Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 211600 CCA

Area Forecast Discussion
National Weather Service Shreveport LA
942 AM CST Sat Jan 21 2017

No update needed at this time. The Forecast is on track with
showers and thunderstorms moving into the area by late this
afternoon, along with severe weather through the overnight hours.
Shreveport will do a special 18z sounding to sample the atmospheric
conditions ahead of the severe weather.


.PREV DISCUSSION... /issued 636 AM CST Sat Jan 21 2017/

An updated ZFP was sent to remove the mention of convection that
has since moved well east of the area. Patchy dense fog has also
started to rapidly develop, especially across East Texas. Have
decided to hold off issuing a dense fog advisory because
confidence is not high regarding how widespread it might be.
However, the situation will continue to monitored.


PREV DISCUSSION... /issued 528 AM CST Sat Jan 21 2017/

Light south winds combined with wet soils from recent rains will
allow for MVFR/IFR visibilities and ceilings across area terminals
through 21/16Z. Showers and thunderstorms possible after 21/18Z
mainly across SHV/MLU/TXK/ELD terminal sites. Convection to exit
the region to the east by 22/04Z. Otherwise, conditions to improve
to VFR with south to southwest winds increasing to 10 knots
overnight. /05/

PREV DISCUSSION... /issued 436 AM CST Sat Jan 21 2017/

The primary forecast concerns this period will be the possibility
of severe weather across portions of the area during the next 24
hours. The first round of convection has moved almost completely
south and east of the CWA this morning as a strong low-level jet
streak also moves eastward. Maintained some pre-first period PoPs
in the zones to account for the lingering precipitation, but an
update is likely to the ZFP within the next few hours to clean up
the wording.

After a brief break for the first half of today, the threat for
severe thunderstorms will return during the late afternoon and
evening hours. Rapid lee cyclogenesis is occurring over the High
Plains of Southeast Colorado, Northeast New Mexico, and the
Texas/Oklahoma Panhandles in response to a strong mid-level trough
and a 120 kt+ jet streak moving from the Desert Southwest towards
the Southern Plains. As this system emerges into the Southern
Plains this afternoon, a warm front will move across the area
placing the entire CWA in the warm sector. Strong to severe
thunderstorms are expected to develop in the warm sector ahead of
an approaching Pacific cold front and the warm front that will
move towards the Interstate 40 corridor. The center of the upper
trough and surface low will generally move along or just north of
the Red River between Oklahoma and Texas by after midnight
tonight, and finally out of the area around sunrise Sunday

Initial convective development is expected across North and
Central Texas, which will then move east northeast into our area.
The greatest severe threat is expected to over Southern Arkansas
and Northern Louisiana after 21z this afternoon. Instability and
lift should be fairly strong as the surface and upper level
troughs will be very well co-located. Deep layer shear is more
than adequate to support rotating updrafts. Backing winds in the
low levels, especially as the surface low approaches and
strengthens, will also support a risk for tornadoes and damaging
winds. Perhaps the most significant threat will be hail.
Temperatures will be very cold aloft, and combined with the close
proximity of the surface low and upper trough, instability and
lift aloft should be quite strong. There will be a potential for
hail larger than two inches in diameter, especially across
Southern Arkansas and Northern Louisiana.

The severe threat will be greatest this evening but could persist
into the early morning hours. However, the risk for severe weather
and the chances for rain will gradually diminish from southwest to
northeast after midnight as the cold front moves through the area
and dry air invades. Some lingering wrap-around showers will be
possible north of Interstate 20 on Sunday. Precipitation should
finally exit the area by Sunday evening. The surface pressure
gradient behind the low and cold front will also be quite strong.
A Lake Wind Advisory may be needed for parts of the area on

Quiet weather and dry conditions should return for Monday and most
of Tuesday. By late Tuesday and into Wednesday, an enlongated,
positively-tilted trough will move across the country and push
another surface cold front towards our area. Deep layer moisture
will be quite meager, so rain chances will generally be low.
However, slight chance PoPs were maintained southeast of a Lufkin
to Monroe line where the greatest moisture will be located. The
flow aloft will transition to northwesterly by the end of the week
bringing Arctic air and chilly nights back to the region during
the extended periods.



SHV  71  51  64  44 /  30  50  10   0
MLU  72  54  65  44 /  20  70  20  10
DEQ  68  47  60  38 /  40  70  30   0
TXK  68  50  61  41 /  40  70  30   0
ELD  70  51  62  41 /  40  70  20  10
TYR  71  50  63  43 /  30  40  10   0
GGG  71  50  63  43 /  30  50  10   0
LFK  73  52  65  44 /  20  40  10   0




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