Key MESSAGE 1, As a potent upper level shortwave moves east through the Mid-Atlantic tomorrow, a strong cold front will track across ENC and bring gusty winds, widespread rain, and a few thunderstorms. Given that the FROPA is expected to reach the area ahead of peak heating, instability will be limited - the HREF average SBCAPE is under 500 J/kg, but a worst case scenario could see values closer to 750 J/kg in more robust pre-frontal warming. Srh and deep layer shear, on the other hand, will be plentiful with average forecast 0-6 km shear in excess of 50-55 kt. While this high shear/low CAPE environment is not a slam dunk for severe storms, there's still a non-zero risk of a few strong gusts north of 50 mph. Hodographs to not appear very favorable for tornadoes, but a brief tornado is not out of the question in mesoscale boundary interactions. The most likely scenario is widespread showers with a few embedded thunderstorms during the afternoon and evening tomorrow.
Of note, a small minority of guidance (WRF ARW and NSSL) is showing a brief changeover to winter precip tomorrow evening on the backside of the front. In regimes where cold air is chasing the moisture, forecasts for winter precip is usually too aggressive. For now, our forecast calls for all rain but trends will continue to be monitored overnight.
KEY MESSAGE 2, We'll still be warmer than average behind tomorrow's front, but we'll feel a notable drop in temperatures with a change as high as 10F/hr immediately behind the front. Friday will reach the low/mid 60s and we'll rebound to the mid 60s to mid 70s on Sunday and Monday. A deep upper level trough will dig across the CONUS late this weekend and reach the East Coast by early next week. At the surface, a strong cold front will cross the area late Monday/early Tuesday. This system will bring increased shower and thunderstorm chances Sunday through Monday night with a slightly stronger signal for severe thunderstorms than Thursday's front. A significantly cooler airmass will build in behind this front with highs on Tuesday and Wednesday forecast to be in the 40s and 50s.
00z Thursday through Monday Pred VFR conditions expected at the TAF sites through Thu AM. Swrly gradient winds will cont to gust through the night tonight with speeds of 15-20 kt. The low level jet at 1-2kft increases tonight as a frontal system approaches from the west. The LLWS threat subsides in the morning as the weak inversion subsides and gusty winds 20-30 kt reach the surface instead of being stuck at the 1-2 kft level. Along a cold front passage Thursday we will see a line of quick moving moderate to heavy showers with a renegade lightning strike possible. In these showers, drops in vis/cigs to IFR levels are possible along with wind gusts very briefly aoa 30 kt. Rapid wind switch from the SW to the n behind the fropa.
Outlook (Thu night through Weekend), Low stratus may build in behind the front for Thursday night/Friday morning. Pred VFR to return Fri later Friday into the weekend.
Update: Have inc swrly winds through tonight, as a very anomalously warm Pamlico sound with sst in the upper 60s to low 70s allowing for well mixed bndry layer and gusts of aoa 25 kt expected to continue through tonight and into Thu AM ahead of appraching cold front.
Seas will build to 4-6 ft north of Cape Hatteras and 4-7 ft to the south. Early tomorrow afternoon, a cold front will move across the area and veer the winds to the north-northwest. The post- frontal north- northwesterly winds will surge to 25-30+ kt with gusts to 35 kt, which will peak tomorrow afternoon/evening. In response, seas will build to 4-8 ft. Gale Warnings have been posted for all offshore waters and the Pamlico Sound. Predominantly SCA conditions will prevail over remaining sounds and waters. For the Albemarle, Croatan and Roanoke sounds, a short jump of winds up to 35 kt are possible in the immediate hour following frontal passage.
Additionally, the cold front will be accompanied by a risk of thunderstorms tomorrow afternoon and evening, the strongest of which may produce enhanced wind gusts and brief waterspouts.
Outlook: Winds and seas will lay down Friday and Saturday with more benign marine conditions expected. Winds and seas will rebuild Sunday into Monday associated with the next strong cold front.
Nc, none. Marine, small craft advisory from 1 pm to 8 pm EDT Thursday for amz131- 136-137-230-231. Gale warning from 3 pm to 8 pm EDT Thursday for amz135-150. Gale warning from 3 pm to 11 pm EDT Thursday for amz152-154- 156-158.
