Swell Matrix

Area Forecast Discussion

National Weather Service Newport/Morehead City Nc

737 am EDT Mon Oct 25 2021

Synopsis

A coastal low will develop and impact the region today. A cold front will then push through the area Monday night into Tuesday morning, with high pressure building in behind it. A large low pressure system will affect the region Thursday into the weekend.

Near Term

Until 6 pm this evening As of 730 AM Mon, Shower and occasional thunder activity beginning to blossom along an area of enhanced moisture convergence along the coast, and surface low is beginning to take shape well east of Savannah. Heaviest showers will remain immediately along the coast while inland locales see just a few passing showers.

Prev disc, Complicated meteorological set-up greets the Carolinas early this morning with an appropriately difficult forecast to boot. There are two upper level disturbances of note today: 1) a vort max over the western Carolinas which will be responsible for the development of a coastal low later today, and 2) a vigorous upper low churning over the central MS River Valley driving a mature surface cyclone over the Midwest. The latter feature is expected to interact with its weaker counterpart late tonight, resulting in a rapidly deepening Nor'easter off the Mid- Atlantic coast through Tuesday.

Coastal low will slowly strengthen off the southeastern coast this morning. Left exit region of a 70 kt upper jet will provide necessary support for expanding shower coverage this morning into the afternoon, especially east of Highway 17 and south of Highway 70. Instability will be hard to come by although hi-res guidance does hint at a brief window of realized instability in the late morning coinciding with surface warming and maximized low-level moisture, before collapsing as winds back easterly ahead of the low. During this window CAPEs could reach 500-1000 J/kg in tandem with bulk shear of 25-30 kt, supportive of perhaps a damaging wind gust or two in any stronger storms.

Cloudy skies and ongoing precip in the morning will put a lid on temperatures east of Highway 17 today, while areas inland have a better shot of seeing a few peaks of sunshine, especially in the afternoon with a lull in precip expected. Highs sit mostly in the mid 70s, with warmest spots likely across the coastal plain.

Short Term

6 pm this evening through 6 am Tuesday As of 410 AM Mon, Second round of showers and perhaps a few storms will come tonight as the surface low over the Midwest races eastward in tandem with the upper low, dragging a cold front across the region. Strongly forced band of precip is likely, and instability recovering to 500-1000 J/kg point to a few thunderstorms impacting the region overnight. Nam soundings show looping hodographs in a region of 40-50 kt bulk shear, pointing to a few low-topped rotating storms. Damaging wind gusts would again be the primary threat, although an isolated tornado cannot be ruled out.

Front blasts across the region overnight with drier and cooler airmass quickly filtering in, with skies expected to be partly cloudy by daybreak. With CAA and lowering Tds lows should be able to dip into the upper 50s inland, low to mid 60s elsewhere.

Long Term

Tuesday through Sunday As of 3 AM Mon, Active weather pattern through much of the period with troughing generally persisting over the eastern US, with cold front pushing offshore Tue morning and another late week and this weekend.

Tuesday through Wednesday, Cold front moves offshore Tuesday morning as low pressure continues to strengthen off the Mid- Atlantic and New England coast. A few showers could linger along the NE NC coast Tuesday, but dry conditions are expected elsewhere with temps near to a few degrees below normal. Breezy WNW winds will continue, especially along the coast. Building heights aloft with continued, but weakening surface CAA keeps a dry and cool forecast in place for Wednesday. Highs in the upper 60s to low 70s.

Thursday through Sunday, Upper ridge axis slides east of the area Thursday and deep moisture advection begins. Stacked low pressure over the Tennessee Valley will slowly work eastward, but destabilization will be slow, with the first part of Thursday remaining mainly dry. A warm front is expected to cross the area Thursday evening or overnight, signaling the return of appreciable rain chances. Increased pops to likely Thu night. Temps near normal during the day, with an increasingly warm and humid airmass filling in Thursday night. Stacked low pressure lifts across the southern Appalachians toward the Mid-Atlantic Friday into the weekend. Precip expected to become more scattered Friday through Friday evening as an occluding cold front crosses the area. However, at least low end chance POPs will continue Sat and Sat night to account for the close proximity of the strong dynamic forcing associated with the stacked low and the timing uncertainty of the cold front. Strong CAA develops Sunday, with a drier and cooler couple of days expected into early next week.

Aviation

12z Monday through Friday Through tonight As of 735 AM Mon, Predominantly VFR conditions continue across the terminals today with a widely scattered 2 kft deck hanging around this morning. This will likely become broken at times as a coastal low brings increasing showers and maybe a thunderstorm or two across the region. Heaviest precip should remain east of all main TAF terminals save EWN, where periods of IFR vis/cigs are possible. Cigs linger at MVFR from roughly a OAJ/EWN line east for the afternoon before collapsing overnight as cold front approaches the area, with periods of IFR likely. Cigs will be short lived as dry air filters in behind the front, scattering cloud cover out by 10-11z.

Confidence Level, Moderate.

Tuesday through Friday As of 3 AM Mon, Lingering sub-VFR cigs possible Tuesday morning, quickly improving to VFR. Vfr expected to prevail through Thursday, with early morning fog the only concern for Wednesday. Unsettled weather returns later Thursday into the weekend.

Marine

Today and tonight As of 425 AM Mon, Boating conditions expected to deteriorate tonight across coastal waters in the form of rising seas as surface low develops offshore. Current obs show S to SE winds 5 to 10 kt with seas generally 2-4 feet across the area. Wind field across the waters will be complex as surface low undergoes cyclogenesis and lifts towards the mid-Atlantic overnight. Se winds expected to back easterly by late afternoon on the northern periphery of the low, increasing to 15-20 kt as it deepens. Winds back further to the NE and then briefly WSW as low lifts to the northeast, then rapidly increases to 15-25 kt with winds veering WNW as cold front quickly crosses the waters late Monday night into Tuesday morning.

SCAs have been hoisted for all area waters, with central and northern offshore waters first in line as waves build ahead of the developing low. Remaining SCAs come into effect Tuesday, see long term section for details.

Tuesday through Friday As of 3 AM Mon, Post-frontal NW flow will steadily strengthen through the day Tuesday as low pressure deepens quickly off the Mid-Atlantic and NE coast. High confidence SCA conditions Tuesday, with Gale conditions possible Tue evening into the first part of Wed depending on the strength and location of the low off the coast well to our north. Strong NW winds 20-25 kt early Wed, slowly diminishing Wed night and Thu as ridging settles over the area. Breezy winds expected again late week with a cold front that could cross the area late Friday or Saturday. Se winds will increase to 15-20 kt with a warm front Thu night, becoming SSW 15-25 kt Fri ahead of the cold front.

Seas 4-7 ft Tue peaking around 5-8 ft Tue night and Wed, then potentially remaining elevated through much of the rest of the week as persistent N to NE swell impacts the waters mainly north and east of Cape Lookout. Dangerous seas 6-10 ft expected again late week with the next system.

Watches, Warnings, Advisories

Nc, none. Marine, small craft advisory from 11 am Tuesday to 2 am EDT Wednesday for amz136-137. Small craft advisory from 8 am Tuesday to 5 pm EDT Wednesday for amz135. Small craft advisory from 11 am Tuesday to 11 am EDT Wednesday for amz131. Small craft advisory from 8 am Tuesday to 2 pm EDT Wednesday for amz230-231. Small craft advisory from 5 pm this afternoon to 8 am EDT Friday for amz152-154. Small craft advisory from 11 pm this evening to 2 pm EDT Wednesday for amz156. Small craft advisory from 8 pm this evening to 8 am EDT Friday for amz150. Small craft advisory from 11 pm this evening to 11 am EDT Wednesday for amz158.

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