Key MESSAGE 1, Remnants of a MCS have moved offshore, with lingering stratiform rain slowly ending from SW to NE through the rest of this afternoon and evening. About 0.1"-0.25" of precip has been observed so far south of hwy 70, decreasing as you go inland. No thunder expected over land for the remainder of today.
KEY MESSAGE 2, Guidance remains in good agreement with a low pressure system passing just off the coast Saturday bringing much needed rainfall to the region. As this is happening, an upper level low centered over Ontario and Quebec will work to deepen an upper level trough that will begin to push a supporting wave out of Texas which will eventually elongate into the frontal system that will accompany the coastal low. The merged systems will push through Saturday into Sunday and move offshore but not before some significant rainfall. Probabilities for at least an inch of rainfall are still high, and decreased a tad inland. While NBM probs for precip greater than one inch inland are greater than 60%, GEFS and EPS show a different story, generally in the 20-60% range. With the best moisture, instability, and forcing along the coast and offshore, the current thinking is rainfall totals inland will trend towards the lower end of guidance. Chances for precip > 1" along the coast S of Oregon Inlet are now 60-90%, decreasing a bit to 30-60% inland west of hwy 17.
As far as convection is concerned, currently most of the instability remains offshore with northerly flow keeping profiles more stable over land. This should keep rainfall rates low enough to preclude any flash flooding threat, especially when paired with the drought conditions in place. Still a lot of uncertainty in the models regarding how strong the low will get and will have to monitor as the system gets closer.
KEY MESSAGE 3, A cold front moves through the middle of next week, with an upper level trough digging towards the mid- Atlantic and SE. Still some uncertainty with the timing, as ECMWF has the frontal passage coming through Thu afternoon, and the GFS has the frontal passage Wed night/Thu morning. Ensemble probs for PWATs greater than 1.5" ahead of this front are currently 30-50%. If the model consensus shifts to the afternoon Thursday, and the upper level support remains just as impressive, instability would be maximized and we would have to start thinking about severe potential. Machine learning severe probs are highest in the mid-Atlantic and SE US Thursday. At this point there is enough uncertainty to just take a wait and see approach.
00z Friday through Tuesday VFR flight cats expected through the 00Z TAF period with all showers now offshore. The one exception to this will be a brief period when winds are expected to be light and variable, potentially decoupling before high pressure begins to build Sward across the region, picking winds back up mixing the near SFC levels out. With the rainfall earlier today, terminals have a small window where patchy fog may develop ahead of this Nerly wind surge should skies be clear enough to radiate well. Have introduced 6sm MIFG for a few sites and advertise the calm winds to show the potential. Vis guidance isn't hinting at this, but given their performance over the past 3-4 days, don't trust leaning on them too much for completely counting this possibility out. Winds pick back up 6Z-ish, which should limit the density with which any potential fog achieves. Thin mid and high clouds will linger overnight, increasing Fri morning ahead of the next system.
Outlook: Conditions will deteriorate Friday night into Saturday as widespread rain, low VIS and CIGs overspread ENC. Expect VFR to return Sunday and continue into early next week.
Thunderstorm chances for warm Gulf Stream waters are decreasing as the MCS moves further offshore. A northerly surge around 15-20 kt develops tonight behind the departing MCS and some of the strongest HiRes models suggesting a brief period of winds approaching SCA criteria. Seas have been around 3-5 ft for waters but the central waters are expected to rise at or above 6 ft again tonight. Despite the relatively lower seas right now, the anticipated increase later today keeps the inherited SCA unchanged.
Outlook: Another low pressure system will pass across or just south of the waters late in the week which will likely bring another round of Small Craft Advisory conditions Saturday into Sunday. Still high uncertainty on gale potential for coastal waters and the Pamlico Sound, with EPS probs of gale force gusts > 60%, but GEFS probs < 20%.
Nc, beach hazards statement from 8 am EDT Friday through Friday evening for ncz203-205. Marine, small craft advisory until 6 pm EDT Friday for amz152-154.
