Area Forecast Discussion
Issued by NWS Shreveport, LA

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402
FXUS64 KSHV 221508
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
1008 AM CDT Mon May 22 2017

.UPDATE...
Swath of scattered to numerous showers continued to push east-
northeast across the ARKLATEX this morning. Latest mosaic radar
analysis displayed precipitation already had come to an end
across southeast OK and portions of southwest AR and northeast TX.
Latest VIS satellite imagery showed clearing skies across the
aforementioned areas. Given the latest radar trend, this update
resulted in several tweaks. The first of which was to adjust the
POP grids to reflect location of precip /dropped POPs below
mentionable across the northwest zones/. Secondly, given clearing
skies across southeast OK and extreme southwest AR, and extensive
cloud cover elsewhere, this will result in temps struggling to
reach the 70 degree mark /within the BKN-OVC cloud cover/ versus
middle 70s across the rain-free and cloud-free areas. Lastly,
tweaked the dewpoint temps and subsequently the relative humidity
values according to recent trends. Otherwise, forecast largely on
track with this widespread showers continuing to shift eastward
with time throughout the aftn, leading to declining precip from
west to east.

&&

.PREV DISCUSSION... /issued 541 AM CDT Mon May 22 2017/

AVIATION...
Cigs remain mostly vfr for time being with mostly mid
lvl moisture. However, cigs to gradually lower with continued
falling lgt to ocnl moderate showers across area. Some isold
thunder possible, mainly southern parts of area including KFLK
terminal. Meanwhile, most of rain to remain south of KTXK and KELD
terminals where daytime vfr should predominate. Most rain movg
east btwn 22/18-21z with patchy fog possible after 23/06z with
daytime temps remaining mostly rain cooled and moist ground
tonight, along with winds becmg lgt tonight. In the meantime,
daytime winds from east 5 to 10 kts expected./07/.

PREV DISCUSSION... /issued 316 AM CDT Mon May 22 2017/

DISCUSSION...
Widespread rainfall this morning across the western half of the
Four State Region, all in response to well defined shortwave
across Central Texas quickly moving our way. Upper level
divergence is already providing the lift necessary across much of
the region with our area firmly entrenched in the left exit region
of a 90+kt upper level jet across Central and Western Texas which
can be seen well early this morning on water vapor imagery. GFS
is hinting at a split upper jet signature later this morning
developing across our southern zones which can only further
enhance forcing for widespread showers and thunderstorms. For this
reason, have bumped pops upward to categorical for the southern
half of our region and likely pops as far north as the Middle Red
River Valley of Northeast Texas and Southern Arkansas where
present radar trends are far outpacing the models northward precip
forecasts. SFC frontal boundary should remain well south of our
region today and that should keep any flooding concerns well south
of our area as well. The Lower Toledo Bend and Sam Rayburn Country
of Deep East Texas into West Central and East Central Louisiana
can take upwards of a couple inches of rain as these regions have
been missed from the more moderate rainfall over the last week or
more. The shortwave to our west early this morning will move
quickly our way today with QPF likely trending downward across our
western zones by afternoon with the best PVA shifting eastward
into our far southeast zones. Temperatures may struggle to reach
70 degrees today as post frontal northeast winds, cloud cover and
high rain chances should result in not much of a warmup today.

Tapered pops back to low end chance variety overnight as our
region will be in between the departing shortwave to our east and
a developing longwave trough to our north and west. This next
upstream trough really begins to dig across the Central/Southern
Plains on Tue with strong upper forcing moving into the region
from the northwest during the day. For this reason, have increased
pops during the day Tuesday to low end likely variety along and
ahead of a strong cold front that will be moving through the
region late Tue aftn/Tue Evng. There will be no surface based
instability to speak of on Tue despite a trending signal in the
latest 00z GFS that a spoke of PVA in association with the
longwave trough may eject our way with a slight negative tilt.

We should see the rain quickly coming to an end from northwest to
southeast across the region Tue Night in the wake of the frontal
boundary as we see drier air becoming entrained into the trough
from Central Texas into the Lower Miss Valley Tue Night as well.
Much cooler temperatures filtering into the region Tue Night as
well with lows ranging through the 50s across most areas with
upper 40s possible across portions of SW AR and SE OK. We should
see some sun returning to portions of the region on Wed with
daytime highs mostly in the 70s with our coldest night likely
occurring Wed Night with lows ranging from the middle 40s north to
middle 50s south, some 15 to 20 degrees below normal for late May.

The upper trough will eject out into the Ohio Valley for Thu as we
begin seeing weak upper ridging move in from the west. A
developing trough of low pressure across the Inter Mountain West
for late week into the upcoming weekend will result in increasing
rain chances as we approach the late weekend into early next
week.

Prelims to follow...13.

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  68  60  75  54 /  90  30  60  50
MLU  71  60  78  57 /  90  40  60  60
DEQ  75  55  73  49 /  20  40  60  30
TXK  70  57  73  53 /  40  40  60  40
ELD  69  56  74  53 /  90  30  60  60
TYR  69  60  73  54 /  80  40  60  30
GGG  67  59  74  54 /  80  40  60  40
LFK  71  63  79  58 /  90  40  60  40

&&

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

$$

29/07/13



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