608
FXUS64 KOHX 270544
AFDOHX

Area Forecast Discussion
National Weather Service Nashville TN
1244 AM CDT Fri Sep 27 2024

...New AVIATION...

.UPDATE...
Issued at 845 PM CDT Thu Sep 26 2024

Hurricane Helene will make landfall shortly SSE of Tallahassee
with the latest NHC advisory indicating 130 mph maximum sustained
winds. Locally, we are seeing the tropical moisture overspreading
the area as it wraps around the upper low centered along the
Mississippi River at the TN/AR border. The rain will increase in
intensity and coverage overnight with the heaviest swath of rain
expected during the morning hours. The 00z CAMS are coming in as I
type, but the early indications is that the heavy amounts may
setup along the I-24 cooridor. One other area the CAMS are pinging
on is the pivot point of the moisture around the upper low. This
will be west of I-65 but east of the Tennessee River. As far as
rainfall amounts through tomorrow evening, the area will likely
see widespread reports of 2-4" with localized amounts of 6". The
Flood Watch is in effect until 12z Saturday.

As far as the winds, gusts will increase along the Plateau near
dawn close to Wind Advisory criteria (40 mph+). Those advisory
level winds will spread westward with the focus on locations along
and north of I-40. The strong gusts may temporarily slack late in
the morning but will increase again in the afternoon as the winds
swing back around to the south. The strongest winds during the
afternoon will likely be over the eastern third of the area where
gusts of 40-45 mph look reasonable. We are still not expecting
severe weather with all of this activity tomorrow. In fact,
lightning in general will be very sparse.

&&

.SHORT TERM...
(Rest of today through Sunday)
Issued at 1200 PM CDT Thu Sep 26 2024

Hurricane Helene is the big weather story and will be the main
impact on our local wx over the next couple of days. The mid
morning update had the center of Helene located 255 miles
southwest of Tampa with max sustained winds of 105 mph. Helene is
expected to make landfall in the Florida Big Bend region this
evening as a large, major Hurricane. The storm will move north
then northwest, weakening to a tropical depression as it moves
over Middle Tennessee and hangs around late Friday through
Saturday.

The main impacts for Middle Tennessee will be heavy rainfall
possibly causing localized flooding and gusty winds with
potential for a few downed trees and scattered power outages. We
have our entire coverage area under a Flood Watch and Wind
Advisory, both from 7 PM this evening until 7 AM Saturday.

Models have remained in pretty good agreement with the general
scenario, moving Helene toward Middle Tennessee, interacting with
a big cutoff low just to our west. Then the low pressure systems
will spin around and merge. A surge of tropical moisture will
precede the main center of Helene causing rain to spread quickly
across the area later today through tonight. Rain will become
heavy at times. As the center of Helene moves closer, winds will
increase with frequent gusts of 20 to 30 mph.

For rainfall, the heaviest and most widespread rain will occur
tonight through midday Friday. During this time, most areas are
expected to have 2 to 3 inches of rain with locally higher totals.
Additional on and off rain is then expected Friday night through
the weekend. Event totals will be mostly in the 2 to 4 inch range
with some areas up to 5 or 6 inches. By Sunday, there will be a
notable decease in coverage of showers as the low weakens and
starts to move out the area. Flooding is expected to be generally
localized, impacting roads and low lying areas. Small streams will
rise, some possibly reaching bankfull. Main rivers are expected
to handle the rainfall without reaching flood stage.

For winds, the strongest winds will occur in the early morning
hours Friday with another peak late Friday as low center
repositions and shifts wind directions from mainly north to
mainly south. Generally, the strongest gusts are expected across
our northeast half (generally along and northeast of I-24) with
some episodes of 40 to 45 mph gusts. Our southwest counties may
not reach advisory level, but given uncertainties about the
wobbling track, we decided to include all areas in the advisory.

Thankfully, parameters for severe storms and tornadoes are
looking low thanks to extensive coverage of showers and clouds.
Still, the setup is a little unusual and we may have a few pockets
of storms this weekend in areas of partial clearing or within
heavier rainfall bands. Very low risk, but something to keep in
mind.

&&

.LONG TERM...
(Monday through next Thursday)
Issued at 1200 PM CDT Thu Sep 26 2024

Some straggling showers may occur Monday, then we may have a few
showers with a cold front Tuesday. Otherwise the trend for next
week is for dry wx with seasonable temperatures.

&&

.AVIATION...
(06Z TAFS)
Issued at 1229 AM CDT Fri Sep 27 2024

Hurricane "Helene" has come ashore now and will be tracking
through Georgia. She was a cat 4 hurricane upon landfall and will
gradually weaken into a tropical storm as she reaches Northern Ga
toward sunrise. Following this she is expected to turn
northwestward and reach our Cumberland Plateau area, as a
weakening depression tomorrow afternoon. This all spells a
continuous bout of rain through the period. Helene is being aided
by a strong upper level low to our west. This is allowing a
divergent pattern aloft to further fuel Helene and keep her going.
Furthermore, any dry air intrusion which can act to weaken the
system at a quicker rate, has been cut off.

In addition to the rain fall of course, will be the increasing
wind speeds. As the depression moves into the area, wind speeds
will pick up in the morning and increase into the afternoon, with
highest gusts across our Plateau. Moreover, a decisive wind shift
will commence once the system slowly moves further west. Gusts as
high as 40 knots will be rather common place across the Plateau
area, with slightly lower wind impacts as you move west.

As for IFR conditions, look for IFR conditions to prevail
throughout the duration of the taf period.

&&

.PRELIMINARY POINT TEMPS/POPS...
Nashville      73  63  69  63 / 100  90  90  60
Clarksville    72  62  68  62 / 100 100  90  70
Crossville     70  58  65  57 / 100  70  80  50
Columbia       69  61  68  61 / 100  90  80  50
Cookeville     70  60  65  60 / 100  80  80  60
Jamestown      71  59  66  59 / 100  80  80  70
Lawrenceburg   68  60  67  61 /  90  80  80  40
Murfreesboro   72  62  68  62 / 100  80  90  50
Waverly        71  59  67  61 / 100 100  90  60

&&

.OHX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Saturday morning for Bedford-Cannon-Cheatham-
Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-Fentress-Giles-
Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-Lewis-Macon-
Marshall-Maury-Montgomery-Overton-Perry-Pickett-Putnam-Robertson-
Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne-
White-Williamson-Wilson.

Wind Advisory until 7 AM CDT Saturday for Bedford-Cannon-
Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-
Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-
Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-Pickett-
Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Van
Buren-Warren-Wayne-White-Williamson-Wilson.

&&

$$

UPDATE.......Reagan
SHORT TERM...13
LONG TERM....13
AVIATION.....21