Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 241232
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
732 AM CDT Fri Mar 24 2017

.AVIATION...
For the 24/12Z TAF period, mostly MVFR conditions affecting our
area terminals this morning as low stratus continues to surge in
from the Gulf ahead of an approaching cold front across the Srn
Plains. This front will make quick eastward progress today with a
line of showers and thunderstorms intensifying east of I-35 with
arrival at TYR/GGG/TXK shortly after 18Z this afternoon and then
by late afternoon into the early evening at SHV/LFK followed by
ELD/MLU. This line of convection may be intense enough to support
severe thunderstorms with damaging wind gusts being the primary
threat. Winds will already be quite strong ahead of the frontal
boundary with southerly winds from 15-20 kts and gusts exceeding
25-30 kts throughout much of today. This will help cigs lift into
the VFR category by mid to late morning through the afternoon as
some scattering of cigs may also occur at times before the line of
convection arrives later in the day. Conditions will improve late
in the period as the front clears from west to east with showers
and storms gradually ending across the region through early Sat.

/19/

&&

.PREV DISCUSSION... /issued 607 AM CDT Fri Mar 24 2017/

DISCUSSION...
We are set to begin an active period of weather over the next 7
days, which will start with a strong but stacked closed low over
SE CO which will drift E across the OK/TX Panhandles this morning
while gradually filling as it enters Wrn OK later this afternoon.
Already seeing a narrow NE to SW line of -SHRA that continues to
shift E just ahead of the dryline over portions of Nrn and Wcntrl
TX, which will continue to gradually spread E across N TX this
morning before entering ECntrl TX this afternoon as the dryline
mixes E to just E of the I-35 corridor before stalling. Dewpoints
have begun to modify this morning beneath the 50kt Srly LLJ, and
should continue to do so until mixing commences by mid to late
morning. However, sfc obs and the 11-3.9u satellite imagery depict
the stratocu field increasing as well, which should deepen with
time today ahead of the approaching closed low. The short term
progs are in reasonable agreement with the ongoing -SHRA spreading
into Ecntrl TX/Ern OK by late morning/midday, before intensifying
by 20-21Z as very steep lapse rates begin to overspread the
increasing warm sector E of the dryline ahead of the closed low.
There still remains some uncertainty as to the extent of svr
potential this afternoon/evening despite the strong deep lyr shear
and increasing lapse rates in place, with the increasing stratocu
limiting heating to some extent today, with the potential for
slightly drier air to mix down to the ground, especially as mid
level dry air entrains E ahead of the low. MUCapes are progged to
only range from 500-1000 J/kg, but this may be augmented given the
very strong shear and steepening lapse rates this afternoon which
may yield a damaging wind and isolated hail threat as a QLCS
develops and shifts E across the region later this
afternoon/evening. Have added svr wording to the forecast for E
TX/SE OK/extreme SW AR and NW LA this afternoon, with this threat
shifting across the remainder of the area this evening. However,
much needed rainfall is in the offing with QPF totals of 0.50-1.00
inches with isolated higher amounts of up to 2 inches possible.

With the pressure gradient tightening as this stacked low
continues E, the current Lake Wind Advisory still looks good, but
wind speeds should drop off this evening with the passage of the
squall line, and thus have moved up the expiration time to 06Z
Saturday. In addition, with 10Z temps not much below 70 degrees,
strong Srly winds and accompanying warm advection should result in
max temps reaching the lower 80s across Deep E TX/N LA/Scntrl AR
before the convection arrives late in the day.

The stationary dryline this evening will mix E late this
evening/overnight across the remainder of E TX/SW AR/extreme NW LA
as the parent sfc low continues to shift E than NE across Srn and
Ern OK into NW AR. This bndry should slow its ewd progress
Saturday afternoon over SW/Cntrl and NE LA, which still could
focus isolated to widely sct convection mainly over the Ern zones
before diminishing during the afternoon. Not expecting much in
the way of cooler air with the bndry passage, although more
seasonal readings are expected over the Nrn zones with above
normal temps along/S of I-20 as wrly winds persist. With the very
dry air in place, temps should fall into the upper 40s/lower 50s
Saturday night, but a warmup will quickly commence Sunday as Srly
winds return and increase ahead of the next upper trough that will
quickly translate into the Srn Plains Sunday afternoon. It should
take a better part of the day for the air mass to moisten, but sct
elevated convection should fire over portions of extreme NE TX/SE
OK/SW AR as lapse rates aloft steepen ahead of the approaching
trough. Can`t rule out a large hail and possibly damaging wind
threat over these areas Sunday night, but one caveat will be the
lack of deep layer moisture available once large scale forcing
increases ahead of the trough. For this reason, have toned down
pops to chance for the I-30 corridor Sunday night, before a
reinforcing sfc front is able to slip SE across the region during
the day Monday and thus tapers convection from W to E.

Above normal max temps will persist through at least mid-week,
with low level moisture return commencing Tuesday night and
Wednesday ahead of the next deepening closed low progged to drop
SE through the Rockies. This could result in another svr threat
for much of the region Wednesday as deep layer shear increases
and lapse rates steepen once the closed low enters the Srn Plains.
Have raised pops to high chance for this portion of the extended,
before convection diminishes by late week.

Prelims to follow below...

15

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  82  59  78  51 /  60  80  10   0
MLU  82  64  80  51 /  20  90  40   0
DEQ  76  51  72  45 /  90  60  10   0
TXK  77  55  74  50 /  80  80  10   0
ELD  80  60  76  48 /  40  90  30   0
TYR  76  54  75  53 /  90  30   0   0
GGG  78  56  76  52 /  80  60   0   0
LFK  80  59  81  54 /  70  70  10   0

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Lake Wind Advisory until 1 AM CDT Saturday for ARZ050-051-
     059>061-070>073.

LA...Lake Wind Advisory until 1 AM CDT Saturday for LAZ001>006-
     010>014-017>022.

OK...Lake Wind Advisory until 1 AM CDT Saturday for OKZ077.

TX...Lake Wind Advisory until 1 AM CDT Saturday for TXZ096-097-
     108>112-124>126-136>138-149>153-165>167.

&&

$$

19/15



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