Special Weather Statement, NWS Shreveport, LA

Area Forecast Discussion
National Weather Service Shreveport LA
713 AM CDT Sun Aug 6 2017

.UPDATE...
Increased POPs to definite category across extreme southeast OK,
extreme northeast TX and extreme southwest AR, given the latest
radar analysis of the line of storms pushing southeast across the
said areas. Frequent lightning, brief moderate to heavy rainfall
and gusty winds may accompany this activity.

&&

.PREV DISCUSSION... /issued 706 AM CDT Sun Aug 6 2017/

.AVIATION...
For the 06/12Z TAF period, widespread low stratus causing IFR/MVFR
conditions at all area terminals this morning. This is occurring as
southerly winds increase and Gulf moisture is surging northward in
advance of a slow-moving frontal boundary just to our north. Line
of convection continues to spread into SE Oklahoma this morning as
the front remains across central and eastern Oklahoma. The primary
forecast challenge today is whether this line of showers and storms
will maintain itself through the remainder of this morning as it
nears TXK and possibly farther south into the afternoon. For now,
am not entirely confident in the current convection getting into
TXK before 18Z but expect some outflow conditions to help initiate
convection later in the afternoon and TXK and possibly down to the
I-20 corridor but have only mentioned VCTS for now down to I-20.
Better chances for more widespread convection will come overnight
as the front edges a bit closer so have trended TAFs as such with
gusty south winds ahead of the convection and possibly contained
within individual storms as well. Cigs/vsbys will deteriorate as
storms increase overnight with MVFR/IFR conditions after 07/06Z.

/19/

&&

.PREV DISCUSSION... /issued 406 AM CDT Sun Aug 6 2017/

DISCUSSION...
Early this morning, an MCS stretched from northeast OK to across the
Rolling Plains in west TX, courtesy of an embedded impulse within
the near zonal flow aloft and a quasi-stationary frontal boundary,
was moving east-southeast nearing the Four-State region. Light
showers developing ahead of the line of storms suggests the
atmosphere is adequately moist, as exhibited by metar reports of
dewpoints in the 70s that has enveloped the entire region and
locales north, thanks to a 15-20 kt LLJ. The best bowing segment
within the line was noted across northeast OK earlier this morning,
which resulted in several warnings /including a few tornado
warnings/. Given the east-southeastward direction of the precip,
this particular segment is unlikely to impinge the region.
However, will be maintaining high situational awareness given the
moist atmosphere and the potential for the cold pool to push
southeastward with time. In fact, the HRRR solution hints at the
southern periphery of the MCS to move across extreme southeast OK
and extreme northeast TX aoa daybreak, and propagate to across
southwest AR and northern LA through the aftn. Can not rule out a
few storms capable of nearing strong levels, with gusty winds
initially the main threat, but by this aftn with daytime
destabilization, steepened lapse rates and 0-6 km bulk shear
values increasing into the 25-40 kt range, hail will also be
possible across the said areas. Concurrently, sea-breeze
convection may affect portions of central LA, whilst a slightly
tightened pressure gradient across east TX results in wind speeds
of 15-20 mph /with higher gusts/. Due to these expected wind
speeds, will elect to hoist a Lake Wind Advisory today that will
run from 16Z-23Z.

With flow aloft veering slightly to the west-northwest, embedded
disturbances moving across the region and the cold front to our
north finally impinging on northern zones by late tonight/early
tomorrow morning /where it then becomes quasi-stationary/, will
make for the start of a wet forecast. PWATs increasing to
2.00-2.50 inches through early next week with a continual upslope
sfc regime and embedded impulses will prompt concerns for moderate
rainfall. The Weather Prediction Center shows rainfall totals
ranging from 1.00 inch across the central Plains to near 5.00
inches across extreme southeast OK and extreme northeast TX valid
for a period from 12Z today through 12Z Wednesday. By late week,
the frontal boundary will have washed out and some locales south
of the Interstate 20 corridor may see a lull in precip due to an
UA ridge across the desert SW expanding northeast to across
portions of east TX, deep east TX and central LA. As such, slight
northwest flow aloft will be most predominate along and north of
the Interstate 20 corridor, whilst embedded impulses within the
flow aloft and PWATs being maintained aoa 2.00 inches will result
in the continuance of rainfall chances through the end of the
extended period.

One more day of near seasonably warm daytime temps today /upper 80s
to lower 90s/ will be followed by daytime temps dropping into the
lower to middle 80s by Tuesday, given the expected rainfall and
extensive cloud cover. Temps will rebound into the upper 80s to
lower 90s thereafter, but widespread 90 degree temperatures looks
unlikely due to the anticipated wet forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  94  75  89  74 /  40  40  60  60
MLU  92  75  88  73 /  40  40  60  60
DEQ  88  73  84  71 /  80  60  70  70
TXK  90  75  84  71 /  60  60  70  70
ELD  91  74  85  71 /  60  60  70  70
TYR  93  75  87  74 /  40  40  70  70
GGG  93  75  87  73 /  40  40  70  70
LFK  93  76  89  76 /  30  20  60  60

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...Lake Wind Advisory from 11 AM this morning to 6 PM CDT this
     evening for TXZ096-108>112-124>126-136>138-149-150.

&&

29/19/29

Hazardous Weather Outlook
National Weather Service Shreveport LA
535 AM CDT Sun Aug 6 2017

ARZ050-051-059>061-070>073-LAZ001>006-010>014-017>022-OKZ077-
TXZ096-097-108>112-124>126-136>138-149>153-165>167-071045-
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-
535 AM CDT Sun Aug 6 2017

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...Today and Tonight...

A line of showers and thunderstorms approaching the Four-State
region early this morning, will likely impinge on extreme
southeast Oklahoma, northeast Texas and southwest Arkansas later
this morning. Frequent lightning, gusty winds, small hail and
moderate to heavy rainfall will be possible. Furthermore, a Lake
Wind Advisory is in effect today from 11 am CDT through 6 pm CDT
across portions of east Texas. Expect wind speeds of 15 to 20 mph
with higher gusts.

.DAYS TWO THROUGH SEVEN...Monday through Saturday...

Thunderstorms will continue to be possible through next week, as a
lingering frontal boundary and a series of upper level impulses
move across the Four-State region. While a few strong storms can
not be ruled out, no organized or widespread hazardous weather is
expected at this time.

.SPOTTER INFORMATION STATEMENT...

Activation of emergency management personnel...amateur radio
operators...and storm spotters will not be needed through tonight.

Special Weather Statement
National Weather Service Shreveport LA
733 AM CDT SUN AUG 6 2017

OKZ077-TXZ096-061315-
McCurtain OK-Red River TX-
733 AM CDT SUN AUG 6 2017

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHWESTERN MCCURTAIN AND
NORTHERN RED RIVER COUNTIES UNTIL 815 AM CDT...

At 731 AM CDT, Doppler radar was tracking a strong line of
thunderstorms 7 miles east of Fort Towson, or 20 miles east of Hugo,
moving east at 55 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this line of storms.

Locations impacted include...
Idabel, Broken Bow, Wright City, Valliant, Millerton, Garvin, Farmers
Hill, Rufe, Redland, Silver City, Holly Creek, Glover, Kiomatia,
Slim, Albion, Oak Hill, Ringold and Golden.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this line of storms, and
may lead to localized flooding. Do not drive your vehicle through
flooded roadways.

Frequent cloud to ground lightning is occurring with this line of
storms. Lightning can strike 10 miles away from a thunderstorm. Seek
a safe shelter inside a building or vehicle.

This line of storms may intensify, so be certain to monitor local
radio stations and available television stations for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3412 9464 3374 9480 3388 9528 3391 9528
      3391 9527 3389 9527 3389 9525 3393 9525
      3396 9523 3394 9516 3424 9515
TIME...MOT...LOC 1231Z 288DEG 47KT 3405 9515

19

Special Weather Statement
National Weather Service Shreveport LA
806 AM CDT SUN AUG 6 2017

ARZ050-051-059-OKZ077-TXZ096-061400-
Howard AR-Sevier AR-Little River AR-McCurtain OK-Red River TX-
806 AM CDT SUN AUG 6 2017

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN LITTLE RIVER...
SEVIER...NORTHERN HOWARD...CENTRAL MCCURTAIN AND NORTHERN RED RIVER
COUNTIES UNTIL 900 AM CDT...

At 806 AM CDT, Doppler radar was tracking a strong thunderstorm near
Broken Bow, or 22 miles west of Horatio, moving southeast at 30 mph.

Half inch hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
De Queen, Dierks, Horatio, Umpire, Idabel, Broken Bow, Lockesburg,
Winthrop, Gillham, Arkinda, Athens, Manchester, Millerton, Haworth,
Garvin, Eagletown, Moon, Cerrogordo, Geneva and Goodwater.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3435 9394 3427 9394 3426 9392 3417 9392
      3400 9412 3377 9446 3373 9463 3374 9496
      3386 9525 3429 9447 3419 9447 3419 9425
      3436 9425
TIME...MOT...LOC 1306Z 311DEG 27KT 3396 9475

19

Special Weather Statement
National Weather Service Shreveport LA
839 AM CDT SUN AUG 6 2017

ARZ050-051-059>061-070-OKZ077-TXZ096-097-061430-
Howard AR-Hempstead AR-Sevier AR-Little River AR-Miller AR-Nevada AR-
McCurtain OK-Bowie TX-Red River TX-
839 AM CDT SUN AUG 6 2017

...SIGNIFICANT WEATHER ADVISORY FOR LITTLE RIVER...HEMPSTEAD...
NORTHERN MILLER...CENTRAL SEVIER...HOWARD...NORTHERN NEVADA...
SOUTHEASTERN MCCURTAIN...BOWIE AND CENTRAL RED RIVER COUNTIES UNTIL
930 AM CDT...

At 838 AM CDT, Doppler radar was tracking strong thunderstorms along
a line extending from 16 miles northeast of Umpire to near Winthrop
to near Blossom. Movement was east at 45 mph.

Winds in excess of 40 mph will be possible with these storms.

Locations impacted include...
Texarkana, Hope, Wake Village, Ashdown, Nashville, New Boston,
Prescott, Clarksville, Mineral Springs, Dierks, Horatio, Foreman,
Boxelder, Nash, Hooks, De Kalb, Red Lick, Lockesburg, Emmet and
Wilton.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with these storms, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

These storms may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3419 9392 3418 9382 3401 9382 3401 9375
      3395 9353 3396 9347 3396 9338 3390 9330
      3384 9329 3381 9319 3352 9352 3330 9459
      3358 9531 3366 9531 3383 9446 3430 9394
TIME...MOT...LOC 1338Z 291DEG 38KT 3437 9378 3381 9440 3363 9530

24