Key MESSAGE 1, This afternoon, a warm front stretches west to east across northern NC. Based on surface obs, the eastern end of the front has recently cleared north of the Albemarle Sound/NRN OBX area, putting all of ENC in a broad warm sector that encompasses much of the Southeast U.S.
South of the front, there appears to be some residual subsidence/capping in the wake of the shortwave that moved offshore this morning, and for now this appears to be delaying the onset of cumulus development. Continued southerly flow and moisture advection plus large-scale forcing for ascent with the arrival of the next shortwave (currently moving out of SC) should prove sufficient for the development of deep convection in a zone along the inland- advancing seabreeze. With deeper southerly flow present, the seabreeze should be more progressive today, and the duration of higher rainfall rates should be limited over any one area. Even so, PWATs of 2"+ and moderate instability should support areas of heavy rainfall along with the potential for minor/nuisance-style flooding, especially in urban and poor drainage areas. The risk of flash flooding looks low today, though, given the expected progressive nature of convection today. Deep, moist profiles today will favor lowered DCAPE compared to yesterday. This plus weak deep layer shear should keep the risk of severe weather LOW.
The environment on Sunday looks fairly similar to today's. However, deep layer shear is forecast to be ever-so-slightly higher (25kt Sunday compared to 15kt today). This may allow a slightly improved storm organization potential and perhaps a slightly better chance of a few storms reaching severe, or near- severe, levels. The primary risk should be strong winds, but perhaps some hail can occur in the tallest, most sustained, cores. The focus for convection should be the seabreeze and an inland trough. The low-level flow may veer to southwesterly, helping keep the seabreeze less progressive compared to today, and storms may not be as progressive. With a high PWAT airmass still in place, this could allow a slight bump up in the risk for urban and poor drainage flooding, with at least a low-end risk of flash flooding.
Finally, a cold front will sweep south through the area on Monday. Guidance continues to trend on the slower side with the passage, and now this sets up the potential for the front to move through during peak heating on Monday. This will be something to watch as deep layer shear is forecast to be higher (~30kt), and may support a strong/severe thunderstorm risk conditional on sufficient instability being realized.
KEY MESSAGE 2, Upper level ridging quickly rebuilds across the Southern U.S. Next week. Meanwhile, a notably strong surface high will nose south along the lee of the Appalachians. Synoptically this is a very dry pattern for the region. Despite warming low-level thicknesses beneath the ridge, the northeasterly flow around the high should help to hold temps down some. Additionally, the airmass will be drier with less humidity, making it feel not as hot. It will feel a little more like fall, especially at night and in the morning.
19z Saturday through Thursday Forecast confidence is moderate over the next 24 hours.
An upper level wave interacting with a very moist and moderately unstable airmass should support a risk of SCT SHRA and TSRA through early this evening across ENC. With this TAF issuance, PROB30s/TEMPOs have been added now that confidence in timing and location have increased. Where TSRA occur, there is the potential for a brief period of IFR/LIFR VIS, as well a wind gusts to 30kt. In the wake of the afternoon TSRA activity, another round of sub-VFR CIGs appears likely overnight into Sunday morning. For now, stratus is favored over BR/FG. The TAFs will continue to show MVFR CIGs during this time, but guidance suggests the potential for IFR CIGs, especially at KISO and KPGV. Low CIG should scatter out and rise to VFR conditions between 14-16z.
Outlook: Another risk of scattered TSRA is expected on Sunday, with an accompanying risk of IFR/LIFR VIS, hail, and wind gusts to 40kt. Drier air begins to move in Sunday night, but doesn't fully knock down the TSRA risk until Tuesday. Vfr conditions are then expected to prevail through mid-week.
South winds of 15-20kt are common across most waters this afternoon, with some enhancement noted in the vicinity of various thunderstorm outflow boundaries moving north through the area. Occasional gusts of 25-30kt will be possible where those outflows move through. Meanwhile, seas are generally 2-3ft at 5-7s. These conditions are expected to last into Sunday as the overall weather pattern remains about the same. There will continue to be a risk of thunderstorms during this time as well.
Outlook: Winds will become westerly Sunday night and lay down to 5- 15kt for a short time. Stronger northerly winds then develop from north to south across all waters Monday afternoon and evening as a reinforcing cold front moves through. The northerly surge of wind is expected to be accompanied by an increased risk of 20-30kt winds. Marine headlines will likely be needed for a portion of the waters Monday into Monday night for the increased winds. For the coastal waters, seas will quickly build to 5-8ft with the northerly wind surge. Guidance suggests an extended period of northeasterly winds and elevated seas, and marine headlines may be needed for much of the upcoming week for the nearshore coastal waters for 6ft+ seas.
Nc, none. Marine, none.
