Severe Thunderstorm Warning 217, NWS Shreveport, LA

Area Forecast Discussion
National Weather Service Shreveport LA
1159 PM CST Fri Nov 30 2018

.AVIATION...
For the ArkLaTex, VFR/MVFR for now as a line of TS is moving into
our cwa. Tornado watch until 08Z now includes KTYR/KGGG/KTXK.
Convection will continue to congeal overnight into a squall line
affecting all terminals shifting E by 08-12Z for the most part.
MVFR/IFR cigs improve 12-15Z to VFR fm W to E. Otherwise, S/SW
winds to increase to 15-20KT with gusts up to 28 knots on
Saturday. /24/

&&

.PREV DISCUSSION... /issued 1125 PM CST Fri Nov 30 2018/

UPDATE...
To add 8 counties to Tornado Watch 430.

SHORT TERM...
Running a little later than earlier expectations with development,
but a decent TS line is coming together over NE TX from Suphur
Springs to Terrell and knocking on our door. This line extends
from SE OK down into S central TX, but the line is still broken
up a bit from Temple to Corsicana and over Red River Co into
McCurtain. We have added TX counties for a potential "Tail-end
Charlie" down into N Cherokee over to Rusk and Harrison and North
to the earlier watch to get us past midnight and closer to the
expiration and possible replacement with anything further for the
overnight. /24/

PREV DISCUSSION... /issued 727 PM CST Fri Nov 30 2018/

UPDATE...
To add headline for Tornado Watch 430 to I-30 and Aviation.

SHORT TERM...
Activity remains sparse in Texas so we have backed off a bit on
pop and weather for now. Lots of showers on our Eastern tier of
Co/Pa. And there is some showers developing in the heart of the
ArkLaTex between Marshall, Shreveport and Texarkana. Thunderstorms
are lining up from Mcalester to near Terrel and more back along
the dry line. We should see accelerate from here with the core low
over the OK/TX panhandles enhancing divergence aloft for SE OK/NE
TX and SW AR. We will continue to monitor storm development and
will add additional TX counties and maybe some NW LA parishes to
the watch that goes until 2 a.m. /24/

PREV DISCUSSION... /issued 244 PM CST Fri Nov 30 2018/

SHORT TERM.../Tonight through Saturday Night/

Emphasis on the short term period will be developing storm system
that will bring widespread convection across the ArkLaTex this
evening and overnight.

Negatively tilted upper-trough combined with a deepening surface
low across the Southern Plains will generate a strong low-level
southerly jet later this afternoon into this evening. This,
combined with steepening lapse rates as cooler air aloft
translates east across the region, will aid allow for sufficient
instabilility and shear to sustain discrete supercells ahead of
an approaching frontal boundary. Tornadoes, damaging winds, and
large hail can be expected with some storms mainly during the
mid-evening hours through predawn.

No adjustments will be necessary for the upcoming Lake Wind
Advisory that is in effect from 3 PM this afternoon through
midnight. Winds forecast to increase to around 15 to 20 mph later
today.

Conditions to improve from the west on Saturday with skies
quickly clearing. However, an enhanced pressure gradient will
support strong southwest winds areawide, likely prompting the need
for another Lake Wind Advisory for the entire area during the day
on Saturday.

Otherwise, temperatures to range from lows around 60 tonight,
highs around 70 on Saturday, and lows in the 40s on Saturday
night. /05/

LONG TERM.../Sunday through Friday night/

There is GFS/ECMWF/Canadian agreement that a closed upper low will
be centered over Iowa with a more broad long wave trough extending
from the Pacific Northwest across the central Plains and into the
Upper Midwest. This broad trough feature will slide eastward across
the United States, leaving southeastern Oklahoma, eastern Texas,
southwestern Arkansas, and northern Louisiana in a northwesterly mid-
level flow. This will ultimately help usher and reinforce a cooler
air mass moving into our area early next week. At the surface, a
cold front is progged to slide southeastward across the area on
Sunday, with the area under cold air advection Sunday night into
Monday and embedded in the cooler air mass into Wednesday. By the
middle of next week, there is model agreement the area will be in
more of a zonal flow Wednesday and Thursday with a dry and
relatively cool air mass remaining in place.

Some uncertainty enters the forecast next Friday resolving the
strength of a potential disturbance ejecting from the Baja peninsula
into the southern Plains. Forecast is closest to a GFS/ECMWF blend,
with the mid-level trough crossing the area Friday into Friday
night, returning the possibility of showers and potentially
thunderstorms to the area.

For temperatures, Sunday will be the last warm day, with highs
ranging from the lower 60s in McCurtain Co, Oklahoma to the mid 70s
in central Louisiana before the cooler air is able to advect into
the region. High temperatures will be noticeably 15-20 degrees
cooler for highs (around 10 degrees below normal) Monday through
Thursday. Low temperatures will be coolest Tuesday and Wednesday
nights, near freezing temperatures across much of the area.
Temperatures will begin to warm on Friday as our area gets into more
of a southwesterly flow ahead of the aforementioned disturbance
ejected into the southern Plains.  /04/

PREV DISCUSSION... /issued 1143 AM CST Fri Nov 30 2018/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  61  71  50  70 /  80  10   0   0
MLU  68  75  49  72 /  90  20   0   0
DEQ  57  67  42  63 /  90  10   0   0
TXK  58  69  46  65 /  90  10   0   0
ELD  63  71  47  68 /  90  10   0   0
TYR  58  71  47  68 /  60  10   0   0
GGG  59  71  47  69 /  70  10   0   0
LFK  62  74  49  74 /  50  10   0   0

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Lake Wind Advisory until midnight CST tonight for ARZ050-051-
     059>061-070>072.

LA...Lake Wind Advisory until midnight CST tonight for LAZ001>004-
     010>012.

OK...None.
TX...Lake Wind Advisory until midnight CST tonight for TXZ096-097-
     108>112-124>126-136>138-149>151.

&&

24/05/04

Hazardous Weather Outlook
National Weather Service Shreveport LA
1221 PM CST Fri Nov 30 2018

ARZ050-051-059>061-070>073-LAZ001>006-010>014-017>022-OKZ077-
TXZ096-097-108>112-124>126-136>138-149>153-165>167-011830-
Sevier-Howard-Little River-Hempstead-Nevada-Miller-Lafayette-
Columbia-Union-Caddo-Bossier-Webster-Claiborne-Lincoln-De Soto-
Red River-Bienville-Jackson-Ouachita-Sabine-Natchitoches-Winn-
Grant-Caldwell-La Salle-McCurtain-Bowie-Franklin-Titus-Camp-
Morris-Cass-Wood-Upshur-Marion-Smith-Gregg-Harrison-Cherokee-Rusk-
Panola-Nacogdoches-Shelby-Angelina-San Augustine-
1221 PM CST Fri Nov 30 2018

This Hazardous Weather Outlook is for portions of south central
Arkansas, southwest Arkansas, north central Louisiana, northwest
Louisiana, southeast Oklahoma, east Texas and northeast Texas.

.DAY ONE...This Afternoon and Tonight...

A significant upper level storm system will combine with a supply
of low level Gulf moisture and favorable strong winds on the
surface and aloft. Severe thunderstorms appear likely to develop
late this afternoon into tonight across parts of the southern
Plains through the Four State Region. Storms will be accompanied
by the risk for a few strong tornadoes (EF2+). There is also the
potential for large hail and damaging wind gusts. Rainfall will be
heavy at times and amounts will range from near one half to one
and one half inches through tonight.

There will be two distinct phases of threats with this event. The
first will be discrete thunderstorms and supercells this afternoon
and lasting through the evening hours. The second will be with a
line of strong to severe thunderstorms during the late evening and
overnight hours.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday...

Under the influence of high pressure on the surface and
drier air, there will be limited chances for rain until
the next significant upper storm and cold front arrives
Thursday night and Friday. No hazardous weather is expected.

.SPOTTER INFORMATION STATEMENT...

Activation of emergency management personnel, amateur radio
operators, and storm spotters will most likely be needed
late this afternoon and overnight.