903
FXUS64 KJAN 091606 AAA
AFDJAN

Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
1106 AM CDT Thu May 9 2024

...New MESOSCALE UPDATE...

.MESOSCALE UPDATE...
Issued at 1042 AM CDT Thu May 9 2024

After setting record warm lows at all of our climate sites
yesterday, this morning was another warm start and temperatures
are already in the low to mid 80s. The 12Z Thu JAN sounding
showed a PWAT of 1.81in and our dew points are running in the mid
70s. The JAN sounding also showed a decent cap at 700mb. The
morning MCS to our north has left a boundary just to the north of
our northeast most zones. Surface analysis showed a cold front
just northwest of our northwest most zones. Thus, our whole CWA
remains in a warm moist airmass and will support shower and
thunderstorm development with daytime heating. The cap should keep
convection tamed through much of the early afternoon but a strong
to possibly severe storm will be possible by late afternoon. The
main severe threat remains on target for this evening through a
few hours after midnight. /22/

&&

.DISCUSSION...
Issued at 505 AM CDT Thu May 9 2024

Today through Tonight...

A more significant severe weather threat will likely evolve late
afternoon into the overnight. Model consensus continue to indicate
shortwave energy digging southward from the upper midwest. This
setup will help to flatten the ridge and allow the cold front to
shift closer to the I-20 corridor by late in the day. During the
day, steep lapse rates and strong heating will make for a very
unstable airmass with ML CAPE approaching 4000 j/kg, but the lack
of forcing combined with a capping inversion will keep the
potential for deep convection relatively low. Isolated showers and
storms could start to redevelop during peak daytime heating later
this afternoon. Any storms that do develop in this environment could
potentially become severe. However, confidence in greatest
convective potential will hold off until the late evening to
overnight hours.

The potential for strong to severe storms will begin to pick up
during the late evening into the overnight period (starting as early
as 9pm) as greater ascent in the mid levels interacts with the
stalled frontal/outflow boundary. This is when forecast confidence
diminishes somewhat due to some spread in the guidance concerning
the convective evolution. Several convective allowing models
indicate a MCS rapidly moving across the I-20 corridor. Confidence
remains less certain on what zone this will propagate across, but
likely some higher probability along the Interstate 20 corridor and
south, with decreased probability to the north in the Highway 82
corridor. While storms will likely develop well to the west over
eastern TX initially, determining how they organize and where they
go from there remains a challenge. It appears likely that the most
probable scenario indicates the potential for an intense linear
convective system/MCS moving west to east across our forecast area.
Main hazards remain to be damaging wind gusts up to 80 mph and large
hail up to golf ball size being the primary concerns with these
storms. A few brief tornadoes cannot be ruled out. Main adjustments
to the graphic were to bump up the wind to 80mph, with some
potential to exceed that. Held off introduction of higher wind gusts
at this time but will need to be assessed in future updates. Also
adjusted the timing to 9PM to midnight along and west of the MS
River corridor, 10PM to just after midnight in the Interstate 55
corridor and just prior to midnight through 3AM in the Interstate 59
to Highway 45 corridors.

The ceiling is relatively high concerning the potential severity of
the late tonight given the extreme thermodynamic parameters combined
with strong deep layer shear. Confidence has increased in the
potential of convection organizing into an MCS to our west late this
evening before surging east across portions of our CWA overnight,
but in terms of probability, there remains some spread in the
position/timing of how any developing MCS propagates across the
region. Enhanced Risk (3 out 5) of severe storms for severe weather
remains in the HWO graphic. With collaboration with SPC, Enhanced
risk was expanded further south in order to include areas south of
Highway 84. The Slight Risk was extended further north. In addition
to the severe potential, there may be some potential of of locally
heavy rainfall of 1 to 2 inches in a short duration of time. This
could lead to minor runoff issues in poor drainage areas along with
the potential for localized flash flooding in a couple of areas.
However, fast moving nature of the storms may limit some of the
flash flooding concerns. We will continue to monitor for addition to
the HWO graphics in future updates. Went ahead and made a few
modifications to the forecast for this timeframe by leaning towards
wetter guidance and increased rain chances across the area.
/CR/DC/

Late week through mid next week (Friday-next Wednesday)...

Late week into weekend (Friday-Sunday): In the wake of the MCS, a
much drier period is in store. Longwave pattern will consist of two
stout shortwaves diving down out of Canada into Great Lakes to the
TN Valley, with the first off the Atlantic seaboard by Saturday &
the other deeper shortwave trough moving through by Sunday. Drying
northwesterly flow will gradually become westerly into the weekend,
but subsidence will remain as sfc high drops southward across the
Plains. This pattern will lead to dry conditions, with limited
clouds through early weekend before increased moist ascent aloft
move back in late weekend on Sunday. This will bring widespread
cloudiness spreading back over from the west. Seasonably cool
conditions are expected, high temps some 3-5 degrees F below normal,
in the upper 70s-low 80s & low temps some 3-5 degrees F below normal
into late weekend.

Next week (Monday-Wednesday): A wetter period period can be expected
as shortwave ridge builds eastward. Moisture transport will pick up
in advance of a cold core aloft progged to swing into the Plains
early next week. PWs will climb to nearly the 90th percentile, with
increased rain totals across the southern half of the region. In
addition, there could be enough forcing/height falls for some
organized convection early next week. We also could have to watch
potential for flash flooding south of I-20 but will hold off now
until we get some good run-to-run consistency on QPF totals. Details
are too uncertain to iron out for both severe & flooding & no HWO
graphics are warranted at this moment. Seasonably cool conditions,
some 5-10 degrees F below normal, in the mid 70s Monday, are
expected to moderate by midweek. Highs will reach into the mid 80s
by Wednesday, while gradually seasonably warm lows are expected in
the low 60s southeast of the Natchez Trace to mid-upper 60s to the
northwest. /DC/

&&

.AVIATION...
(12Z TAFS)
Issued at 611 AM CDT Thu May 9 2024

A mixture of MVFR/VFR ceilings across all TAF sites to start off
the period. Southern TAF sites will continue to see MVFR
conditions due to low stratus until 15Z Thursday. Between 16Z-23Z
Thursday, VFR ceilings will prevail across central Mississippi.
Storm chances will start to increase around 05Z Friday with
several TAF sites dropping down to MVFR/IFR. Some of these storms
will have the potential to become severe. HBG & PIB could drop
down to potential LIFR conditions around 09Z Friday as the storm
system races east across the area later in the evening. A brief
period of low-level wind shear will occur across several southern
TAF sites between 05Z-06Z Friday. Amendments may be necessary
around this timeframe as conditions worsen. Rain chances will end
on Friday with VFR conditions prevailing. /CR/

&&

.PRELIMINARY POINT TEMPS/POPS...
Jackson       90  66  81  57 /  30  80  10   0
Meridian      91  65  84  56 /  50  80  20   0
Vicksburg     90  66  82  58 /  20  80   0   0
Hattiesburg   93  70  86  59 /  30  80  30   0
Natchez       91  66  83  58 /  20  80   0   0
Greenville    89  66  79  59 /  20  50   0   0
Greenwood     89  64  79  56 /  40  50   0   0

&&

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

$$

22/DC/CR