Area Forecast Discussion
Issued by NWS Gaylord, MI

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797
FXUS63 KAPX 241711
AFDAPX

Area Forecast Discussion
National Weather Service Gaylord MI
111 PM EDT WED AUG 24 2016

.UPDATE...
Issued at 937 AM EDT Wed Aug 24 2016

Surface low center has pushed east into Western Ontario...with the
associated cold front trailing southward thru the Upper Mississippi
Valley into the Central Plains. Northern end of the initial area
of convection is moving thru our CWA attm...taking shape as mainly
showers with isolated areas of embedded thunder. Convection is
driven by a rather potent wave riding NE thru the upper level flow
ahead of the cold front...and fueled by the northern edge of a
pronounced 850 mb theta e ridge and LLJ along with modest MUCAPES
of around 500 J/kg. The wave will slide thru our CWA this
afternoon as MUCAPES increase to around 1000 J/kg. Highest POPs
will gradually shift eastward throughout the rest of the day as
focus of lift...moisture and instability does so as well. Wind
fields actually weaken just a bit throughout the day...with bulk
shear values generally below 30 kts. While a marginally strong/svr
thunderstorm wind gust is not out of the question...certainly do
not expect big chances of severe storms given much better
ingredients remaining well south and west of our CWA. Have made
some minor adjustments to timing of POPs. Otherwise...Northern
Michigan will see a generally cloudy and humid day with waves of
showers and a few embedded storms. High temps will warm into the
70s.

&&

.SHORT TERM...(Today and tonight)
Issued at 429 AM EDT Wed Aug 24 2016

High impact weather potential: Chance for thunderstorms into this
evening. Marginal chance for severe weather with the main threat
being damaging winds.

Pattern synopsis and forecast:

Closed off upper low spinning into srn Manitoba with the associated
sfc low in western Ontario. A cold front is draped south of the low
slowly approaching the mid and upper Mississippi valley. The main
warm front extends east of the low, bisecting Ontario. SW flow aloft
is showing a couple of shortwaves, both associated with areas of
showers and thunderstorms. These storms are fed by much higher theta-
e advection due to a 35-40kt LLJ, underneath the advection of
steeper lapse rates aloft and forcing from DPVA and upper
divergence. Additional elevated storms have been developing across
nrn IL and to some extent into srn Lake Michigan, along and north
of a secondary warm front marked by upper 60s sfc dew points.

The two shortwaves dampen out to some degree as they roll on through
today, and the aforementioned forcing does weaken some, along with
the LLJ. Regardless, we will have steeper lapse rates aloft
advecting in with the DPVA from the shortwaves. Seeing showers and
some thunderstorms still seems likely for most of nrn Michigan. We
are in a marginal threat for isolated damaging winds, but wind
fields are not impressive with a 40kt mid level jet and bulk shear
values just below 30kts. Instability looks to be no greater than
several hundred j/kg of either MUCAPE or SBCAPE, so updraft
strengths not to be too impressive. The main upper wave opens up and
works into Ontario late tonight, with the sfc cold front finally
reaching nrn Michigan around daybreak Thursday at minimum heating.
Additional shortwave activity does look to roll up into srn lower
Michigan, which may provide better chances for showers late tonight.
Otherwise, just some isolated showers possible by late tonight.

Lowered high temps a touch today due to incoming thicker clouds and
showers. Readings will be more in the 70s but humid. Lows tonight
quite mild with mid and upper 60s and dreary with most areas
socked in low clouds.

.LONG TERM...(Thursday through Tuesday)
Issued at 429 AM EDT Wed Aug 24 2016

(8/25)Thursday...The cold front stalls out in SE Lower as the 500 mb
shortwave trough dropping into the Upper Great lakes. GFS brings
rain into the SE counties by 18z, with the ECMWF right along the
shore of Saginaw bay in our area. NAM barely gets anything in our
area. So will probably go middle of the road with the ECMWF idea
during the day. The sfc low, to the north, continues to move east,
with the drier air moving into the region. Models suggest that the
area should remain dry overnight as the 850 mb temperatures haven`t
fallen that far to produce LE rain, not to mention some very dry mid
levels (700-500 mb layer RH<20%). However, it does look like it
should begin to get cloud overnight as the 850 mb moisture begin to
push into the region.

(8/26)Friday...models are trying to print out some precipitation, as
the 850 mb temperatures fall to around 8 or 9c which would just put
us into the LE rain delta Ts, and the 500 mb 50 knot RRQ of the jet
streak moves through the area. Moisture on the soundings is pretty
shallow, so would think that the LE rain is possible with help from
the 500 mb jet, but by the evening that things will dry out and we
should get clearing skies.

Extended (Saturday through Tuesday)...The next wave along the fast
500 mb flow expected to come into the Upper Great Lakes is
Saturday/Sunday. There are some disagreements on how the storm will
evolve with the ECMWF very slow solution compared to the GFS. Monday
at this point looks dry as high pressure builds into the region, but
the models keep trying to produce rain near the region. then on
Tuesday, the GFS brings a wave in while the ECMWF keeps the region
dry. So with the uncertainty, will keep the pops low for now.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 111 PM EDT Wed Aug 24 2016

Periods of showers and thunderstorms will continue to impact all
Northern Lower Michigan TAFs thru this evening ahead of an
approaching cold front. Mainly MVFR/occasional IFR conditions are
expected thru the forecast period as ample low level moisture
lends to low cigs...as well as the development of fog late
tonight into early Thursday. S/SW winds of 10 kts gusting to 15 to
20 kts will diminish this evening and then shift to the W late
tonight into Thursday in the wake of the cold front.

&&

.MARINE...
Issued at 429 AM EDT Wed Aug 24 2016

Advisory level winds will continue over many of the nearshore waters
today, and into this evening for Lake Michigan. These advisory level
winds will be joined by the arrival of showers and thunderstorms.
There is only a small, marginal threat for severe storms for
damaging winds. The gradient weakens while a cold front moves in
later tonight and Thursday which will also result in a lingering
chance for showers and storms. Behind the front, winds turn NW
Thursday night, and there is a small chance for additional advisory
winds.

&&

.APX Watches/Warnings/Advisories...
MI...BEACH HAZARDS STATEMENT until 11 PM EDT this evening for MIZ015-
     016-019-020-025-031.

LH...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LHZ348-349.

LM...SMALL CRAFT ADVISORY until 11 PM EDT this evening for LMZ341-342-
     344>346.

LS...SMALL CRAFT ADVISORY until 6 PM EDT this evening for LSZ321.

&&

$$

UPDATE...MLR
SHORT TERM...Dickson
LONG TERM...JSL
AVIATION...MLR
MARINE...Dickson



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