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fxus64 kohx 211924 
afdohx

Area forecast discussion
National Weather Service Nashville Tennessee
224 PM CDT Sat Oct 21 2017

Discussion...

One last dry day today before rain chances move in tomorrow. Not
much change in regards to timing with the next wave, and still
looking dry and cooler from Tuesday night through early Friday.
Next chance at rain and a possible strong cold front for next
weekend still on The Table, although model spread is quite large
for temperatures next weekend.

Diving right in to tomorrow's onset of precipitation, still looks
like the earliest chances at rain will be just across the Tennessee River
in the late morning and spreading to areas west of I-65 before
sunset. Have in slight chance of thunder mention as models have
been trending downward with instability as a result of slightly
warmer temperatures aloft. Kept that trend going and removed
thunder mention on Monday as instability is extremely weak with
current model runs and has been trending downward. A few rumbles
of thunder may be possible on Monday however with any stronger
updrafts embedded with heavier precipitation. Looking at the main
trough, models still have the low separating from the larger
trough by Monday morning and becomes a closed low, however it
does not dig as far south as previous runs. This should move the
system through the area just a bit faster and get precip chances
confined to eastern zones by early Tuesday morning. The GFS is
quite bullish with getting rainfall out of the area and has the
rain out by Monday evening, while the European model (ecmwf) has some backside
precip developing with the second push south of the large trough.
Kept persistence in the forecast and still have some lingering
precip chances Tuesday, but the main event still looks to be late
Sunday night through the afternoon Monday where 1-3 inches of rain
will be possible across the area. Some localized flooding may
occur, especially with short duration heavy rainfall in flood
prone areas, but with the long stretch of drier weather before
this event not expecting too much in the way of widespread
flooding.

As the large Midwest trough dives southward again, cold air advection will be
reinforced across the mid state, and overnight lows Wednesday and
Thursday mornings will see the mid to upper 30s in many areas.
This may result in patchy frost development those mornings,
however shortwave ridging sliding in later on Thursday and Friday
will help increase temps slightly to finish off the week. Both the
GFS and European model (ecmwf) have a strong trough diving southward across the
area yet again next weekend. Both models have slowed down the
trough, but are still 24 hours or so off from eachother, so still
hard to pin down when precip will occur. However, both models have
below 0c 850 mb temperatures over the mid state late Sunday and
Monday, so if that pans out we may see our first freezing temps
for fall 2017. Next Monday is October 30, and the average first
freeze just happens to be October 29 for Nashville. Clarksville
has an average first freeze of October 25, and Crossville is
October 20, so overall this would be around average to slightly
after the first fall freeze should that occur.

&&

Aviation...
18z taf discussion.

Ckv/bna/mqy/csv...VFR thru 22/18z. Mainly high level cloudiness
with not significant directional wind change expected thru
22/18z. Sustained winds may diminish slightly due to the end of
diurnal heating influences after 22/00z. However, the continuation
of a defined sfc pressure gradient should not let wind speeds
drop too much, and will not break out additional prevailing
groups to address. Thus, will continue to forecast only one line
tafs for bna/mqy/csv. Ckv will be the exception here, with
possibly enough low level moisture advection by 22/17z to support
overcast ceilings around 5kft.



&&

Preliminary point temps/pops...
Nashville 60 80 62 67 50 / 10 20 90 80 20
Clarksville 61 77 57 65 47 / 10 40 80 70 20
Crossville 53 73 59 65 46 / 0 10 80 90 30
Columbia 59 78 59 67 47 / 10 30 90 70 20
Lawrenceburg 59 78 58 67 46 / 10 40 80 60 10
Waverly 61 77 58 66 47 / 10 60 80 60 10

&&

Ohx watches/warnings/advisories...
none.

&&

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