textproduct: Newport/Morehead City

SYNOPSIS

High pressure builds into Eastern NC through the weekend with dangerous heat and humidity. A wavy frontal boundary will bring scattered to numerous thunderstorms this afternoon into early next week. The front will push through the area Monday, with high pressure ridging in from the north through mid-week.

NEAR TERM /THROUGH SATURDAY/

As of 145 PM Friday...

Key Messages

- Severe thunderstorms with damaging winds and flooding possible through tonight

- Dangerous heat to impact the area through Saturday

A weak cold front is currently draped west to east across southern Virginia (as of 2pm). A very moist and unstable airmass resides along and south of the front across all of ENC this afternoon. The airmass is characterized by MLCAPE of 3000+ j/kg and PWATs of 2- 2.25". Deep layer shear is weak (10-20kt), but is relatively stronger than what we have seen the past few days.

The front is forecast to slowly drift south through tonight, aided by the glancing influence of an upper wave passing well to the north of the region. The front will provide an area of increased low-level convergence, with a local max in convergence where the front interacts with the various sea/sound/river breezes. We're currently seeing this in action across the NRN OBX where scattered strong convection is ongoing. To the west and south of that area, visible satellite shows some modest cumulus development, but sustained convection has yet to develop due to weaker convergence. With time, I expect convergence to gradually increase as the front sinks further south into the area, and this should lead to a gradual expansion in the coverage of convection later this afternoon and, especially, this evening into tonight.

Boundary-parallel storm motions, high PWATs, and a deep warm cloud layer will support very efficient rainfall processes, which favors high rainfall rates and the potential for flooding. Ensemble mean guidance suggests a widespread 1-3" of rain focused along the HWY 264 corridor. However, where training convection occurs, rainfall amounts of 3-7" are within the realm of possibility. Flash flood guidance is around 2-4" over a 6hr period, which is well within the guidance envelope for rainfall today. This, then, appears supportive of flooding and flash flooding, and the Flood Watch continues to look solid for the northern half of ENC.

Meanwhile, deterministic, machine learning, and ensemble guidance show a moderate to strong signal for water-loaded downdrafts with the tallest and most sustained cores today. Additionally, the shear/instability combination appears supportive of weakly rotating updrafts, which adds to the damaging wind potential, but also potentially brings in a low- end risk of large hail (up to quarter size).

The main question mark through tonight is how widespread the convection will be. Guidance is mixed between 1) scattered convection lasting through the night, and 2) a larger convective complex developing and impacting much of the area. The potential hazards are the same regardless, but scenario 2 would lead to a larger area at risk.

Temperature-wise, heat indices are currently 105-110 degrees for areas outside of ongoing convection, and the dangerous heat will last into the evening hours.

SHORT TERM /SATURDAY NIGHT/

As of 145 PM Friday...

The latest expectation is for a weak frontal boundary to be stalled over, or just south, of ENC around sunrise Saturday morning. This front is then forecast to lift north through the day as a mid-level shortwave approaches the area from the west. The combination of the advancing front and the shortwave should support another round of convection on Saturday. That said, if convection today and tonight is widespread, there is the potential that the airmass will be slower to recover on Saturday, which would tend to limit the coverage. The airmass on Saturday is expected to be about the same as today, so where convection does develop, there should be a subsequent risk of gusty/damaging winds and flooding.

Dangerous heat is once again expected on Saturday. However, with the front lifting north through the day, it's possible that the northern half of the area may not get quite as hot and humid as areas to the south. While there is a risk of dangerous heat areawide, the highest probability is south of HWY 70, and a Heat Advisory has been issued for the highest confidence areas. The advisory may need to be expanded if the front lifts north faster than forecast and/or if convection through tonight isn't as widespread.

LONG TERM /SUNDAY THROUGH FRIDAY/

As of 3 AM Friday...

Key Messages...

- Highest rain chances Sunday through Monday

- Potential for hazardous heat continues this weekend.

- Isolated diurnal storms possible Tuesday through Thursday

Frontal boundary lingers over NC/VA Sunday as high pressure sits to our south. Shortwaves continue to ride along the northern periphery of the high along the wavy frontal boundary bringing elevated rain/tstorm probs through Monday. Sunday ridging weakens over ENC with the SW shift of the high, bringing temps down a notch (but still flirting with heat advisory criteria). Monday a back door cold front moves through the region, increasing PoPs to above climo as additional forcing is expected to increase storm coverage. Tuesday through Thursday subsidence aloft dries up the mid and upper levels, bringing PoPs down as storm coverage along boundaries is expected to be isolated to scattered at best. Dewpoints also drop to the upper 60s, leading to a very pleasant couple of days over ENC next week.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

SHORT TERM /through 00z Sunday/... As of 740 PM Friday...

Key Messages

- Iso TSRA threat continues through tonight; renewed TSRA risk Sat afternoon

Busy evening for the airspace over eastern NC with strong thunderstorms across the Albemarle Peninsula and more iso to sct activity developing across the southern coastal plain. TSRA activity likely continues through at least 03z, but environment will remain marginally supportive for further iso shower activity although confidence is too low to include in TAFs. Outside of showers and storms, VFR conditions expected to prevail.

Typical convective forecast for Saturday, starting dry but with convection redeveloping along a stalled frontal boundary in the afternoon and posing a threat for all terminals through at least 00z. Torrential rainfall and brief but severe visibility restrictions are possible in the strongest storms.

LONG TERM /Saturday night through Wednesday/... As of 330 AM Friday...There will be a chance for showers and thunderstorms through Tuesday, bringing with it reduced vis and cigs within thunderstorms. Tstorms could also bring frequent lightning, torrential downpours, and gusty winds. There will be a fog and low stratus threat at night as well with light to calm winds and moist low levels, exacerbated by any areas that see meaningful rainfall during the daytime.

MARINE

SHORT TERM /through Saturday/... As of 230 PM Fri... Cold front is currently noted to the north near the Virginia Beach vicinity as of this update. This front is expected to continue to slowly drop S'wards this afternoon and evening eventually stalling tonight along our northern sounds and waters before lifting north as a warm front on Sat. Out ahead of this front, we already have ongoing shower and thunderstorm activity, primarily across our northern waters, but do expect continued shower and tstm activity to gradually spread S'wards through the afternoon and evening. These storms will bring a threat for strong wind gusts, frequent lightning, small hail, and an isolated waterspout or two. Shower and thunderstorm activity should gradually diminish late tonight. Otherwise, recent obs generally show winds coming from a WSW to SW'rly direction at 5-15 kts, though a few areas such as the Pamlico Sound and central waters near Diamond Shoals Buoy have slightly stronger winds closer to 10-20 kts with isolated gusts up near 25 kts at times. Do not expect to issue SCA's and any 25 kt gust will likely be infrequent in nature. As we get into tonight expect winds to become light and variable near the aforementioned frontal boundary in our northern waters with 5-15 kt SW'rly winds expected anywhere south of the front. As the front lifts north on Sat, winds across the entire area become S-SW'rly at 5-15 kts with gusts up near 20 kts. Seas along our coastal waters generally remain around 2-4 ft.

LONG TERM /Saturday night through Wednesday/... As of 2 PM Friday...As we get into the weekend ridging weakens, allowing SW`rly winds to remain at 10-15 kts on Sun. Monday morning a back door cold front moves through, bringing behind it north/northeast winds 10-20kt which continues through Tuesday. Seas 2-4 ft expected through the long term. Diurnal showers and thunderstorms will be possible through the period, with highest probs Saturday and Monday.

HYDROLOGY

As of 145 PM Friday...

Boundary-parallel storm motions, high PWATs, and a deep warm cloud layer will support very efficient rainfall processes through tonight, which favors high rainfall rates and the potential for flooding. Ensemble mean guidance suggests a widespread 1-3" of rain focused along the HWY 264 corridor. However, where training convection occurs, rainfall amounts of 3-7" are within the realm of possibility. Flash flood guidance is around 2-4" over a 6hr period, which is well within the guidance envelope for rainfall today. This, then, appears supportive of flooding and flash flooding, and the Flood Watch continues to look solid for the northern half of ENC.

An additional flood risk may develop over the weekend depending on how widespread convection is, and if it occurs over the same areas hit with the heaviest rain through tonight.

MHX WATCHES/WARNINGS/ADVISORIES

NC...Heat Advisory until 8 PM EDT this evening for NCZ029-044>047- 079>081-090>092-094-193>196-198-199-203>205. Flood Watch until 4 AM EDT Saturday for NCZ029-044>047-080-081- 203-205. Heat Advisory from 11 AM to 8 PM EDT Saturday for NCZ079- 090>092-094-193>196-198-199. MARINE...None.