Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 201127

Area Forecast Discussion
National Weather Service Shreveport LA
627 AM CDT Tue Oct 20 2020


For the 20/12z TAFs...Surface observations and recent satellite
imagery are showing areas of fog across much of the area this
morning. As a result, widespread MVFR/IFR with occasional LIFR
conditions are being observed this morning. Expecting this trend
to continue this morning before clearing starting to return to VFR
around 20/15z. Skies will begin to clear from the southeast to
the northwest by this afternoon, clearing across the area by this
evening. Another round of low cigs and patchy fog will be possible
for most, if not all, terminals Wednesday morning. /33/


.PREV DISCUSSION... /issued 352 AM CDT Tue Oct 20 2020/

SHORT TERM.../Today through Tomorrow/

For the rest of tonight...latest surface observations are showing
patchy fog in and around a line from Nacogdoches, TX to
Natchitoches, LA to Monroe, LA, to El Dorado, AR. To account for
these trends have added patchy fog to the forecast for portions
of the area through 15z.

Surface observations from early this morning also indicate the
stalled frontal boundary is located near Tyler, TX to Mount
Pleasant, TX, to near De Queen, AR. This frontal boundary will
slowly begin to push back northward after day break and through
the day as a warm front. Latest radar imagery is showing some
lingering showers along and near the frontal boundary. Chances for
showers and perhaps a thunderstorm or two will remain possible
for areas along and north of I-30 this morning and into the early
afternoon hours. Precipitation chances will then diminish as we
move into the evening and overnight hours.

Southerly low-level flow will return to the entire area today as
the frontal boundary pushes back to the north. As a result, the
area will see warmer and more humid conditions return. Aside from
the lingering chances for precipitation for areas north of I-30,
most of the area will remain dry through Wednesday. Clouds will
begin to lift out of the area on Tuesday afternoon generally
clearing from southeast to northwest. I trended temperatures
slightly warmer than what was given for this afternoon with the
clearing skies and southerly flow. Look for afternoon highs to
generally range near the mid 80s across the area with lower 80s
expected north of I-30. Temperatures on Wednesday will be a degree
or two warmer than what we see today. /33/

LONG TERM.../Wednesday Night through Monday Night/

Very warm and humid conditions will continue through late week, as a
deep Srly flow continues across the region. A weak upper
trough/shear axis will linger Wednesday night across ECntrl TX,
before an upper trough begins to dig SE through the NCntrl Rockies.
A lead shortwave trough ahead of the larger longwave remains progged
to pick up the weak upper trough/shear axis over E TX Thursday, and
shift it E into the Lower MS Valley Thursday night. The progs and
NBM are in good agreement this morning with even less in the way of
isolated convection Thursday afternoon over Ncntrl LA ahead of the
ejecting trough, with the convection largely confined just SSE of
the area over Cntrl/SE LA and SW MS. Thus, have scaled back pops as
well which has effectively removed pops for this area and thus
maintaining dry conditions in place.

The aforementioned large scale troughing from the Pac NW through the
Rockies and into the Plains and Upper Midwest Thursday night and
Friday will help to reinforce a cold front SE through the Ozarks and
into the Srn Plains, although this front will become increasingly
more shallow as it enters portions of Wrn AR and extreme NE TX
during the afternoon. The ECMWF has slowed the frontal progression
quite a bit more than 24 hrs ago, although the GFS/Canadian remain
more progressive yet slightly slower as well with the fropa, with
the higher terrain over SE OK/Wrn AR slowing the frontal progression
Friday night/Saturday morning with the stronger sfc ridging
remaining W of the area over the Srn Plains. The progs continue to
suggest though the moisture will remain shallow and large scale
forcing weak with the fropa, and thus have maintained slight chance
pops for all but Deep E TX and Wrn LA. The NBM remains a bit too
cool with max temps ahead of the front, and thus have nudged temps
up 2-3 degrees across the warm sector characteristic with a slightly
slower fropa as suggested by the progs. Given the uncertainty with
the speed/depth of the post-frontal air mass, have stayed close to
the NBM for temps Friday night through the weekend, with the
potential for weak overrunning lingering Friday night for SE OK/the
Nrn sections of SW AR.

The front should begin to stall by Saturday night somewhere over E
TX/N LA, before quickly returning back N as a warm front Sunday. The
Nwd advancement of the warm sector remains in question though late
this weekend, before a deeper and strongly positive tilt longwave
trough begins to dig through the Plains/Rockies and into the Great
Basin Sunday, and into the Srn Rockies by early next week. Although
timing remains uncertain early next week, the attendant cold front
should sweep SE through the Srn Plains and into the region Sunday
night or Monday, with increasing convection becoming more post-
frontal by Monday and Tuesday with the fropa. By the end of the long
term period, a return to much cooler and below normal temps is
expected, with the potential for near-freezing temps by Tuesday
morning across SE OK and possibly portions of extreme NE TX,
signaling what could be the coldest air so far this Fall season.



SHV  85  65  87  66 /  10   0   0   0
MLU  85  63  89  64 /  10   0   0   0
DEQ  83  63  86  63 /  30   0   0   0
TXK  83  63  85  65 /  20   0   0   0
ELD  84  61  86  63 /  10   0   0   0
TYR  86  66  87  66 /  10   0   0   0
GGG  86  64  88  66 /  10   0   0   0
LFK  86  65  89  65 /  10   0   0   0




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