Key MESSAGE 1, Anomalously warm low-level thicknesses and dewpoints beneath strong ridging aloft will continue to keep temperatures well above normal with potential record breaking heat continuing through Saturday, with heat index values peaking at 105-110 deg Friday for inland and nrn OBX zones, and possibly again for srn zones on Saturday.
Friday continues to have the strongest signal for the peak of this week's heat wave, with highs ranging 95-100 for the interior coastal plain, with low 90s coast. Thermal gradient should be strong enough to allow for fast seabreeze progression and thus preclude heat indices reaching 105 for immediate coast outside nrn OBX, with HREF probs indicating this as well, but the combo of hot temps well above 90 inland coupled with TD's well into the 70s bring heat indices 105+ once again inland. Some locales may once again flirt with vals above 110 again, but not long enough or widespread for issuance of heat warnings. Href probs remain below 20%.
Saturday a cold front will begin sinking in, but at the same time TD vals inc with moisture gradient tightening ahead of it, and with temps fcst to reach into the mid to possibly upper 90s in swrn zones, another day of heat indices 105-110 degrees is possible before expected numerous showers and storms ends the heat later in the day. Best chances to reach criteria are generally along and s of Hwy 70.
KEY MESSAGE 2, A strong upper level trough will develop off the U.S. East Coast over the weekend, and this will help drive a strong cold front south through the Carolinas on Saturday. Strong heating of a moist boundary layer ahead of the front should allow strong instability to develop from the Mid- Atlantic south into North Carolina on Friday. While some residual subsidence/capping may be present beneath the ridge, especially across NC, guidance show a decent signal for convection developing upstream of ENC, and making a run towards the nrn zones as early as late afternoon, but esp through the evening hours. If convection can arrive early enough, severe potential is there, esp north of Hwy 70 and best chances north of Hwy 264. Cams have generally inc in covg here, and thus raised pops and thunder chances to likely after 22Z. Instability is above the climo max for the first week of September, and deep layer shear above 25 kt.
On Saturday, the ridge will continue to get suppressed further south and west with less influence across the Carolinas. This plus increased forcing along the cold front should support an improved risk of deep convection, and less limiting factors, compared to Friday. Pw's/td's inc further and with lowering hts aloft, instability will be very strong. In fact, vals will be well above the avg max for first week of September according to the KMHX sounding climatology, with ML CAPE vals advertised by the 03/12Z RRFS/ECM/NAM3k reaching or exceeding 4,000 J/KG! If convective timing aligns with fropa/shortwave passage in the afternoon, a significant severe weather signal may be met as this aligns with deep layer shear of 35-45kt. Csu severe probs for damaging wind have increased to over 30% for parts of ENC and may suggest a higher risk than the current Day 3 'slight' risk from SPC if aforementioned parameters are met together.
In addition to the severe threat, will have to watch for potential ff threat, as PW's surge to 2.25" or higher, and with the expected numerous convection, very heavy rain rates are possible with deeper convection and lend to instances of flash flooding.
KEY MESSAGE 3, Behind the front, temperatures and humidity will finally get knocked down closer to normal for early September, with more comfortable conditions lasting into early next week. Still some residual moisture lingering on Sunday and may see some sct showers, but overall trend is for drier esp as we begin the work week with pops less than 20% lasting through mid week. Highs in the mid 80s with lows in the 60s is fcst and is where our temps should be for the first half of September.
01z Friday through Tuesday No real change to the aviation forecast as primarily VFR conditions are expected across ENC through much of the period. Any storms this evening should remain north and west of all TAF sites. The biggest challenge tonight will be where patchy fog or low stratus may develop especially along the Crystal Coast. Guidance is fairly muted on this threat, but the NAM/GLAMP show at least a low end threat for some low stratus and with the CONSHORT AND HREF showing low end probs for patchy fog/low stratus as well, kept the TEMPO group of 5SM vis and BKN003 ceilings at OAJ between 08-12Z and added a TEMPO group at EWN to account for the threat. Probs are too low to the north and west so have kept a VFR TAF at ISO/PGV tonight. Light swrly winds again expected on Friday. Any patchy fog/low stratus quickly dissipates by about 13Z with VFR conditions then returning to all of ENC through Fri evening. Afterwards potential for showers/tstms bringing sub VFR conditions begin to increase across our far northern zones, especially after 21-00Z. Still a touch to early to add in any mention of tstms at the TAF sites but one could be included in future updates depending on trends. Greatest risk would be to PGV/ISO terminals.
NOTE: AMD NOT SKED has been appended to the EWN TAFs as the site is not transmitting through normal channels. The site is still reporting via telephone so it will be monitored, but not as frequently as when it is completely operational. The next closest ASOS is at Cherry Point (KNKT).
Outlook (Fri night through Tue): Chance of TSRA Fri evening for mainly KPGV as some storms from VA make a run into nrn parts of ENC. Better chances for widespread showers and storms on Sat as cold front drops through the area. Sub-VFR conditions will be possible with any TSRA during this time. Behind the front, a northeasterly wind shift will occur, with northeasterly flow continuing into early next week.
Latest obs show S-SW winds 5-15 kt with seas 2-3 ft. Se long- period swell (2-3ft at 10-11s) from the remnants of "Dolly" will continue to diminish across the waters today. Stronger thermal gradient develops with some gusts aoa 20 kt this evening. Yet stronger winds expected later Fri afternoon into evening with several hours of 25+ kt winds possible esp for eastern sounds/Alligator river and nearshore ctrl waters. Will hold off on any SCA headlines attm however due to uncertainty. Strong to severe thunderstorms could affect nrn sounds and waters late Fri afternoon and esp evening as storms move south into the region from VA. Strong wind gusts are the main threat with these storms.
Outlook (Sat through Tue): More widespread storms could affect the remainder of the ENC waters Saturday as a cold front moves through. The front will bring winds around to the NE for Sun into early next week with seas building to 4-6 ft for the nearshore waters north of Ocracoke. Winds and seas will begin to ease Tuesday as high pressure builds in.
Nc, heat advisory from 11 am to 8 pm EDT Friday for ncz029-044>047- 079>081-090>092-094-193-194-198-203. Marine, none.
