Area forecast discussion
National Weather Service Nashville Tennessee
1209 am CDT Tuesday Jun 18 2013
Update...
06z taf discussion.
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Aviation...
Rain showers and a few -tsra spreading across ckv/bna currently and will
reach csv in a few hours. Expect MVFR ceilings/visible overnight with IFR
in heavier thunderstorms and rain. Improving conditions after 12z with precipitation moving
east of airports but MVFR ceilings to continue through 17z. Light
northeast winds tonight will back to north and northwest during
the day as mesoscale convective vortex moves across.
Shamburger
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Previous discussion... /issued 936 PM CDT Monday Jun 17 2013/
Update...
convection across SW Tennessee beginning to fill in and increase in
intensity. Leaning more toward HPC quantitative precipitation forecast now with the greatest
amounts expected across the southern half of the County Warning Area. Latest storm
total quantitative precipitation forecast does show 1 to 2 inch amounts...from the earlier
rainfall over our southern counties. EST quantitative precipitation forecast totals through 18z
tomorrow look like 1 1/2 to 2 1/2 across the watch area. Latest
ffg from the rfc's have lowered a bit as well.
Will opt to issue a Flash Flood Watch for roughly our southern
tier of counties. Perry...Lewis and Maury will also be included.
Thanks to surrounding offices for coordinate.
Previous discussion... /issued 717 PM CDT Monday Jun 17 2013/
Update...
this evening...strong shortwave located over Illinois with the axis
extending SW across MO. Meanwhile...associated surface low is located
over east central Arkansas. With positive vorticity advection merging with the expected
surface track toward the east...we expect this low level feature to
strengthen as it moves eastward overnight. Models are in
reasonable agreement with moving the surface low directly over the middle
state by 12z. Thus...with low level forcing increasing and
combining with the passing shortwave...plentiful dynamics look to
be coming together to promote an additional 1 to 2 inches of
rainfall across the area.
An examination of the latest storm total precipitation amounts and
the latest rfc ffg does not suggest a widespread flooding event.
Furthermore...the progressiveness of the aforementioned shortwave
should prevent the required heavier quantitative precipitation forecast return for widespread flooding.
GFS model does show impressive circular quantitative precipitation forecast structure but the
associated vorticity maximum looks blown up and does not correspond well
to the apparent upstream curvature and shear. Additionally...the
model initializes too far south with the bullseye and thus...if it
were to pan out...the heavier rain would remain north of Tennessee.
For the update...not a whole lot of change to the grids other than
a 20% upward quantitative precipitation forecast adjustment. All in all...low level instabilities
have lessened. The overnight looks more and more like a solid rain
event with 1 to 2 inches across the area.
Previous discussion... /issued 625 PM CDT Monday Jun 17 2013/
Aviation 00z discussion...
a series of frontal boundaries will drop southward across the middle
state tonight and Tuesday morning. As a result...unsettled weather
can be expected with numerous showers and thunderstorms
overnight...particularly after 04z. Conditions will improve after 12z
as drier air begins to move in behind the southward moving
boundaries. Partial clearing will commence after 18z.
Previous discussion... /issued 252 PM CDT Monday Jun 17 2013/
Mesoscale update...
band of convection currently extends from Clarksville southeast
down through Franklin...Lewisburg into north Alabama. The strong
storm currently is on the Dickson and Cheatham County line just
southwest of Ashland City. Expect this activity to continue to
lift northeast over the next 2 to 3 hours and be more aligned from
Clarksville down through the Nashville area and between Interstate
40 and Interstate 24 on toward Chattanooga by 5 or 6 PM.
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Ohx watches/warnings/advisories...
Flash Flood Watch through Tuesday afternoon for tnz056-058-060-
061-075-077-079-093>095.
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