Severe Thunderstorm Warning 313, NWS Shreveport, LA

Area Forecast Discussion
National Weather Service Shreveport LA
539 AM CST Sat Dec 28 2024

...New AVIATION...

.SHORT TERM...
(Saturday through Sunday)
Issued at 400 AM CST Sat Dec 28 2024

Bottom line up front: An outbreak of severe weather is expected
across the region today with all modes in play to include a few
strong tornadoes, particularly across the southern half of the
region from East TX eastward into all of North and Central LA.

Analyzing the setup this morning, of note is a warm front that
continues lifting back northward as it nears the I-20 corridor
with lower to mid 60s dew points in its wake. The expectation is
for the warm front to reach as far north as I-30, leaving a good
majority of our region in an expansive warm sector environment.
Prior to that and the eventual onset of severe convection later
today, we are dealing with dense fog across roughly the SE half
of the area this morning. Therefore, a Dense Fog Advisory is in
effect through 9 AM for areas extending along and SE of a line
from Jacksonville, TX to Magnolia, AR.

Deeper synoptic analysis reveals a very robust shortwave pivoting
from eastern NM into the TX panhandle/west TX early this morning.
It is this mid/upper-level feature that is expected to eventually
interact with the expanding warm sector air mass south of the
warm front and the attendant sfc low located across NE TX. Storm
initiation is expected to begin by mid to late morning across NE
TX and expand across the remainder of the region throughout the
morning. Initially, this morning convection will likely pose a
primary threat of large hail with thunderstorm clusters before the
threat of damaging wind gusts and tornadoes become the overarching
concern as the event evolves through this afternoon/evening with
increasingly warm and moist advection south of the warm front.

By the midday timeframe, the shortwave trough is expected to be
near I-35 across North and Central TX with upper forcing becoming
maximized over much of the Central Gulf Coast and Lower MS Valley
through the afternoon and evening hours. Given the late day timing
of trough ejection across the expanding warm sector environment
coupled with the sfc low tracking through the heart of the region,
a marked increase in both deep-layer shear as well as low-level
shear is expected across the aforementioned areas. As a result,
SPC has upgraded most of NE and Central LA to a Moderate Risk
along with the areas immediately adjacent of Toledo Bend Country
in Deep East TX. Likewise, areas farther north and west have also
seen a category upgrade given the extent of warm sector expansion
that is expected. The northern extent of the Enhanced Risk area
now stretches roughly from Henderson, TX to Shreveport/Bossier
City to near El Dorado, AR. These points along with the Moderate
Risk area farther SE are both included in a 10-15% "hatched" area
potential for strong tornadoes (EF2+) due to the marked increase
in 0-1 km SRH in the range of 200-300 m2/s2 by this afternoon. The
environment across these areas will be supportive for supercells
and even a few long-track tornadoes this afternoon into the early
evening. This threat will occur ahead of a larger linear complex
that is expected to bring more of a damaging wind threat along an
advancing QLCS later on in the event with some embedded tornadoes
still possible as well before the event finally concludes across
all of our region just prior to midnight.

Last but not least among the all modes severe weather concerns is
the threat of heavy rainfall and localized flash flooding. Slight
Risk for excessive rainfall encompasses the vast majority of the
region today with another widespread 1-2 inches of rain expected
and isolated higher amounts possible.

The remainder of the short-term period will be mostly benign with
the exception of another round of fog possible overnight in the
wake of additional rainfall. Expect sunshine to finally return on
Sunday with temperatures remaining above average through the rest
of the weekend before cooler weather finally arrives later next
week.

/19/

&&

.LONG TERM...
(Sunday Night through Saturday)
Issued at 400 AM CST Sat Dec 28 2024

By the start of the long-term period on Sunday night, look for a
pleasant night with mostly clear skies and temperatures dropping
off into the 40s for overnight lows. Moving ahead to Monday night
through Tuesday, the next shortwave shifting out of the Rockies
will usher in the next cold front to the region, quickly followed
by an even stronger cold front with some Canadian influence by
mid-week just in time for New Year's Day.

Widespread rainfall is not anticipated in association with these
fronts, but temperatures will finally return back near seasonal
averages during the remainder of next week. Expect highs to range
through the 50s areawide beginning Wednesday, and overnight lows
will fall to either side of the freezing mark each night during
this mid to late week timeframe before yet another cold front
arrives by Friday night into Saturday. This will maintain the
trend of seasonal temperatures through the first weekend of
January.

/19/

&&

.AVIATION...
(12Z TAFS)
Issued at 534 AM CST Sat Dec 28 2024

A hazardous weather day is in store for all terminals today as a
strong storm system moves through. Most terminals are currently
dealing with dense fog and low ceilings, with vsbys 1SM or less
and ceilings below 500 ft. Not much improvement is expected over
the next few hours and heavy rain showers and thunderstorms will
be rapidly developing. Expect strong to severe thunderstorms to
impact terminals in the 15z-00z window today, resulting in very
gusty winds, hail, and torrential rain. There will be a brief
break in the stormy weather from W to E through the late afternoon
and evening, with perhaps a brief period of some low ceiling
scattering. Despite this, given heavy rainfall and little change
in the airmass as the system exits, areas of fog and widespread
low ceilings are anticipated after midnight and into Sunday
morning.

Kovacik

&&

.SPOTTER INFORMATION STATEMENT...
Issued at 400 AM CST Sat Dec 28 2024

Spotter activation will be needed throughout today and into this
evening.

/19/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  70  51  68  50 / 100  30   0   0
MLU  73  52  67  48 / 100  60   0   0
DEQ  62  43  64  43 /  90  40   0   0
TXK  65  48  68  48 / 100  40   0   0
ELD  66  47  66  45 / 100  50   0   0
TYR  70  50  68  51 /  90  10   0   0
GGG  69  48  68  48 / 100  20   0   0
LFK  73  50  69  49 / 100  10   0   0

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Dense Fog Advisory until 9 AM CST this morning for ARZ072-073.

LA...Dense Fog Advisory until 9 AM CST this morning for LAZ001>006-
     010>014-017>022.

OK...None.
TX...Dense Fog Advisory until 9 AM CST this morning for TXZ138-
     149>153-165>167.

&&

SHORT TERM...19
LONG TERM....19
AVIATION...23

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