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FXUS64 KSHV 072006 AFDSHV

Area Forecast Discussion National Weather Service Shreveport LA 206 PM CST Thu Dec 7 2023

New SHORT TERM, LONG TERM

SHORT TERM
(This evening through Friday Night)
Issued at 201 PM CST Thu Dec 7 2023

The synoptic pattern this afternoon is characterized by a low- amplitude, broad mid and upper level trough extending from the far Eastern Pacific through the Rockies and into the Great Plains, with shortwave ridging located just downstream across the Midwest and MS Valley. Near the surface several areas of low pressure exist in the lee of the Rockies, with a frontal boundary noted across the Northern and Central Great Plains while high pressure encompasses much of the southern and southeast US.

Weather conditions will remain tranquil through the rest of this afternoon and through the evening with some high level cloud cover.
Increasing south winds will allow for highs this afternoon in the mid 60s. For tonight a shortwave trough, currently located over northern Mexico, will move E/NE into the ArkLaTex early Friday morning. As this occurs, the sfc high influencing the region will begin to shift east, allowing low level moisture to continue to increase, evidenced by dew point temperatures increasing into the upper 50s to lower 60s across central and east TX. Low level cloud cover will also begin to increase, with much of the area waking up to overcast skies, and possibly areas of drizzle and/or light rain showers, especially across east TX and W LA. A moistening airmass and low level cloud cover will make for much warmer low temps into early Friday, generally upper 40s east and mid 50s west.

Cloud cover will be stubborn to lift through the first half of Friday as a sfc low begins to deepen across OK and WWA increases across the Four State Region. This may help enhance drizzle and light rain through the morning hours and into the afternoon. Despite cloud cover, WAA and southerly flow should help yield high temps in the low 70s across TX and LA and mid to upper 60s north.

Concerning the severe potential later Friday, cloud cover will remain an issue. Hi-res model guidance and CAMs suggest better SBCAPE developing across E TX late Friday afternoon and into the evening, which will be aided by the approach of a subtle mid level speed max. As this source of lift approaches and the instability develops amidst dewpoints in the mid to upper 60s, SRH values become quite impressive (0-1km 200-300 m2/s2) with mid level lapse rates surpassing 7C/km. While this does increase the concern for the development of some robust cells, model soundings do show enough of a warm nose around 850mb to potentially keep the environment capped across E TX through the evening while severe ingredients remain favorable. This is currently supported by the lack of convective development within the hi-res guidance suite, but this will still be monitored closely over the next 12-18 hours for any changes.

Further north late Friday across S AR, the severe threat will also exist within a slightly different environment. Cloud cover is expected to remain high enough to prevent the development of surface- based instability, however, noticeable MUCAPE should exist out ahead of an approaching cold frontal boundary Friday night (1000-1500J/kg) with steep mid level lapse rates of around 7.5C/km. This will yield the potential for a few strong updrafts capable of carrying a threat for severe hail into Saturday morning. Cells may begin to develop into clusters as the forcing becomes more linear along the cold front into early Saturday. As most of the area remains in the warm sector Saturday night, with lows in the 60s.

Kovacik

LONG TERM
(Saturday through next Wednesday)
Issued at 201 PM CST Thu Dec 7 2023

As we move into Saturday, all eyes will be on a longwave, positively tilted trough entering the Upper Great Lakes into the Central and Southern Plains. Our region of the country will be under southwesterly flow aloft with upstream forcing in advance of the trough, possibly as early as sunrise Saturday Morning with a few elevated strong storms, mainly near and northwest of the I-30 Corridor to start the day but the bigger show will hold off until the afternoon and evening.

The upper trough will continue digging into the Upper and Middle Red River Valley by late afternoon on Saturday with more widespread upper forcing underneath the right-rear quadrant of 125kt upper jet streak moving quickly out of the Texas Hill Country and into the Ozarks of Central Arkansas. A strong cold front will accompany this upper level trough with the boundary fcst to begin entering our northwest zones as early as sunrise Saturday Morning. Look for the boundary to be near or just south and east of the I-30 Corridor of NE TX and SW AR by Noon on Saturday and it's from the Noon hour and through the evening when the window will open up for the development of strong to possibly severe thunderstorms Sat Aftn and Evng. The atmosphere across the warm sector ahead of the frontal boundary Sat Aftn can best be described as moderately unstable with MUCAPE values near 1500J/KG across Deep East Texas into Northern Louisiana and South Central Arkansas where sfc based returning dewpoints near 65 deg will be common. While there will be plenty of deep layer bulk shear, on the order of magnitude of 50-60kts in the 0-6km layer, the saving grace may be that as the front continues to push south and east into the warm sector, low level winds begin to veer around to more of a southwesterly direction, thus maybe limiting the overall tornadic threat across our region. A parallel wind profile in advance of the shortwave trough can still support supercell structures but with more of a wind/hail threat than a tornado threat but these trends will continue to be monitored. The degree of low level shear will be highly dependent on if we see sfc cyclogenesis somewhere along the frontal boundary itself, something that short term progs continue to struggle with. For now, SPC continues to highlight much of our region in a Slight Risk for severe thunderstorms and this still looks possible, yet conditional on just how widespread severe thunderstorms can become before we begin to lose the instability to our east the later in the evening we go.

Not to be lost with the severe weather threat on Saturday is the much colder temperatures and strong pressure gradient in advance of the front and definitely behind the front. Southwest winds of 10 to 20 mph with higher gusts will describe the warm sector on Saturday with a 20-25 degree drop behind the frontal boundary and winds shifting around to the northwest with speeds of 15 to 25 mph with higher gusts. Winds will stay up Saturday Night and much of Sunday before winds begin to decouple Sunday Night.

The trough moves through quickly on Sunday but northwest flow aloft is not here long before yet another trough begins to carve its way out across the Intermountain West Tue into Wed of next week. This will result in quickly moderating temperatures with increasing southwest flow aloft and rain chances returning to the forecast just beyond this 7-day forecast cycle.

13

AVIATION
(18Z TAFS)
Issued at 1109 AM CST Thu Dec 7 2023

High level cloud cover will continue through the rest of today, yielding VFR ceilings. Later this evening, expect mid level clouds to move into the area, especially from S AR into NE TX. After midnight and through Friday morning, low level cloud cover will then develop as low level moisture increases, providing for MVFR ceilings with perhaps areas of drizzle and/or light rain showers.
These conditions will persist through 18z before lifting and scattering some in the afternoon. Winds will be breezy out of the S from N LA and across NE TX into S AR and OK 8-12kts with some gusts to 20kts. Breezy winds have the best potential to maintain themselves across E TX overnight before winds become breezy area- wide Friday 10 to 15kts with gusts 20 to 25kts out of the S.

Kovacik

PRELIMINARY POINT TEMPS/POPS
SHV 54 72 66 74 / 0 10 40 70 MLU 45 70 62 77 / 0 30 40 90 DEQ 48 68 53 64 / 10 20 60 40 TXK 51 69 61 69 / 0 20 70 50 ELD 47 69 60 72 / 0 10 60 80 TYR 58 74 63 71 / 0 10 20 40 GGG 55 74 64 74 / 0 10 30 50 LFK 55 74 65 77 / 10 20 20 60

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

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