Key message 1,
As of 910 AM Mon, We are already seeing a blossoming of broken shower and thunderstorm activity along the I-95 corridor this morning. Instability is modest in this area which will limit overall severe potential in the near term, but given healthy shear already in place and a strong background wind field this line will have the potential to produce gusty winds in excess of 40-45 mph.
As we move into the late morning hours the severe risk will increase as axis of higher shear (40-50+ kt effective) and helicity (~150-250 m2/s2 0-1 km) migrates eastward, in conjunction with an uptick in surface-based instability to around 1000 J/kg. Observations and satellite already show breaks in cloud cover across much of the area this hour, so confidence is high that sufficient instability will be achieved for convective development. Near-term probabilistic guidance points to an uptick in tornado and damaging wind risk in the 11am-12pm time period and remaining elevated through 6-7pm west of Highway 17 and 9-10 pm for the Outer Banks.
Prev disc, A potentially significant severe weather event is taking shape across parts of ENC this afternoon into early evening. Spc has all of ENC under an Enhanced Risk (level 3 of 5) with best chances of severe likely across interior zones. Overall the upper level pattern remains the same, with an impressive upper level trough digging south through the OH Valley and continuing E'wards today while taking on a more negative tilt as it moves E'ward towards the Ern Seaboard. At the surface, strong surface low (sub 990mb) will track NE'wards across the Great Lakes and Interior Northeast while its associated strong cold front tracks across the Carolinas through the day pushing offshore tonight.
Dynamics increase today as strong 60-70 kt llj develops invof eastward advancing cold front and aforementioned deepening low. Strong albeit mainly unidirectional shear today in the range of 30-50 kt, combined with skinny ML CAPES approaching 1000 J/KG inland, with closer to 300-500 J/KG coastal counties due to marine layer, will lend to a damaging wind threat with any storms that can become organized. Semi discreet clusters this afternoon will be capable of producing a tornadoes (a couple which could be on the stronger end) while bowing line segments will produce a threat for damaging wind gusts given the strong llj dynamics in place. Strongest shear and instability will be concentrated along and west of Hwy 17, and this is where REFS props are highest for a higher end (75+ mph) severe potential.
Moving into the early evening hours, one final round of precip will occur associated with an organized line of showers and some embedded thunderstorms along the strong cold front. Instability will be waning with loss of daytime heating, though strong winds may still accompany convection along the main line along the quickly eastward advancing cold front. Precip sweeps quickly offshore with the cold front prior to midnight.
With the aforementioned strong wind field in place, gusts of up to 50 mph still possible for the OBX and Down East Carteret, though even remaining adjacent coastal counties will see wind gusts of 40-45 mph this afternoon, and may eventually need to be upgraded to a wind adv if winds come up a bit more than expected. High Surf Advisory remains in effect through Mon with beach erosion and ocean overwash remaining a concern for vulnerable locations susceptible to S'rly wave directions.
KEY MESSAGE 2, The initial blast of CAA directly behind Mon's front will lead to MinTs in the 30s, though above freezing as atms will be mixed with ongoing CAA. Arctic high pres builds in Tue through Thu. The afternoon's CAA and the center of the high settling almost directly overhead late Tue night/early Wed will lead to clearing skies and calming winds. These conditions will prime the FA for strong radiational cooling effects, leading to MinTs well down in the 20s for mainland areas, with 30s DownEast, beachfront, and OBX nearer the warmer waters. Another subfreezing night Wed night with high pres still nearby. As a result any planting that has been done given our recent stretch of warm weather should take proper precautions to protect plants and any outdoor pipes before we warm Thursday and beyond.
12z Monday through Friday Mostly VFR conditions at TAF issuance. Llws mentioned throughout the TAFs until strong cold front goes through the FA from W to E this evening. This very strong front will bring gusty Serly winds (G30-40KT at times) ahead of it, and periods of MVFR flight cats in showers and thunderstorms. Thunderstorms may be strong to severe with SPC placing ENC in an enhanced risk (level 3 5) of severe tstorms with a moderate risk (level 4 ) W of our local TAF sites. Have introduced PROB30s for prefrontal tstorm risk. Tstorms will be capable of producing damaging wind gusts, isolated strong tornadoes, and large hail. Best chances would be noon to 2100EST. A line of storms directly along the front poses the most likely chance for subVFR due to CIGs and VIS. Precip threat ends directly behind the front with winds turning Werly but significantly calming. Some MVFR CIGs could linger for ~an hr behind the front but will quickly clear to SKC behind that.
Outlook, Pred VFR conditions will return by late Monday night behind the front. Winds turn WNWerly but fall off drastically speedwise. Uneventful reinforcing cold front crosses through TUE and high pressure dominates the forecast through the remainder of the work-week, keeping VFR flights cats in place.
A strong cold front is forecast to cross from W to E tonight. Strong srly gradient develops today with gale gusts for all marine area of ENC, and thus expanded gale warnings for all zones, mainly due to afternoon mixing coinciding with strongest wind field and gusts exceeding gale gusts even on the inland rivers and sounds. In addition to the strong background wind field, a risk of strong to severe thunderstorms mainly in form of gusty winds expected through early this evening before winds diminish towards midnight as cold front sweeps eastward and offshore.
Guidance continues to show patchy dense sea fog developing across the northern waters this evening and continuing into the first part of Monday, as dewpoints increase combined with onshore flow. However the warmer SST's over the last couple of weeks and strengthening wind speeds will limit sea fog concerns.
Outlook: Winds become N-Nerly mid-week behind TUE's reinforcing front remaining generally 5-15G20kt through the remainder of the work week. Sea-driven SCAs likely to remain active into Wed morning, continuing to improve through late week. Low pressure system well offshore late week expected to increase swell and could further the need for extending SCAs that follow the Gales MON and TUE.
Nc, wind advisory from 2 pm this afternoon to 10 pm EDT this evening for ncz046-047-080-081-092-094-194>196-198-199- 203>205. High surf advisory until 2 am EDT Tuesday for ncz196-204-205. Marine, gale warning from noon today to 10 pm EDT this evening for amz131-136-137-230-231. Gale warning from 2 pm this afternoon to midnight EDT tonight for amz135. Small craft advisory until 4 pm EDT this afternoon for amz150. Gale warning from 4 pm this afternoon to midnight EDT tonight for amz150. Gale warning until midnight EDT tonight for amz152-154. Small craft advisory until 10 am EDT this morning for amz156- 158. Gale warning until midnight EDT tonight for amz156-158.
