Key MESSAGE 1, Latest surface analysis shows a weak surface low sitting over southeastern VA and associated surface trough draped across central NC and SC this morning. The main frontal boundary that has been of focus for the past few days is slightly farther north, roughly bisecting Virginia. This leaves eastern NC once again firmly locked into a warm and very muggy airmass along with most of the southeastern CONUS. With highs today expected to reach the mid to upper 90s (in line with 1000-850 mb thicknesses 1430-1435 m), and Tds hovering in the mid to potentially upper 70s, widespread heat index (HI) values of 105-110 will continue through this afternoon.
Front will eventually sag southward across the region tomorrow, although how far south is uncertain. This will offer some relative relief over the weekend, but locations along and south of Highway 70 have the highest probability of seeing HI values at or exceeding 105 both Saturday and Sunday. The frontal boundary will lift back across the mid-Atlantic on Monday, entrenching the entire FA again in potentially dangerous heat and humidity as highs climb back into the upper 90s.
Heat Advisories remain in effect areawide for the rest of this afternoon. A new set of Heat Advisories has been issued from Pitt and Beaufort counties southward towards the coast for Saturday. We continue to encourage anyone planning on spending time outdoors to stay hydrated and to limit exposure to the heat, if able.
KEY MESSAGE 2, Overall pattern based on observational trends appears favorable for convective development with a highly unstable environment expected this afternoon with MLCAPEs forecast to climb to 2000-3000 J/kg, ample moisture, and favorable upper-level support with a mid-level shortwave forecast to progress through WNW flow around the periphery of a sub-tropical ridge that has been sitting over the southeastern CONUS for days. All that is left, then, are sufficient lifting mechanisms. The remnant surface trough and always reliable sea and sound breezes are suitable candidates for this afternoon, followed by an MCV currently driving decaying showers and storms over WV and VA but likely to reinvigorate convective activity push towards NC this evening.
CAM guidance has been in poor agreement over today's convective threat for both the 00z and now 12z suites. The HRRR and 3km NAM have been rather pessimistic on afternoon coverage, likely owing to depicting CI from a far more overcast cloud bank than current satellite depicts. The WRF-ARW, however, shows far more activity developing along sea sound breezes as well as off the inland thermal trough. It was also one of the minority of hi-res guidance that depicted this morning's earlier convection over area waters and the Outer Banks. Because it seems to more accurately be capturing the higher and more widespread instability we're currently observing, the forecast leans heavily in its direction for at least isolated to scattered activity this afternoon focused closer to the water. More CAMs are bullish on activity from the aforementioned MCV approaching the region early evening and decaying through the overnight hours.
If any severe threat does develop, it will be in the evening hours associated with the approaching MCV-driven complex as shear increases marginally up to 20-25 kt, mainly focused across far NE NC and SE VA presenting a damaging wind threat. Outside of this, a wet microburst threat cannot be ruled out from stronger iso cells. Additionally, with slow storm motions an isolated flooding threat can also not be ruled out.
Shower and thunderstorm risk will likely persist through the weekend as frontal boundary sags south and meanders over the area. With convective evolution each day at least partially reliant on mesoscale factors from the day before, larger than normal changes in model guidance can be expected from run to run. The bottom line is the overall environment will remain at least marginally favorable for stronger storms and a flooding risk through the weekend, wherever activity manages to develop.
KEY MESSAGE 3, A second frontal boundary looks to approach early next week after a brief lull Sunday. Still plenty of details to hammer out, but medium- range AI NWP guidance points once again to at least a marginal risk of stronger storms for portions of the Carolinas, along with a heavy rainfall risk as humid airmass remains unyielding.
18z Friday through Wednesday VFR conditions in place this afternoon across area terminals under southwesterly winds, gusting up to 15-20 kt at times mainly for near-water locales. There is a low risk (20-30%) of isolated convection to impact terminals closer to the coast, like EWN and OAJ, through early this afternoon as sea breeze circulations advance inland, while inland sites should remain dry. Pgv, ISO and sites farther north will be under threat from a convective complex forecast to advance out of VA and into NC closer to 00z and lasting as late as 04z. Direct impacts to terminals pose a risk of erratic and strong winds in excess of 40 kt, as well as torrential rainfall restricting visibility.
Frontal timing has slowed somewhat, and the risk of low stratus has decreased from the previous forecast. There remains a risk of low stratus mainly for PGV and ISO, although the probability is between 10-20%.
Outlook (Saturday through Tuesday): Continued chances for sub- VFR conditions will persist into Sat afternoon with a stalled front draped over ENC bringing additional rounds of shower and thunderstorm activity. More isolated activity is possible mainly Sun evening. Next more widespread threat is possible on Monday ahead of the next front.
Latest observations show south to southwesterly winds at 5-10 kt across area waters, with winds closer to 10-15 kt in sounds and northern waters. Offshore, seas remain at 2-3 feet. Expect winds today to increase further with the thermal gradient, with a few isolated gusts to 25 kt not out of the question, mainly for soundside waters and coastal zones north of Hatteras. The front will also be a focal point for showers and thunderstorms, mainly focused across northern sounds and waters into the evening hours.
Outlook (Saturday through Tuesday): Front will gradually push south across area waters tomorrow and stall, bringing at least a brief period of northeasterly winds to portions of the water, highest probability north of Ocracoke. The front will likely meander through Sunday before lifting back northward and ushering back area-wide southwest winds of 10-20 kt. There is a low risk of SCA conditions on Monday into Tuesday with this feature. Each day will bring a low to moderate risk (20-40%) of showers and thunderstorms to area waters.
Nc, heat advisory until 8 pm EDT this evening for ncz029-044>047- 079>081-090>092-094-193>196-198-199-203>205. Heat advisory from 11 am to 8 pm EDT Saturday for ncz044-079- 080-090>092-094-193>196-198-199. Marine, none.
