textproduct: NWS Wilmington

WHAT HAS CHANGED

Slightly faster frontal passage Sunday, otherwise no significant changes from the previous forecast with this update. Aviation discussion updated for 06Z TAFs.

KEY MESSAGES

1) Record warm temperatures and persistently dry weather may create fire weather hazards through Saturday.

2) A strong cold front, accompanied by scattered showers, and possibly a few thunderstorms, is expected to move west to east across the area during Sunday morning, before shifting off the coast by early afternoon. A period of below normal temperatures is expected Sunday night through Tuesday night.

DISCUSSION

KEY MESSAGE 1...Record warm temperatures and persistently dry weather may create fire weather hazards through Saturday.

A modest shortwave currently extending from New York State southward into North Carolina will move off the coast later today, helping nudge a subtle cold front down to the coast by mid morning. There will be little if any discernible airmass change with this feature and inland highs should once again rise toward 90 degrees, only slightly below daily records at Florence and Lumberton.

The light north to northwest wind behind the front should delay in the inland progress of the seabreeze this afternoon. This reduction in cooler marine influence will give Wilmington a chance to run toward at least tying a record high today.

Record highs today and Saturday: .............Fri Apr 17...Sat Apr 18 Wilmington......89 in 2006...93 in 1976 Lumberton.......91 in 2006...91 in 1941 Florence........93 in 2006...93 in 1981 N Myrtle Beach..87 in 1995...89 in 1967

Another factor to watch closely will be dry air brought down from aloft via deep daytime mixing expected to reach 8000-9000 feet AGL. Dewpoints inland from the seabreeze will fall into the 50s this afternoon, with some models showing some 40s possible along the I-95 corridor. This will drop minimum relative humidity down to near 25 percent during the mid afternoon hours. Fire weather concerns today may be alleviated in part by light wind speeds.

Behind the departing shortwave, the upper level ridge will build overhead tomorrow with 500 mb heights rising by about 20 meters versus today. With 850 mb temps anticipated to rise to +17C Saturday, highs inland should reach the lower 90s - again threatening records at Florence and Lumberton. Slightly stronger wind speeds on Saturday along with still-low humidity could enhance adverse fire weather conditions.

KEY MESSAGE 2...A strong cold front, accompanied by scattered showers, and possibly a few thunderstorms, is expected to move west to east across the area during Sunday morning and early afternoon, before shifting off the coast by mid afternoon. A period of below normal temperatures is expected Sunday night through Tuesday night.

H5 trough moving across the Eastern U.S. on Sunday will drive a cold front across the forecast area, and offshore during early Sunday afternoon. Basin average QPF remains limited given the limited return flow prior to the front's arrival and quick progression. However, NBM probabilities for >0.01" have increased some recently, especially across southeast NC zones. Either way, any rainfall with this system will not provide any drought relief especially with deep drying expected by 21Z Sunday-00Z Monday. Based on Thursday's updated drought monitor most of the forecast area is highlighted in a severe drought, along with portions of Marlboro County in an extreme drought. Also, can't rule out an isolated thunderstorm or two given a brief ribbon of instability just ahead/along the front as it moves across the forecast area.

Otherwise, the air-mass in the wake of Sunday's frontal passage will result in cooler conditions with below normal temperatures Sunday night through Tuesday night. The sheltered/cold spots could drop down into the upper 30s late Monday night into Tuesday morning given optimal radiational cooling. Temperatures will rebound back above normal Wednesday into the end of the upcoming week.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

We have high confidence VFR conditions will continue over the coming 24 hours. A weak cold front will reach the coast between 12-14z, but will largely dissipate as afternoon's seabreeze forms. Aside from southerly seabreeze winds which could reach 12-14 knots at KCRE and KMYR after 18-19z, light wind speeds are expected today.

Extended Forecast...Isolated showers and thunderstorms may accompany a cold frontal passage on Sunday. Northerly winds behind the front could gust to 25 knots Sunday afternoon into Sunday night. Otherwise VFR conditions should prevail through Tuesday.

MARINE

Through tonight...Bermuda high pressure centered well offshore will help maintain light to moderate southwest winds across the Carolina coastal and offshore waters. A very weak cold front will make it down to the beaches between 8-10 AM this morning, but the seabreeze circulation developing by noon should overwhelm any brief period of offshore winds. Nearshore winds should turn firmly southerly by early afternoon with speeds 10-15 knots.

Yesterday's strong seabreeze will keep seas near 4 feet early this morning. A 2 foot 9 second east-southeasterly swell will combine with local wind chop for seas this afternoon mainly in the 3 foot range, subsiding to only 2 feet inside 20 miles from shore tonight.

Saturday through Tuesday...A weak SWly pressure gradient will prevail Saturday with seas around 2 ft across the coastal waters and around 3 ft offshore. The pressure gradient will increase Saturday night into Sunday ahead of a cold front. The front is expected to move off the coast early afternoon, and across the offshore waters by mid afternoon. Cold air advection across relatively warmer SSTs will allow winds in the wake of the cold front to increase. Gusty N to NEly winds will continue across the coastal waters through Sunday evening with Small Craft conditions possible for a short timeframe. Winds farther offshore will remain higher through a good part of Sunday night. The N-NEly fetch will likely lead to steeper waves near/along the Gulf Stream.

Marine conditions will improve during Monday, though a minor surge could bump things up a notch Monday night before improving again during Tuesday as surface high pressure moves overhead.

ILM WATCHES/WARNINGS/ADVISORIES

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