textproduct: Raleigh

WHAT HAS CHANGED

* No significant changes; updated aviation discussion

KEY MESSAGES

As of 930 PM Tuesday...

1) An upstream complex of showers and storms will continue moving south into the southern Appalachians overnight tonight, but the most intense widespread activity looks to stay west of central NC.

2) More excessive heat is possible on Wednesday, particularly over the southern Coastal Plain, but confidence in details is still too low for a Heat Advisory at this time.

3) The heat and humidity will continue into late week, with daily afternoon chances for isolated thunderstorms.

DISCUSSION

As of 930 PM Tuesday...

KEY MESSAGE 1... An upstream complex of showers and storms will continue moving south into the southern Appalachians overnight tonight, but the most intense widespread activity looks to stay west of central NC.

The line of storms with gusty winds associated with the first MCS has largely moved south of our region and is now over northern SC and far SE NC. There is a cool, stable pool in its wake with temperatures in the 70s and plenty of CIN across central NC. Only some light to moderate stratiform rain trails the initial line, and this will also push to our south over the next few hours.

Another MCS is located over the TN Valley and southern Appalachians, with a leading bowing line of storms stretching across KY, eastern TN and far western NC. While earlier high-res guidance was mixed on the track and strength of this storm complex and whether it would impact portions of central NC later tonight, based on latest radar trends and latest runs of the HRRR, as well as the widespread stability across the area, the worst of it appears to pass to our west overnight. Still can't rule out a gusty shower and perhaps rumble of thunder over mainly the western Piedmont between about 02z and 05z.

KEY MESSAGE 2... More excessive heat is possible on Wednesday, particularly over the southern Coastal Plain, but confidence in details is still too low for a Heat Advisory at this time.

Within the complex forecast pattern, there are many failure modes for Wed in terms of dangerous heat. The lingering cloud cover from upstream MCS activity over the Mid-Atlantic will be more probable over the Carolinas on Wed and could temper highs by a few degrees and prevent reaching the thermodynamic potential through the afternoon. This factor along with the locations of outflow boundaries from convection expected later today will likely keep temp/dew point forecast confidence low until later tonight when the dusts settles.

KEY MESSAGE 3... The heat and humidity will continue into late week, with daily afternoon chances for isolated thunderstorms.

Hot and humid conditions will persist through late week, accompanied by daily chances for isolated afternoon thunderstorms. High temperatures Thursday and Friday will range from the low 90s in the northwest to the mid/upper 90s elsewhere. High dew points in the mid 70s will yield peak heat indices in the low to mid 100s.

Relief arrives over the weekend as a frontal boundary approaches Thursday and pushes through late Friday. Expect isolated to scattered showers and storms in the afternoon and evening. Highs will be in the upper 80s to low 90s, keeping heat indices predominantly below triple digits. However, southwest flow quickly returns early next week, bringing another round of temperatures in the mid/upper 90s paired with triple-digit heat indices for much of the area.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

As of 830 PM Tuesday...

An area of showers and storms with locally gusty winds (as high as 30-50 kts) and possible IFR/MVFR ceilings and visibilities has now moved south of the northern terminals (INT/GSO/RDU/RWI), leaving mainly mid/high clouds and VFR conditions in its wake. Farther south at FAY, showers and storms with gusty winds just moved through and conditions should improve, but periods of light to moderate rain will be possible until about 03-04z.

VFR and dry weather should mostly prevail overnight, but can't rule out very patchy fog/mist where the heaviest rain fell today. There is also a second area of convection currently diving south into western NC, but based on latest radar trends and the latest HRRR runs, the worst is likely to pass to the west of INT/GSO. Still can't rule out a brief shower or storm there from 03-06z.

More isolated showers and storms are possible again on Wednesday afternoon and evening, but overall coverage in the latest high-res guidance looks less than it was today, so didn't include mention in the TAFs at this time.

Outside of any storms, winds will be largely from the W/NW and less than 10 kts through the period.

Outlook: Primarily diurnally maximized showers/storms will be possible again on Thursday and especially Friday ahead of a frontal passage and northeasterly post-frontal onshore winds late Friday into Saturday. Isolated convection may still linger into the weekend. Morning mist/stratus will be possible each morning through the period, localized where the heaviest rain falls from the afternoon and evening convection.

RAH WATCHES/WARNINGS/ADVISORIES

None.