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.
18z Wednesday through Monday Pred VFR conditions expected at the TAF sites through much of the TAF period. Sw winds have become gusty this afternoon with the inversion breaking with gusts to around 20-25 kt. Moderate SW winds around 10-15 kt continue tonight with higher gusts possible at times. The low level jet at 1-2kft increases tonight as a frontal system approaches from the west. The LLWS threat subsides a bit after 14Z Thursday as daytime heating erodes the inversion 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, and a few thunderstorms. In these showers, drops in vis/cigs to IFR levels are possible. Just behind the front Thursday afternoon, gusty SW winds quickly shift to become gusty N/NW winds.
Outlook, Sub-VFR expected Thursday with scattered to numerous showers, isolated storms and gusty winds along a cold front. Low stratus may build in behind the front for Thursday night/Friday morning. Pred VFR to return Fri later Friday into the weekend.
Light southerly winds of 10-15 kt and 2-3 ft seas are expected to continue into early this evening. Conditions will then deteriorate ahead of an approaching cold front that will pass on tomorrow. Tonight, southwesterly winds will increase to 20-25 kt with gusts to 25-30 kt. 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.
