Area Forecast Discussion
Issued by NWS Shreveport, LA

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000
FXUS64 KSHV 211808
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
1208 PM CST Sun Jan 21 2018

.AVIATION...
For the 21/18z TAFs, some brief instances of VFR ceilings are
possible early in the period, but MVFR or lower flight conditions
will prevail at most TAF sites before conditions improve from west
to east after 22/08z. Robust convection is expected to develop
across Texas and Southern Oklahoma later this afternoon ahead of
an approaching dryline. After sunset, the convection will surge
eastward and across the area, likely reaching KSHV around midnight
local time, and moving east of all TAF sites and out of the area
by 22/16z. Storms may be strong to severe at times.

The surface pressure gradient will be very tight through the
period, so southerly winds will remain rather strong and gusty. A
strong southerly low-level jet of 40+ kts around 500 meters AGL
will develop and move east ahead of the convection tonight. Behind
the convection, ceilings should quickly lift into the VFR range.
Surface wind speeds may diminish back to around 10 kts briefly
behind the storms, but the winds will veer to the west and
increase in speed to between 12 and 15 kts with gusts up to 25 kts
after sunrise Monday.

CN

&&

.PREV DISCUSSION... /issued 1013 AM CST Sun Jan 21 2018/

DISCUSSION...
Southwest flow aloft supplying sufficient instability and low-
level moisture to generate showers across east Texas. Until
upper-level low across four corners region moves across the
midwest later this evening, showers will remain confined across
east and northeast Texas. Cold front and upper-low to generate
more substantial convection later tonight with locally heavy
rainfall possible and a slight risk of severe thunderstorms across
much of the ArkLaTex. Current temperature, dewpoint, and wind
trends are on track. No updates at this time. /05/

PREV DISCUSSION... /issued 717 AM CST Sun Jan 21 2018/

DISCUSSION...
Early this morning low level moisture continued to stream
from the Gulf of Mexico around the back side of a large surface
high pressure system centered over the Southeast States and
front side of tightly wound surface low pressure over the Southern
Plains and another surface low over the Southern Rockies. This
moisture was producing early morning fog and low clouds from the
Western Gulf Coast States, into the Southern and Central Plains
and Upper Midwest and Great Lakes region. Rain and showers will
be increasing during the day today as an upper closed low over the
Four Corners Region this morning ejects across the Southern
Rockies and out into the Plains as the associated surface low
and associated frontal boundaries lift East. Weak high pressure
ridging aloft this morning will shift to the East and with the
approach of the upper low to the West the upper level pattern will
become more Southwest increasing moisture in the middle and
upper levels to provide a very moisture laden and increasingly
unstable atmosphere to help increase showers and thunderstorms
later this afternoon. Thunderstorms will be increasing over
North Texas and Oklahoma and quickly form into a squall line
ahead of the cold front associated with the surface low lifting
into the plains and ahead of the upper trough axis. The
convection will spread across the Four State Region overnight
with some of the storms becoming severe and capable of producing
damaging winds and possible tornadoes. Rainfall will be heavy
at times in the stronger storms as they shift across the
forecast area with heavier rates of one to one and one half inches
per hour. The surface cold front will extend near a De Queen
Arkansas to Tyler Texas line near midnight and a Monroe Louisiana
to Lake Charles line around 6 AM CST Monday. Rain will have ended
for most all locations by mid day Monday with passage of the
cold front and upper trough axis. Temperatures for the rest of the
week will be near seasonal normals with highs in the 50s and 60s
while overnight lows will be in the 30s. A similar surface and
upper system will arrive near the end of the work week with
moisture returning around the back side of high pressure moving
into the Southeast States and upper ridging moving into the
Southeast States with low level moisture returning fog and
possible light rain or drizzle followed by middle and upper level
moisture in the returning Southwest flow aloft in advance of the
next upper low/trough moving across the Western states and
Rockies into the plains. This late week and early weekend
upper trough will be less amplified but expected to produce
showers and thunderstorms. /06/

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  73  51  63  36 /  40  90  10   0
MLU  72  56  64  36 /  20  90  30   0
DEQ  70  43  55  32 /  70  80  10   0
TXK  71  47  58  34 /  60  80  10   0
ELD  71  52  60  35 /  40  90  10   0
TYR  73  45  63  35 /  70  80   0   0
GGG  73  47  63  35 /  50  80   0   0
LFK  73  51  66  35 /  50  80   0   0

&&

.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Lake Wind Advisory until midnight CST tonight for ARZ070-071.

LA...Lake Wind Advisory until midnight CST tonight for LAZ001>003-
     010>012.

OK...None.
TX...Lake Wind Advisory until midnight CST tonight for TXZ096-097-
     108>112-124>126-136>138-149>153.

&&

$$

09/05



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