792
FXUS64 KHUN 270138
AFDHUN

Area Forecast Discussion
National Weather Service Huntsville AL
838 PM CDT Thu Sep 26 2024

...New NEAR TERM...

.NEAR TERM...
(Tonight)
Issued at 838 PM CDT Thu Sep 26 2024

Hurricane Helene has strengthened to a Category 4 hurricane and is
forecast to make landfall tonight in the Big Bend area of the
Florida coastline. Just northwest of this, a stationary front
resides along the Florida panhandle northeastward through the
Appalachians. This has been the driver for the predecessor rain
event (PRE) throughout the southeast ahead of Helene and has
resulted in 0.5-2" throughout the I-65 corridor and northeastern
AL as well as portions of southern middle TN.

This frontal boundary is set to continue to provide forcing for
shower development ahead tropical banding from Helene overnight
during which higher chances of showers move into the area
(especially east of I-65). Training of showers will cause a
medium-high flood concern along and east of I-65 as 2-4" is
forecast to move over the area overnight. A Flood Watch is in
effect through 1 AM Saturday throughout all of northern AL and
southern middle TN to account for the period of prolonged
rainfall we are about to experience. This initial wave of rainfall
and subsequent flooding threat will be particularly hazardous due
to it occurring overnight when flooding is harder to see. Never
drive through flooded roadways and report any flooded roadways to
law enforcement.

In addition to the flooding threat, gusty winds also begin to
increase overnight as Helene moves inland. Sustained winds around
15-20 mph with gusts up to 25-35 mph (potentially higher in areas
of higher elevation) will likely be realized by daybreak and will
increase throughout the day Friday. A Wind Advisory will be in
effect beginning at 1 AM to account for this. Due to saturated
soils, downed trees and power lines are likely to occur which will
result in power outages. Be prepared for power outages by making
sure your devices are charged, using flashlights instead of
candles to avoid fires, and practicing generator safety to avoid
carbon monoxide poisoning.

As far as a severe threat goes, we are not forecasting severe
weather at this time. Lapse rates are weak and will result in a
very low chance of thunder/lightning along our eastern edge of the
CWA. Instability is very low as well, resulting in no tornado
threat at this time.

Small changes in Helene`s track will affect the forecast, so we
encourage everyone to stay up to date on the latest information.
If Helene shifts westward, we could have locally higher rainfall
totals as well as higher wind gusts.

&&

.SHORT TERM...
(Friday through Sunday)
Issued at 312 PM CDT Thu Sep 26 2024

Helene will continue to impact the area through Friday and additional
flash flooding and river flooding though could occur. Thus, a
flood watch remains in effect from 1 am CDT on Friday through 1 AM
CDT on Saturday. Guidance is showing the energy from the remnant
of Helene being absorbed into a upper low along/just behind the
front. Some additional moderate to heavy rainfall could linger
flash flooding and areal flooding to 1 AM CDT on Saturday. Thus,
the flood watch was extended through that time.

There should be a good gradient in rainfall totals in a transition
zone from NW Alabama further NE across the remainder of the area.
One to three inches looks more likely in NW Alabama, with the
higher amounts more likely further northeast between 3 and 5
inches with some isolated higher amounts around 7 inches possible
through Saturday morning. Flash and areal flooding concerns should
ease Saturday afternoon into Saturday night.

&&

.LONG TERM...
(Sunday night through Thursday)
Issued at 312 PM CDT Thu Sep 26 2024

Global models suggest that the deep-layer cyclone to our north
will continue to lift slowly northeastward on Sunday night, with
SW flow to the east of a trailing trough axis maintaining a moist
airmass across the TN Valley. It appears as if the drying trend
aloft will be complemented by a drying trend in the low-levels by
the middle of next week, as a cold front tracks southeastward
through the TN Valley. Although the cold front may indeed advect a
drier continental airmass into the region, highs will warm back
into the l-m 80s by Tuesday/Wednesday due to abundant sunshine
each afternoon. A dry forecast may return by next week.

&&

.AVIATION...
(00Z TAFS)
Issued at 622 PM CDT Thu Sep 26 2024

VFR conditions are forecast to continue, but will be short-lived
as Helene begins to make local impacts to our area overnight. IFR
to MVFR conditions are forecast to move in overnight into the
early morning hours as ceilings and visibilities drop at both
KMSL and KHSV. By 11Z, MVFR conditions are forecast to prevail
with a low chance of IFR conditions due to continued lowered
ceilings and visibilities as showers move over the area. In
addition to this, gusty winds are forecast to become prevalent
with gusts up to 22 kts from the northwest, which will increase in
speed (up to 35 kts) and become southwesterly by the end of the
TAF period. A low chance of LIFR conditions exists by the end of
the TAF period as ceilings could drop as low as 400 ft accompanied
by visibilities around 2SM.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Flood Watch through late Friday night for ALZ001>010-016.

     Wind Advisory from 1 AM Friday to 1 AM CDT Saturday for
     ALZ001>010-016.

TN...Flood Watch through late Friday night for TNZ076-096-097.

     Wind Advisory from 1 AM Friday to 1 AM CDT Saturday for TNZ076-
     096-097.

&&

$$

NEAR TERM...HC
SHORT TERM....KTW
LONG TERM....KTW
AVIATION...HC