Swell Matrix

Area Forecast Discussion

National Weather Service Newport/Morehead City Nc

930 pm EDT Wed may 24 2017

Synopsis

A stationary front will lift north of the area tonight. A cold front will move through from the west Thursday morning. High pressure will pass to the south Friday and Saturday. A cold front will slowly approach from the west early next week.

Near Term

Overnight As of 930 PM Wed, Have cancelled tor watch early as warm front with associated convection has moved north and east of the FA. Still advertising categorical pops through early morning hours though this is mostly for stratiform rain with just some embedded thunder possible. May see a somewhat better chance of a few thunderstorms in the pre dawn hours with a bkn line of convection associated with advancing cold front that is draped across wrn SC and middle GA attm.

Previous discussion, As of 7 PM Wed, Tornado Watch #266 remains in effect through midnight tonight for Eastern NC.

Latest sfc analysis shows 994mb low over northern Kentucky/southern Ohio, with attendant cold front draped through the Appalachians, and stationary front draped from about Rodanthe to Williamston back into central/western NC. Upper low over the MO valley region will continue to dig SE weakening slightly as surface cold front pushes eastward tonight. Stationary front will gradually lift northward this evening and tonight, as cold front pushes through the area late tonight and early Thursday.

Latest radar imagery shows scattered showers and thunderstorms across Eastern NC. Severe threat continues. Models continue to show good lift/instability as upper forcing increases this afternoon and early evening as sfc cold front and upper trough approach from the west. Eastern NC is outlooked in a Enhanced to Slight Risk of severe weather. The primary threats will be damaging wind gusts, hail, moderate to heavy rainfall as well as an isolated tornado. It still looks like the best severe threat will continue through about midnight. Latest mesoanalysis shows SB CAPE values 1000-2000 J/kg. Forecast soundings show instability indices MU CAPE values 2500-3000 J/kg, LI -6/-9C, with increasing shear, 0-6 km bulk shear 40-50 kt and low level helicity values increasing. Pwat values increase to around 2 inches again this evening. So periods of moderate to heavy rain will be a concern, esp for locations that saw heavy rain last night. An additional 0.5-1.5" inches of rain possible, which could produce localized flooding. Will continue pops increasing to categorical this evening, with mention of severe/heavy rain wording. Per latest high res guidance, expect convection to push east off the coast after 06z, though some scattered activity could re-develop behind the main line.

Short Term

Thursday As of 3 PM Wed, Stacked low will move into the Mid-Atlantic as attendant cold front pushes through Eastern NC. Could still be enough forcing and instability to trigger scattered showers and storms. Spc keeps the region in a Marginal Risk for svr storms, though parameters looks less impressive than Wed with drier air in place. Looks colder aloft, -15C at 500mb with freezing levels around 10kft. Still cannot rule out an isolated strong storm developing with gusty winds and hail. Breezy gradient winds develop in the afternoon, with gusts 20-30 mph. Low level thickness values support highs in the upper 70s to around 80 degrees.

Long Term

Thursday night through Wednesday As of 315 PM Wednesday, Drier weather is expected for Friday and most of Saturday as high pressure surface and aloft builds over the area. This will be followed by broad upper troughing/more zonal flow aloft which will result in a more unsettled weather pattern from Sunday afternoon through early next week as a sluggish cold front moves slowly through the area.

Friday and Saturday, Expecting warm and mainly dry weather this period with high pressure over the area. Will continue slight chance PoPs north Saturday afternoon but not expecting much aerial coverage.

Sunday through Wednesday, More unsettled weather expected this period as the pattern will become more favorable for scattered convection as a series of weak disturbances rotating through the flow interact with a slow moving cold front forecast to be in the area. Will continue 30-40% PoPs Sunday and Monday and 20-30% Tuesday and Wednesday. Highs will be well into the 80s through the period.

Aviation

02z Thursday through Monday Through Thursday As of 7 PM Wed, Currently a mixed bag of VFR/MVFR with some areas of broken 2kft ceilings. Widespread sub-VFR conditions expected to develop this evening as convection overspreads the area. Could see brief periods of IFR in heavier showers. Strong to severe storms will be possible this evening. Conditions will likely improve to VFR Thursday morning. Scattered showers/storms develop in the afternoon. Gusty SW winds Thu afternoon/evening, with gusts 20-30 mph.

Thursday night through Monday As of 315 PM Wednesday, VFR expected Fri-Sat in drier regime but increasing moisture will lead to scattered showers and Thunderstorms Sunday and Monday with brief periods of sub VFR conditions possible.

Marine

Through Thursday As of 930 PM Wed, Stationary front has lifted north and out of the marine domain this evening. Latest obs show winds generally E 10-15 kt north of the boundary and S/SW 10-20 kt south, with seas 3-5 feet north of Ocracoke and 4-7 feet south. Expect conditions to deteriorate this evening and overnight as gradient tightens ahead of approaching cold front. The front will move through the waters early Thursday. Sca in effect for the sounds, coastal waters and inland rivers. Strong SW winds tonight, 20-30 kt, may diminish a bit early Thursday, but remain gusty into Thu night. Winds could gust to near gale force over the coastal waters south of Oregon Inlet tonight, but will be brief. Nwps and Wavewatch have seas building to 6-11 feet tonight, subsiding to 5-10 feet Thu.

Thursday night through Monday As of 315 PM Wednesday, Poor boating conditions linger into Fri evening with improvement expected for most of the Memorial Day weekend.

Southwest winds 20-30 Thursday night will gradually veer toward the west and diminish to 20 to 25 kt by daybreak Friday and 15 to 20 kt Fri afternoon. 8-12 ft seas will subside to 7-9 ft Fri morning and 4-6 ft Fri afternoon.

Much improved conditions are expected over the waters this weekend. Winds are forecast to be southwest 10-15 kt Saturday through Sunday morning with seas 2-4 ft. The SW winds are then forecast to increase Sunday afternoon and Sunday night to 15 to 20 kt with seas building to 3 to 5 ft. Monday SW winds are forecast to be 10 to 15 knots but seas are forecast to remain 3 to 5 ft.

Watches, Warnings, Advisories

Nc, beach hazards statement through Thursday evening for ncz095- 098-103-104. Marine, small craft advisory until 7 pm EDT Thursday for amz136-137. Small craft advisory until 2 pm EDT Friday for amz135-150. Small craft advisory until 11 am EDT Friday for amz130-131. Small craft advisory until 11 pm EDT Friday for amz152-154. Small craft advisory until 5 pm EDT Friday for amz156-158.

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