Key MESSAGE 1, A complex and initially disorganized surface and upper level pattern today will begin to consolidate into a notable East Coast coastal low mid to late-week with a long duration of strong winds, very high seas, and coastal flooding across the OBX and adjacent coastal waters, sounds, and rivers.
Currently, ENC remains wedged between two systems, with an upper low and cold front to the north and west, while weak coastal troughing off the coast. The cold front will continue to slowly sag south from Virginia into North Carolina and strengthen nerly flow over the next 12-24 hours. Periods of showers will break out today as vorticity advection slowly increases with fgen banding aloft leading to the rounds of showers. A few storms may develop as well, though with weak instability present due to widespread cloudiness, the thunder threat is minimal and certainly no strong to severe expected.
Late tonight into Wed morning, the above- mentioned weak low is then forecast to deepen along the consolidating, and strengthening, frontal/baroclinic zone off the East Coast. 22/00z model suite has trended quicker with pressure falls and resultant strengthening northeasterly winds, with gusty winds becoming gales as early as early Wed morning for northern coastal areas and quickly spreading south through the afternoon.
Confidence continue to increase regarding a sub-1000mb low developing offshore during this time, and this is strongly supported by deterministic, ensemble, and machine learning guidance. Because of the blocky nature of the upper level pattern over the Atlantic, the low will be slow moving and meander about off the Mid Atlantic coast through late in the week, and thus a prolonged duration of high winds on the coast will lead to high impacts regarding coastal flooding on the OBX.
Periods of rain, some heavy at times, may lead to rainfall totals of 2-3" across parts of the area, though with this rain being drawn out over several days (Tuesday through Thursday), significant rainwater flooding is not expected at this time.
The strongest winds and greatest risk of coastal impacts is expected Thursday into Friday, especially along the OBX. Persistent northeasterly winds coupled with a longer fetch across the Atlantic should support long-period swell of 10-13s and seas of 10-16+ ft leading to breaking wave heights of over 10 ft for beaches from Duck to Cape Lookout. Not only will this create dangerous surf conditions, but this will also present a risk of beach erosion, ocean overwash at vulnerable locations, and coastal flooding (both soundside and oceanside), with the potential for significant impacts on Hatteras and Ocracoke Islands where a Coastal Flood Watch has been issued. Large battering waves may last into the weekend even as winds diminish due to the low potentially retrograding towards the Mid Atlantic coastline to the north of ENC, as the AIFS and a decent handful of ECM ensembles indicate. The strong winds on the OBX may eventually warrant Wind Advisory issuance on Thursday and potentially into Friday.
06z Tuesday through Saturday Large bank of lowering stratus is expected to afflict the terminals overnight into Tue morning. Lifr stratus appears likely, and have this in fcst through mid morning. During the day Tue, showers are expected to break out, with even a few embedded storms possible. Cigs may lower back down to IFR or lower on Tue night.
Outlook (Wed through Sat): A coastal low will deepen offshore Wed supporting periods of continued rain and low clouds, along with gusty nerly winds Some showers may linger into Thu along with continued gusty winds before drying out Thu night into Fri.
Nerly winds will increase through today and into tonight as low pres begins to take shape offshore along the cold front that drops south. Speeds of 10-20 kt today increase to 15-25 kt tonight along with building seas of 6+ ft tonight.
Outlook (Wed through Sat): A notable coastal low is forecast to impact the area mid to late week with a period of hazardous winds and seas. Confidence continues to increase in widespread gale- force winds for the waters and sounds, along with Alligator River, and have thus issued gale warnings for these zones beginning as early as early Wed morning, while SCA has been issued for the inland rivers (Pamlico and Neuse, along with their tributaries). At the peak, the central and northern coastal waters (nearshore and outer along with Eastern Pamlico Sound) may see gusts of 40-45kt with the most likely timing of highest winds on Thursday. Additionally, very highs seas will peak at 10-15 ft for the nearshore waters, and 15-20 ft for the offshore waters.
A long duration event is expected, and while gales are expected to finally dimish Thursday night through Friday, large dangerous seas are expected to linger through the weekend, as the large area of low pres begins to retrograde towards the Mid Atlantic coast north of ENC.
Nc, none. Marine, gale warning from 7 am Wednesday to midnight EDT Thursday night for amz131-230-231. Gale warning from 7 am Wednesday to 6 am EDT Friday for amz135. Small craft advisory from 4 am Wednesday to 8 am EDT Friday for amz136-137. Gale warning from 7 am Wednesday to 6 pm EDT Friday for amz150- 152-180-182. Gale warning from 2 pm Wednesday to 6 pm EDT Friday for amz154- 184-186. Gale warning from 2 pm Wednesday to midnight EDT Thursday night for amz156-158-188.
