Key MESSAGE 1, A potent upper level shortwave will swing east through the Carolinas/Mid-Atlantic on Thursday, with an associated cold front passage Thursday morning. Ahead of this feature, strengthening southerly flow will develop associated with a notable southwesterly LLJ. This will support strengthening moisture transport, with PWATs climbing to 1-1.50", and dewpoints rising into the low-mid 60s.
Despite increasing moisture and instability, upper level ridging building into the area should keep a fairly tight lid on convective potential Wednesday and Wednesday night. Then, by the time the front reaches the area on Thursday, the timing looks less favorable for severe weather, primarily due to limited heating and weak instability. It should be noted, though, that this will be a high shear/low CAPE scenario that can sometimes support some stronger wind gusts or a very brief, weak tornado. While this risk appears low, machine learning guidance and pattern recognition suggests the risk isn't zero. The most likely scenario is widespread showers with a few embedded thunderstorms during the day Thursday.
Ahead of the front, breezy south winds and increasing low-level thicknesses beneath the ridge will support well above normal temperatures. The ECMWF's EFI guidance continues to show a very strong signal for above normal to record high temps. A few inland locations could approach 90 degrees. Very warm conditions continue into Wednesday night. In fact, lows Wednesday night will likely be warmer than our normal highs for this time of year.
KEY MESSAGE 2, Yet another strong cold front is forecast to move through the U.S. East Coast late this weekend or early next week. Similarly, strong southerly flow ahead of the front should support increasing moisture with 1"+ PWATs and 60+ dewpoints. This should once again allow a narrow ribbon of modest instability to develop in the warm sector. The timing of the cold front looks more favorably timed for peak heating/destabilization. Consequently, machine learning guidance show a slightly stronger signal for severe thunderstorms during this time. This is several days away, but something to monitor as we approach the weekend and early next week.
Temperatures will quickly rebound with increasing southerly flow ahead of the front this weekend. This looks to be followed by a notable surge of cold air next week. In fact, the Climate Prediction Center has highlighted a portion of our area for a risk of below normal temperatures. This may lead to frost/freeze potential which is notable because it comes after some greenup is ongoing during this recent stretch of above normal temps.
18z Tuesday through Sunday Light SW winds and VFR conditions this afternoon with scattered mid clouds overhead. Patchy sea fog possible this evening, although warming SSTs the past week may indicate that models are too bullish on sea fog. Ncep SST parameterization is 5-10F too high for our nearshore and inland waters given the recent warming. While it may occur, it likely won't be as widespread as model guidance suggests. As we get into tonight, weak moisture advection from the evening brings dewpoints to the low 60s with clear skies and light to calm winds. Fog setup looks good, although models really don't seem to agree. Given the relatively unchanged airmass (outside of some weak moisture advection) decided to follow more of a persistence forecast, expecting fog and low stratus to start forming after 6Z across eastern NC. With this update, increased wording from MVFR vis to IFR vis. For now capped at 2SM, although LIFR fog is not out of the question. Any flight reductions should burn off by 14Z, leading to VFR conditions and breezy SW winds.
Outlook, Sub-VFR may return Thursday with scattered to numerous showers, isolated storms and gusty winds. Pred VFR to return Fri into the weekend.
Sea Fog: With moistening srly light flow cont today into tonight, sea fog may return and become dense again, and will continue to monitor cams and obs for potential for additional dfa.
Light south winds of 5-10kt are expected to continue into early Wednesday morning, with seas of 2-3ft common. These low impact conditions won't last long, though, as winds and seas begin to build on Wednesday in advance of an approaching cold front. Ahead of the front, southerly winds of 10-20kt are expected, with seas building to 3-5ft. Behind the front, strong cold air advection and enhanced mixing is expected to support widespread 15-25kt winds, with frequent gusts of 30-35kt+. Of note, some guidance suggests gusts of 40kt possible. Given the recent warming of SSTs into the 60s, this seems very reasonable as this will help enhance mixing (compared to earlier this year when SSTs were much colder). In light of all of this, confidence continues to steadily increase regarding the potential for gale- force gusts, and a Gale Watch has been issued where confidence is the highest. Expansions of the watch will be possible, with additional marine headlines eventually needed. The cold front will be accompanied by a risk of thunderstorms on Thursday, 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 impacts expected. Winds and seas will rebuild Sunday into Monday associated with the next strong cold front.
Nc, none. Marine, gale watch from Thursday morning through Thursday evening for amz150-152-154.
