Area Forecast Discussion
Issued by NWS Nashville, TN

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FXUS64 KOHX 302217
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
517 PM CDT Sun Apr 30 2017

.UPDATE...
FOR MESOSCALE DISCUSSION...
Line of strong to severe thunderstorms now moving east across the
Cumberland Plateau at 35 mph. Bowing line segments observed on
radar, with strong straight line winds continuing to be the main
threat, along with the possibility for a few spin-up tornadoes.

Recently cancelled a batch of counties near the I-65 corridor from
TOR Watch #183, and will likely do another row of counties
immediately behind the main convective line by the top of the next
hour.

Much more stable air behind the convective line, and even the
showers ahead of the cold front near the Mississippi River are
pretty lackluster. As a result, have trimmed back thunder
expectations behind the main line of convection overnight and made
some adjustments to pops and weather grids.


&&

.MESOSCALE DISCUSSION...



&&

.PREV DISCUSSION.../ISSUED /

Focus for this forecast will be today as a tornado watch is in
effect until 7 pm for most of the mid state. A few of the short
term models such as the HRRR have indicated 2 waves of precip; one
being this initial line currently approaching the I-65 corridor
and the second band of precip closer to the cold front that will
pass through the area this evening and early overnight. The
initial band will be the best shot at any severe thunderstorms as
instability falls off rapidly after sunset, even with the help of
fropa later on. With the initial band, 0-1km shear is quite high,
along with decent helicity, so isolated tornadoes will be a
possibility. Overall, any strong to severe thunderstorm will have
the potential to produce damaging winds with the strong low to mid
level flow along with decent instability. Model consensus is to
drop instability quickly after 00Z as mentioned earlier, but
thunderstorms will remain possible with the next band of precip
moving through this evening and overnight.

Monday morning will have showers mainly confined to the Plateau
before skies clear out a bit from west to east. NVA isnt too
strong behind the front, so clouds may stick around a bit longer
as the upper low spins northward towards the Great Lakes. Winds
will also be strong similar to today, with wind advisory criteria
probably being met across most of the area, so may need to issue
another wind advisory for Monday mid morning through the
afternoon. As the upper low continues to migrate northward then
eastward by Wednesday, the mid state looks to stay dry Monday and
Tuesday. By Wednesday, another upper trough develops in the
Plains, and some shortwave disturbances out ahead of the trough
will provide enough lift for another round of showers and
thunderstorms Wednesday into Thursday. The ECMWF is just a bit
faster with precip along the warm front Wednesday morning, but
generally agrees with the GFS by Thursday morning. Therefore have
likely pops Wednesday night into Thursday afternoon for the mid
state.

The GFS and ECMWF differ on the upper low for the end of the work
week, as the GFS has it spinning overhead bringing continued
chances for showers, while the ECMWF has the low spin off to the
northeast. Kept in mention of showers for now on Friday and early
Saturday to lean more towards consensus. The remainder of Saturday
and Sunday are back to looking drier as upper ridging tries to
move in by the end of the weekend. The upper low may trigger a few
showers in the northeast as it travels towards New England, but
for now kept the mid state dry for Saturday afternoon through
Monday morning.

&&

.AVIATION...
18Z TAF DISCUSSION.

Strong winds will continue across the region into this evening
thanks to strong gradient and mixing, but will decrease some later
this evening. Expect band of showers and storms to sweep across
Middle TN...with arrival 19-20Z CKV, 20Z BNA and after 00Z CSV.
Expect additional areas of showers and isolated storms after the
main band passes...and continuing until about 06Z CKV/BNA...but
lingering until after 12Z at CSV. Becoming VFR Monday
morning...though expect gusty winds again most of the day.


&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      56  70  51  77  54 /  90  10   0   0  20
Clarksville    53  65  49  75  52 /  70  10  10  10  20
Crossville     59  67  47  70  50 / 100  40   0  10  10
Columbia       55  69  50  77  54 /  70  10   0  10  20
Lawrenceburg   55  70  49  77  54 /  90  10   0  10  10
Waverly        53  66  50  76  54 /  70   0   0  10  30

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 10 PM CDT this evening FOR Bedford-Cannon-
Cheatham-Clay-Coffee-Davidson-De Kalb-Dickson-Giles-Hickman-
Houston-Humphreys-Jackson-Lawrence-Lewis-Macon-Marshall-Maury-
Montgomery-Perry-Robertson-Rutherford-Smith-Stewart-Sumner-
Trousdale-Wayne-Williamson-Wilson.

&&

$$

DISCUSSION......19
AVIATION........08



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