High Wind and Strong Wind in Alabama, February 27, 2023

Area Forecast Discussion
National Weather Service Huntsville AL
1125 AM CST Mon Feb 27 2023

...New AVIATION...

.NEAR TERM...
(Rest of Today)
Issued at 940 AM CST Mon Feb 27 2023

An overcast layer of low stratus clouds has overspread the TN
Valley this morning, in the lower-tropospheric warm/moist
advection regime downstream from a mid-level trough and related
surface cyclone currently positioned across northeastern
MO/southeastern IA/western IL. Recent trends in radar data suggest
that light showers embedded within this regime will continue to
expand in coverage across the local area, with a recent increase
in heavier/convective showers noted in the vicinity of an ill-
defined surface trough from southwestern TN into northwestern MS.
Present indications are that the more persistent band of broken
convection to our west will shift quickly eastward through our
CWFA later this morning, and should exit our southeastern zones by
mid-afternoon. Although a couple of lightning flashes could
certainly occur with the stronger updrafts, the presence of a
strong mid-level inversion will make this risk very low, and
generally confined to locations south of the TN River.
Southwesterly gradient winds of 20-30 MPH (gusting to 45 MPH) will
occur in the wake of the surface trough, and a Wind Advisory
remains in effect through 6 PM CST. As skies clear from W-to-E
this afternoon, temperatures will rise into the l-m 70s (warmest
across northwest AL).

&&

.SHORT TERM...
(Tonight through Friday)
Issued at 316 AM CST Mon Feb 27 2023

Showers will taper off from west to east late this afternoon into
the evening as winds veer to the WSW and west in wake of the
frontal passage. Drier air will temporaily erode cloud cover --
though we won't get a meaningful air mass change by any stretch
of the imagination. In fact, by Tuesday WSW flow and ample
sunshine should warm us right back into the mid 70s in most
locations in what will be a welcome dry day. Wednesday will be a
transition day across the Tennessee Valley as deep southwesterly
flow increases well ahead of a developing low pressure system over
the Desert Southwest -- helping to advect in a warm, moist air
mass. This is easily seen by PWATs which are progged to increase
into the 1.4" to 1.6" range by Wednesday evening/night -- which
would be record high values per OHX sounding climatology.

For Wednesday evening/night, the feature of greatest importance
will be a surface low over the Plains shifting into the Great
Lakes, dragging a cold front through the Ohio and Tennessee
Valleys. Guidance continues to indicate this boundary will
decelerate as it moves into our area Wednesday night, serving as
a focus for widespread (80-100%) showers and thunderstorms.
Instability isn't overly impressive, but the environment may be
favorable enough for a few strong to perhaps marginally severe
storms capable of producing hail and some gusty winds. The main
concern during this Wednesday evening/night into early thursday
timeframe will be the potential for multiple rounds of moderate to
heavy rainfall, depending on where the frontal boundary stalls.
In this setup, convection would roughly parallel this boundary and
be efficient rain producers which will potentially heighten our
concern for flash flooding -- with most guidance dropping between
1" to 2" during this 12-18 hour timeframe. With more rain on the
way Thursday night into Friday, this would also set us up for
rises on rivers, creeks, and streams.

Speaking of late Thursday into Friday, the aforementioned front
will likely lift back to the north during the day on Thursday as a
warm front, placing much of the Tennessee Valley in a broad warm
sector by the afternoon/evening. Convection may become more
scattered during this timeframe as a lull develops ahead of the
main cold front to our west. Mid/long range guidance continues to
trend northward with a closed upper-low that will be shifting
from the ArkLaTex into the Mid South Thursday night. Two days ago,
guidance placed the surface low across the I-20 corridor of MS/AL
at 06z Friday -- but now favors Arkansas into northwest
Tennessee. Synoptically speaking, this would place the Tennessee
Valley more in line with a severe weather threat than a Hydro one
during the Thursday night into Friday period -- but it all
depends on how this system evolves. Under the current forecast, a
likely strong to severe line of storms would push across the lower
Mississippi Valley and into the Tennessee Valley late Thursday
night into Friday morning. Potentially, all modes of severe
weather would be possible given the very strong shear in place
and appreciable instability. Some fluctuations in timing are
possible and guidance may slow this system down some -- putting
our area more under the gun for Friday. Still a bit of
uncertainty with the timing aspect, so stay up to date on the
latest forecast information this week.

&&

.LONG TERM...
(Friday night through Sunday)
Issued at 316 AM CST Mon Feb 27 2023

The line of storms will have cleared the area by Friday
evening/night as a drier air mass advects in. Expect a bit of a
cool down this weekend as highs will drop back into the upper 50s
to mid 60s. The good news is that we'll have a decent amount of
sunshine, allowing the ground to dry out and any swollen rivers
levels to recede. High pressure will build back into the area and
help to maintain these conditions through Sunday.

&&

.AVIATION...
(18Z TAFS)
Issued at 1123 AM CST Mon Feb 27 2023

Off/on showers will plague the TAF sites through early this
afternoon, along with gusty winds (sustained SSW winds up to 25kts
and gusts up to 40kts) through this evening. Current MVFR conds
will give way to VFR once the line of showers moves through both
terminals in the next few hours, clearing MSL shortly after 27/20Z
and HSV after 28/00Z this evening. Winds will subside overnight
tonight with light/variable winds expected by sunrise Tuesday
morning.

&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory until 6 PM CST this evening for ALZ001>010-016.

TN...Wind Advisory until 6 PM CST this evening for TNZ076-096-097.

&&

NEAR TERM...70
SHORT TERM....AMP
LONG TERM....AMP
AVIATION...12