textproduct: NWS Wilmington

WHAT HAS CHANGED

Forecast rainfall amounts have increased slightly Sunday into Sunday evening. Otherwise, no significant changes have been made to the forecast over the next seven days.

KEY MESSAGES

1) Unseasonable Warmth Continues Through the Weekend.

2) Chances for showers and thunderstorms will peak Sunday into Sunday night ahead of a cold front.

3) Much cooler weather is expected behind the front Monday through Tuesday next week.

DISCUSSION

KEY MESSAGE 1...Unseasonable Warmth Continues Through the Weekend.

Offshore high pressure will continue to pump in warmer than normal temperatures through the weekend. High temps will generally be in the low to mid 80s away from the cooler coastal areas with lows generally around 60 tonight and low to mid 60s Sat night.

KEY MESSAGE 2...Chances for showers and thunderstorms will peak Sunday into Sunday night ahead of a cold front.

Models have been extraordinarily consistent over the past five days with their timing of the cold front reaching the eastern Carolinas Sunday night. Latest GFS/ECMWF blends suggest the front will move across I-95 prior to midnight, then reach the beaches between midnight and 3 AM.

An upper level shortwave moving across IL/IN during the day Sunday should reach the central Appalachians Sunday Night. This will break down the persistent upper ridge along the East Coast and will briefly turn our mid level flow southwesterly, advecting in a ribbon of deep moisture off the Gulf. Today's models have actually reversed the drying trend we saw yesterday and now show precipitable water values climbing above 1.6 inches Sunday afternoon and evening, perhaps feeding into a little better rainfall potential too.

Daytime heating ahead of the front Sunday afternoon should help develop clusters of showers and thunderstorms which may persist up until the front's arrival Sunday night. Helicity values do not look impressive and 0-6 km bulk shear only increases to around 25 kt. There should be enough instability plus shear to organize multicells, but doesn't argue for organized severe weather with jet dynamics likely remaining displaced to the north. Our best case scenario is that waves of showers and storms can help verify storm- total rainfall predictions of 0.25 to 0.50 inches across the area. That's not enough to really alleviate drought across the Carolinas, but it may slow further degradation next week.

KEY MESSAGE 3...Much cooler weather is expected behind the front Monday through Tuesday next week.

After what might be six consecutive days of above-normal temps, a new airmass arrives behind the front Monday. Monday's highs may have trouble reaching 70 degrees for parts of the eastern Carolinas Monday into Tuesday as Canadian high pressure pushes in from the north.

A shortwave zipping rapidly eastward through New England Tuesday should push a reinforcing cold front southward through the Carolinas Tuesday night. Confluent upper level flow behind the departing shortwave will reinvigorate the Canadian high to our north Wednesday when both the Canadian and GFS show a 1040 mb surface pressure at its center. A renewed push of cold air moving down the East Coast may keep our Wednesday highs in the mid 60s, about 6-10 degrees below normal for the 2nd week of April.

Low temps Mon, Tue, and Wed nights will likely end up in the 40s. Some normally colder spots across interior SE North Carolina should dip into the 30s. For what it's worth NBM probabilistic data for 36 degree low temps (frost?) shows a 10-15 percent potential in Burgaw, NC both Monday and Tuesday nights next week.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Moderate to high confidence through the 18Z TAF period. Mostly VFR conditions are expected across SE NC and NE SC, although a low to moderate risk for restrictions due to low clouds/showers/possible thunderstorms is expected today at the inland terminals (KLBT/KFLO). There is also a low to moderate risk for restrictions late tonight/early Saturday due to low clouds/fog, mainly inland at KLBT/KFLO.

Extended Forecast...Mainly VFR conditions are expected Sat aftn thru early Sun and again late Sun night thru Tue. A moderate to high risk for restrictions comes late Sun into Sun night as a cold front moves through with showers/storms.

MARINE

Through Saturday...High confidence with no significant marine issues expected with a more summer-like pattern in place with high pressure centered offshore. Southerly winds mostly 10 kt or less and seas up to 4 ft are anticipated. Model guidance continues to suggest a risk for sea fog but think chances will stay pretty low as dewpoints aren't too much greater than water temps.

Saturday night through Wednesday...The light south to southeast winds we've enjoyed for the past several days will be replaced by strengthening southwest winds on Sunday as a cold front approaches from the west. Increasing Gulf moisture should fuel clusters of showers and thunderstorms across the area Sunday afternoon into Sunday night, ending when the front finally moves offshore after midnight. At this time it appears we may stay below Small Craft Advisory thresholds as pre-frontal winds top out in the 15-20 kt range with seas building to 4-5 feet.

Behind the front Monday morning there will be a period of breezy northeast winds that could reach 20-25 kt at times, particularly for the waters east of Cape Fear and east of Winyah Bay. There should be a short window for such winds as Canadian high pressure building toward the area Monday afternoon leads to winds falling to 10-15 kt then.

Light northeast winds will begin to increase late Tuesday as a secondary surge of cool Canadian air works its way south into the Carolinas. Wind speeds may increase substantially Tuesday night with odds increasing we'll get to Small Craft Advisory thresholds (25+ kt winds and 6+ foot seas) before daybreak Wednesday.

ILM WATCHES/WARNINGS/ADVISORIES

NC...None. SC...None. MARINE...None.