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fxus64 kshv 300442 
afdshv

Area forecast discussion
National Weather Service Shreveport la
1142 PM CDT Wed Mar 29 2017

Update...
one more update for the remainder of the night. Tornado Watch #100
for NE Texas/SW Arkansas will be expiring at midnight. After talking with
spc, we believe the airmass across Tornado Watch #101 has been
worked over enough such that there will no longer be a tornado/
severe thunderstorm threat overnight. For this reason will be
canceling Tornado Watch #101 at midnight. Also lowered pops to
chance variety across the eastern half of our region for the
remainder of the night.

13

&&

Previous discussion... /issued 1124 PM CDT Wed Mar 29 2017/

Aviation...
the only remnants of the earlier convection are just a few isold
shwrs. These will affect kshv within the next hour, but it is more
uncertain for keld/kmlu, so will handle with amendments as needed.
Otherwise, VFR to prevail throughout the pd, with sly winds
overnight becoming wly 10-15 kts after sunrise. Wind speeds will
diminish again around sunset Thursday. /12/

Previous discussion... /issued 951 PM CDT Wed Mar 29 2017/

Update...
sent an update to remove a couple counties from tornados watch # 100
which remains in effect until midnight and to remove pops west of
the dry line which is the back line of convection to our west.
Also reduced pops east of the dryline which in compasses the
remainder of our County Warning Area. Tornados watch # 101 for portions of central and
northeast la remains in effect until 3 am. Cold front to the west
and northwest of the dryline will eventually catch the dryline
later this evening/overnight and help to advance what is left of
the convection eastward. Over the last hour, the line of
convection which developed on the dryline had weakened
considerably as we continue to lose instability this evening.

13

Discussion...

A Tornado Watch is in effect until 9 PM CDT for Angelina, San
Augustine, Sabine County and Sabine Parish...

Earlier model run iterations struggled with the speed of the line of
showers and thunderstorms from earlier this morning, as it was
exhibited to impinge on the arklatex and southeast OK much later
than what actually occurred. The line has since dissipated but
scattered showers and thunderstorms persisted across southeast Texas
which drifted northeast to across portions of deep East Texas and
central Louisiana late this aftn, which was a result of being co-
located with the best low level moisture axis and lingering old
outflow boundaries. Given this morning/S precip activity, the
atmosphere has been worked over/stabilized a bit, which was
validated by isolated showers struggling to develop. However, the
upper air storm system is still to our west across southern Kansas and drier
air aloft ahead of the system, is infringing upon east TX, deep
East Texas and southeast OK and portions of southwest AR, thus
resulting in thinning middle to upper level clouds. Consequently,
daytime destabilization may come to pass whilst a 35+ kt low level jet
persists leading to increased instability and moistening low-mid
levels respectively. In addition, a nearby sfc low has promoted a
tightened pressure gradient, leading to breezy southerly sustained
wind speeds of 15-25 mph. A notable decline in wind speeds is
expected shortly after sunset.

At this time, best severe indices are noted across portions of deep
east tx: MUCAPE of 1000 j/kg, 0-6 km bulk shear of 50 kts, 0-3 km
srh of 300-400 m2/s2, 0-1 km shear of 20-25 kts, low local/S and
curvature in the low levels per progged hodographs. What these
parameters suggest is that storms will have the potential to
become severe, with damaging wind gusts, hail and isolated
tornadoes being the main threats. At 20z, a severe storms was
located approximately 30 miles south of Zavalla, Texas just south of
the cwa, with a movement to the northeast. The neighboring office
issued both a Severe Thunderstorm Warning and a Tornado Warning
with this storm. This could be the start of this afternoon/S
severe storm activity, with additional storms expected. A Tornado
Watch is in effect until 9 PM CDT for Angelina, San Augustine,
Sabine County and Sabine Parish.

This evening into tonight, the upper air low across the Southern Plains
is expected to lift east-northeast to across the Central Plains
and near the lower to middle Mississippi Valley region. Southwest
flow aloft will sharpen and an embedded impulse within the flow
aloft will move across the region, resulting in an additional
catalyst for new storm development moreso along and east of a
dequeen Arkansas to near Shreveport la to near Natchitoches la line.
Models hint at the resurgence of a cluster of storms/line of
storms once again posing a threat for damaging winds, hail and
isolated tornadoes. This may result in the Tornado Watch /or a
Severe Thunderstorm Watch/ being expanded to portions of the
aforementioned areas later this evening into tonight. Make sure
you stay abreast to the latest weather information by going to our
website at www.Weather.Gov/shv, listening to your National oceanic and atmospheric administration weather
radio or tuning in to your favorite media outlet. Concurrently,
the precipitation activity will gradually get shoved from west to
east courtesy of the upper air system/S cold front/Pacific front that
will usher in a stabilizing airmass. Although some wrap around
cloud cover/light rain/drizzle may linger across portions of
southwest Arkansas and north central la tomorrow late morning into early
afternoon, the severe threat will be diminishing as best severe
indices exit the region.

Thereafter, the progressive synoptic flow will continue with quiet
weather expected Friday /and temps rebounding from the 60s and 70s
tomorrow to the 70s and 80s on Friday/ given the passage of a low-
amplitude upper Air Ridge. Rain chances will return for late weekend as
an upper air low slowly digs east-southeast across the Desert Southwest,
to across northern old Mexico, to across northeast central Texas by
Sunday night. Sharpening southwest flow aloft and increased ul
support will raise concerns for severe potential. Furthermore, the
slow movement of the storm coupled with rich Pacific moisture
being transported to across the region resulting in precipitable waters of
1.50-2.00 inches is why long term solutions are hinting at high
rainfall totals /several inches/. This is something we will be
paying close attention to in the coming days as we want to make
sure models are consistent from run-to-run. We will then get a
reprieve from significant wet conditions Monday-Wednesday though
an upper air low passing to our north may encourage isolated to scattered
showers along its sfc counterpart Tuesday-Wednesday.

Fb

&&

Preliminary point temps/pops...
shv 56 72 50 84 / 20 20 0 0
mlu 61 75 50 83 / 50 40 10 0
deq 50 63 42 80 / 10 20 0 0
txk 53 66 48 82 / 10 20 0 0
eld 55 69 47 81 / 30 30 10 0
tyr 52 73 52 86 / 10 0 0 0
ggg 54 72 51 85 / 10 10 0 0
lfk 56 77 52 89 / 10 10 0 0

&&

Shv watches/warnings/advisories...
Arkansas...none.
La...none.
OK...none.
Texas...none.
&&

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