Key MESSAGE 1, Local and regional observations show a warm and increasingly moist airmass continuing to advect over eastern NC in moderate southwesterly flow, ahead of a stalled front currently analyzed over the VA/NC state line and forecast to push southward later this evening. Already seeing some broken shallow showers developing along a pre-frontal trough oriented from roughly Kenansville through the northern Outer Banks.
Mid-level shortwave currently pushing south over the Great Lakes will continue to rotate around a trough sitting over the northeastern CONUS, and the surface front will drop into the Carolinas later this afternoon. While a few showers and isolated storm will be possible in the warm sector through this afternoon, the front will provide the focal point for better coverage of showers and storms, moving from north to south. Coverage will likely be higher farther south where a more unstable pre-storm environment is in place, up to 1000-1500 J/kg per SPC mesoanalysis.
Overall conditions remain only marginally conducive for strong storms. Effective shear, especially south of Highway 64, is forecast to be around 20-30 kt which could aid in some modest organization, but lapse rates will be quite poor (at or under 6.0 C/km even at lower levels). 12z MHX sounding did some some mid-level dry air and forecast DCAPEs are forecast to rise to around 400-800 J/kg, so if a stronger storm is realized some gusty winds of 40+ mph are possible. Overall probability of this occurring within 25 mi of a point is less than 5%.
Cooler air floods in behind the front in strong northeasterly flow with skies gradually clearing behind it. Unseasonably cool air will knock lows down into the upper 50s to low 60s. The coolest conditions are expected Tue evening with high pressure overhead and decoupling likely, with lows potentially dipping into the upper 40s in well sheltered spots.
KEY MESSAGE 2, Previously mentioned positively tilted upper- level trough will swing across the Mid Atlantic on Tuesday, which will help keep a developing coastal low well offshore. Guidance continues to trend this low farther offshore, and odds of any associated shower activity bleeding onshore continues to fall in this afternoon's update. The more noticeable impact from this feature will be stronger northerly gradient winds, which could gust to 20-25 mph inland and 25-35 mph along the coast.
KEY MESSAGE 3, As we get into the end of the week, low offshore is forecast to push further out to sea with high pressure building overhead Thurs and then becoming anchored off the coast this weekend. This will bring steady SW'rly flow, increasing low level thicknesses, and warming temps with highs forecast to get back into the 90s inland and 80s along the coast and OBX bringing a return to more summer like temps. Long term probabilistic guidance suggests there is room for forecast highs to trend higher (probability of a Moderate or higher HeatRisk is already 50-60%+ from Saturday onward), so those sensitive to heat issues are encouraged to keep an eye on trends over the next few days.
18z Monday through Saturday A modest increase in the potential for MVFR and potentially IFR vis/cigs is forecast in shower/thunderstorm activity this afternoon and evening. Threat starts from the north and pushes south through tonight. Sct SHRA and TSRA with reduced VIS and gusty/erratic winds are forecast along and just out ahead of the southward moving cold front. Behind the front there will be a northeasterly wind shift with gusts up around 20 kts inland and 25-30 kts along the OBX and immediate coast with these elevated winds persisting into Tue morning. Of note, where TSRA occur, the forecast environment appears supportive of a risk of 30-45kt downburst winds and small hail (<0.5" in diameter).
Overnight medium confidence in MVFR cigs developing between 06Z and 12Z all terminals with improvement to VFR near sunrise Tuesday.
Outlook: Tuesday looks to remain dry, but it will be quite breezy throughout the day with NE gusts to 15-20 kt inland and 20-30 kt along the coast. Winds will remain out of the NE on Wednesday but gradually ease with a slight chance of showers (highest along the coast). Winds eventually shift to S'rly direction by late Thursday and into Friday and remain light. Predominantly VFR conditions are expected for the remainder of the period.
Main features of interest over the waters is a cold front pushing south out of the mid-Atlantic this afternoon, and a compact but strengthening offshore low currently a few hundred miles off the coast of South Carolina. Regional observations show moderate south to southwesterly flow ahead of the approaching front with sustained 15-20kt and occasional gusts to 25 kt. Scattered shower and iso thunder coverage is occasionally bringing down higher gusts. Increasing shower and thunderstorm chances expected this afternoon and evening. A few of these storms could be strong in nature bringing a threat for locally elevated winds and seas to all waters.
Cold front is forecast to cross the waters later this afternoon into the evening hours, with a hearty northerly surge of winds in its wake. Increasing shower and thunderstorm chances expected this afternoon and evening. Sustained winds of 15-25 kts with gusts up around 30 kts are expected while seas build to 6-9 ft north of Cape Lookout and 4-7 ft south of Cape Lookout. This will once again bring SCA conditions to all our waters starting tonight. Persistent north to northeasterly fetch behind the departing low will keep seas elevated for much of the week, and the duration of SCA seas has increased from the previous forecast. Extended SCA into Thursday and Friday for offshore zones north of Cape Lookout. Signal remains for a brief window of Gales over the waters south of Hatteras beyond 20 nm, but is still too weak to include headlines this afternoon.
Outlook: SCA conditions come to an end by the weekend with a return to more typical warm-season patterns in south to southwesterly flow and localized surges in the late afternoon and evening associated with thermal gradients.
Nc, beach hazards statement until 8 pm EDT this evening for ncz196- 203>205. Marine, small craft advisory from 2 am to 11 pm EDT Tuesday for amz131- 230-231. Small craft advisory from 3 am Tuesday to 8 am EDT Wednesday for amz135. Small craft advisory from 6 am to 11 pm EDT Tuesday for amz136- 137. Small craft advisory from 2 am Tuesday to 2 am EDT Friday for amz150. Small craft advisory from 2 am Tuesday to 8 am EDT Friday for amz152-154. Small craft advisory from 6 am Tuesday to 2 am EDT Thursday for amz156-158.
