textproduct: NWS Wilmington

WHAT HAS CHANGED

Chances for rain have continued to go down over the next few days. Aviation discussion updated for 12Z TAF issuance.

KEY MESSAGES

1) Summerlike Bermuda high pressure will maintain southerly winds and unseasonably warm weather this week with low chances for rain.

2) The next cold front should arrive late Sunday accompanied by an increased chance of showers and t-storms.

DISCUSSION

KEY MESSAGE 1: Summerlike Bermuda high pressure will maintain southerly winds and unseasonably warm weather this week with low chances for rain.

Guidance has continued a drier trend each day this week as an offshore upper level ridge remains locked in place and is slow to break down or shift eastwards. This nudges the forecast chances for diurnal showers downward slightly by eroding what was already marginal CAPE below the subsidence inversion aloft. If we get an isolated daytime shower Thursday through Saturday, it's most likely to be inland where surface temperatures will be higher and the capping inversion aloft slightly weaker.

Forecast highs each day through Sunday are in the 80-85 range inland, with mid to upper 70s expected at the beaches. This is due to synoptic onshore flow supplemented each day by the seabreeze circulation. Both day and nighttime temperatures should run about 10 degrees above seasonal norms through Sunday.

KEY MESSAGE 2: The next cold front may arrive late Sunday accompanied by an increased chance of showers and t-storms.

Models continue to show surprising agreement with timing of the next cold front, still anticipated to reach the area Sunday night.

The persistent upper level ridge will erode along its western periphery as a shortwave moves eastward across the Great Lakes on Sunday. Mid level flow should veer southwesterly which will advect a stream of Gulf moisture across the eastern Carolinas during Sunday's afternoon and evening hours. With the capping inversion aloft gone, this is our best chance of seeing more widespread shower and thunderstorm activity across the eastern Carolinas. GFS MOS agrees with NBM guidance with 50-70 percent chances for measurable rain as this system crosses the area Sunday into Sunday night. Two week-observed rainfall has ranged from 0 to 10 percent of normal across the area (1.3 to 1.6 inches below normal) since March 17 so we would dearly like to see some rain from this system.

It's still too early to read too much into severe weather chances on Sunday. Forecast 700 mb wind speeds Sunday afternoon and evening vary from 25-45 knots between the models which implies very different values of 0-6 km bulk shear, and the timing may not be optimal should the precip arrive in the evening into overnight. We'll hopefully get a clearer picture over the next few days.

The post-frontal airmass Monday and Tuesday looks significantly cooler with highs in the 60s to around 70 diminishing rain chances.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Predominantly VFR is expected through the period. Expect another round of mid-level altocumulus across portions of the area and a low-level cumulus field to develop by midday. These clouds will fade this evening underneath a thin veil of cirrus, leaving a chance for patchy fog or low stratus late in the period, limited by the relatively stout LLJ of 20-25 kts once again.

Extended Forecast... Mainly VFR conditions are expected, although the potential exists for early morning fog/stratus Fri/Sat. Sea fog may become an issue beginning for the coastal terminals toward the end of the week and thru the weekend.

MARINE

Through Tonight... Offshore high pressure will maintain steady south to SSW winds between 5-15 kts over the waters through the period. Nearshore enhancement due to the sea breeze can be expected, along with slightly backed winds towards SSE. Seas are expected to hold primarily in the 2-3 ft range, mainly driven by a southeasterly swell with a period around 7 sec and some southerly wind chop nearshore.

Thursday through Sunday... Sub-SCA conditions continue over this time period. With Bermuda high pressure locked in place well offshore and low pressure systems off to the north and west, winds will average out of the S to SE at only 5-15 kt, with daily enhancement nearshore from the sea breeze, and increasing to 15-20 kt by late Sunday ahead of the next cold front. Seas mainly 2-4 ft, largely consisting of 8-9 second SE swell.

CLIMATE

Both January and February ran 2 to 4 degrees F below normal across eastern North and South Carolina. March has reversed that trend and heading into the last day of the month March's average temperature has run 3 to 4 degrees F above normal.

Assuming daily temperatures through the coming weekend run 8-10 degrees above normal, we should completely eliminate the remaining accumulated temperature "deficit" since January 1.

Location Current YTD Departure Forecast YTD Departure April 5 Wilmington -0.1 F +0.6 F N Myrtle Beach -0.2 F +0.3 F Florence -0.6 F +0.1 F Lumberton -0.3 F +0.3 F

ILM WATCHES/WARNINGS/ADVISORIES

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