textproduct: Jackson

DISCUSSION

Issued at 359 AM CST Thu Dec 26 2024

Through tonight: A batch of light showers is lifting across the Golden Triangle area early this morning, but most other areas are dry for the time being. Low cloudiness has been expanding overnight, and areas of fog have developed across parts of south MS and south LA. For the time being, this fog hasn't become dense, but we'll be closely monitoring for that potential through shortly after sunrise, when visibilities should improve everywhere. Aside from a persistent low stratus deck in strengthening southerly flow, conditions should be mostly quiet today, with just isolated warm advection showers. Even with the overcast, temps will be above normal.

As we head into this afternoon and tonight, a potent shortwave will swing from the ArkLaTex through the Mid South, initiating thunderstorms over East TX. Storms will organize into a line as they move into LA, reaching our SE Arkansas counties and North LA parishes after sunset. Though instability will be increasingly marginal, especially the farther north you go, a strong 55-65 kt low level jet will accompany the shortwave, resulting in a threat for damaging wind gusts to mix down to the surface. There will also be potential for tornadoes due to strong low level shear, particularly where there is sufficient instability and with any line segments that turn more northeastward in favorable alignment with southwesterly 0-3 km bulk shear vectors. Even outside of the storms, winds will become quite gusty overnight with any mixing down of the strong LLJ and a 5-10 mb surface pressure gradient. A general downward trend is anticipated as storms move farther east into early Friday morning, but given strong wind fields, at least some severe threat will persist into the morning. /DL/

Friday through late next week....

The long term will see continued warmer, moister conditions, with increased storm chances towards the beginning of the period. Rain and storms will continue Friday as a secondary shortwave ejects over Arkansas. Much of the forcing, however is expected to lift north of the area, so severity should wane through the morning into the afternoon. The primary concern is Saturday as northern stream energy rounding the base of an upper trough supports a surface low, progged to eject across the Ozarks. This will elicit a stronger low level response than Friday's system, resulting in dewpoints in the mid to upper 60s across the area in advance of a surface cold front. This leads to increased buoyancy as noted by ~1800 CAPE up to the I-20 corridor. Deep shear 40-50kts overspreads this environment and supports organized storms. Damaging wind gusts appear to be the primary threat given linear mode. Low level shear around 35kts would be enough to support a quick spinup as well, especially in any NW/SE bowing segments. The window for this appears shortened, however, as flow is veered ahead of the front. The primary area of focus appears to be along and south of the Natchez Trace as this is where there is greatest overlap of ingredients. Severe threat should decrease into early Sunday morning with waning instability. The surface front should clear the area by later Sunday morning into early afternoon. To capture all this, an areawide slight has been introduced in the HWO graphic. In addition, repeated convective rainfall events could add up in some areas and some localized flash flooding could be possible in deeper cores, especially if storms train over a certain area. For this, there is a slight risk highlighted, mainly west of I- 55, where greatest rainfall totals are expected.

In the wake, a dry airmass settles over the region. This is short lived however, as another trough ejection will increase rain chances once again Tuesday. That said, instability appears far weaker, especially with the preceding dry airmass, so convective rain looks fairly limited. Beyond this point, we will see a return of cooler temperatures for later next week. How cool and when still is the question with the pattern evolution a bit uncertain. The Euro and Canadian appear to have colder intrusion around 1/2, while the GFS is a bit more delayed and favors 1/3. Either way, freezing temps should make a return towards the back end of the period./SAS/

AVIATION

(12Z TAFS) Issued at 557 AM CST Thu Dec 26 2024

A mostly IFR/MVFR stratus deck encompasses most of the region this morning, with areas of fog also limiting visibility in parts of south MS and LA. Fog should dissipate by mid-morning, but low stratus will persist through the day. Ceilings may improve to MVFR or briefly VFR, but limitations will continue at most sites throughout the day. Wind will become increasingly gusty this afternoon into tonight, with gusts over 30 kt possible. A line of SHRA and TS will move eastward across the area from mid evening through Fri morning, with gusts to 50 kt and tornadoes possible. Ahead of the line, low ceilings will continue to plague most sites. /DL/

PRELIMINARY POINT TEMPS/POPS

Jackson 65 59 73 61 / 20 80 70 60 Meridian 61 54 70 60 / 20 50 90 70 Vicksburg 67 59 74 57 / 50 90 40 40 Hattiesburg 67 60 75 61 / 20 50 80 60 Natchez 69 62 74 60 / 40 90 50 50 Greenville 62 57 68 55 / 50 100 20 20 Greenwood 63 56 71 57 / 20 90 40 40

JAN WATCHES/WARNINGS/ADVISORIES

MS...None. LA...None. AR...None.