Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 211957
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
357 PM EDT THU JUL 21 2016

.SHORT TERM...(This evening and overnight)
Issued at 355 PM EDT Thu Jul 21 2016

Overview...Convective line of showers and thunderstorms that
prompted the watch earlier today is now offshore into Lake Huron. To
the west is a weak sfc trough with a small cluster of thunderstorms
in the Upper Mississippi Valley, that is attached to a sfc low near
James Bay. At 500 mb there is relatively flat flow over the northern
tier of states from the N Plains to New England, with relatively
weak shortwave troughs moving through the flow.

A little further to the west is another area of high pressure, in
the N Plains.

Tonight...main concern is the sfc trough that is expected to cross
the forecast area overnight. some models have been showing another
line of showers and thunderstorms to move over the region. however,
there are a few models, that show little happening overnight. One in
particular (HRRR) which handled the event much better than the rest
which shows that little happens. So have some low chance pops as the
trough moves through overnight. Otherwise, the trough moves through,
and the dewpoints begin to fall, as high pressure builds into the
region by 12z.

.LONG TERM...(Friday through Thursday)
Issued at 355 PM EDT Thu Jul 21 2016

High impact weather potential: Lingering heat. Potential for more
stormy weather to end the weekend.

Pattern synopsis/expected evolution: Massive central plains heat
dome begins to feel the affects of rather aggressive/progressive
flow across southern Canada and the northern CONUS in the coming
days...essentially squashing the northern extent of the ridge axis
this weekend. Weak front sags south in the process, shunting current
active weather regime to our south to start the weekend and bringing
a shot of somewhat drier air overhead in the process.
Soupy/unstable airmass does not go far however, with a fast moving
wave trying to surge it back north into the northern Lakes to end
the weekend. Not sure if it will ever make it, although its
attendant mass adjustment will likely result in another round of
showers and thunderstorms, some of which could be rather
significant.

Primary forecast concerns/challenges: Temperature trends through
Saturday. Shower and thunderstorm evolution Saturday night and
Sunday.

Details: Definitely still warm to end the week on into the start of
the weekend (plenty of sun sure won`t hurt the cause), although not
quite as moist at the lower levels. Simple thermal progs supports
highs into the lower/middle 90s over much of northern lower Michigan
Friday, and just a couple degrees cooler on Saturday.
As mentioned, humidity values will not be quite as high as those
observed today, especially by Saturday. Expect apparent temperatures
to mimic those of the actual highs, negating any type of heat
advisory concerns.

Next chance for showers and thunderstorms arrives later Saturday
night into Sunday as the next fast moving wave (perhaps convectively
agitated) arrives, bringing with it the northern extent of one very
juicy corn belt centered airmass. Still plenty of details to work
out, as is always the case when dealing with convection. Really hard
to get into any specifics, with expected upstream convection likely
playing absolute havoc with what unfolds over our area. Will simply
load that which a consensus blend approach gives, highlighting
greatest shower and thunderstorm concern on Sunday. Marginally fast
mid level flow and what could be some decent instability does raise
some concern for severe weather. Will definitely continue to monitor
trends in the coming days.

Extended (Monday through Thursday) issued at 300 PM EST THURS Jul 21
2016

To begin the work week there is an upper level low at 500mb in NE
Ontario moving out. The flow behind behind the low turns to a zonal
flow before a subtle wave slides through on the day Thursday.
This pattern will provide some relief from the hot conditions of
last week while still keeping Northern Michigan in the seasonable
temp range.

At the surface Monday through Wednesday looks quieter with the zonal
flow aloft and a sfc high pressure moving in from the plains.
Thursday the pops increase as the wave moves through resulting in
some isolated showers. Overall set up looks too weak to produce any
thunderstorms.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 136 PM EDT Thu Jul 21 2016

Line is through the TAF sites this afternoon. Models are showing
that little if anything will happen this afternoon and probably
tonight as well. At little concerned about LLWS, but like last
night, it will be marginal as the winds at 2000 feet are only 20
to 25 knots with sfc winds 5-10 knots. So at this time, will leave
it out and mention the possibility here. High pressure will
continue to build into the region for Friday, so will continue
with the dry forecast.

&&

.MARINE...
Issued at 355 PM EDT Thu Jul 21 2016

Tonight Through Saturday...Winds will continue into the evening with
the small craft criteria, with the waves subsiding by 06z. After 06z
through Saturday, high pressure builds into the region and relaxes
the gradient. Winds and waves are expected to remain below small
craft criteria.

&&

.APX Watches/Warnings/Advisories...
MI...BEACH HAZARDS STATEMENT until 8 PM EDT this evening for MIZ020-
     025-031.

LH...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LHZ345>347.

LM...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LMZ341.

     SMALL CRAFT ADVISORY until 8 AM EDT Friday for LMZ323-342-
     344>346.

LS...SMALL CRAFT ADVISORY until 8 PM EDT this evening for LSZ321-322.

&&

$$

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


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