SPC Mar 16, 2025 2000 UTC Day 1 Convective Outlook
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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