will sweep in behind the cold front
Sunday night, and forecast soundings show the column rapidly
drying out from top down through the mid levels. Still some
residual low level moisture expected to hang on through daybreak
Monday, which combined with clearing skies behind the front, fresh
rainfall, and light winds will likely lead to some areas of fog.

Some additional patchy fog will be possible Monday night (mainly
over northeast Lower where clouds will be fewer) as high pressure
sits overhead. Increasing mid/high level clouds will likely preclude
fog development across the rest of northern Michigan.

Models differ with how far north a moisture plume will extend late
Monday night into Tuesday. The NAM is especially dry and therefore
keeps pretty much all the rain out of northern Michigan. Other
models are still in good enough agreement to warrant chance PoPs
during this timeframe, though. Rain chances look to diminish through
the afternoon as the shortwave pushes east.

.LONG TERM...(Tuesday night through Saturday)
Issued at 303 PM EDT Sat Sep 16 2017

High amplitude ridging is expected to build over the eastern CONUS
through the extended. Currently progged H5 heights are pretty
impressive for this time of year and temperatures are expected to
run well above normal. Some spots may even make a run at record
highs next weekend. Best chance for showers looks to be around mid-
week, as a front extending from a low moving through Canada could
provide some forcing to get showers and a few rumbles of thunder
going. It`s not uncommon to see these wash out a bit, and the better
forcing to remain further north, but that picture will develop a bit
more over the coming days.


.AVIATION...(For the 06Z TAFS through 06Z Sunday evening)
Issued at 1055 PM EDT Sat Sep 16 2017

...VFR weather tonight...

Northern Michigan stuck in between high pressure in the eastern
lakes and low pressure in the upper Midwest. Some increasing high
cloud cover will begin to spread into the region tonight. But any
associated showers will hold off until Sunday.

On Sunday...low pressure will slide up into Ontario with an
associated cold front slipping through northern Michigan. Narrow
corridor of thicker cloud cover and a band of sct-nmrs showers
will accompany the front. A period of MVFR cloud cover is possible
with the front Sunday afternoon into the evening.


Issued at 303 PM EDT Sat Sep 16 2017

Pressure gradient expected to slowly ramp up tonight as a
cold front to our west slowly approaches the region. Southerly winds
will be on the increase, and likely become a bit gusty at times,
especially over the open waters of northern Lake Michigan. Current
trends continue to support mostly sub-advisory wind gusts across the
nearshores.  Winds steadily veer and decrease in speed later Sunday
and Sunday night as the cold front passes.  A generally light wind
pattern expected early this upcoming week.





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