textproduct: Newport/Morehead City

WHAT HAS CHANGED

The Heat Advisory has been allowed to expire.

The forecast has trended somewhat drier overnight.

KEY MESSAGES

1) A more active pattern persists into midweek, with showers and storms expected each day, some of which could bring gusty winds and heavy rain.

2) Another round of dangerously high heat and humidity builds mid to late week into the weekend.

3) A very unstable atmosphere develops in tandem with the high heat and humidity mid to late in the week, and could produce a few strong to severe thunderstorms.

DISCUSSION

KEY MESSAGE 1...As of 740pm, there was an ongoing cluster of strong to severe thunderstorms impacting portions of Beaufort, Hyde, and Washington Counties. The storms appear to be hitting their peak, and should gradually weaken with time as the airmass gradually stabilizes with increasing inhibition. Meanwhile, there is another convective cluster near Raleigh that is generally tracking slowly east. The downstream airmass across our northwestern coastal plain counties is still unstable, but with increasing inhibition, we expect that convection to gradually weaken as it shifts east this evening. In light of this, it appears that we will have another night with a reduced risk of convection (like last night).

PREVIOUS DISCUSSION: At first glance today had a rather similar setup across ENC compared to yesterday as weak upper ridging extends N towards ENC keeping the area under a hot airmass. With that in mind, initial thought was substantial coverage of showers and storms along and ahead of the sea breeze this afternoon. However, this has not materialized to this point. Current thinking is slightly drier conditions above 500mb noted on the 12Z sounding today compared to yesterday, paired with less instability (2-3k instead of 4-6k) might be the reason for the lesser coverage. Still, scattered showers and tstorms are expected ahead of the sea breeze as updrafts slowly saturate the air above 500, eating way at the "cap" aloft. Of note, near Alligator River and NOBX there is enough convergence to overcome the drier air aloft, and this region is still expected to see numerous to widespread tstorms. Weak shear keeps storms more "pulse-like" with weak steering flow making the storms slow moving and back building. With all this in mind, storms will be capable of heavy rain, frequent lightning, gusty winds, and small hail. Where heavy rain rates linger, flash flooding will be a concern today.

Tomorrow a backdoor cold front/seabreeze combo will be the focus for thunderstorm activity. Guidance continues to suggest PoPs remain around the 50-80% range as the back door cold front provides some additional forcing. Instability however should be less as more cloudy skies get in the way. SPC has portions of ENC under a marginal risk (level 1/5) for severe weather as well on Wed with damaging winds (40-60 mph) being the main hazard within the strongest storms. WPC has kept much of the area under a marginal risk for excessive rainfall tomorrow as well.

Beyond mid week, PoPs return back to climo (20-40%) as more typical seabreeze showers/storms return. Hts/thicknesses slowly build in the process as ridging begins to build once again, with heat indices 100-110 in the forecast.

KEY MESSAGE 2...Not much change in forecast thinking from Thurs onwards as low level thicknesses remain around normal values which places inland temps in the mid to upper 90s across ENC. With dewpoints in the 70s there could be widespread heat indices around 100-110 each afternoon from Thurs into Sat. Probabilistic heat risk shows a 60% + chance for reaching major heat risk values with the greatest risk coming on Thurs/Fri so additional heat advisories may come into play later this week.

KEY MESSAGE 3...With the aforementioned high heat and humidity expected Thurs into this weekend, a very unstable atmosphere develops with the potential for ML CAPES to near 3500 J/KG each day, and SFC based instability between 4000-5000 J/KG. As is typical this time of year, deep layer shear will not be too strong, but any storms that can develop with some upper level support could produce strong downdraft/microburst winds and very heavy rain characterized by PW's exceeding 2". Will also be monitoring Sunday as the next potential front makes an appearance across ENC which could help to focus thunderstorm activity and bring more shear to the area.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

TSRA activity continues to primarily impact areas of ENC east of the TAF sites, and it appears that the risk of additional TSRA will remain low the remainder of the night. Therefore, TSRA have been taken out of the TAFs until tomorrow afternoon. Another round of SCT TSRA appears likely again then. In the meantime, there may be another risk of sub-VFR stratus and/or reduced VIS tonight, especially for areas that saw rainfall today.

Outlook (Wednesday night through Sunday): Beyond Wed, more typical iso to widely sct activity expected as ridging rebuilds into ENC so a much lower threat for sub-VFR conditions.

MARINE

15-25 kt SW winds this evening with 2-5 ft. Expect winds to ease close to daybreak Wed once again. Scattered showers and thunderstorms will also be possible across our waters again on Wednesday as a shortwave moves through bringing a threat for locally enhanced winds and seas.

Outlook (Wednesday through Sunday): Weakening front moves into the waters on Wed, though as is typical in July, the front appears to wash out, with any N'rly flow behind it short lived with return flow developing Wed evening. SW'rly winds look to strengthen some on Thurs/Fri as a thermal trough strengthens across the area bringing our next potential threat for SCA's to the waters.

MHX WATCHES/WARNINGS/ADVISORIES

NC...None. MARINE...None.