textproduct: Newport/Morehead City

WHAT HAS CHANGED

An initial round of marine headlines have been issued for portions of the ENC waters for this week's coastal low. Additional headlines, both land and marine, will likely be needed with future updates.

KEY MESSAGES

1) Coastal low to impact ENC mid to late week with periods of rain, scattered thunderstorms, and a risk of multiple coastal hazards.

MARINE: Coastal low to produce hazardous winds and seas mid to late week.

DISCUSSION

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 impacts being felt from the Carolinas north.

Aloft, an upper level shortwave will lift north off the Southeast U.S. coast, supporting the development of a weak area of low pressure along a stationary front. Meanwhile, a cold front will continue to slowly sag south from Virginia into North Carolina over the next couple of days. The above-mentioned weak low is then forecast to deepen along the consolidating, and strengthening, frontal/baroclinic zone off the East Coast. Deepening of the low will become more rapid Thursday and Friday as an upper low translates from the Ohio Valley to the Mid- Atlantic Coast. The deepening will also be aided by the entrance region of an upper jet which will reside over the Northern Atlantic.

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, there is some uncertainty regarding the eventual track of the low. While confidence is high regarding a notably deep low developing, confidence is lower regarding the magnitude of winds which especially factors in regarding coastal and marine impacts.

The most likely scenario at this point is for there to be an initial round of showers and scattered thunderstorms late tonight into Tuesday as the above-mentioned cold front moves into the area from the north. Rain and perhaps a few thunderstorms are then forecast to expand in coverage, and become more widespread, Tuesday night into Wednesday night as lift increases along the moistening frontal zone. During this time, some guidance suggests an area of enhanced lift from the Delmarva region south into NE NC, and this is where the highest rainfall totals are expected. While instability will be waning with time, rainfall totals of 2-3" appear plausible in this area, which could support some minor hydro impacts in poor drainage areas.

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 wave heights of 8- 12ft in the surf zone 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). As mentioned above, the strength and duration of the stronger winds varies some in the guidance depending on the track of the low. Stay tuned as we continue to refine the coastal impacts, and where coastal headlines may be required. Coastal impacts may last beyond Friday. In addition to the coastal impacts, guidance supports a risk of reaching Wind Advisory criteria for portions of the OBX Thursday into Friday.

AVIATION /19Z MONDAY THROUGH SATURDAY/

Forecast confidence is moderate over the next 24 hours.

VFR conditions are expected to prevail into at least early this evening, along with a reduced risk of SHRA and TSRA. Later this evening and into tonight, increasing low-level moisture is expected to support an increased risk of IFR, or lower, CIGs. A period of LIFR CIGs is possible during this time as well. CIGs are then forecast to rise some (IFR/MVFR) during the day Tuesday, but it appears likely that sub-VFR conditions will prevail through the day Tuesday. SHRA may begin to develop near the coast Tuesday morning, eventually spreading inland during the day with an accompanying risk of TSRA. Confidence is too low to mention TSRA in the TAFs for now, but this may need to be added in later forecasts.

Outlook: A coastal low will deepen offshore mid to late week supporting periods of RA, SCT TSRA, low CIGs, and breezy NE winds.

MARINE

A cold front will move slowly south into the northern waters this evening and this should support easterly winds building to 10-15kt. South of the front, light easterly winds of 5-10kt are expected. Winds will continue to build through the day Tuesday as the front settles into the area, and as the gradient along it begins to strengthen. By Tuesday afternoon, most waters are expected to have northeast winds of 10-20kt. Seas of 2-3ft today will build to 3-5ft by Tuesday afternoon.

Outlook: A notable coastal low is forecast to impact the area mid to late week with a period of hazardous winds and seas. Guidance differ some on the strength and the track of the low, but confidence continues to increase in widespread gale-force winds for most, if not all, waters, with winds peaking Thursday into Friday. At the peak, the central and northern coastal waters (nearshore and outer) may see gusts of 40-45kt. Additionally, seas of 10-15ft+ are forecast for all outer waters. For the nearshore coastal waters, seas of 8-12ft are likely from Duck to Cape Lookout. South of Cape Lookout, seas of 4-8ft are forecast. The longer fetch across the Atlantic should allow wave periods to build to 10-13s by Thursday and Friday.

Given the increased confidence, a Gale Watch has been issued for portions of the central and northern coastal waters, as well as the northern rivers and sounds. Gale-force winds may begin as early as Wednesday morning, but most likely will begin Wednesday afternoon and then continue into Friday. It looks like there will be about a 24hr period of 25kt+ winds leading up to the gales, and a Small Craft Advisory has been issued leading into the Gale Watch for those same waters. Elsewhere, the Gale Watch is likely to be expanded, but confidence in timing and magnitude is lower.

MHX WATCHES/WARNINGS/ADVISORIES

NC...None. MARINE...Small Craft Advisory from 5 PM Tuesday to 5 PM EDT Wednesday for AMZ131-150-230-231. Gale Watch from Wednesday afternoon through Friday morning for AMZ131-150-180-230-231. Small Craft Advisory from 8 AM Wednesday to 2 AM EDT Thursday for AMZ135. Gale Watch from Wednesday evening through Friday morning for AMZ152-182. Small Craft Advisory from 8 AM Wednesday to 2 PM EDT Thursday for AMZ154-156.