Area Forecast Discussion
Issued by NWS Nashville, TN

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FXUS64 KOHX 251933
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
233 PM CDT Sat Mar 25 2017

.DISCUSSION...

Well, things are quiet so far across the mid state. Models came
in this morning slightly weaker than what was seen yesterday, and
the slight risk was pushed further south, leaving the marginal
behind. MUCAPE values this afternoon may climb into the 500-1000
J/kg range along with 30 to 40 knots of 0-6km shear. Lining up
short term models does match up well with this axis of unstable
air during the mid to late afternoon, so strong to severe storms
will remain possible today. Showers that have developed thus far
have weakened once crossing the TN River, and so far the HRRR has
tracked the precip pretty well. Should that trend continue with
the HRRR, there will be 2 bands of convection that will pass
through the mid state. One will be moving in from the south around
2-3 pm and push through the eastern zones by 9 pm or so, and
trailing showers/isolated thunderstorms will follow behind this
evening and overnight. The better severe threat as mentioned
earlier will be with that first band that lines up with the more
unstable air mid to late afternoon and even into the evening. With
MUCAPE and lapse rates decreased, the main threat with stronger
to severe storms will be damaging winds, but wont rule out some
hail should cells ramp up a bit this afternoon.

Sunday will have some lingering showers and even some
thunderstorms in the morning, and carry to the east for the
afternoon. The shortwave ridge that was between the 2 troughs has
weakened over the past few runs, so the dry period does not look
to be long lived late Sunday into Monday. The next Plains trough
begins to impact the mid state by late morning on Monday, and
keeps chances for showers and thunderstorms in the forecast with
this trough until late Tuesday. Models have been consistent with
MUCAPE values around 1000-1500 J/kg or so, and shear around 30-40
knots, so the potential for severe thunderstorms is there Monday
late morning through the afternoon. The upper trough does weaken a
bit as it approaches the mid state, but there`s enough instability
and shear for some severe storms Monday. SPC does have a slight
risk for the western zones, so will definitely keep an eye on how
models handle Monday over the next few runs.

Kept mainly dry conditions Tuesday night into early Wednesday
before another trough moves in from the southern Plains. The GFS
has this trough holding its strength as it crosses the south, and
keeps a closed low aloft, while the ECMWF weakens the trough and
progresses it northeast. Since disagreement is pretty high, its
uncertain on timing with this event, but the potential is there
for another shot at some strong to severe storms. There is some
agreement for Friday, and further west into the MS River Valley
Thursday, but right now its too uncertain to pinpoint the better
day for the area. Do have thunderstorms mentioned for both days as
the potential will be there. Saturday may also have some trailing
showers/thunderstorms behind the trough via the GFS, but the ECMWF
has things cleared out with the upper trough over the Atlantic
Coast. Sunday looks to be dry, but have in chances for precip
Saturday and Saturday night should models line up for the first
half of the weekend.

&&

.AVIATION...
18Z TAF DISCUSSION.

Winds have been the main topic so far today with TAF sites
generally gusting up to around 30 kts. Breezes will continue until
pressure gradient decreases tonight. The anticipated storms have
been slow to develop today as areas of showers continue
weakening/dissipating as they move from West TN into Middle TN.
Still expect a general increase in precip coverage later this
afternoon although instability should remain unimpressive so any
strong/severe storms will be very isolated. Put the best chance
for storms in the 20Z to 00Z window for BNA and CKV TAFs but held
off until after 00Z at CSV. Rain chances will decrease after 06Z
except at CSV where showers should continue through the night and
possibly into Sunday. Widespread MVFR conditions mainly for
ceilings overnight and into Sunday but should see improvement
toward the late morning.


&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      59  75  55  78  59 /  80  40  10  50  70
Clarksville    55  72  53  76  57 /  80  30   0  60  60
Crossville     57  68  54  72  56 /  80  80  20  50  70
Columbia       58  74  56  76  60 /  80  40  10  50  80
Lawrenceburg   58  74  57  77  60 /  80  50  10  40  70
Waverly        56  73  55  76  58 /  80  20  10  60  80

&&

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

&&

$$

DISCUSSION......Barnwell
AVIATION........49



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