Flash Flood Watch 1, NWS Shreveport, LA

486 
WGUS64 KSHV 241058
FFASHV

Flood Watch
National Weather Service Shreveport LA
558 AM CDT Sat Apr 24 2021

LAZ017>022-TXZ152-153-165>167-241200-
/O.CAN.KSHV.FF.A.0001.000000T0000Z-210424T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Sabine-Natchitoches-Winn-Grant-Caldwell-La Salle-Nacogdoches-Shelby-
Angelina-San Augustine-Sabine-
Including the cities of Colfax, Pineland, Natchitoches, Columbia, 
Center, Zwolle, Olla, Many, Dry Prong, Hemphill, Winnfield, 
Montgomery, Jena, Pleasant Hill, San Augustine, Lufkin, Grayson, 
Nacogdoches, Clarks, and Midway
558 AM CDT Sat Apr 24 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch for portions of Louisiana and east Texas, 
including the following areas, in Louisiana, Caldwell, Grant, La 
Salle, Natchitoches, Sabine and Winn. In east Texas, Angelina, 
Nacogdoches, Sabine, San Augustine and Shelby has been cancelled.

Flooding is no longer expected to pose a threat. Please continue to 
heed remaining road closures.

$$

20

Area Forecast Discussion
National Weather Service Shreveport LA
1233 PM CDT Fri Apr 23 2021

AVIATION...

For the 23/18z TAFs...Widespread MVFR cigs are being observed
across the area from overcast skies around 15-20Kft. Showers and
thunderstorms will increase across the area this afternoon as a
warm front moves through. As thunderstorms get going, expect cigs
and visibility to drop to IFR and occasionally LIFR this
afternoon/evening and into the overnight hours. Winds will
continue to be out of the SE around 5-15kts with some higher gusts
expected with the convection later in the afternoon. MVFR
conditions will settle in once the showers come to an end before
improving towards the end of the period. /33/

&&

.PREV DISCUSSION... /issued 1106 AM CDT Fri Apr 23 2021/

UPDATE...

Surface analysis shows a warm front near the Gulf of Mexico coast.
Expecting this to gradually shift to the north and into our area
through the day. Strong to severe thunderstorms will gradually
overtake the area by this afternoon and continue into the
overnight hours. Made a few changes to PoPs and temperatures to
account for current trends and new model data. Still expecting
temperatures this afternoon to range from the mid 60s to lower
70s. Otherwise, will be paying attention to the severe weather
threat this afternoon. /33/

PREV DISCUSSION... /issued 450 AM CDT Fri Apr 23 2021/

SHORT TERM.../Today through Saturday Night/

An active weather day expected today as isolated to scattered
severe thunderstorms with damaging winds, large hail, isolated
tornadoes, and possibly isolated flash flooding will be possible
during the afternoon and evening hours.

An upper trough will continue to eject eastward out of the
Southwest CONUS into the Southern Plains, and eventually into the
lower Mississippi Valley by late tonight. A weak sfc low will
likely develop across the Texas Panhandle this morning and push
eastward across North Texas just south of the Red River. A dryline
will develop southward from the low, with a cold front trailing.
Storms will likely start to fire along the dryline across western
North Texas by early afternoon as it pushes eastward with the sfc
low before stalling near the I-35 corridor. Ahead of this feature,
low-level moisture will be on the increase as a strong low-level
jet will develop, pushing a warm front northward into our region
today. Models continue to suggest that showers and isolated
thunderstorms will start to develop as the warm front pushes
northward across the region. In the warm sector, in wake of the
warm front, a weak disturbance will move across the region. With
the aid of warm air advection, thunderstorm activity will quickly
develop and spread northeastward through the afternoon and evening
hours. Mid-level lapse rates will be favorable in this
environment along with wet-bulb zero heights for severe hail to
form. It also appears that deep layer shear could favor damaging
wind gusts as well. Although hail and damaging winds are the
higher threat, there still remains the chance for isolated
tornadoes as Effective Storm Relative Helicity will be on the
increase this afternoon. In addition to the severe weather,
locally heavy rainfall will be possible, especially in areas where
thunderstorms train. We continue to anticipate widespread QPF
values of an inch, with 2-3 inch plus pockets. This could lead to
some isolated flash flooding.

Convection should move out of the region by Saturday morning, as
the aforementioned sfc low continues to push east, and the
associated cold front sweeps through the region. A dry northwesterly
flow aloft will settle over the region, with dry conditions and
party cloudy skies expected on Saturday.

Rain and cloud cover will keep temperatures today near or just
below seasonal averages, with a slight warm up near climatic
normals for Saturday. /20/

LONG TERM.../Sunday through Thursday Night/

Dry conditions expected at the start of the period as upper-level
ridging builds from the west. Subsident northwest flow aloft to
support mostly clear skies areawide. Temperatures forecast to fall
into the lower 50s on Sunday morning.

A mainly dry forecast to continue through Monday night as both
surface and upper-level ridging prevail across the region. However,
as the surface high drifts east, temperatures to gradually climb
each day ranging from highs around 80 on Sunday to the mid 80s on
Monday. Accordingly, low temperatures to climb from the mid 50s on
Monday morning to the mid 60s by Tuesday morning.

Pattern to shift on Tuesday as upper-level ridge drifts east
allowing for flow to become southwest across the region. This will
allow for increased  areawide. Progressive eastward moving
upper-level trough across the Rockies combined with a surface
boundary across Texas to support increased convection areawide by
Tuesday night. There is still some uncertainty regarding the severe
weather threat with this system. Both the Euro and GFS suggest that
the frontal boundary will be fairly slow moving, allowing for
showers and embedded thunderstorms to persist through Wednesday
night. However, both models diverge drastically with the Euro nearly
stalling the front allowing for elevated post-frontal precip to
persist through the end of the period while the GFS is more aggressive
on clearing the precipitation out of the region on Thursday morning.
 For this forecast package, sided more with the faster GFS solution
but left slight chance pops through Thursday night just to
communicate forecast uncertainty. /05/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  62  78  53  80 / 100   0   0   0
MLU  59  81  53  78 / 100  10   0   0
DEQ  55  74  48  78 / 100  10   0   0
TXK  59  76  52  78 / 100   0   0   0
ELD  56  76  49  79 / 100  10   0   0
TYR  60  76  53  80 /  80   0   0   0
GGG  59  76  52  80 /  90   0   0   0
LFK  64  79  55  83 /  80   0   0   0

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&

20/05/33

Hazardous Weather Outlook
National Weather Service Shreveport LA
509 AM CDT Fri Apr 23 2021

ARZ050-051-059>061-070>073-LAZ001>006-010>014-017>022-OKZ077-
TXZ096-097-108>112-124>126-136>138-149>153-165>167-241015-
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-
509 AM CDT Fri Apr 23 2021

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...

Showers and thunderstorms will become widespread this afternoon.
Some storms could be severe from this afternoon through the very
early hours of Saturday morning. Tornadoes, damaging winds, and
large hail will be possible. Locally heavy rainfall could also
lead to flash flooding. The severe weather threat should end a
few hours after midnight with thunderstorms gradually diminishing
through daybreak Saturday morning.

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

Strong to severe thunderstorms will be possible again Tuesday
afternoon through late Wednesday.

.SPOTTER INFORMATION STATEMENT...

Activation of emergency management personnel, amateur radio
operators, and storm spotters will be needed from this afternoon
through tonight. Please relay any information about observed
severe weather to the NWS while following all local, state, and
CDC guidelines.