SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0301 PM CDT Sun Mar 16 2025
Valid 162000Z - 171200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
UPSTATE NEW YORK...THE MID-ATLANTIC...AND THE SOUTHEAST...
...SUMMARY...
Damaging wind and a few tornadoes remain possible through the
remainder of this afternoon and evening across parts of upstate New
York, the Mid-Atlantic and the Southeast.
...20z Update...
The main forecast changes for 20z have been to reduce probabilities
behind the squall line ongoing over PA and western NY state, and
expand slightly ahead of the more persistent bowing segments over
northern NY. Lingering cloud cover and modest surface moisture
greatly limit available buoyancy ahead of the line. With only a few
hundred J/kg of MUCAPE, decreasing with eastward extent, a gradual
loss in intensity is expected over the next several hours over
northeastern PA and NY. Still, very strong gradient winds and flow
aloft will support some potential for convective-enhanced damaging
gusts through this evening. 300-400 m2/s2 of 0-3km SRH may also
support the threat for a couple of brief QLCS tornadoes while the
line maintains intensity.
Probabilities have also be trimmed farther south over parts of the
western Carolinas, GA and northern FL as the main convective band
and cold front have shifted east. Some isolated thunderstorm
redevelopment remains possible over parts of the Blue Ridge
Mountains of western VA and into the central Carolinas where diurnal
heating has steepened low-level lapse rates immediately ahead of the
synoptic cold front. While confidence in severe potential is modest
given meager buoyancy, the steep lapse rates could support damaging
gusts or marginal hail, should more sustained convection redevelop
as indicated by some CAMS. These storms may eventually shift
eastward into the mid Atlantic late this afternoon and into the
early evening, where low-level synoptic flow remains fairly strong.
Will maintain the Slight Risk for damaging gusts and isolated
tornado potential over parts of the Mid Atlantic into tonight.
..Lyons.. 03/16/2025
.PREV DISCUSSION... /ISSUED 1128 AM CDT Sun Mar 16 2025/
...Ohio Valley into the Mid-Atlantic...
A highly amplified upper trough over the MS Valley this morning will
advance eastward over much of the eastern CONUS today. An embedded
100+ kt southwesterly mid-level jet and associated large-scale
ascent will overspread the upper OH Valley and western Mid-Atlantic
regions through this evening. The primary surface low over eastern
Lower MI will develop northeastward into Ontario and Quebec through
the day, while an attendant cold front sweeps eastward across the OH
Valley/Mid-Atlantic through the period. Recent visible satellite
imagery shows some clearing ahead of the synoptic cold front in
eastern OH and western PA. Although low-level moisture will be
somewhat limited, with surface dewpoints generally in the mid to
upper 50s, cool mid-level temperatures will overspread the narrow
warm sector this afternoon. This, combined with daytime heating,
will support a narrow zone of up to 250-500 J/kg of MLCAPE just
ahead of the cold front and/or pre-frontal trough, which should be
sufficient for surface-based convection.
Bands of low-topped thunderstorms have developed both along and just
ahead of the cold front. This activity will move quickly
east-northeastward across WV, western/central PA, and parts of NY
through the day. With strong low/mid-level flow already in place per
area VWPs, this line should pose a threat for mainly scattered
damaging winds, with peak gusts perhaps reaching up to 60-70 mph.
There will also be rather strong low-level shear in place, which may
support some threat for a few tornadoes embedded within the line,
especially if low-level flow can remain backed more to a
southeasterly component. The northeastward extent of this severe
wind and tornado risk into the Mid-Atlantic and NY remains unclear,
as persistent cloud cover will inhibit daytime heating to some
extent. Still, most guidance shows one or more lines persisting
through the afternoon and evening while posing some wind threat.
Severe probabilities have been adjusted northeastward across parts
of the Mid-Atlantic to account for latest observational and guidance
trends.
...Southeast/Carolinas...
The southern portion of the highly amplified upper trough will
continue eastward across the lower MS Valley and Southeast today, as
an intense southerly low-level jet shifts east across north FL and
the Carolinas through this evening. Ongoing pre-frontal convection
has mostly weakened late this morning/early afternoon, with a couple
of stronger cells persisting over southeast GA and north FL where
greater low-level moisture and instability is present. Adequately
enlarged low-level hodographs within a gradually destabilizing
airmass (1000-1500 J/kg MLCAPE across north-central FL, with weaker
instability over the coastal Carolinas) should continue to support
organized convection through the afternoon and evening, before
activity eventually moves offshore. Broken line segments (mainly
Carolinas) and some supercells (mainly southeast GA and north FL)
will pose a threat for scattered damaging winds (peak gusts up to
55-70 mph) and a few tornadoes.
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