textproduct: NWS Wilmington

WHAT HAS CHANGED

1 AM EDT... Updated for the 06Z aviation discussion.

3 PM EDT... Rain chances have been cut to 10-30 percent after 6 AM Monday morning as drier air should punch in behind the departing front rather quickly. Otherwise no significant changes have been made to temperatures, winds, or rain chances.

KEY MESSAGES

1) Well above normal temperatures will continue through Sunday.

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...Well above normal temperatures will continue through Sunday.

An upper level ridge just off the Southeast coast will peak in strength Friday as the 5840 meter height contour punches as far west as the NC mountains. Bermuda high pressure (1032 mb at the surface near Bermuda) will pump a subtropical airmass air northwestward across the Carolinas for the remainder of this week into Sunday.

Forecast 850 mb temps near +13C are near or just below the 90th percentile according to the SPC sounding climatology for MHX and CHS. Accordingly, model guidance has remained consistent with inland highs ranging from 80-85 each day with coastal locations topping out in the mid to upper 70s due to onshore synoptic winds plus a diurnal seabreeze enhancement. This is about 10 degrees above early April normals but is well below daily records.

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

The upper level ridge will break down Sunday as a hefty shortwave moves from the Great Lakes into southern Quebec, pushing an upper trough eastward toward the Carolinas. Local 500 mb heights should fall by 70 meters between Saturday evening and Sunday evening. As the ridge breaks down, the mid level flow should veer southwesterly which should advect a narrow band of Gulf moisture across the Carolinas.

While we're still maintaining relatively high (70-80 percent) chances for showers and t-storms in the forecast Sunday afternoon through Sunday night, I'm beginning to notice that low level wind trajectories never introduce Gulf moisture to the eastern Carolinas. Hysplit back-trajectories show that boundary layer flow Sunday evening will originate from the Atlantic off the GA and N FL coastline, but not the Gulf. Model peak precipitable water values near 1.4 inches Sunday evening are a bit lower than was indicated yesterday. The expectation is most locations will see rain, but odds of a drought-busting rain do not appear substantial.

GFS, Canadian, and ECMWF are beginning to converge with their forecast 700 mb winds in the 30-40 kt range Sunday afternoon and evening. This would imply 0-6 km bulk shear values near 25 knots, sufficient for multicell organization but otherwise not terribly indicative of severe weather. SPC's latest Day 4 convective outlook has no risk outlines across the area which seems a good call given the latest models.

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

Canadian air will spread across the area Monday behind the front on Monday. Cold advection will continue through Tuesday night when models show 850 mb temps bottoming out in the +1C to -2C range, near the 10th percentile for the MHX upper air site for early April.

Highs should remain in the 60s Monday through Wednesday. Northerly winds should veer northeasterly by Wednesday as the Canadian high moves off the Mid Atlantic coast. Lighter winds with the approaching high should allow good radiational cooling to occur Tuesday and Wednesday nights. Lows in the 40s could dip into the 30s in normally colder locations across interior SE North Carolina.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

VFR expected for most of the 06Z TAF period. A stray shower is possible this morning until around 17Z for our I-95 counties, better chance in northeast SC. A moist boundary layer may produce MVFR in the vicinity of showers prior to 15Z. Showers will be light due to the poor depth of the cloud layer. Mixing will bring an end to showers by early afternoon. Southerly flow continues tonight.

Extended Forecast... Mainly VFR conditions are expected, although the potential exists for early morning fog/stratus each morning through Saturday. Sea fog may become an issue beginning for the coastal terminals toward the end of the week and up until the cold frontal passage late Sun.

MARINE

Through Friday...Bermuda High remains in place keeping winds capped at 10kt. With such light winds the shorter period waves will be minimal. The continuation of SE swell energy will keep seas in the 3- 4 ft range.

Friday night through Tuesday...Bermuda high pressure will hold firm through Saturday night with light southerly winds and an 8-second southeasterly swell expected. The high will retreat farther offshore ahead of an approaching cold front Sunday. Winds should veer southwesterly and increase to 15-20 kt. Scattered showers and thunderstorms should also overspread the area ahead of the front.

The front itself should push off the beaches late Sunday night accompanied by a shift to northerly winds which could remain in the 15-20 kt range while veering northeasterly during the day. Lighter northeast winds are expected Monday night into Tuesday as Canadian high pressure builds slowly eastward toward the Great Lakes.

ILM WATCHES/WARNINGS/ADVISORIES

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