Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 222102

Area Forecast Discussion
National Weather Service Shreveport LA
402 PM CDT Sat Apr 22 2017

The cold front has just about cleared the CWA as of mid-afternoon,
and extends just E of a GWO, to W of a TVR and AEX, to DRI and BPT
line as of 20Z. Convection has recently become sct along the
frontal zone, and will diminish across SE Grant and La Salle
Parishes here shortly. However, radar imagery does depict an
uptick in elevated convection along the I-20 corridor of E TX this
afternoon, associated with the H700 theta-e ridge near and N of
the H850 front. H700-500 lapse rates are just steep enough to
garner isolated -TSRA near TYR/GGG, with even a report of pea size
hail recently near Longview. Although the short term progs
(including the HRRR) do not suggest much of any QPF early this
evening along the H700 theta-e axis, have extended slight chance
pops through this evening for portions of E TX and extreme Srn AR
with a band of low chance pops farther S along/S of I-20 to
account for the ongoing convection, and the model compromise of
the placement of the elevated theta-e axis/H850 front as it swings
ESE across these areas this evening. Did maintain slight chance
pops after 06Z for the Ern sections of Ncntrl LA before the
primary upper trough, noted on the afternoon water vapor imagery
digging SSE across SW KS, swings into the Red River Valley into
Srn AR/N LA late tonight.

Much cooler and drier air also continues to spill SE in wake of
the fropa, with a considerable post-frontal stratocu field noted
as far N as Srn KS/Cntrl MO. This has limited the extent of mixing
this afternoon despite the somewhat tight pressure gradient in
place, and thus has limited the gustier winds. With little change
expected this afternoon/evening, have cancelled the Lake Wind
Advisory for areas along/N of the I-20 corridor of E TX/N LA. Cold
advection will resume after dusk, with below normal temps expected
tonight. Given the winds and extensive cloud cover tonight, have
bumped up min temps a tad over much of the area, with the lower
stratocu field expected to diminish by late morning/early
afternoon Sunday with the passage of the main upper trough.
However, additional cu cigs should develop and fill back in with
especially along/S of I-20 by afternoon, with breezy N winds
limiting the afternoon warmup. As a result, below normal afternoon
temps are again expected, with max temps hard pressed to reach 70
degrees. The post-frontal clouds/winds should finally
diminish/clear the region Sunday evening as sfc ridging builds S
into the Srn Plains/Lower MS Valley, setting the stage for ideal
radiational cooling. Min temps Monday morning should still remain
above records low for the date, but very cool and comfortable
conditions will greet the region to start the new work week.

A warmup will commence Monday as the sfc ridge begins to drift E
of the area and low amplitude upper ridging builds over the region,
although RH`s will not respond until Tuesday once the pressure
gradient tightens over the Srn Plains in response to shortwave
troughing over the Srn Rockies and TX S Plains. This troughing
should continue to amplify Tuesday night/Wednesday morning over N
TX/OK, with enough moisture advection and forcing along a Swrly
LLJ to maintain slight chance pop mention for SE OK/adjacent SW AR
especially in the higher terrain. However, low level moisture will
continue to deepen Wednesday as the associated cold front begins
to dig SE into the region. The 12Z GFS has trended very similar to
the 00Z ECMWF in stalling the cold front out somewhere over E TX/N
LA Wednesday night, although the new 12Z ECMWF run suggests a
much more progressive fropa eventually stalling it over SE TX/Srn
LA Thursday. Did increase pops to chance across the stronger
forced areas of SE OK/SW AR/extreme Nrn LA Wednesday as deep lyr
moisture will still be in recovery mode with the fropa, and
maintained slight chance/low chance pops through Thursday as the
front should begin to lift back Nwd across the area.

The latter portion of the extended (Thursday and beyond) still
remains a low confidence forecast given the variation in the sfc
front during this period, with the 12Z ECMWF keeping the bndry
stalled out along the I-20 corridor of E TX/N LA, while the GFS
maintains the bndry well N of the region under an expansive
warm/moist sector. However, the flow aloft should become more SW
by next weekend as longwave troughing digs SSE through the Rockies
and into the Cntrl/Srn Plains. The GFS is in agreement with this
scenario as well, with convection expected to become more numerous
at some point next weekend with the risk for svr convection as

Prelims to follow below...



.PREV DISCUSSION... /issued 106 PM CDT Sat Apr 22 2017/

Cold front movg slowly east across north LA and will cross KMLU
btwn 18-19z. Brief shower possible with wshft. NW winds 10 to 15
kts to continue areawide this aftn and remain around 10 kts for
most of fcst period. Mostly low mvfr with ocnl ifr cigs, becmg low
vfr later in aftn. However, additional mvfr decks back into area
overnight and into mrng. Dry slot after 23/06z into east TX with
scattered to skc skies gradually spreading across ne TX. Further
east across AR/LA portions of area, high mvfr to low vfr cigs
achieved by end of the 23/18z fcst cycle. /07/


SHV  49  70  45  82 /  30   0   0   0
MLU  52  68  46  79 /  30  10   0   0
DEQ  44  70  39  78 /  10   0   0   0
TXK  47  70  43  78 /  10   0   0   0
ELD  48  68  43  78 /  20  10   0   0
TYR  47  71  45  80 /  20   0   0   0
GGG  47  70  44  80 /  30   0   0   0
LFK  49  72  47  81 /  20   0   0   0




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