Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 270143

Area Forecast Discussion
National Weather Service Gaylord MI
943 PM EDT TUE JUL 26 2016

Issued at 943 PM EDT Tue Jul 26 2016

Weak frontal boundary combined with lingering low level
convergence via this afternoon`s lake breeze continues to produce
a line of showers and thunderstorms across Upper Michigan late
this evening. Overall intensity has diminished with sunset/decreasing
diurnal instability. Latest RAP13 does suggest some weak widely
scattered convection will continue to fire along this boundary as
it sinks southward thru our CWA overnight. This seems reasonable
given MUCAPES of 500-1000 J/kg and some 850 mb theta E ridging
holding on along the front thru the night. Have slightly increased
POPs overnight for much of our CWA...and better defined timing of
these POPs. Still do not expect severe storms for the balance of
the night thanks to weak wind fields and diminishing instability.


.SHORT TERM...(This evening and overnight)
Issued at 250 PM EDT Tue Jul 26 2016

Overview...A cold front in Northern Minnesota/Western Lake
Superior is slowly moving toward the forecast area. It is
connected to a low pressure system near James Bay. South of the
front is the High pressure system that has been producing mostly
sunny skies over the forecast area.

Tonight/Wednesday...Main concern over the next 24 hours is the
cold front in northern Minnesota as it sags south into the
forecast area. The models continue to try and kick off
thunderstorms that are supposed to move into E Upper this
afternoon/early evening. As noted in previous update AFD, closest
precipitation is well west in Minnesota with the front. As the
front approaches the forecast area, we get more and more stable,
and with a weak front like this, less of a chance for showers, let
alone thunder. GFS is the wettest of the models with a cluster
that moves into the region. The ECMWF, on this run, has something
with the front. Hires models and NAM, have brief showers that pass
through. So have kept the pops low as it moves through the region.
The better chance will be on Wednesday as the low slows to a crawl
near M-72 and produces scattered showers and thunderstorms through
the day, especially in the afternoon with the heat of the day.

.LONG TERM...(Wednesday through Tuesday)
Issued at 250 PM EDT Tue Jul 26 2016

Wednesday night through Friday...

High impact weather potential: Scattered thunderstorms possible
across parts of the area at various times throughout the period.

Pattern synopsis/expected evolution: Weak mid-upper level troughing
is present at the start of the period with a more pronounced
shortwave trekking through the upper Mississippi Valley and into the
Great Lakes Wednesday night-Thursday. Another, more subtle wave,
approaches the region from the west late in the day Friday. Both of
these features will ultimately result in increased precip chances
through the period.

Forecast concerns/challenges: PoPs and thunder chances.

Wednesday night - Thursday: Aforementioned shortwave approaches from
the northwest Wed night into the day Thursday, ultimately leading to
low end chance PoPs, mainly along and south of M-72 as dry surface
high pressure is anchored to the north and the greatest forcing for
ascent lies from there south. As hinted at by the aforementioned
PoPs, would expect that any scattered precip able to develop or
survive the trip across Lake Michigan would be fairly scattered in
nature. While instability remains marginal, there certainly could be
a rumble of thunder or two so have no reason to remove inherited
thunder chances.

Thursday night - Friday night: Very similar feel during this portion
of the forecast with another, although more subtle, shortwave
rotating through mid-level flow. High pressure centered to the north
is expected to limit the overall moisture and associated precip
across northern Michigan. Latest trends suggest much, if not all,
showers and storms will remain south of M-55 through Friday night.
Run-to-run model inconsistencies preclude removing PoPs completely
south of M-55, but did decrease somewhat for this forecast package
and if trends continue, would find it hard to see more than just a
widely scattered shower or storm prevail.

Little in the way of temperature concerns with near-normal
temperatures expected Thursday and Friday as highs ranging from the
upper 70s to lower 80s. Lows in the middle to upper 50s.


Extended (Saturday through Tuesday) issued at 300 PM EST TUES Jul 26

At 500mb... A broad trough will position itself over the Great Lakes
basin for the remainder of the weekend. The troughing is weak and
should not result in any significant weather as the the model suite
has converged on a weaker, larger trough that lacks any vorticity.
Ridging will takeover for the rest of the forecast period.

At the surface... Saturday through Tuesday looks to remain dry with
a surface high located over Ontario keeping our flow from the
northeast. The air associated with that flow will be dry limiting
any precip chances. The period looks to be dominated by that surface
high keeping our temps in the upper 70s to mid 80s.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 729 PM EDT Tue Jul 26 2016

A weak cool front will slide thru Northern Michigan tonight into
Wednesday...producing small chances of showers and thunderstorms.
However...chances of convection are too small to include in the
TAFs for now. Overall conditions will remain VFR thru Wednesday
evening away from any showers/storms that do form. West winds AOB
10 kts tonight will become N/NW on Wednesday behind the front.


Issued at 250 PM EDT Tue Jul 26 2016

Tonight through Thursday...A weak pressure gradient is expected to
settle in over the Upper Great Lakes for the next 60 hours. this
will leave the winds at 10 knots or less, with gusts no higher
than 20 knots, and the worst would be on Thursday as the sfc
trough forms in the Ohio Valley and high pressure builds into the
Upper Great Lakes from the north. Waves for the most part will
remain 3 feet or less through the period.


.APX Watches/Warnings/Advisories...


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