textproduct: Newport/Morehead City

WHAT HAS CHANGED

SPC has added a Marginal (level 1/5) Risk of Severe Thunderstorms across the Sern half of the forecast area for today and tonight.

KEY MESSAGES

1) A cold front will move through today bringing gusty winds with widespread showers (80-90%), along with a slight chance (20%) of embedded thunderstorms. Strongest storms have low end chance of producing marginally severe wind gusts.

2) High pressure will build in tomorrow and bring a brief round of dry conditions.

3) Another round of unsettled weather for this weekend into early next week as several low pressure systems and fronts move through the region bringing scattered to numerous (40-70%) coverage of showers, along with slight chance to chance (20-30%) of thunderstorms.

DISCUSSION

KEY MESSAGE 1...A positively tilted upper-level trough will move across the Midwest and Great Lakes region today. At the surface, a slow moving cold front will move into ENC, pushing offshore this evening. Subtle timing differences still exist in guidance, but the window has narrowed significantly relative to this time yesterday.

Plentiful moisture along with mid to upper level lift is in place for widespread beneficial showers. There is a low, but non- zero, chance for some stronger storms to develop, but lapse rates are quite weak due to the widespread morning clouds and showers, and thus instability is in the form of long skinny CAPEs, which would yield some gusty winds even if no lightning is present. Continued capping of thunder chances at SChc over land areas. Current QPF for 12Z today-6Z FRI still ranges from 0.25-1" with highest totals over NWern half of the FA. In addition to showers and storms, today will bring gusty SW winds with gusts to 20-25 mph inland and 25-30 mph along the coast. Best chance for strong gusts outside of showers/storms is immediately ahead of the front. Convective showers and storms with greater vertical development, if some sunshine is realized, may mix down some of the stronger winds aloft, making strong convective wind gusts the greatest threat for the area. Greatest chance of this occuring lies over the Sern half of the FA when FROPA coincides with peak heating. Typically more excitable guidance shows MUCAPE values reaching ~1kJ/kg in a small pocket just ahead of the front, but model consensus is generally on the order of 500-700J/kg.

KEY MESSAGE 2...Surface high pressure will briefly build in tomorrow leading to a mild, mostly dry day with MaxTs in the low 70s (60s OBX). The high shifts offshore FRI night ahead of a shortwave to move through the Carolinas Saturday. This will lead to warmer, cloudier conditions to start the weekend with moisture advection ramping up in the Serly flow developing on the W side of the high.

KEY MESSAGE 3...Rain chances increased again steadily on the weekend, with the first wave on Sat with sheared mid level energy swinging through as weak warm front lifts north northeastward, producing chances for showers, then a better chance later SUN into MON with likely PoPs ahead of another front and stronger wave of low pressure that is forecast to cross the FA. We will monitor this system for a strong to severe storm threat, as better dynamics are in place, with potentially more robust instability, which will depend on diurnal timing of mesoscale features.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Multiple rounds of SHRA will traverse the Carolinas over the next 12 hours or so thanks to a deep layer of moisture interacting with a southward-sagging cold front. There is just enough instability to support a low risk of TSRA (10-30% chance). The heaviest SHRA will be capable of brief reductions in VIS to as low as IFR/LIFR. Behind the cold front, winds will flip around to the northeast. Of note, recent model guidance has trended slower with the passage of the front, which means south to southwest winds are likely to last longer than previously anticipated. Once the front passes, widespread IFR CIGs are expected to linger well into this evening, and there may be reduced VIS in BR, especially tonight into early Friday morning.

Outlook: Drier air moving in behind the front should support improving aviation conditions by Friday. Looking ahead, the next opportunity for sub VFR conditions looks to be over the weekend, along with a risk of TSRA.

MARINE

SSW winds in place 10-15G20kt inside with 15-20kt of coastal waters where choppy seas continue in the 2-5ft@6sec range, lowest up N. Moderate to gusty SSW winds will continue as a slow moving cold front approaches and finally crosses through the day. Front will be slow moving, with the Central and Sern waters, especially S of Hatt remaining in gusty SWerly flow most of the day, and thus the SCA will be in effect here, starting south of Ocracoke at 15Z Thu. Gusts of up to around 30 kt will be common, building seas to 5-7ft coastal waters, 7-9ft offshore waters with a chance for some gale force gusts immediately ahead of the front once it starts reaching the warmer Gulf Stream waters. Showers and storms likely ahead of the front this afternoon into early evening. Winds turn sharply N to NNE behind front, with a thump of winds to 25 kt or higher for a brief period on sound waters adjacent to OBX and Nern coastal waters, but too brief to warrant issuance of any SCAs.

Outlook (Friday through Monday): Winds will decrease to 5-15 kt with gusts to 15-20 kt by Friday morning with good boating conditions returning by the afternoon as high pressure builds in. The improvement will be short lived with showers and storms expected again SAT, then again later Sun into Mon with troughing traveling over regional waters behind the high pressure sliding further offshore. SCA conditions on the nearshore waters poss late Sun into early Mon ahead of strong front, with brief gale gusts poss on the offshore waters.

MHX WATCHES/WARNINGS/ADVISORIES

NC...None. MARINE...Small Craft Advisory until 2 AM EDT Friday for AMZ152-154. Small Craft Advisory from 11 AM this morning to 2 AM EDT Friday for AMZ156-158.