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 today for most of the area, and possibly again for srn zones on Saturday.
Today 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 portions of the immediate coast. The combo of hot temps well above 90 inland coupled with Tds 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.
Saturday a cold front will begin sinking southward through the area, 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 SWern 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. A heat advisory has been issued for this general area. Went below NBM for Tds for tomorrow with today's obs showing NBM was overdone. Have some heat advisory criteria AppTs in the grids all the way up to the Nern tier despite the slightly lower HiRes blend Tds, but opted not to go with a heat advisory this far north with increasing clouds and shower and storm coverage likely to cut down on the heat in this area earlier in the afternoon.
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 and Saturday night. 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 this afternoon and evening. While some residual subsidence/capping was present earlier beneath the ridge, especially across NC, guidance, and now radar, shows a decent signal for convection developing north of the Albemarle Sound and into the Coastal Plain, and making a run towards the nrn zones late this afternoon and evening. Severe potential is there, esp north of Hwy 70 and best chances north of Hwy 264 with afternoon CAPE values in excess of 3kJ/kg, and deep layer shear is above 25 kt. Main threat will be potential for damaging wind gusts, but strongest storms may contain some hail as well. Severe watch is currently set to expire at 2200EDT though this may be extended in both time and area.
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 4kJ/kg. If convective timing aligns with fropa/shortwave passage in the afternoon, a significant severe weather signal may be met as this aligns with stout deep layer shear, possibly in excess of 35-45kt. Machine learning severe probs for damaging wind have increased for parts of ENC. In addition to the severe threat, will have to watch for potential flash flood threat, as PWs 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, especially with potential for training of storms. Nbm's deterministicQPF values did not tell the whole story by any means, with even the bulk of the higher percentile output still advertising less than one inch over 24h for the entire area. Went with WPC QPF which shows a 24h total QPF of 1-2" for areas adjacent to the mouth of the Neuse River, which the bulk of guidance is showing has the best chances of seeing training storms. As a deterministic forecast, this will suffice, but there is absolutely potential for 24h rainfall totals in excess of 2-3" in spots.
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.
00z Saturday through Wednesday VFR flight cats are currently noted across the TAF sites but that may soon change, primarily across PGV where thunderstorms to the north are slowly dropping southwards. These storms could bring gusty and erratic winds, frequent lightning, and MVFR to IFR vis to PGV and have put in a TEMPO group to account for this. Elsewhere, dont think the thunderstorm activity survives long enough to preclude a line for precip. As we get into tonight any leftover shower or thunderstorm activity quickly dissipates allowing for partly to mostly cloudy skies tonight as debris clouds from dissipating convection overspread the region. This should limit any fog or low stratus threat tonight.
As we get into Saturday, expect VFR conditions to start the day, but better chances for widespread showers and storms forecast Sat afternoon and evening as cold front drops through the area. Sub- VFR conditions will be possible with any TSRA during this time. Some storms have the potential to be strong to severe with winds in excess of 50kt and strongest storms having hail as well. For now given how far out in time it is, put in PROB30 groups in all TAF sites Sat afternoon to account for the tstm threat.
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 (Sat night through Wed): Behind the front, a northeasterly wind shift will occur, with northeasterly flow continuing into early next week and pred VFR returning.
Winds through the day have shown that NBM has been underdone by 3-5kt. Latest obs show SW winds 5-10kt inside, 12-18kt outside with seas 2-3 ft. Thermal gradient continues to strengthen through this evening, with winds increasing to 10-20g25kt, for the eastern sounds/Alligator river and nearshore ctrl waters. Continued SCA for the Pamlico Sound and central waters, but did extend it slightly longer than previous issuance. Strong to severe thunderstorms could affect Nern sounds and waters late this afternoon and esp evening as storms move south from VA. Strong wind gusts and freq lightning 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. Winds will shift becoming NE behind the front Sat and Sat night. Moderate to gusty NE winds will develop Sunday and continue into Monday, with seas building to 4-7 ft, highest across the outer waters. Winds and seas will begin to ease Tuesday as high pressure builds in.
Nc, heat advisory from 11 am to 6 pm EDT Saturday for ncz044- 079>081-090>092-094-193>196-198-199. Marine, small craft advisory until 3 am EDT Saturday for amz135. Small craft advisory until 5 am EDT Saturday for amz152-154.
