Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 051202
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
602 AM CST Mon Dec 5 2016

.AVIATION...
For the 05/12Z TAFs, IFR/MVFR conditions will prevail this period
with occasional LIFR cigs as low clouds plague all sites. Periods
of light to moderate and occasional heavy rainfall will persist
for today as vast surge of moisture spreads northward ahead of an
ejecting upper level low crossing Big Bend Country into SW Texas.
Rain will pick up in intensity through the morning hours and into
the early afternoon before gradually decreasing to mostly light
rain and drizzle later in the period through the overnight hours.
Cigs and vsbys will remain degraded throughout the period with no
real improvement expected until after 06/12Z Tuesday morning as
the upper low finally exits the region. Northeast winds from 5-10
kts today will become more light and variable after 06/00Z.

19

&&

.PREV DISCUSSION... /issued 345 AM CST Mon Dec 5 2016/

DISCUSSION...
The closed ua low we have been monitoring the last several days, is
now located across north central Mexico, and moving east-northeast
thus nearing southwest Texas early this morning. As such, sharp
southwest flow aloft dominated across the Four-State Region, thereby
continuing to tap into mid-upper level Pacific moisture. A sfc low
was noted off the southeast Texas coast with cyclogenesis/sfc low
deepening gradually taking shape. 850 mb wind speeds have increased
into the 10-15 kt range and is expected to increase further
throughout the day, as the sfc low lifts northeast to across
southern LA early this aftn, and to across the southeast zones by
the evening hours. The ua low drawing near thereby resulting in a
slight increase of ul support, coupled with the proximity of its sfc
counterpart and the llj is all aiding to generate scattered showers
with a few isolated thunderstorms located from southern Texas north
and east to across east Texas and portions of central Louisiana per
09Z mosaic radar. The best lightning was occurring near the Texas
and Louisiana coasts, coinciding with the best moisture axis. It is
noteworthy to mention that the 05/00Z SHV sounding is a bit drier in
the mid-levels, as indicative by PWATS declining from 1.17 inches on
04/12Z to 0.94 inches by 05/00Z. This drier air intrusion occurred
yesterday across the central and northern zones yesterday, which
resulted in a lull in precip. Hence, current thinking is that it is
going to take a little time for top-down moistening to take effect
for some locales, though it likely will not take too long as the
atmosphere has obviously showed signs of moisture recover via the
scattered showers.

In the near term, the HRRR appears to have the best handle on the
current precip activity, therefore it shows the precip continuing to
move northeast across portions of east Texas, central, north central
and northeast Louisiana throughout the day, with the heaviest
rainfall occurring across deep east Texas and central Louisiana. The
Rainfall totals throughout this entire rainfall event ranged from
1.00-5.00 inches with the highest amounts occurring across the
southern zones. The Weather Prediction Center indicated rainfall
amounts ranging from 0.25-2.00 inches expected today through
tonight, with the highest amounts hitting the southern zones once
again. Extensive flooding possibilities are low as this rainfall
will fall over the course 18-24 hours and the amounts are not
overly high. This is also a tribute to the soils being so
receptive to the rainfall, given the extensive dry prolonged
period which has resulted in drought conditions /though the
rainfall these last several days should certainly help ease if not
 eradicate the drought/ However, motorists should still exercise
caution as the ponding of water can definitely occur along low-
lying or poor drainage areas. Late tonight, the ua low will be
exiting the region, and the light to moderate rainfall will come
to an end. Can not rule out drizzle tomorrow during the morning
hours /with patchy fog/ as low clouds hang on for a little while
before lifting.

Long term solutions still hint at a Pacific longwave trough moving
east-southeast across the Rockies and onto the Plains by mid-late
week. It will send down a slightly breezy cold front which will
encourage the development of showers and thunderstorms. The main
weather feature associated with the fropa continues to be the CAA as
progged 850 mb temps dip to between 0C and -5C across the CWA by
Thursday night/early Friday morning. A widespread freeze is
therefore expected during the said time, with temps cooling into the
upper teens across southeast OK and southwest AR to lower to middle
20s elsewhere. This is nearing Hard Freeze criteria so we will keep
a close eye on this phenomena. Thereafter, could see another shot
 at precip by the weekend as a sfc trough near the region and taps
 into Gulf moisture.

Daytime temps will remain below seasonal avg today and tomorrow, but
could near seasonal norms by mid-week. This will be short-lived once
that Arctic cold front moves in with temps dropping into the 30s and
40s by weeks end. It will rebound back into the 50s and 60s by
the weekend with the return of srly sfc flow.

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  49  46  57  44 / 100  50  10  10
MLU  51  48  57  43 / 100  60  10  10
DEQ  48  44  55  39 /  90  70  10  10
TXK  46  45  55  41 / 100  70  10  10
ELD  47  45  55  40 / 100  70  10  10
TYR  49  44  55  45 / 100  40  10  10
GGG  49  46  57  44 / 100  50  10  10
LFK  53  47  61  46 / 100  20  10  10

&&

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

$$

19/29



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