ACUS02 KWNS 090600
SWODY2
SPC AC 090559

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Tue Jul 09 2024

Valid 101200Z - 111200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
CENTRAL/NORTHERN PENNSYLVANIA AND WESTERN/CENTRAL NEW YORK...

...SUMMARY...
Damaging gusts and a few tornadoes are possible mainly over portions
of central/northern Pennsylvania and western/central New York.

...Synopsis...
In mid/upper levels, a large anticyclone -- presently centered over
south-central CA, will drift erratically northeastward to the
southern Great Basin through day 2.  Downstream, large-scale
mid/upper-level troughing will persist over the central CONUS and
mid Mississippi Valley through the period, with very slow net
eastward shift.  That will occur as the remains of TC Beryl eject
northeastward from present position over AR, where it already is
interacting with a midlatitude/low-level frontal zone.  By the start
of the period at 10/12Z, the associated deep-layer low should be
over northern IN, with 500-mb trough southwestward across southern
IL to the Arklatex region.

The surface occluded/cold front should arc from that low across
portions of OH to a triple point in PA, then southwestward over the
central/southern Appalachians to northern/western GA and the coastal
FL Panhandle, bending west-northwestward over the coastal LA region
as a stationary front, then a warm front over central/west-central
TX and southern NM.  An eastern warm front should extend from the PA
triple point east-northeastward over eastern PA, southeastern NY and
central/eastern New England.  The eastern warm front should move
northward to central NY, and portions of VT/NH by 00Z.  Meanwhile,
the cold front should reach central/eastern portions of PA/VA, NC,
and western SC, becoming quasistationary to warm over parts of
southern GA/AL/MS, then continuing as an increasingly diffuse warm
front from southern LA to north-central NM.

...Northeastern CONUS...
Widely scattered to scattered thunderstorms are expected to develop
along/ahead of the cold front, near the warm front, and possibly
near a prefrontal surface trough over the outlook area from midday
through afternoon and shift eastward to northeastward.  Activity
near the warm front will encounter a favorable parameter space for
supercells and a tornado risk, along with short lines or clusters of
thunderstorms with damaging to severe gusts.

Veering winds with height should contribute to enlarged low-level
shear/hodographs and deep shear (effective-shear magnitudes in the
45-55-kt range).  Forecast soundings also suggest that a corridor of
diurnal heating in the warm sector will combine with rich low-level
moisture (surface dewpoints commonly upper 60s to low 70s F) to
offset modest mid/upper-level lapse rates, for low LCL and peak/
preconvective MLCAPE in the 1500-3000 J/kg range.  Given the lack of
CINH and abundance of moisture, confidence in convective coverage
and supercell potential has increased enough to raise unconditional
severe probabilities a notch over the region.

...Portions of NM and west TX...
Strongly difluent flow aloft will exist over this region east and
southeast of the mid/upper high, while a series of minor shortwave
perturbations and vorticity maxima move over the region in
northwesterly to northerly flow aloft.  Moisture return into this
region over the next couple days, near the western limb of the
diffuse warm front, should support increasing thunderstorm
potential, with preferential initiation over higher terrain and
convective/differential-heating boundaries.  Low/middle-level flow
and shear will be weak, leading to multicellular storm mode.  Enough
offset of strong heating/mixing by moist advection should persist
through much of the afternoon to sustain favorably deep/robust,
widely scattered to scattered thunderstorms atop high DCAPE over the
"marginal" area.  As a result, an unconditional threat for isolated
severe downbursts exists, and a few small clusters may aggregate
outflow for a couple hours to boost convective wind potential
locally.  The threat should wane quickly during the evening as the
near-surface layer stabilizes.

..Edwards.. 07/09/2024

$$
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