textproduct: Raleigh

WHAT HAS CHANGED

* The Air Quality Alerts for ozone around the Triad and Triangle have expired, but Air Quality Alerts continue near the Virginia border in the eastern Piedmont and northern Coastal Plain for poor air quality due to wildfire smoke. * Updated aviation discussion

KEY MESSAGES

As of 150 PM Friday...

1) Air Quality Alerts remain in effect for main metropolitan areas of the Triad and Triangle as well as near the NC and VA border.

2) Heat Advisory remains in effect for the Coastal Plain, eastern Sandhills, and the urban areas around the Triangle.

3) Becoming unsettled Saturday into Monday with increased chances of severe storms Saturday, Sunday, and Wednesday.

DISCUSSION

As of 150 PM Friday...

KEY MESSAGE 1... Air Quality Alerts remain in effect for main metropolitan areas of the Triad and Triangle as well as near the NC and VA border.

In collaboration with the NC Department of Environmental Quality, the Air Quality Alert has been expanded to include the counties near the NC/VA border due to poor air quality from fine particulates (wildfire smoke). Visible satellite imagery, particularly the CIMSS Natural Color and CIRA Geocolor products, nicely show the aerial footprint where near-surface smoke is resulting in both poor air quality and surface visibility restrictions.

Alerts associated poor air quality due to ozone are expected to improve with loss of diurnal heating and isolation, but poor air quality from wildfire smoke will likely persist until around midnight. A return of southwesterly flow at the surface overnight and into Sat is expected to lift the smoke well north of our area by Sat morning.

KEY MESSAGE 2... Heat Advisory remains in effect for the Coastal Plain, eastern Sandhills, and the urban areas around the Triangle.

Dangerously hot temperatures are occurring over the advisory area with most sites currently observing heat index values of 102 to around 109. Elsewhere, values are still unseasonably hot and ranging from 96 to 103 degrees. Although not strictly reaching the heat advisory criteria, light to nearly stagnant surface winds, abundant sunshine and hot temperatures will still provide a favorable air mass for heat related illnesses to occur even outside of the advisory area.

A similarly hot and humid air mass is expected over the area on Saturday and heat advisories may be need once again, primarily around the I-95 corridor eastward to the Triangle. One glimmer of good news however is the pressure gradient over the region begins to tighten due to the low level mass response from the passing shortwave though over the Great Lakes and Northeast. This will provide for a less stagnant air mass and noticeably lower WBGT values.

KEY MESSAGE 3... Becoming unsettled Saturday into Monday with increased chances of severe storms Saturday, Sunday, and Wednesday.

A rather active weather pattern remains in place starting tomorrow and continue into next week. On Saturday, a rather strong trough over the Great Lakes will track into the Mid-Atlantic states in the evening. At the surface, there will be a cold front dropping down into the lower OH valley Saturday night. A pre-frontal trough will exist over NC and VA and aid scattered storm development across the western Piedmont in the afternoon and evening. Outflows from storms will aid eastward propagation into the Triangle and Coastal Plain in the mid to late evening hours. While shear will be present, the biggest factor driving the marginal to slight risk of severe appears tied to very high DCAPE of 1400 J/kg. This will allow for damaging wind gust potential with any strong storms.

On Sunday, the front over the lower OH valley will approach NC and provide a more focused threat of showers and thunderstorms. The trend has increased for both severe threat via AI guidance but also storm coverage. Storm coverage looks to develop in the afternoon but may persist well into the evening to early overnight hours. Much of the area is in a slight risk of severe storms, with continued high DCAPE over 1100 J/kg, but also with stronger effective shear of 25 kt. Damaging winds remain a primary threat on Sunday. Additionally, given a more favorable setup for training storms with the boundary stalling, heavy rainfall capable of flash flooding will be a secondary threat.

The unsettled weather trend continues Monday, from any lingering surface boundary. Additionally, an area of low pressure over the northeastern Gulf is favored to bring increased moisture into the SE US at this time. Regardless of its development, that moisture should increase rain chances. The NBM has also shown an increase in storm coverage related to the aforementioned forcing and possible sea- breeze.

While isolated storm coverage is possible Tuesday, coverage appears limited. But storm chances increase yet again next Wednesday. Most guidance from deterministic and ensemble data show a strong cold front advancing in Wednesday night. The trough looks fairly strong for late July, with effective shear of 25-35 kt. Right now, SPC has us outlooked for a 15-percent slight risk and this seems warranted given the pattern. All in all, an active stretch for central NC.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

As of 830 PM Friday...

Surface observations indicate any sub-VFR visibilities due to wildfire smoke are not reaching further south than the NC/VA border, and VFR conditions are expected to prevail across central NC through Saturday morning. A brief and isolated shower can't be ruled out for a couple more hours, but any convection should quickly diminish with loss of daytime heating. Isolated to scattered showers and storms are expected to develop on Saturday afternoon and evening. The best chance is across the north and west (including INT, GSO and RDU), but it can't be totally ruled out at any of the TAF sites. Strong gusty winds and sub-VFR conditions will be possible with any storms. Even outside of any precipitation, SW winds will increase in the afternoon, gusting to 15-20 kts at times.

Outlook: An approaching cold front on Sunday and Monday may result in a more active weather pattern to support sub-VFR conditions from stratus/mist overnight and scattered to locally numerous showers/storms in the aft/eve. After a relative minimum in storm chances on Tuesday, chances increase once again on Wednesday as a strong cold front looks to move through.

CLIMATE

Record temperatures within 3F of forecast ones...

Record Highs: July 18: KGSO: 97/1986

Record High Mins: July 18: KGSO: 76/1986 KFAY: 77/2025 July 19: KGSO: 75/2016 KFAY: 77/2023

RAH WATCHES/WARNINGS/ADVISORIES

Air Quality Alert until midnight EDT tonight for NCZ007>011.