Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 231938
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
338 PM EDT SAT JUL 23 2016

.SHORT TERM...(This evening through Sunday)

Issued at 313 PM EDT Sat Jul 23 2016

High impact weather potential: Thunderstorms possible later tonight
into Sunday.

Pattern synopsis/expected evolution: Water vapor imagery says it all
early this afternoon, with energetic flow rotating around steadily
flattening central Plains heat dome. Embedded mid level waves within
the former, working on northern extent of instability axis,
continues to kick off clusters of showers and thunderstorms back
across the Corn Belt and Northern Mississippi Valley. Much more
defined shortwave trough rotating across southern Saskatchewan, with
low pressure and a developing cold front helping drive an area of
storms across the northern Plains. No such weather closer to home,
with high pressure and still dry air through the low/mid levels
resulting in another sun-filled and warm mid-summer day.

Above features remain transient overnight into Sunday, with the
developing cold front and mid level waves working on a northward
surging moisture/instability axis likely to drive additional showers
and storms (MCS?) through this evening and overnight. Strong late
night moisture advection will likely allow at least some of this
activity to survive into our area, with the actual "cold" front
passage perhaps driving additional showers and storms through the
day Sunday.

Primary forecast concerns/challenges: Shower and thunderstorm
evolution and intensity tonight and Sunday.

Details: Per the usual with summer convection, a rather complex and
low confidence forecast heading through tonight and Sunday. With
that said, confidence is actually rather high that additional
clusters of showers and thunderstorms will continue to develop this
evening to our west in favored moisture/instability advection axis
along nose of developing low level jet. This jet steadily veers and
weakens with time, although remains strong enough to drive rather
substantial moisture into northern Michigan by morning (precipitable
water values reach near 2 inches levels during Sunday morning).
However, steady loss of mass convergence on nose of weakening jet
and loss of better instability will likely cause a diminishing trend
in shower/storm intensity and areal coverage as they push into our
area later tonight and Sunday morning. Really think per the above
any storms will remain sub-severe, although may result in some brief
gusty winds and heavy rains (heads up Chicago to Mackinac race
participants!).

Atmosphere will likely take quite a bit of time to recover behind
the morning activity Sunday given lingering cloud cover and simple
post convection subsidence. Timing of actual arrival of front still
uncertain, with a later day frontal timing allowing that much more
time for destabilization to occur. Kinda feel lack of good morning
heating may give a nod to some of the faster frontal progs, which
would suggest most additional late day activity focusing across
central and southern Michigan into Ontario. Unfortunately, simply
cannot be this deterministic just yet, so will continue to advertise
at least some potential for more showers and thunderstorms through
the afternoon. If storms can indeed fire, some limited severe
weather potential is there with deep layer shear ranging from 25
knots south (in a region of potentially more instability) to 40
knots north. Isolated severe wind gusts and large hail would be the
primary threat. Of course, above is completely conditional on
frontal timing and ability to destabilize before frontal passage.
Area remains in latest SPC day 2 marginal risk, with they too citing
much uncertainty on exact convective evolution.

.LONG TERM...(Sunday night through Saturday)
Issued at 313 PM EDT Sat Jul 23 2016

Sunday night through Tuesday...

(7/24)Sunday night...As the 500 mb trough moves into the Upper Great
Lakes, drier and cooler air will begin to push into the region. The
Showers and thunderstorms look to end by the early evening as the
cold front pushes the rain out over Lake Huron by 03z. Overnight,
the trough begins to dig a bit into the Upper Great Lakes, as the
850 mb cold front pushes into the region as well. Will be expecting
breezy conditions by morning with clearing skies.

(7/25)Monday...Sfc high pressure builds into the Upper Great Lakes,
with 500 mb heights building as well. This will keep the region dry,
with temperatures around the normal highs. Skies will clear out
during the day and remain that way through the night.

(7/26)Tuesday...The high pressure pressure remains over the region
through the day, keeping the region dry with light winds. The GFS
shows that it may have some clouds moving in from Wisconsin late in
the afternoon, but for the most part, thinking it will remain mostly
sunny.

Tuesday night through Saturday...

Flow over the northern tier of the CONUS will remain nearly
zonal, while the warm dome setup over the southern tier persists.
Will see a small chance for some scattered showers as we near mid-
week...with a weak moving through ahead of deeper troughing to the
west. This deeper troughing will move overhead late in the week,
with more scattered showers possible ahead of the trough axis
clearing the state. There looks to be a bit of a pattern change as
these height falls start to arrive late in the week and persist
over the eastern CONUS into next week. This should help to get
temperatures back down to near normal values, with the amplified
ridging remaining west of the Rockies.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 135 PM EDT Sat Jul 23 2016

...VFR conditions into this evening gives way to much uncertainty
later tonight into Sunday...

Mainly clear skies and light winds will prevail across the TAF
locations into this evening. Deep moisture advection arrives later
tonight, likely bringing showers and thunderstorms along with it.
Still plenty of uncertainty on the exact timing or
impacts/magnitude of these shower and thunderstorms. Will
cautiously play it more optimistically for now, keeping vfr
conditions. Of course, any stronger storm activity will likely
bring periods of significantly greater impacts.

The threat for Showers and thunderstorms will continue through at
least the first half of Sunday morning, with perhaps a break
developing from west to east later during the morning hours. More
scattered thunderstorms are possible heading into Sunday
afternoon...just beyond this TAF period.

&&

.MARINE...
Issued at 313 PM EDT Sat Jul 23 2016

Light winds into early this evening will become increasingly
gusty out of the southeast and south later tonight, with winds
veering more southwesterly Sunday morning. Wind gusts will likely
approach/exceed SCA criteria across much of northern Lake Michigan
and Whitefish Bay on Lake Superior very late tonight into Sunday.
A passing cold front will veer winds around more westerly Sunday
night, with wind speeds also decreasing. Marginally gusty west to
northwest winds are expected to start the work week.

In addition, the threat for showers and thunderstorms will be on the
increase late tonight into Sunday. Some of these thunderstorms could
bring locally very heavy rain and brief periods of gusty/variable
winds.

&&

.APX Watches/Warnings/Advisories...
MI...NONE.
LH...NONE.
LM...SMALL CRAFT ADVISORY from 5 AM to 6 PM EDT Sunday for LMZ342-
     344>346.

LS...SMALL CRAFT ADVISORY from 5 AM to 6 PM EDT Sunday for LSZ321.

&&

$$

SHORT TERM...MSB
LONG TERM...JSL/Mayhew
AVIATION...MSB
MARINE...MSB


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