SPC 1300Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0640 AM CST Tue Mar 02 2021

Valid 021300Z - 031200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are possible today through tonight across parts of the
central/northeastern Gulf Coastal Plain eastward to coastal Georgia,
southern South Carolina and northern Florida.

...Synopsis...
A split-flow pattern in mid/upper levels exists over the central
CONUS, related to a strong shortwave trough, and accompanying
compact cyclone centered over eastern OK.  The cyclone should open
up at 500 mb, but remain a strong shortwave trough, while moving
eastward across the Mid-South and Delta regions around 00Z, then to
portions of GA/western SC by 12Z.  Another, greater split-flow
regime is evident offshore from CA, with a large synoptic cyclone
centered near 35N131W in latest moisture-channel imagery.  Potential
convective influences from that feature along the southern CA Coast
should be delayed until the day-2 period.

At the surface, 11Z analysis showed a wavy, quasistationary frontal
zone across central FL and the north-central Gulf, to a low roughly
south of LCH and east of CRP.  The front is expected to drift
northward across central/northern FL through 00Z while the low
migrates to shelf waters south of the western FL Panhandle.  Between
00-12Z, the Gulf low will move east-northeastward across the AAF
area and weaken, engaging in an effective cross-peninsular "handoff"
process as a new low forms over the Atlantic near the GA shoreline
or extreme northeastern FL East Coast during the last few hours of
the period.

...Northern/northwestern FL late overnight...
Scattered thunderstorms are forecast to move across the southern
GA/eastern FL Panhandle/northern FL area tonight, in a regime of
low-level warm advection and strengthening flow ahead of the
mid/upper trough.  Activity over GA should be rooted atop a stable
layer north of the front.  Deep/speed shear will become favorable
(45-55-kt effective-shear magnitudes) across the region, ahead of
the mid/upper trough.  Some of the more aggressively destabilizing
forecast soundings from deterministic progs suggest that the air
mass along and south of the front, over northern FL, may support a
severe threat late tonight.  Sufficient low-level destabilization to
yield nearly surface-based inflow parcels is possible after 06Z,
along parts of the FL coastal bend and perhaps inland across the
CTY/GNV/JAX vicinity.

Near-surface flow should veer across northern FL during the
weakening of the Gulf low and formation of the Atlantic cyclone. 
Because of the antecedent, relatively small/stable boundary-layer
theta-e values inland, that veering is needed to advect better-
modified Gulf air inland over this region -- but also, would reduce
low-level hodograph size, shear vectors, storm-relative surface
flow, and convergence.  Most (but not all) in the SREF, MREF and
GEFS suites also appear weak on instability/lift, with modest lapse
rates both in and above the boundary layer.  Given these
counterbalancing influences, especially involving uncertainty of
enough inland destabilization and warm-sector lift, the severe
potential still appears too conditional/isolated to introduce an
outlook area at this time.  However, prognostic and mesoscale trends
will be monitored through the period for stronger and more-
consistent evidence.

..Edwards/Jewell.. 03/02/2021

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