Area Forecast Discussion Issued by NWS Jackson, MS
000
FXUS64 KJAN 150623 AAA
AFDJAN
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
123 AM CDT Fri Mar 15 2024
...New AVIATION...
.MESOSCALE UPDATE...
Issued at 845 PM CDT Thu Mar 14 2024
Rest of tonight...
Most of the evening convection has waned, with the exception of a
few showers persisting across the I-55 corridor. Evening upper
air/water vapor analysis indicates upper low situated over the
Desert Southwest to Baja Peninsula area, with broad southwesterly
flow on the northwest periphery of anomalous ridge centered over
the Caribbean Sea into the Bahamas. Sfc analysis this evening
indicate broad sfc high with southwesterly warm-advection ongoing
& sfc dewpoints in the upper 60s-low 70s. Majority of cloud tops
have cooled across the ArkLaMiss-Gulf Coast, with the exception
over the Ozarks & Mid South region where earlier vigorous
convection persists & deep cloud tops remain. Capping inversion
has eroded this evening from special 21Z sounding to this
evening`s 00Z sounding, but only broad ascent/low-level forcing
have aided in isolated development of earlier convection. Recent
Warn on Forecast (WoFS) & hi-res convective allowing models (CAMs)
indicate convection potential developing in the extreme northwest
ArkLaMiss Delta around midnight to 1AM & then organized severe
threat sagging in the northwest Delta just before daybreak. There
are still indications that some storms could orient north-south,
which is more orthogonal to the 0-3km shear vectors, which would
bring favor bowing segment/enhanced wind & some tornado
potential. Timing could be a tad earlier, around 3-4AM in the
extreme northwest ArkLaMiss Delta counties. Will likely make some
minor adjustments to the onset timing of severe to the graphic
overnight but otherwise looks mostly intact. Main threats remain
to be damaging winds, large hail up to golf ball size & a tornado
can`t be ruled out. In addition, these storms should begin to
become more line-parallel & conducive for heavy rain. CAMs & HREF
prob match mean >3 inches, still support the current messaging of
up to 3 inches likely & locally higher amounts possible,
especially in north-central MS into northwest ArkLaMiss Delta.
Updates are out & only forecast changes were to adjust some of
the timing & rain/storm chances. /DC/
&&
.DISCUSSION...
Issued at 254 PM CDT Thu Mar 14 2024
This Evening through Friday:
This morning`s 12Z soundings from KJAN and KSHV showed a decent cap
at 825mb which developed in response to expanding influence of the
ridge to our east. Modification of the air mass has been slowly
occurring through the day today, with temps creeping into the low
80s across central LA/southwestern MS and dew points rising into the
upper 60s. Southwesterly flow aloft was expected to reduce the cap,
and a planned special sounding will evaluate this over the KJAN area
shortly. Over the last hour, radar and satellite imagery trends have
shown an increase in showers and convective cloud features across
the forecast area. Decent mid-level lapse rates (6.5-7.5 C/km) and
modest deep-layer wind shear (25-35 kts) could allow for a few
robust updrafts or supercells to develop. Latest few WoFS runs have
favored convective initiation around the Mississippi River even down
to around the southwestern corner of MS/central LA. Therefore
expanded the Marginal risk area for severe storms to encompass the
Miss-Lou over through the I-55 corridor as well as previously
advertised areas. Any of these storms will primarily carry the risk
for hail up to the size of golf balls, but the steepening low-level
lapse rates and drier mid-level air also increase the risk for
damaging wind gusts (especially if melting hail is taken into
account).
This threat is separate from a more organized threat for severe
weather late tonight into Friday that will accompany convection
spreading southeast into our area from the Ozarks. High-res
convective allowing model guidance is within the window that some
detail could be provided for storm timing tonight into tomorrow, so
that has been included on the latest iteration of our severe risk
graphic covering Friday. The greater threat for damaging wind gusts
and a possible tornado look to be focused from central/southern
Arkansas into northern Mississippi late tonight into early Friday
morning as convection in the Ozarks organizes and spreads east in
alignment with low-level shear vectors. Cold pool dynamics are
expected to push the threat of thunderstorms south of Interstate 20
by Friday afternoon, though the boundary becoming more parallel to
the flow will pose less of a direct severe threat apart from gusty
winds along the cold pool itself. Therefore the risk at this time
appears to remain Marginal for much of the forecast area tomorrow.
Also made an update to the Flash Flood potential outlook to
highlight the greatest risk of locally heavy rainfall through the
daytime tomorrow (generally northern half of our area) as short-term
guidance has come into better focus. /NF/
Friday Night through next Wednesday:
A closed mid/upper level low pressure system will continue to
anchor itself across the desert southwest through much of the
forecast period. Beginning the forecast period and through the
upcoming weekend, this low will be responsible for sending a
couple of disturbances east into and through the Lower Mississippi
River Valley. This will result in at least two bouts of showers,
along with an isolated thunderstorm or two, affecting the forecast
area. The first such disturbance will be in the process of moving
through the CWA overnight Friday, with rainfall coming to an end
Saturday. With a lull in activity forecast for much of the
Saturday day period, the second disturbance will bring showers to
the forecast area Saturday night, while gradually tapering off
through the course of the day Sunday.
On Monday, a longwave trough rounding the base of a closed low
centered over southeast Canada, will cut off the flow of
disturbances across the region. This will bring an end to rain
chances across the forecast area as we begin the work week. This
trough will result in northwest flow aloft across the region,
while strong high pressure at the surface builds into the forecast
area from northwest to southeast Monday into Tuesday. This will
result in a cooler and noticeably drier airmass advecting into the
CWA through mid-week.
Highs on Monday will range from the middle 50s north to middle 60s
south. Lows Monday night will be chilly as they range from the
low to middle 30s. This will likely result in some areas of frost
across portions of the CWA as day breaks on Tuesday. Highs will be
a little warmer on Tuesday, and will continue to warm through
Wednesday as high pressure at the surface becomes centered east of
the region. Chances for rain will also begin increasing across
the CWA late in the day Wednesday and into Wednesday night. This
is as a result of the once closed low pressure system anchored
over the desert southwest, weakening and shifting east into and
through the Lower Mississippi River Valley Wednesday night into
Thursday. /19/
&&
.AVIATION...
(06Z TAFS)
Issued at 117 AM CDT Fri Mar 15 2024
MVFR cigs wl prevail for the next hour or two but lower flying
conditions are expected to develop across the area tonight and
prevail into Saturday aftn before improving from the west.
Widespread -SHRA/TSRA are expected across the area ahead of a cold
front that will drop through the region. IFR/LIFR conditions are
expected Saturday evening in the wake of the cold front. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 58 73 56 68 / 40 10 50 40
Meridian 58 75 53 69 / 50 10 40 50
Vicksburg 56 73 56 68 / 30 10 50 30
Hattiesburg 62 78 60 71 / 50 20 50 70
Natchez 59 74 58 68 / 30 20 60 40
Greenville 52 68 54 65 / 20 0 30 10
Greenwood 53 71 52 68 / 30 0 30 20
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
NF/22