Key MESSAGE 1, Surface cold front has made some southward progression this afternoon and now sits just north of Highway 24 this hour per mesoanalysis and surface observations. Cooling stratus, as well as outflow and torrential rain from thunderstorms progressing northward, has cooled much of the area down into the upper 70s to low 80s but a sliver of upper 80s with Tds hovering near 80 is still hanging on south of this boundary. Opted to cancel the Heat Advisory for all but these coastal counties through 8PM, although these may also be dropped ahead of schedule as convection fills back in.
Beyond today, oppressive heat indices above 100 appear unlikely (less than 20%) through the next week.
KEY MESSAGE 2, Forecast through tomorrow will be heavily dependent on various mesoscale features, which in turn will dictate where stronger storms and flooding will be focused. Fluctuation's in risk areas are likely as ongoing convective evolution is analyzed.
Environment today has indeed been favorable for strong storms and torrential rainfall. Convection got an early start, developing as early as 11 AM and blossoming along the stalled frontal boundary, then compounding with convergent outflows and diurnal sound and sea breezes. Overall environment remains very favorable for a severe and flooding risk to continue with PWATs of 2-2.25" observed, hefty MLCAPEs of 2500-3000 J/kg, and respectable deep layer shear for the summer (25-35 kt). The primary threat remains damaging winds primarily due to wet microbursts, but some cells today have been rotation and could pose a hail risk. Additionally, with so many boundaries in play orientated in various directions cannot rule out a threat for a brief, short-lived tornado or two.
The combination of strong instability and an anomalously moist airmass should continue to support the potential of 2-3"/hr rainfall rates. While thunderstorms are likely to propagate along various outflows and mesoscale boundaries, those rates should support a risk of flooding of urban and poor drainage areas, with an associated risk for flash flooding. This risk looks to be the highest in some of the more urbanized areas from Jacksonville to New Bern and north through Kinston and Greenville. Current QPE trends suggest the Flood Watch remains in good shape today, and no changes to headlines were made.
Evolution beyond this afternoon's activity remains a question mark, although there is a slightly stronger signal for convection, growing upscale across across upstate SC, to progress along the stalled frontal boundary and impact southeastern NC after nightfall. Instability will remain elevated tonight but there will be a modest decrease in shear. Still, a marginal threat for damaging winds will remain with this complex. Additionally, it will not take much additional rainfall to aggravate flooding concerns for those locales who already saw appreciable amounts this afternoon.
Convective threat remains tomorrow as front remains stalled over the region. Like today, convection could get an early start as soon as 15z and spread inland through the afternoon. Shear will be quite a bit weaker and the severe threat will be less than 5%, but high forecast PWATS point to another day of efficient rainmakers and potential flooding concerns.
18z Friday through Wednesday Convectively active period expected for aviation interests over the next 24 hours as stalled front fuels widespread convection across much of eastern NC. Vcts is expected through 00z tonight, but another loosely organized convective complex is forecast to push across terminals, most likely those south of ISO, after 00z and potentially as late as 04-05z. Any direct hits from storms will pose a risk of LIFR visibility, gusty/erratic winds potentially up to 50 kt, and hail up to 1" in diameter. Farther north, especially of EWN, a persistent MVFR stratus deck will continue to plague the area through much of the period, potentially lowering to IFR overnight.
Outlook: An increased TSRA risk is expected to last into Saturday with similar impacts to today. The TSRA risk should take a step down on Sunday, but the risk isn't low either. It may not be until Monday before the risk substantially lowers.
Local and regional observations show a frontal boundary has pushed south and stalled over area waters, orientated roughly from Ocracoke to the mouth of the Neuse River. Winds on either side of the boundary are around 10 kt with seas a subdued 2-3 feet. Main threat for marine interests through tonight and into tomorrow will be convection, especially overnight as a complex originating over SC progresses and begins to impact waters close to midnight. These storms will pose a risk of strong winds potentially exceeding 40 kt as well as waterspouts, especially for cells close to the frontal boundary.
Outlook: An active thunderstorm pattern is expected to last into at least tomorrow, with a somewhat lower risk by Sunday and Monday. A more dominant southerly flow is expected to become established on Saturday and last into Sunday. A cold front then moves through late Sunday with a west to northwest wind shift. Seas build to 3-5ft on Saturday, then lay down to 2-3ft by late Sunday as winds also lay down. Light winds and reduced seas are then expected into the middle of next week.
Nc, flood watch through Saturday morning for ncz044-079-080- 090>092-094-193-194-198. Heat advisory until 8 pm EDT this evening for ncz195-196-199. Marine, none.
