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SPC May 9, 2024 2000 UTC Day 1 Convective Outlook

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SPC 2000Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0248 PM CDT Thu May 09 2024

Valid 092000Z - 101200Z


Very large hail with multiple supercells appears probable across
parts of north and central Texas into the ArkLaTex vicinity this
afternoon and evening.  A broader corridor of severe hail and
damaging-wind potential will extend from east Texas into the lower
Mississippi Valley and Southeast.


The main changes with the 20z update were to remove most severe
probabilities from much of SC/NC. Convection has mostly moved
offshore and redevelopment is not expected. Furthermore, instability
will remain very weak across much of NC and any storms that may form
into the evening/overnight should remain fairly weak. Probabilities
were not changed much over AL/GA from the previous outlook given
expected MCS moving into these areas overnight and posing a risk for
damaging wind gusts. 

...OK/TX to Lower MS Valley...

The Marginal risk (level 1 of 5) was extended northward into central
OK where ongoing thunderstorms will pose some risk for marginally
severe hail this afternoon/evening with eastward extent into AR. 

The Enhanced risk (level 3 of 5) has been nudged a small amount
south across southeast TX and LA based on latest short term guidance
and CAMs trends. Damaging gusts and hail will be the main concern as
thunderstorms congeal over north/central TX into an eastward
progressing MCS during the evening/overnight.

..Leitman.. 05/09/2024

.PREV DISCUSSION... /ISSUED 1146 AM CDT Thu May 09 2024/

Water-vapor imagery late this morning shows a mid-level trough over
the western Great Lakes/Upper MS Valley and a mid- to upper-level
low situated over eastern UT.  A broad belt of strong westerly
500-mb flow will extend from the Desert Southwest eastward across
the southern Great Plains and to the Mid-Atlantic and Southeast U.S.
coast.  Satellite imagery also depicts an embedded disturbance
quickly moving east across AL into western GA late this morning. 
Another upstream disturbance is currently moving east-northeast
across northern Mexico into the Rio Grande Valley/Edwards Plateau
late this morning.  In the low levels, a surface low over the OH
Valley is largely displaced from the area of greatest severe
thunderstorm concern today, which is located from TX east to the
GA/SC vicinity.  A myriad of ongoing thunderstorm bands and
convective outflow over the Southeast will serve as corridors for
additional and continued thunderstorm activity through at least the
early to mid afternoon.  Farther west, a dryline and west-east
oriented frontal zone over north TX east to the ArkLaMiss will also
act to focus severe thunderstorm development later today and

...North, central and east TX...
Scattered thunderstorms are forecast to develop this afternoon and
evening ahead of the aforementioned mid-level disturbance across
central and eventually into eastern portions of TX.  Storm
development will likely initially favor near and north of a frontal
zone draped across north TX with dryline storms later this
afternoon.  The Fort Worth and Del Rio, TX raobs sampled 8-9 deg
C/km 700-500 mb lapse rates.  Very large CAPE via a very moist
boundary layer will likely favor explosive updraft growth as storms
quickly become supercellular.  Low-level shear will likely be
subdued due to lack of a strong low-level mass response, thereby
acting to limit overall tornado potential.  Nonetheless, a few
supercells within an environment characterized by very large
buoyancy and moist low levels will potentially yield some tornado
risk via local storm-scale processes such as mergers and boundary
interactions.  Large to giant hail --potentially 3+ inches in
diameter -- as well as locally severe gusts and perhaps a tornado or
two will be the primary threats.  The wind threat could evolve
upscale and start forward-propagating eastward into LA wherever
early cells can aggregate into clusters.  QLCS tornadoes are also
possible with any MCS.

Bands of strong to severe thunderstorms ongoing during the midday
will likely continue to propagate east-southeast across eastern AL
into GA and SC.  A very moist/unstable airmass evident in the 12z
Birmingham and Atlanta raobs (1800 and 1300 J/kg MLCAPE) will
continue to gradually destabilize, despite considerable cloud
coverage across AL/GA.  Fewer clouds across south-central GA into
the coastal plain of SC will continue to heat more rapidly
downstream of the ongoing storms and yield an environment favorable
for a continued damaging-wind risk through the mid to late
afternoon.  For short-term convective details and environmental
analysis, please refer to MCD #728 and forthcoming MCDs over the

Farther west, from western AL westward into LA this afternoon, weak
large-scale subsidence in wake of the AL/GA impulse will probably
act to limit storm coverage during the day.  Isolated severe storms
are possible as the airmass continues to destabilize and potentially
yield an isolated hail/wind threat.  Later this evening into the
overnight, a cluster of thunderstorms is forecast to evolve over the
Arklatex and move east across LA into MS and eventually MS/AL/FL
Panhandle.  Severe gusts (60-85 mph) and the risk for a few
tornadoes will probably accompany this activity as it moves east
during the evening and overnight.

...Mid/upper Ohio Valley to Tidewater...
Isolated to widely scattered thunderstorms are possible this
afternoon across portions of the OH Valley, with damaging gusts and
marginally severe hail possible.  Some heating coupled with lower
60s surface dewpoints will contribute to MLCAPE ranging from
500-1500 J/kg.  Though upper flow will be strong, nearly
unidirectional profiles and lack of greater midlevel winds should
keep effective-shear magnitudes in the 30-40 kt range over much of
the area.

Farther east/southeast, cool/stable air north of a damming/preceding
frontal zone across VA and the Delmarva should limit the northern
end of severe potential.  Destabilization and available moisture
will be substantially limited today in the nominal warm sector,
between the damming front and a great deal of MCS/outflow activity
to the south over the Carolinas/GA.  Therefore, while thunderstorms
are possible this afternoon and deep shear may be adequate for a few
organized cells, severe potential appears isolated.

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