textproduct: Raleigh

WHAT HAS CHANGED

* Areas of fog developed early this morning in the southern Coastal Plain. * Precipitation chances and amounts are increasing for Friday.

KEY MESSAGES

As of 305 AM Tuesday...

1) This morning will be the coolest morning of this stretch with one last day of dry weather and less humid conditions before humid weather returns later this week.

2) Diurnally maximized convection returns to central NC as early as Wednesday, but more likely Thursday into Saturday before shifting towards the coast through the weekend.

DISCUSSION

As of 305 AM Tuesday...

KEY MESSAGE 1... This morning will be the coolest morning of this stretch with one last day of dry weather and less humid conditions before humid weather returns later this week.

The morning surface analysis shows a surface trough moving across Central NC early this morning with a modest surge of drier air and lower dewpoints moving into the area from the northwest. In fact, morning low level thickness values this morning at 12Z will be about 10m cooler than yesterday. Lingering low level moisture confined to the southern Coastal Plain, where dew points are still in the lower 70s, has supported the development of fog, mainly across Sampson, Wayne and Edgecombe Counties. This fog should be eroded from the west by the arrival of drier air early this morning and if still present, it should be burned off after sunrise.

Mainly clear skies are expect today and tonight although there may be a few wisps of high cirrus clouds and possibly a few clouds fair weather clouds. No convection is expected. Highs today should range in the mid to upper 80s which is near if not a degree or two above average. Lows tonight will range in the 60s. Winds will be light although a brief gust or two is possible after daybreak through mid morning as the surface inversion breaks and the shallow low level jet mixes to the surface.

KEY MESSAGE 2... Diurnally maximized convection returns to central NC as early as Wednesday, but more likely Thursday into Saturday before shifting towards the coast through the weekend.

A broad mid/upper lvl trough will persist over the northeastern CONUS on Wed before gradually sharpening Wed night into Thurs as a pair of shortwave troughs carousel across the Upper Great Lakes and southern Ontario through Thurs night. At the surface, weak high pressure, progged to be located over the northern Mid-Atlantic Wed morning, is expected to shift offshore by Wed afternoon and return initially easterly, then southerly flow to the Carolinas Wed. Initially, moisture return will be quite shallow with 70s dew points in the morning mixing out into the 60s through the afternoon, especially over the eastern Piedmont. Isolated to scattered afternoon showers remain possible Wed, but likely organized around the inland spreading seabreeze and the NC mountains, where southerly flow and terrain circulations could provide surface forcing within weakly unstable air mass.

Wed night into Fri: Continued sharpening of the slow-moving trough axis to our west is expected with deep layer moisture returning to near-normal values, but increasingly perturbed from upstream convection. This will favor increasing cloud cover and showers/storms possible along the track of any disturbance. Destabilization will be a tricky forecast challenge and will likely impact the coverage and intensity of showers/storms each day. However, a favorable pattern for repeated rounds of heavy rain appears possible in this window with the slow-moving and sharpening trough to the east, persistent southwesterly moisture advection, and saturated and perturbed lower/mid tropospheric flow. As a result, excessive rain remains possible Thurs and perhaps more probable on Fri as low-lvl convergence from an approaching front and enhanced and stationary moisture transport persists over the Coastal Plain of the Carolinas.

AVIATION /11Z TUESDAY THROUGH SATURDAY/

As of 620 AM Tuesday...

VFR conditions and fair weather are expected to dominate the weather across central NC over the next 24 hours.

High pressure over the OH Valley continues to extend into central NC early this morning. A reinforcing shot of drier air spread across central NC overnight with dew points dropping into the 50s across much of the area. Areas of fog that developed earlier in the overnight across the southern Coastal Plain have dissipated as drier air moved into the region. At 10Z there were no observations of visibilities less than 7 miles.

Mainly clear skies are expected through the 24-hour TAF period with just a few wisps of high cirrus clouds and possibly a few clouds at 5 to 8kft, mainly tonight. Light north winds are expected today at 4 to to 8kts although a brief hour or two of gusty winds are possible after daybreak through mid morning as the nocturnal inversion mixes out. Winds will decrease this afternoon and light to calm winds are expected tonight.

Outlook: Low and mid level moisture will begin to increase on Wednesday and continue into the weekend as a southerly flow develops across the region. This will support an increase in the chances of mainly afternoon and evening showers and storms that will be the greatest on Thursday and Friday. In addition, the risk of more widespread late night and morning fog and stratus will return on Wednesday and especially Thursday morning.

RAH WATCHES/WARNINGS/ADVISORIES

None.