Tornado and Flash Flooding in Alabama, March 1 to 2, 2023

Area Forecast Discussion
National Weather Service Huntsville AL
827 PM CST Wed Mar 1 2023

...New NEAR TERM...

.NEAR TERM...
(Tonight)
Issued at 827 PM CST Wed Mar 1 2023

A couple of supercellular type of storms has crossed into parts of
NW AL this Wed evening, although fortunately they look to be on a
weakening trend. However, very impressive Bulk/Effective Shear
profiles in excess of 70kt are in place over much of the central
TN Valley and a Tornado Watch is in place for all of the CWA thru
2AM CST. A weak frontal boundary remains located to the NW of the
area and is not expected to settle more to the SE until early Thu
morning. Latent instability though along/south of the front is
expected to weaken heading into the overnight hrs, which should
lower the threat of severe wx. Multiple waves of showers/perhaps a
few embedded tstms though remain possible along/ahead of the front
into Thu morning and likewise may transition into a threat for
localized flooding in some locations. A Flood Watch is also in
effect for all of the mid TN Valley thru tonight and into Thu. So
bottom line is the threat for severe wx remains in place thru at
least the evening hrs before tapering off overnight, while more of
a potential flooding threat develops late tonight. Current temps
are mainly in the mid 60s/lower 70s, although given a continued
influx of moist air ahead of the frontal boundary to the NW, temps
into early Thu may struggle to fall past the 60F mark.

&&

.SHORT TERM...
(Thursday through Saturday)
Issued at 121 PM CST Wed Mar 1 2023

Ongoing MCS activity may tend to wane Thursday morning, but with
the east-west frontal boundary in place, CAMS and short range
deterministic models continue to support redevelopment of
convection at times through Thursday, although the threat of
widespread heavy rain will diminish with time. The warm sector is
still forecast to overspread the area with a likely capping
inversion which will severely limit development Thursday night. We
have lowered PoPs from suggested blends to account for this
drop off. The models continue to vary somewhat on timing of the
cold front/squall line, with arrival around 12Z/Fri +/- 2 hours or
so. The ARW is a bit slower than the HRRR, but would likely side
with the faster solution. The CAMS seem to be favoring more
vigorous convection and possible supercells closer to the upper
level shortwave/strong -divQ field in western TN into southeast MO
and western KY. The capping inversion and a skinny CAPE profile
may suppress development a bit further south along the line in MS
into AL where a thin squall line is depicted. Nevertheless, this
doesn't reduce the risk of damaging winds and perhaps tornadoes
associated with the line given the very large low level SRH values
and shear will be present.

The strong deep layer wind fields, ample mixing and pressure
gradient behind the cold front all point to the potential for a
high wind event. As of now, wind gusts of 40-50 mph are forecast
in our grids. We will hold off on hoisting a advisory or warning
at this point, preferring to wait until after tonight and
Thursday's severe/flood threat has passed. But will likely issue
one by Thursday afternoon at the latest.

A welcome tranquil weather day will arrive on Saturday as high
pressure builds into the lower Missouri and Mississippi Valleys.
Highs will still reach the upper 50s to lower 60s after morning
lows in the lower 40s.

&&

.LONG TERM...
(Saturday night through Wednesday)
Issued at 121 PM CST Wed Mar 1 2023

Low impact weather will continue through early next week as 5h
heights gradually rise across the Gulf of Mexico and southern
states. Southerly flow will develop Monday and Tuesday bringing
temperatures back into the 70s, but also a chance of light shower
activity spreading northward into the mid South and TN valley. A
greater chance of more widespread showers will occur on Wednesday
as a shallow cold front drops south beneath the upper ridge across
the south.

&&

.AVIATION...
(00Z TAFS)
Issued at 535 PM CST Wed Mar 1 2023

Mid/high cloud cover continues to spread into the area from the
WSW heading into the evening hrs this Wed. MVFR cigs though near
3K ft are expected to develop around 02-03Z, as -shra along/ahead
of a weak frontal boundary settles into the area from the NW.
Embedded tsra are possible within increasing shra around 03-07Z
and a TEMPO group has been added to account for additional cig/vis
reductions. Shra will begin to taper off Thu morning, although
IFR cigs near 700-900ft look to develop/prevail thru the remainder
of the period. Light/var winds will also become south near 10kt
with higher gusts this evening, before turning WSW overnight.

&&

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

TN...Flood Watch through Friday afternoon for TNZ076-096-097.

&&

NEAR TERM...09
SHORT TERM....17
LONG TERM....17
AVIATION...09