textproduct: NWS Wilmington

WHAT HAS CHANGED

Aviation discussion updated below for 12z TAFs.

KEY MESSAGES

1) Unsettled weather pattern underway with periods of widespread showers and storms through mid week

2) Strong southerly winds and hazardous marine conditions expected to develop Sunday into Monday.

DISCUSSION

KEY MESSAGE 1...Unsettled weather pattern underway with periods of widespread showers and storms through mid week.

A potent shortwave trough/compact upper low over the Ohio Valley will split into two distinct features over the next 24-36 hours. The northern stream portion will progress northeastward, re-amplifying into a closed over the NE US and into SE SE Canada early this week. Meanwhile, the southern stream cutoff low will linger over the SE US/southern Appalachians through midweek before gradually weakening and lifting northeast Wednesday into Thursday.

At the surface, a warm front will continue to lift north through early today, placing the forecast area firmly with a warm tropical airmass ahead of a slow moving cold front that will approach from the west through midweek.

Persistent deep southwesterly moisture transport between the western Atlantic subtropical ridge and the cut-off low and associated trough to our west will maintain an axis of anomalously moist air across the eastern Carolinas. PWATs of 2.0-2.50"(125-150% of normal) will support periods of widespread showers and storms through mid week, heavy at times.

Convection has diminished in coverage with isolated to widely scattered showers expected through the early morning hours as the warm front lifts farther north of the area. However, widespread showers and storms are expected to re-develop as moderate buoyancy combines with embedded shortwave impulses and seabreeze convergence. This pattern changes little through Tuesday night and possibly Wednesday, with repeated rounds of showers and storms expected each afternoon and evening as the cut-off low meanders nearby. By Thursday, as the upper trough weakens and lifts away, convective rain chances should transition to a more typical diurnally driven summertime pattern.

Repeated rounds of storms tracking over the same location could produce isolated totals well in excess of the 1-2" areal average expected over the next few days and could result in localized flooding. This scenario occurred this past evening near Kingstree in Williamsburg County, where an isolated 6-7" or rainfall fell. The Local Probability Matched Means(LPMM)from the 00z/02 HREF highlights the potential for some isolated pockets of 3"+ across western/inland portions of the forecast area Sunday afternoon, with the corridor of heavy rain potentially shifting closer to the coast late tonight and into Monday.

Additionally, despite widespread cloud cover and generally weak lapse rates, highs in the 80s combined with dew points in the mid to upper 70s should support moderate instability, allowing for an isolated severe threat each day, with wet microbursts being the primary threat.

The widespread cloud cover and frequent rounds of showers and storms should keep daytime highs below early August climatology, with highs generally 85 to 90 through Wednesday. As the upper trough weakens and rain chances decrease, intervals of sunshine should allow temperatures to rebound into the lower 90s late week.

KEY MESSAGE 2...Strong southerly winds and hazardous marine conditions expected to develop Sunday into Monday.

Small Craft Advisory in effect. See the Marine section below for more details.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Increasing low-level moisture will maintain areas of low stratus this morning with mainly MVFR ceilings up through 13-14z. Tempered daytime heating will result in gradual lifting of any MVFR ceilings through the late morning and afternoon. However, showers and storms are expected to re-develop by early this afternoon as moderate buoyancy combines with embedded shortwave impulses and seabreeze convergence. Intermittent showers and storms are expected to continue into tonight with intermittent ceilings expected.

Light S-SE winds early this morning will increase to 12 to 17 kts by late morning into the afternoon, gusting to 20 to 25 kts, especially at the coastal terminals.

Extended Forecast... A slow moving upper trough settling over the region, combined with an anomalously moist airmass, will support periods of showers and storms through at least midweek. Periodic sub-VFR restrictions will be possible in heavier showers and thunderstorms. The moist low-level airmass will also support a greater potential for morning stratus each day.

MARINE

Through Thursday...Moderate breeze out of the SE veer to the S tonight, as a warm front lifts back to the coast. Seas start to increase modestly at first, going from 2-3 ft to 3-5 ft. Winds increase considerably Sunday as the pressure gradient tightens and the front lifts north of the area, resulting in a fresh to strong breeze out of the S to SSW. Small Craft Advisory goes into effect at noon EDT Sunday for the coastal waters from Surf City, NC to South Santee River, SC out 20 nm, expiring at 8 PM EDT Monday. In response to these gradient winds, seas rapidly increase to 4-7 ft out 20 nm, up to 7-8 out 60 nm, before improving gradually towards 3-4 ft Monday night and Tuesday. Winds back slightly to the S Tuesday, improving to a moderate breeze, and then towards a gentle breeze by Thursday. Seas continue to improve to 2-3 ft.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Beach Hazards Statement through this evening for NCZ106-108. SC...Beach Hazards Statement through this evening for SCZ054-056. MARINE...Small Craft Advisory from noon today to 8 PM EDT Monday for AMZ250-252-254-256.