Scientific Forecaster Discussion
fxus64 kohx 222339
Area forecast discussion
National Weather Service Nashville Tennessee
639 PM CDT Thu Jun 22 2017
for 00z aviation discussion.
First round of rain so far has mainly impacted areas near I-65 and
south of I-40 today, with amounts around an inch to an inch and a
half this morning. Other areas received around a tenth or so up to
three quarters of an inch per radar estimated totals. Models
continue to show activity becoming more scattered this afternoon,
and more isolated overnight between the 2 upper lows. Remnants of
Cindy will begin to impact the mid state Friday morning as the
upper low begins to phase with the Midwest/Great Lakes low later
on Friday and Saturday. Current model consensus has precip moving
into the northwest zones Friday morning, then spreading across the
area Friday afternoon, and finally ending off with continuing
across areas east of I-65 and the plateau in the evening and early
morning hours Saturday. As for the strong to severe storm threat,
models have increased shear slightly, and the potential for
isolated tornadoes and some damaging winds remains a possibility
during the afternoon and evening tomorrow. Low level shear and
helicity remain impressive, and most of the shear is concentrated
in the 0-1km layer, so some stronger cells that develop within the
showers may be able to produce some weak short lived tornadoes.
Since the deep layer shear has improved, stronger cells will also
have the potential to produce damaging winds as well especially
with a dynamic low as remnants of a tropical system.
A Flash Flood Watch has been issued for Friday for the potential
for heavy rainfall causing flood concerns. An additional 1 to 3
inches of rain looks to fall in the watch area, with locally
higher amounts should stronger storms develop within the showers.
Precipitable water values are still above 2 inches for most of the area with the
tropical like soundings, so models may be underestimating rainfall
amounts a bit especially if the low is a bit stronger than
anticipated. Therefore the watch will go from Friday morning
through Saturday morning. Additional flooding impacts may occur
this weekend as area rivers and lakes rise from the rainfall over
the past few days.
Rain looks to clear out pretty quickly Saturday morning, with
chances confined to the plateau and far south. The afternoon looks
to be rain free for now, and that trend looks to continue for most
of next week. A broad trough will sit over the Great Lakes region,
but models have backed off a bit on precip potential during the
work week, even as the trough strengthens and dips southward late
Tuesday into Wednesday. Afternoon showers and storms may be
possible, but for now kept things dry. Best chances so far next
week may be Thursday afternoon into Friday as a shortwave trough
may finally provide enough lift to kick off some showers and
00z taf discussion.
Bna/mqy/ckv/csv...MVFR conditions expected for the next 24 hours.
Bna...mqy...and ckv will experience a break in rain through 12z
when thunderstorms in the vicinity will come back into the forecast. Thunderstorms and rain will start again
around 15z. Csv and the Tennessee plateau will have -shra for the next
several hours through 03z. After a couple hour break vcsh will
come back into the forecast by 09z and thunderstorms and rain by 16z.
Cloud forecast for the next 24 hours will be a challenge. Expect
MVFR between 15k and 25k. Can/T rule out IFR below
10k...especially with thunderstorms. Where thunderstorms do
occur...precipitation will be heavy at times. A Flood Watch has
been issued from 12z Friday through 12z Saturday for ckv/bna/mqy.
Alternate scenario...lower clouds than forecasted overnight and
during thunderstorms. Winds could gust overnight as the remnants
of ts Cindy approach middle Tennessee.
Flash Flood Watch from Friday morning through Saturday morning