Apr 9, 2021 0600 UTC Day 1 Convective Outlook
Click to see valid 1Z - 12Z Day 1 Convective Outlook
Updated: Fri Apr 9 06:09:21 UTC 2021 (Print Version | | )
Probabilistic to Categorical Outlook Conversion Table
Categorical Day1 1200Z Outlook
Day 1 Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
Jackson, MS...Monroe, LA...Hattiesburg, MS...Meridian, MS...Vicksburg, MS...
Birmingham, AL...Shreveport, LA...Tyler, TX...Broken Arrow, OK...Fort Smith, AR...
Dallas, TX...Memphis, TN...Atlanta, GA...Tulsa, OK...Arlington, TX...
Houston, TX...Detroit, MI...Indianapolis, IN...Fort Worth, TX...Oklahoma City, OK...
SPC AC 090609
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0109 AM CDT Fri Apr 09 2021
Valid 091200Z - 101200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PARTS OF
EXTREME SOUTHEAST ARKANSAS INTO FAR NORTHEAST LOUISIANA INTO CENTRAL
A complex severe-weather scenario is expected to unfold across the
Mid-South into the Southeast late this morning through the afternoon
and overnight hours. Significant severe storms, including widespread
damaging winds, and at least a few tornadoes are expected across
portions of northeast Louisiana into Mississippi, especially
overnight. Large hail is also expected to be a concern, mainly
during the day across parts of eastern Oklahoma into the Arklatex
Broad cyclonic mid-level flow will prevail across the eastern half
of the CONUS through the period, with multiple embedded impulses
supporting deep moist convection across several areas spanning from
the Southeast towards the Mid Atlantic and extending into portions
of the Ohio Valley. Scattered strong storms (a few of which may be
severe) are expected to first initiate by mid morning into early
afternoon within a warm-air advection regime across portions of AL
into GA and the FL Panhandle as a weak mid-level impulse exits the
area. Later in the day, this same mid-level impulse is expected to
support an organized cluster of storms across VA into NC. However,
the main severe threat will begin during the afternoon hours and
continue into the overnight period as multiple, potentially highly
organized rounds of storms are expected to traverse portions of the
Southeast, with all facets of severe possible. More isolated severe
is possible along portions of the cold front, mainly during the day,
across portions of the Ohio Valley.
...Portions of the Southeast - Midday...
Storms are expected to gradually expand in coverage and intensity
across portions of eastern AL into western GA with the onset of
diurnal heating. Deep-layer wind fields are not expected to be
overly strong, with small looping hodographs supporting multicells
and occasional transient supercell structures. Modestly steep (7
C/km) low and mid-level lapse rates will support damaging gusts and
large hail with the more organized updrafts.
...Portions of the Southern Plains into the Mid-South...
As the first in a series of mid-level impulses traverses portions of
the Mid-South area by early afternoon, the first rounds of
convective initiation are expected across the warm sector, from
southeast KS, eastern OK into southern MO and western AR. 7-8.5 C/km
low and mid-level lapse rates atop mid to upper 60s surface
dewpoints are expected to foster MLCAPE over 2000 J/kg in advance of
a dryline, though convective inhibition is expected to limit the
coverage of convection southwestward to a degree across portions of
east-central TX into southwest LA. Relatively weak wind fields,
especially below 3 km, suggest that multicellular clusters with an
occasional transient supercell will be the predominant storm mode
initially, with a few clusters potentially growing upscale into MCSs
via cold pool mergers. The steep low-level lapse rates will promote
an organized damaging-wind threat with any of the more intense
linear segments that form, while large hail (including a few stones
exceeding 2 inches in diameter) and perhaps a tornado may accompany
the longer-lived, more discrete updrafts. Currently, confidence is
lowest in the coverage of severe hail (especially 2+ inch stones)
given the possibility for linear modes, and downgrades to hail
probabilities may be needed in future outlooks.
...Parts of the Southeast - late afternoon and overnight...
By late afternoon into early evening, the main mid-level impulse and
associated forcing for ascent is expected to eject into the
Southeast, with a potentially more organized MCS expected to develop
somewhere near the Arklatex area and progress across Mississippi
into Alabama overnight. Despite the potential for multiple rounds of
multicellular clusters across the Southeast (a few of which may
support damaging winds, large hail, or a brief tornado), a healthy
fetch of steep low to mid-level lapse rates is expected to accompany
the nocturnal MCS, promoting a widespread damaging-wind threat. The
approach of the main upper support will also result in a
considerable low-level mass response and subsequent strengthening of
the low-level flow. Over 200 m2/s2 0-1km SRH will support organized
QLCS circulations embedded within the MCS and associated tornado
threat. The MCS will continue into central AL through 12Z Saturday,
with a damaging-wind threat persisting.
...Virginia into North Carolina...
Modest ascent associated with a passing mid-level impulse is
expected to be timed with the diurnal heating cycle across portions
of VA into NC, with organized thunderstorm development during the
afternoon. 7+ C/km low and mid-level lapse rates are expected to
emanate east of the Appalachians supporting vigorous updraft
development and sustenance. Relatively weak tropospheric wind
profiles suggest that multicellular convection will be the dominant
mode, with damaging gusts and large hail possible. However, a warm
front is expected to be draped across southern VA during the day.
Any storms that can anchor to the warm front may acquire more
transient supercell structure with a locally heightened threat for
wind and hail, and a brief tornado cannot be completely ruled out.
The warm front will continued to be monitored for a possible Slight
risk upgrade in later outlooks.
...Portions of the Ohio Valley...
A cold front is expected to persist across the Ohio Valley during
the day, with modest upper support overspreading the region. While
convective coverage will be relatively sparse in nature, any storms
that develop will be atop a dry boundary layer and associated steep
lapse rates. With up to 60 kt 700 mb flow expected atop this dry
boundary layer, efficient downward momentum transport may support a
couple damaging gusts with the more robust convection, mainly during
the mid to late afternoon hours