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Area forecast discussion...updated 
National Weather Service Huntsville Alabama
612 PM CDT Thursday Sep 3 2015

Update...
for 00z tafs

&&

Discussion...
/issued 133 PM CDT Thursday Sep 3 2015/
isolated convective cells have developed from middle Tennessee into northestern Alabama
early this afternoon. This development has been along a weak
convergence zone within the northwestern quadrant of compact upper circulation
that is exiting northestern Alabama per water vapor imagery. The hrrr suggests
that this "band" of cells will move S-SW this afternoon and
deteriorate quickly by 23-00z. For now, will leave a dry forecast for
tonight. Another muggy night is ahead along with patchy fog likely
given dew points remaining in the u60s-l70s, light flow and a mostly
clear sky. Friday should be another very warm and muggy day. The tail
end of a weak wave dropping southeast in the upper flow along with some
uplift along the Cumberland Plateau may instigate a few cells again
Friday afternoon. I presume that these will be similar in areal
coverage and mostly weak-moderate intensity like we are observing
today. This would be mainly in southern Tennessee and northestern Alabama where we have
posted isolated T in the forecast. Forecast will side with the NAM/men
dew point values over the raw GFS/gfsmos which continue a trend of
being too low, especially during the daylight hours.

Over the weekend, a surface/800 mb anticyclone will be located over the
middle and lower Ohio Valley. There will also be a continued presence
of an upper level low over the Carolina coastline with a few spokes
of vorticity circulating on its northern quadrant. This system also
produces a "back door" cold front which arrives Saturday evening in
our eastern counties. At this point, most of the area should remain
dry on Saturday, with low chances of a few rain showers/thunderstorms in our eastern
counties as the front arrives. The GFS appears to over-forecast
areal coverage of precipitation Saturday night into Sunday, so have opted
closer to the NAM.

The low to middle level high pressure cell over the Ohio Valley builds
further southeast early next week. The 500 mb upper trough axis plaguing the far
southeastern U.S. Begins to shift a bit further northwest by middle week before a fall-
like cold front tracks to the I-40 corridor Thursday. It would appear
that this front will not proceed through the Tennessee Valley which will
certainly play a role in the forecast beyond d7.

&&

Aviation...
for 00z tafs...lingering convection over a few areas associated with
a departing upper disturbance to the east should continue to diminish
over the next 1-2 hours. This should give way to VFR conds heading into
the overnight period...before some -br/MVFR visible develop. Conds/visible may
briefly lower into the IFR range early Friday morning...before improving
back to VFR shortly after daybreak.

09

&&

Hun watches/warnings/advisories...
Alabama...none.
Tennessee...none.
&&

$$

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