Area Forecast Discussion
Issued by NWS Shreveport, LA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS64 KSHV 251831
AFDSHV

Area Forecast Discussion
National Weather Service Shreveport LA
131 PM CDT Wed Apr 25 2018

.DISCUSSION...
Resent zones and rec to remove morning wording in fcst.

&&

.PREV DISCUSSION... /issued 1149 AM CDT Wed Apr 25 2018/

AVIATION...
Cold front moving through the ArkLaTex region this Wednesday morning
with leading edge along a line from KADF to KTXK to KTYR as of about
16Z. Expect this front to continue moving SE through Thursday morning
with postfrontal light rain and showers as well as MVFR ceilings.
Weak negative vorticity advection during Thursday morning near
sunrise spreads from W to E and with ceilings lifting to VFR near and
after sunrise. /VIII/.

PREV DISCUSSION... /issued 1105 AM CDT Wed Apr 25 2018/

DISCUSSION...
Areas of showers and isold tstms, remaining postfrontal in very
elevated instability. This front making slow progress into the
area and have delayed rain chances for all but extreme nw cwa
until late this aftn, and even lowering pops somewhat for this
time frame. High temps reaching the mid 60s nw to the lower 80s
se cwa still appear on track./07/

PREV DISCUSSION... /issued 727 AM CDT Wed Apr 25 2018/

AVIATION...
For the ArkLaTex, mid and high clouds are spreading into the heart
of the area with a cold front on the way stretching from KTRL to
KPRX. Rain will be well behind this shallow frontal boundary this
evening and overnight. SFC winds are light SW/W or calm and will
be NW and gusty later in the day behind the front. Patchy FG/BR
will improve shortly with cigs expected to remain VFR until late
today and especially this evening with IFR/MVFR conditions into
the overnight, but improving toward daybreak with rain ending.
/24/

PREV DISCUSSION... /issued 500 AM CDT Wed Apr 25 2018/

DISCUSSION...
The morning satellite imagery reveals an AC and cirrus shield
spreading quickly E into the region, with even a few elevated areas of
-RA which continues to diminish along the Red River of extreme SE
OK/adjacent sections of NE TX. However, sct elevated convection has
recently developed farther W over Cntrl and Wrn OK, associated with
PVA ahead of a well-defined upper trough that is diving SE across
NE/NW KS into Ern CO. This trough will continue to sink S into OK
this afternoon, with upper diffluence increasing ahead of the trough
resulting in an increase in elevated convection from portions of N TX
E into extreme NE TX/SE OK and SW AR. However, the air mass will
have to saturate from the top down given the lack of a Srly low level
return flow ahead of the trough, with the best QPF amounts across
the Nrn fringes of the region where this elevated convection will
develop/train longer through the day. Timing of this convection
remains similar to what was progged Tuesday, so did not make many
changes to pops today, maintaining chance pops this morning across
the Nrn zones, before ramping pops up to likely/high chance across
much of NE TX/SW AR/SE OK.

Meanwhile, the morning sfc analysis indicates a cold front extending
from Ern OK into N TX W of the DFW Metroplex, with the ongoing convection
expected to remain post-frontal as the front slides SE into the region
today. The leading edge of the front will remain shallow, thus temps
should warm well into the 70s to near 80 across much of N LA/Deep E TX
despite the increasing AC/cirrus shield which continues to spread E
from Cntrl TX. However, temps should quickly cool this evening as the
upper trough pivots more SW to NE, allowing for an increase in H850
theta-e advection as a SWrly low level wind component develops from
Deep E TX into Ncntrl LA. Did bump pops back up to likely this
evening over Scntrl AR/N LA/extreme Ern TX, as large scale forcing
increases ahead of the trough, but this convection should taper off
quickly this evening and overnight from W to E as drier air quickly
entrains E beneath the trough. In fact, the morning progs are
depicting this occurring several hours faster than the runs Tuesday,
and for this reason, have dropped mention of pops Thursday morning
across the Ern zones. Will still have to contend with an extensive
wrap-around stratocu field Thursday in wake of the trough passage,
which should maintain below normal temps in the upper 60s/lower 70s.

The progressive pattern will continue Thursday night, with the next
shortwave trough quickly diving SE through the area. As is the case
with the initial trough, there will not be any Srly low level moisture
advection into the area, with cold mid level temps contributing to
enough instability for isolated elevated convection late Thursday
night over the Nrn half of the area. However, QPF amounts will remain
light, under a tenth of an inch, before this trough quickly exits the
region Friday morning. Did maintain low pops across the Ern zones
Friday morning, with another weak cold fropa through the area in wake
of the trough. Cigs should clear during the afternoon and evening,
giving way to very cool conditions Friday night as good radiational
cooling sets up with sfc ridging moving over the region.

A warming trend will commence Saturday as upper ridging shifts E
across the Plains and MS Valley, well ahead of a closed low that will
shift E  into the Pac NW and Great Basin. Thus, more seasonable temps
will return areawide Saturday, with a gradual modification iN RH`s as
well as a SSE low level flow develops in wake of the departing sfc
ridge Sunday and to start the new work week. A dry forecast will
continue through Monday, before the ridging aloft begins to shift E of
the area, with the flow expected to gradually transition to SW by
Tuesday/Wednesday. Considerable discrepancies exist amongst the
GFS/ECMWF by the midweek period with the overall position of the upper
low or troughing features, but subtle impulses in the SW flow may
yield isolated convection over the area Tuesday and Wednesday once low
level moisture is able to deepen. Warmer and more humid conditions
also typical for this time of year will also persist as we move
forward into the first several days of May.

Prelims to follow below...

15

&&

.PRELIMINARY POINT TEMPS/POPS...
SHV  78  49  70  54 /  20  60  10  20
MLU  80  54  69  53 /  10  70  10  10
DEQ  65  47  70  50 /  60  30  10  20
TXK  71  49  70  53 /  30  50  10  20
ELD  77  51  69  51 /  20  60  10  20
TYR  72  47  72  53 /  20  50   0  20
GGG  75  48  70  53 /  20  50   0  20
LFK  81  52  73  53 /  10  50   0  10

&&

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

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.