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FXUS64 KJAN 300350 AFDJAN

Area Forecast Discussion National Weather Service Jackson MS 950 PM CST Wed Nov 29 2023

New MESOSCALE UPDATE

MESOSCALE UPDATE
Issued at 950 PM CST Wed Nov 29 2023

All is on track for this near term forecast update with temperatures not quite as chilly as they were last night.
Southeast wind is beginning to pick up and clouds are increasing ahead of an approaching shortwave trough as expected. No significant adjustments were necessary. /EC/



DISCUSSION
Issued at 221 PM CST Wed Nov 29 2023

Tonight and Thursday: It will be dry tonight but rain chances return Thursday. Temperatures tonight won't be as cold but will still be cooler than normal. Temperatures Thursday will be near normal.

Split flow regime will continue through the Thursday with an active southern stream across our CWA. Mid afternoon water vapor imagery/RAP analysis showed our winds aloft nearly zonal with high moisture aloft streaming up from the southwest. Mid afternoon surface analysis had a weakened 1025mb high centered over southwest Alabama. This high will continue to shift east while ridging back to the west across the Gulf coast states through Thursday. This will result in return flow that will gradually increase low level moisture back across our CWA. The JAN morning sounding had a PWAT right at a quarter inch. PWATs will be back near an inch and a half over our southwest and back above one inch southwest of northwest most zones by Thursday evening. Tonight will be dry but the deep moisture increase will combine with a few subtle disturbances within the southern jet to increase rain chances Thursday morning from the west. The rain chances will increase from west to east through the afternoon. By afternoon a more potent shortwave over the southern Plains will help deepen a surface low near the Red River. This will increase the pressure gradient across our CWA resulting in some gusty winds and help increase instability enough for a few rumbles of thunder to be heard over the western half of the CWA. /22/

Thursday night through Friday: As a compact mid/upper shortwave shifts from the Southern Plains toward the Midwest, a surface low will track from the Red River Valley into the Mid-MS River Valley, dragging a front into the area by the daytime Friday. In advance of the system, a 55-65 kt low level jet streak will stream across the area overnight Thursday into Friday. This, along with a tightening surface pressure gradient, will result in rather windy conditions across much of the area even outside of any convection that may occur. We will begin highlighting this potential with an HWO graphic for strong gradient wind, but a Wind Advisory may ultimately be needed for some portion of the area.

Otherwise, coverage of showers will already be increasing across the area by Thursday evening. Meanwhile, more vigorous convection ongoing across TX and west LA will advance eastward through the evening, beginning to reach our central LA parishes mainly after midnight, and gradually spreading eastward through Friday morning.
As previously mentioned ample wind shear, both deep layer and in the low levels, will be in place in advance of this convection.
However, instability is expected to be rather limited and focused mainly in our southernmost zones. After sunrise Friday, there may be some opportunity for greater instability to spread further north as storms begin to reach central and east MS, however the stabilizing influence of considerable stratus coverage and ongoing rain cast doubt into how far north and low level shear will also begin to decrease around this time. Thus we will maintain the current marginal severe risk area in our graphics. We did tweak the timing a bit to indicate potential for isolated severe a bit sooner in the early morning hours. Additionally, 12z CAM guidance suggests most convection will be moving out by midday with only scattered lingering showers into the afternoon. If any severe weather does occur, damaging wind gusts or a brief tornado would be the most likely hazards given the high shear/low instability setup.

HRRR PMM show strong potential for parts of central LA and southwest MS to receive upwards of 2-3" of rain, with some individuals guidance members depicting locally higher amounts.
While we can't rule out localized flooding, most areas should be able to handle these amounts so long as it doesn't fall in too short of a time frame.

Friday night through Monday: The surface front will stall across the area Friday night into early Saturday as strong upper level flow becomes nearly parallel to it. And as additional upper disturbances transit this active upper flow pattern, more bouts of rain will be possible from Friday evening through Sunday or early Monday. Most of this additional rain will be focused on the warm/moist side of the stalled front, so generally south and east of the Natchez Trace. Additional rainfall amounts of 1-2" are expected, and once again, rates are expected to be low enough to avoid flooding unless convection results in locally higher amounts/rates.

Tuesday to next Wednesday: The upper trough will finally shift eastward, nudging the front out of the area and bringing drier weather for the end of the forecast period. /DL/

AVIATION
(00Z TAFS)
Issued at 544 PM CST Wed Nov 29 2023

VFR conditions will prevail through the forecast period. There will be a gradually lowering of mid/high level ceilings as the next system approaches Thursday, and south to southeast surface wind will pick up and become gusty from late morning through the afternoon. Conditions will deteriorate as we go into the evening with widespread IFR ceilings expected to develop by late Thursday night. /EC/

PRELIMINARY POINT TEMPS/POPS
Jackson 40 63 53 75 / 0 70 100 40 Meridian 34 63 47 74 / 0 40 90 60 Vicksburg 41 63 53 75 / 0 80 100 30 Hattiesburg 36 66 55 76 / 0 50 90 60 Natchez 43 63 55 75 / 0 80 100 30 Greenville 40 58 51 71 / 0 80 100 20 Greenwood 41 60 49 73 / 0 70 100 30

JAN WATCHES/WARNINGS/ADVISORIES
MS...None.
LA...None.
AR...None.

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