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Area Forecast Discussion

410
FXUS64 KOHX 271012
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
512 AM CDT MON JUN 27 2016

.UPDATE...
FOR 12Z AVIATION DISCUSSION.

&&

.SHORT TERM...
(Today thru Wed Night)

Broke out early this morning wording in the zone forecast product
to deal with lingering convection chances across the mid state,
mainly upper Cumberland Region, thru the remainder of the early
morning hours. Otherwise, one thing that we can say, although
still muggy in locations that may not experiencing rainfall by
this afternoon, and end to afternoon heat index values ranging
from 100 to 105 degrees for locations west of the Cumberland
Plateau Region is expected to occur. This due to a surface summer
time cold front approaching the mid state as the day progresses,
bringing with it, by the afternoon hours, likely shwr/tstm to the
mid state. Detailed the grids today to show a progression to these
likely shwrs/tstm chances by the afternoon hours. SPC has placed
the mid state under a marginal risk today of svr tstms for this
afternoon, and certainly can not rule out a rogue svr tstm or
two, but this will mostly be your usual strong diurnal driven
summer time tstm event with an approaching front, with good
surface based CAPE values, negative LI`s, and precip water values
in the 1.75 to around 2 inch range, but not a lot of low level
shear of note. Some moderate to isolated heavy rainfall may occur
at times, with ponding of water possible, but an organized flood
threat is not anticipated. Upper level ridging influences will
continue to shift wwd, and can not rule out a weak upper level
disturbance transversing the mid state aiding in convective
development also. Still looks like an upper level trough will try
to dig down into the mid state area tonight also. This sfc front
will push south of the mid state by the evening hours, as yet
another secondary summertime cold front moves close to the
vicinity of the TN/KY border by the overnight hrs tonight. This
should keep a slight chance to chance of shwrs/tstms in the
forecast thru tonight.

As secondary weak cold front moves through the mid state region
on Tuesday, enough low level moisture may still be around across
locations approaching the TN/AL border and the Cumberland Plateau
Region to support a slight chance of mainly light showers and
thunderstorms on Tue.

From Tue night thru Wed night, with a western Ohio River Valley/
Middle MS River Valley 1020mb sfc high pressure center building
into the mid state region, along with a dry nwly nwly upper level
flow pattern, dry conditions along with mostly clear skies are
expected.

As for temps...temps should close to or a few degrees above
seasonal normal values through Tuesday night. With the above
mentioned western Ohio River Valley/Middle MS River Valley 1020
mb sfc high pressure center building into the region Wed into Wed
night, temps will cool to a few degrees below seasonal normal
values. This cool down reflected well in 850 mb temp profiles with
around 18C temps on average across the mid state early in the work
week to more of a 12C northwest to 16C southwest spread by late
Wed afternoon. All in all, SuperBlend temp forecasts leaned toward
the most thru the short term forecast period with minor tweaks
here and there taken.

.LONG TERM...
(Thu thru Sun)

Thursday`s weather map will feature a sw-ne sfc high pressure ridge
with the mid state on the southwestern edge. An inverted surface
trough will reside across the north central gulf and northeast
along the spine of the appalachians. CAPE values will be minimal
and all the moisture will be along the eastern side of that
aforementioned trough.

Going forward, surface high will weaken considerably by Friday.
CAPE values still look rather weak but with an overall minimal
broad troughing pattern, will opt to include a slight chance of
showers and thunderstorms.

Convective potential increases on Saturday as dewpoints begin to
climb. Surface boundary will be on approach and we should see better
convective coverage at that time. Pops to increase, further still,
on Sunday as the boundary will be in closer proximity. Furthermore,
mid/upper level upstream curvature and shear appears to increase.
40 pops look good for now.

For the extended temps, broad troughing will translate nicely to
some cooler thermal parameters, especially on Thursday. Highs will
generally be in the 80s with plentiful sunshine. 850 mb temps to
remain between 16c and 18c for the remainder of the extended period
as the weak broad upper troughing hangs on. Highs should hold in the
upper 80s, but we will see low temps inch up a few degrees, to
near 70 west of the Plateau by Sunday.

&&

.AVIATION...
12Z TAF DISCUSSION.

CONVECTION WILL BE ON THE INCREASE TODAY AS A FRONTAL BOUNDARY
PRESSES SOUTHWARD TOWARD THE AREA. COVERAGE SHOULD MAX OUT BETWEEN
17Z AND 21Z TODAY. HIGH PRESSURE WILL BUILD IN OVERNIGHT BEHIND
THE FROPA...ALTHOUGH SOME LIGHT FOG WILL BE POSSIBLE TOWARD 12Z.

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

DISCUSSION......31
AVIATION........21



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