textproduct: NWS Wilmington

WHAT HAS CHANGED

12Z Aviation discussion has been updated.

245am update...The Winter Storm Watch has been upgraded to an Ice Storm Warning for Dillon and Darlington Counties of SC. The remaining county in the Winter Storm Watch, Bladen County of NC, has also been upgraded to a Winter Weather Advisory. The main threat will be accumulating ice from the freezing rain, up to 0.25 inches within the Ice Storm Warning and 0.10 to 0.20 within the Winter Weather Advisory.

KEY MESSAGES

1) The winter storm system will provide a wintry weather threat across Southeast NC and Northeast SC this weekend, with mainly ice accumulating from freezing rain. Locations further away from the coast appear to bare the brunt of the freezing rain, with up to one quarter of an inch possible across the Ice Storm Warning areas. Closer to the coast, a trace to less than one tenth of an inch possible. Influx of milder air from off the Atlantic will help keep freezing rain limited at the coast during this event and could farther inland during Sun.

2) Expect dangerous cold temperatures both Mon night and Thurs night with temps running much below normal most of the week ahead.

DISCUSSION

KEY MESSAGE 1: The winter storm system will provide a wintry weather threat across Southeast NC and Northeast SC this weekend, with mainly ice accumulating from freezing rain. Locations further away from the coast appear to bare the brunt of the freezing rain, with up to one quarter of an inch possible across the Ice Storm Warning areas. Closer to the coast, a trace to less than one tenth of an inch possible. Influx of milder air from off the Atlantic will help keep freezing rain limited at the coast during this event and could farther inland during Sun.

Through Sun, CAD weather features will be present across the FA with Arctic high pressure ridging down the East Coast. It remains quite shallow in height given progged SkewT soundings across the FA. Initially, the Arctic air depth around 2700 ft is progged to decay to below 1400 ft later tonight inland...and to less than 700 ft at the coast. This in response to S-SW flow eating away this Arctic air mass from above. At the sfc, winds to veer from N-NNE to to NE-ENE, pushing in mild air from off the Atlantic, even with flow across SSTs around 50 pushing inland, its enough to put a damper and limit wintry pcpn especially at the coast.

Expect moisture, with origins from the Pacific and Gulf, to further overspread the sfc based Arctic air mass later today and continuing tonight into Sun. The warm nose to expand in depth later tonight thru Sun, and this will limit pcpn to possible sleet at the start, but mainly a freezing rain event later tonight into midday Sun. The pcpn will mix with and change to plain rain as this warm nose increases along with sfc temps climbing above freezing. The question resides of whether above 32 readings reach the Ice Storm warning areas during Sun. At this point, model consensus says yes, but prior to those mild temps reaching there, total ice accumulations/accretions will reach 0.25 inches. Elsewhere, likely ranging from a trace to less than 0.10 inches at the coast to 0.10-0.20 inches in between.

These above freezing temps will persist thru Sun night as a weak sfc low pushes across the Carolinas, further drawing in milder air. At this point, have indicated 40s to 50s at the coast for late day highs Sun and remaining above freezing altogether Sun night. Thus the pcpn that falls later Sun aftn thru Sun night, as the low passes by, will be plain rain.

KEY MESSAGE 2: Expect dangerous cold temperatures both Monday night and Thursday night with temps running much below normal most of the week ahead.

Once the storm system lifts away from the region Sun night into Mon, deep upper trough will maintain lowering heights through Tues with the 850 temps dropping close to -10 C. Although temps warm slightly through midweek, they will still remain below normal and another blast of arctic air will arrive Thurs as next shortwave digs down pushing cold front through. This will lead to some of the coldest temps of the season with teens for lows both Mon night and Thurs night. The winds will contribute to even colder apparent temps or wind chills. Therefore would expect a Cold Weather Advisory both Mon night and Thurs night with wind chill temps less than 15c. Temps during the day will struggle to get out of the 30s both Mon and Thurs, with other days maintaining below normal temps as well.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR conditions expected thru generally 18Z with 4k-6k ft ceilings dominating. There-after, ceilings will begin to lower as the remainder of Sat aftn progresses, possibly reaching MVFR prior to sunset. Look for ceilings continuing to lower as overrunning type clouds and eventually pcpn fill in across SE NC and NE SC, generally between 01z-08z, which will be covered with Prob30 IFR groups. With temps cold enough, have indicated freezing rain potential for ILM/FLO/LBT. Have even gone with predominate fzra for the inland terminals after midnight and thruout the pre-dawn Sun hrs. Plain ole liquid rain will dominate the coastal terminals, although as mentioned, ILM may see a period of FZRA b4 temps climb above 32 prior to daybreak Sun. Winds NNE to NE 10-15 kt g20+ kt to dominate this morning and continue into this evening b4 dropping back to around 10 kt.

Extended Forecast...The winter storm will continue impacting the area Sun thru early Mon with prolonged flight restrictions expected. The freezing rain and sleet threat will primarily occur at LBT/FLO thru midday Sun.

MARINE

Through tonight...Cold front has pushed thru with CAA and drier air at the lower levels pushing across the waters. North- northeast winds will dominate this period with speeds 20-30 kt with 35 kt gusts possible across the far outer waters off Cape Fear thru today. Seas will build to 4 to 8 ft, with 9+ footers possible across the outer waters off Cape Fear. The pinched gradient relaxes-some later tonight allowing NE winds to diminish to around 20 kt with g25+ kt. Seas will hold in the 4 to 8 ft range. Weak and small underlying SE swell will occur but dominant-wise, the short period wind driven waves win. Patchy light rain or drizzle today but the main reducing vsby pcpn occurs tonight.

Sunday through Wednesday...A Small Craft Advisory will continue through Sun although winds will diminish a bit. Seas will run 5 to 8 ft until subsiding through Mon. Winds will reach SCA thresholds once again Mon into Mon night as a surge of arctic air moves over the waters behind the front. A wave of low pressure along the coast will maintain northerly winds initially on Sunday, but once this moves north up the coast, winds will come around to the SW Sun aftn ahead of stronger area of low pressure tracking up through the western Carolinas. Once this low tracks northward into Sun night, a cold front will push eastward. S-SW winds ahead of the front will become NW into Mon once front moves through and farther offshore.

Winds and seas will drop off through Tues and into Wed as high pressure migrates across the Southeast, but will increase once again ahead of next cold front Wed night into Thurs.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Ice Storm Warning from 7 PM this evening to 1 AM EST Monday for NCZ087. Winter Weather Advisory from 7 PM this evening to 7 PM EST Sunday for NCZ096-099-105>110. SC...Ice Storm Warning from 7 PM this evening to 1 AM EST Monday for SCZ017-023-024. Winter Weather Advisory from 7 PM this evening to 7 PM EST Sunday for SCZ032-033-039-054-055-058-059. MARINE...Small Craft Advisory until 7 AM EST Tuesday for AMZ250-252-254- 256.