textproduct: NWS Wilmington

WHAT HAS CHANGED

Forecast grids have been updated mainly for PoPs/Wx for the next 4-6 hours for current observations and radar trends with inland activity expected to decrease, and coastal showers expected to continue to periodically move onshore overnight.

KEY MESSAGES

- 1) Wet and unsettled pattern Sunday through at least mid week.

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

DISCUSSION

KEY MESSAGE 1...Wet and unsettled pattern Sunday through at least mid week.

Latest surface analysis shows an old frontal boundary that snakes through middle TN to metro Atlanta to the southern portions of the CSRA to SC Lowcountry and offshore. Aloft, an upper low is spinning over Illinois and Indiana, while ridging holds on over the Atlantic. Increased gradient flow has been noted between these two upper level features, and the coastal Carolinas are in perfect position to soak up lower level moisture from the SE to SSE. In the 300-700 mb layer, deep SW flow is ushering even more rich moisture form the Gulf. Convection is already starting to stir up along the shortwaves in the SC Pee Dee region.

Scattered showers and storms expected to continue this afternoon and evening, mostly in northeast SC. Tonight should have an overall lull in the activity, besides a few stray showers or storms trying to push into the Pee Dee region, or offshore storms attempting to scrape the coast.

Moisture continues to load into the air Sunday, creating a tropical atmosphere without the tropical system. Precipitable water (PWAT) values jump up into the 2.00-2.25" range, which is right around 125-150% of normal for this time of year. The warm front will lift northward, aiding in the initial lift for showers and storms to the area. Showers and storms are expected to become more widespread along the coast at first, translating to the inland areas by later Sunday afternoon.

Forecast guidance shows that the upper low doesn't appear quite as stagnant as it did 24 hours ago. Even so, the trough axis will amplify and dig as far south as the Gulf coast. This enhances the ribbon of moisture transport across the eastern Carolinas, allowing for healthy doses of rain to continue through at least Tuesday. The trough appears to loosen up a bit by Wednesday, although guidance is shaky on the details. Periods of rain could easily go into Wednesday if the moisture regime is maintained.

The system appears to favor coastal areas with the most rainfall amounts, potentially 1-2 inches. Inland areas look more like 0.50-0.75". Locally higher amounts are possible everywhere. Training in storms may create isolated flooding in some spots.

Widespread dewpoints in the mid-to-upper 70s will promote healthy buoyancy, leading to moderate instability each day. Isolated severe weather possible each day, particularly damaging winds.

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 /00Z SUNDAY THROUGH THURSDAY/

There are two causal factors for potential IFR/MVFR conditions over the coming 24 hours: - Convection: Scattered showers developing across the nearshore ocean will move generally N to NW overnight. There is a low potential for MVFR ceilings at KMYR and KCRE overnight, and a moderate potential for impacts at KILM. Warming temperatures on Sunday will likely reignite convection with moderate to high potential for impacts at all local airports. - Late night/early morning low stratus: With weakening winds inland and a very humid airmass in place, models agree with our suspicions that KFLO and KLBT have a moderate to high potential for MVFR/IFR ceilings developing before sunrise. Cloud ceilings may only slowly rise through the morning hours.

Extended Forecast...A slow moving upper trough settling over the region, combined with an anomalously moist airmass, will support periods of showers and storms from Sunday night through Tuesday and perhaps Wednesday. Periodic MVFR/IFR restrictions will be possible in heavier showers and thunderstorms. The moist low-level airmass will also support a greater potential for morning low 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 on Sunday as the pressure gradient tightens and the front lifts inland, resulting in a fresh to strong breeze out of the SW 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 from 6 AM EDT Sunday through Sunday evening for NCZ106-108. SC...Beach Hazards Statement from 6 AM EDT Sunday through Sunday evening for SCZ054-056. MARINE...Small Craft Advisory from noon Sunday to 8 PM EDT Monday for AMZ250-252-254-256.