Key MESSAGE 1, Weak low pressure has begun to develop along the Southeast coast near FL/GA along a stalled boundary. This weak low is forecast to track northwards with its associated warm front forecast to lift north across ENC this evening into the overnight hours. This will bring increasing chances for showers and thunderstorms and strengthening onshore flow starting this afternoon. Showers and storms become more widespread during the evening hours as the low and front near and track across ENC, warm sectoring the CWA and increasing dynamic forcing. As the warm front lifts Nward, SE'rly winds will continue to veer to a S'rly direction overnight, allowing for moisture and instability to be advected northward across the area. Latest Hi-Res CAMs suggest anywhere around 500-1500 J/kg of MUCAPE advecting in from south to north tonight. Latest HREF probs show a 60-80% chance for seeing instability values at or above 500 J/kg tonight across ENC with closer to a 10-30% chance of seeing over 1000 J/kg of instability across much of ENC outside of the Crystal Coast and OBX where higher probabilities for stronger instability lie. Pwats will also gradually increase today and tonight increasing to 1-1.5 inches, and with wind shear increasing to 25-35 kts and SRH values topping out around 100-150 M2S2 the environment will be marginally conducive for a few strong to severe thunderstorms, with the greatest risk of seeing a stronger storm being along the Crystal Coast and OBX tonight. Strongest storms could be capable of producing damaging wind gusts and perhaps small hail, though an isolated tornado can't be ruled out either as any potential waterspout that develops across the coastal waters could reach the coast and move inland. The strengthening onshore flow this afternoon and evening will rapidly build seas, which will bring high surf conditions to portions of our waters and as a result have kept the high surf advisory in place. Beaches susceptible to a SE'rly wave direction could be at risk for wave runup issues and maybe ocean overwash for particularly vulnerable locations.
KEY MESSAGE 2, A potentially significant event is taking shape across the Carolinas on Monday as widespread severe weather remains increasingly likely across the CWA. Overall the upper level pattern remains the same, with an impressive upper level trough digging in across the Plains this evening and continuing E'wards on Monday while taking on a more negative tilt as it moves E'ward across the Mississippi River Valley and into the Eastern 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 Mon night. Forecast continues to suggest several rounds for shower and thunderstorm activity through the day on Mon.
The first chance at stronger storms will be Mon morning as a prefrontal surface trough sharpens early and the LLJ strengthens. This will bring our first threat for organized convection with storm mode likely being in the form of thunderstorm clusters. With instability likely remaining elevated in nature for at least the first part of the morning, main threats would be hail and damaging wind gusts though an isolated tornado or two couldn't be ruled out either.
The environment will then remain very favorable for strong to severe thunderstorms through the rest of the day, as instability builds with MLCAPE values between 500-1500 J/kg, deep layer shear values of 60+ kts, and SRH values increasing to 200-300+ m2s2 Mon afternoon. This will promote our second round of scattered to potentially widespread thunderstorms in the afternoon and early evening hours with storm modes potentially becoming a mix of thunderstorm clusters and isolated supercells out ahead of an incoming line along a strong cold front to the west. With ample instability, strong low and deep layer shear, and elongating hodographs during the afternoon hours, all severe weather hazards will be possible. Damaging wind gusts and a few tornadoes being the most likely threat, while hail being a lesser threat within the strongest storms. Given the strong shear and SRH, there is a notable threat for a stronger tornado or two, especially for areas west of Highway 17 where the best juxtaposition of SRH and shear axes will likely reside.
Moving into the evening and overnight hours, one final round of precip will occur associated with an organized line of showers and thunderstorms along a strong cold front. This line will lead to the potential for damaging straight-line winds, with gusts potentially in excess of 75+ mph, and a QLCS tor threat.
While this is a low threat and not as likely of an outcome, would be remiss if we didn't mention the possibility of a slightly lower severe threat than currently anticipated in the later afternoon and evening hours. If morning shower/tstm activity and cloud cover keep the area in a more stable environment through the day, any severe threat would be lower than currently anticipated. However, regardless of the eventual evolution of the morning shower and tstm activity, given the kinematics associated with tomorrows event, even meager instability could still produce strong to severe tstorms. Because of the higher end environment forecast to be in place, think the more pessimistic forecast or higher end threat will be the more likely to verify.
With this all in mind, SPC has kept the entire area outlooked in an Enhanced risk (3/5) for severe weather, with a Moderate (4/5) risk just to our W from SC Nward into VA, where the greatest chance dynamics will coincide with peak heating, and therefore greatest confidence chance for higher instability values to feed storms and potential supercell development. Forecasts like this are uncommon for most parts of the United States, let alone eastern NC (the last two Day 2 Moderate for our FA were in 2012 and 2021), so tomorrow's convective episode should be taken seriously. Users are strongly encouraged to keep a close eye on forecasts and ensure multiple ways to receive warnings through tomorrow evening.
The strong pressure gradient and stout LLJ ahead of the front will lead to a strong background wind-field, and a Wind Advisory has been placed across Down East Carteret, and OBX south of Oregon Inlet Mon afternoon into Mon night. 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 3, The initial blast of CAA directly behind Mon's front will lead to MinTs approaching freezing across the Coastal Plain. A second reinforcing cold front will cross ENC early Tue with cold high pressure filling behind it. 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 in the upper 20s for the majority of the mainland area, mid to upper 30s DownEast and OBX. 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 Mon night and especially Tue night before we gradually begin to warm Wed and beyond.
18z Sunday through Friday VFR conditions currently with sct-bkn STCU advecting across the area with bases 4-6kft. A better chance for sub-VFR cigs (up to 70-90%) develops later this afternoon and evening as a warm front lifts across the area bringing scattered showers and thunderstorms. Brief period of IFR possible, mainly between 22-3z. Instability and shear increases this afternoon and tonight and could see isolated storms producing damaging wind gust or a brief tornado. Spc has the region in a marginal risk (level 1/5) for severe storms late today and tonight. Could see a period of VFR conditions develop after midnight but expect sub- VFR conditions to prevail into Mon. Sct to numerous showers and storms expected Mon, with the potential for strong to severe thunderstorms. Best chances will be between noon-9 PM.
SE winds 10-15 kt with gusts around 20-25 kt this afternoon. Winds become Sly around 10-25 kt this evening and will see LLWS concerns develop this evening as a strong low level jet develops ahead of an approaching cold front. S winds will gust 20-30 kt Mon ahead of the cold front.
Outlook, A strong frontal system will impact ENC Monday bringing gusty winds and periods of sub-VFR conditions in showers and thunderstorms. Thunderstorms may be strong to severe with SPC placing ENC in an enhanced risk (level 3/5) of severe thunderstorms with a moderate risk (level 4/5) across the piedmont and western coastal plain. Thunderstorms will have the capability of producing damaging wind gusts, isolated strong tornadoes and large hail.
Pred VFR conditions will return by late Monday night and continuing through mid week.
E'rly winds have begun to increase this afternoon and seas have already begin to build in response to the increasing winds as 10-20 kt E'rly breezes and 20-30kt gusts are noted across our waters, while seas have already built to 6-9ft across portions of our coastal waters. This already places much of our waters outside the northern sounds and inland rivers in SCA conditions with conditions forecast to continually deteriorate as we go through tonight and Monday as a warm front approaches from the S and lifts Nward through area waters. A strong cold front is then forecast to cross from W to E late Mon/early Tue. In response to all of this, winds are forecast to veer to a SE and then S direction tonight and strengthen through the day on Mon peaking Mon evening/night with much of the area seeing 15-25kt winds with gusts up to 30kt over smaller inland waters, and 20-30kt winds with gusts up to 35 kt across the northern coastal waters and larger sounds, with even stronger winds over the Gulf Stream waters at 30-35kt with gusts up to 40-45kt. Have kept all hazards the same with similar timing outside of the one gale watch along our northern waters. This watch was upgraded to a gale warning given the expected strong winds. Showers and tstorms, some of which could be strong to severe, will be possible from this afternoon through Mon night until drier air arrives behind Mon night's front and Tue's reinforcing front. Waterspout threat in place for cells along and near the warm front lifting forward this afternoon and evening. Supercell potential increases overnight tonight and into Mon, increasing risk of waterspouts. Any of Mon's storms with even modest vertical development could bring strong winds aloft down to the SFC. Strongest cells could also produce small hail.
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. Will continue to monitor obs and cams with the need for a Marine DFA.
Outlook: Winds become N-Nerly mid-week behind TUE's reinforcing front remaining generally 10-15G20kt 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, high surf advisory from 8 pm this evening to 2 am EDT Tuesday for ncz196-204-205. Wind advisory from 2 pm to 11 pm EDT Monday for ncz196-204-205. Marine, small craft advisory from 11 am Monday to 8 am EDT Tuesday for amz131-230-231. Gale warning from 2 pm Monday to 2 am EDT Tuesday for amz135. Small craft advisory from 2 pm Monday to 8 am EDT Tuesday for amz136-137. Small craft advisory until 2 pm EDT Monday for amz150. Gale warning from 2 pm to 11 pm EDT Monday for amz150. Small craft advisory until 6 am EDT Monday for amz152-154. Gale warning from 6 am Monday to 2 am EDT Tuesday for amz152- 154. Small craft advisory until 10 am EDT Monday for amz156-158. Gale warning from 10 am Monday to 4 am EDT Tuesday for amz156- 158.
