SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0753 AM CDT Thu Mar 31 2022
Valid 311300Z - 011200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHEAST INTO THE HUDSON VALLEY...
...SUMMARY...
Damaging thunderstorm gusts and a few tornadoes are possible today
across parts of the Southeast into the Hudson Valley.
...Synopsis...
A progressive mid/upper-level pattern features broadly cyclonic flow
over most of the CONUS, except for a narrow zone of ridging now
located from the Four Corners region to central Canada. An upstream
trough will move across the northern High Plains and central/
southern Rockies. Its field of UVV/cooling aloft will support
isolated thunder potential in the four Corners region, in concert
with marginal low/middle-level moisture.
Downstream, a complex synoptic trough extends from northern ON
across the lower Missouri Valley and southern Plains States. One
previously intense shortwave trough is located over portions of the
Lake Michigan region, and will continue to weaken as it ejects
northeastward today. Another perturbation is evident in moisture-
channel imagery over eastern KS, western OK and the TX Panhandle.
This feature will pivot eastward across the Mid-South by 00Z, then
weaken and eject to the inland Mid-Atlantic by 12Z tomorrow. Strong
southwest flow aloft (e.g., a 120-140-kt 250-mb jet, and 90-105 kt
at 500 mb) will extend from the Gulf Coast States to the Carolinas
today, ahead of the second shortwave trough.
At the surface, 11Z analysis showed a deep (978 mb), occluded
surface low near HTL, which will eject northeastward across ON and
northern QC through the period. The associated surface cold front
was drawn across western OH, eastern parts of KY/TN, northern AL,
and extreme southeastern LA. This front should sweep eastward/
southeastward to central portions of NY/PA/VA by 00Z, extending
southwestward across the FL Panhandle to the central Gulf. By 12Z,
the front should extend from portions of ME, near Cape Cod, to near
the NC Outer Banks, and across northern FL.
...Southeastern CONUS to Hudson Valley region...
The earliest threat area is ongoing -- across portions of the FL
Panhandle, southern GA and northwestern FL. See SPC tornado watch
85 and related mesoscale discussions for details on the near-term
threats with this activity.
A broad plume of low-level theta-e advection will combine with muted
diurnal heating to at least marginally destabilize the boundary
layer today, in a broad swath from the Carolinas into the northern
Mid-Atlantic. This will support additional bands of scattered to
numerous showers, and widely scattered to scattered thunderstorms,
expected to develop from the southern Piedmont to the central
Appalachians and move quickly northeastward across the outlook area
today. A mixed mode of QLCS (bows, LEWPs and embedded mesovortices)
and a few supercells are possible, supporting a threat for damaging
gusts (a few severe at 50+ kt intensity) and a few tornadoes.
With weakly unstable lapse rates, preconvective dewpoints reaching
the mid 50s north to mid 50s south will be counterbalanced by
somewhat colder air aloft in the mid-Atlantic, warmer over the
Carolinas to Delmarva. The 12Z IAD sounding sampled a likely narrow
ribbon of a remnant of the southern Plains EML, within a broader
area of weak 600-800-mb lapse rates. Peak warm-sector MLCAPE should
reach the 100-500 J/kg range over the Mid-Atlantic and 500-1000 J/kg
over the Carolinas, and 1000-1500 J/kg in southeastern GA and
northern FL.
As noted above, the strongest mid/upper winds will be over the
middle parts of the outlook area today, while a 60-75-kt LLJ takes
shape from the Carolinas into the eastern Mid-Atlantic. This will
foster effective-shear magnitudes peaking around 60-75 kt in the
NC/VA/MD region, decreasing but still strong northward and
southward. Meanwhile, lengthy hodographs will support effective SRH
in the 200-400 J/kg range over much of the corridor. Strongest
forcing for ascent should be ahead of the front in the northern
parts of the area where buoyancy is weakest, in a strong-shear/
low-CAPE scenario. Uncertainty remains as to coverage of severe
gusts reaching the surface given some constraints on low-level lapse
rates, but even subsevere winds will be capable of minor structural
damage and trees down.
..Edwards/Broyles.. 03/31/2022
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