textproduct: NWS Wilmington

SYNOPSIS

A powerful arctic cold front will blast through the Carolinas today. High pressure following the front will bring very cold temperatures Sunday night through Monday night. Temperatures will then gradually warm up Tuesday and Wednesday with another mainly dry cold frontal passage expected Thursday night.

UPDATE

Aviation and WWA update.

NEAR TERM /THROUGH MONDAY/

Big story continues to be the frigid air mass that will follow the cold front moving into the forecast area right around daybreak. The mid to late morning timing of the front will result in high temperatures occurring in the morning, making the high temp forecast very uncertain. Impressive cold advection begins within an hour or two of fropa and by noon the entire forecast area will be under the influence of strong cold advection. Temperatures will tumble through the afternoon, on their way to mid teens tonight. Strong, gusty winds develop with the arrival of the cold air, and as skies clear out gusts get an extra boost. Gusts approaching 40 mph are not out of the realm of possibility in areas where skies clear out several hours before sunset. Breezy conditions continue this evening and overnight. Near record cold coupled with winds 15-20 mph will lead to wind chill values under 10 degrees. Winds do start to ease a few hours prior to daybreak which helps keep wind chills above the magic 5 degree mark needed for an Extreme Cold Warning. Have dropped the Extreme Cold Watch and opted for a Cold Weather Advisory based on the latest forecast.

The front will be accompanied by a narrow band of scattered to widely scattered showers. Just ahead of the front there is narrow band of precipitable water in excess of 200% of normal. Frontal convergence should be enough to overcome the somewhat stable surface layer and tap into the weak elevated instability. Limited moisture above 10k ft, barely above the freezing layer, so no concern of thunder given the low topped nature of any showers that develop. Low level jet of 30-40 kt may lead to some gusty winds with stronger showers, but nothing damaging. Overall rainfall will be limited due to the narrow nature of the moisture and rapid movement of the showers, 30+ mph. Most areas will see no more than 0.10".

SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/

Modified Arctic air mass will be settling over the Carolinas into Monday. This very dry and chilly air will lead to temps struggling to reach 40 degrees. Could be near record low max aftn temps with dewpoint temps in the single digits, down close to 0 by aftn. The very dry air mass will maintain zero chance of rain through the period.

The stiff northerly winds will diminish through the day as the center of the high migrates nearly overhead. By Mon eve, the winds will back around to the SW as the center shifts offshore, but winds should die off keeping overnight lows down close to 20 degrees most places inland of coast with better radiational cooling.

Air mass will begin to modify with WAA in southerly return flow. H5 heights will rise with weak ridging in the mid to upper levels. The 850 temps will be on the rise after bottoming out around -8c early Monday morning. Temps will rebound a good 25 to 30 degrees up to near or above 50 Tues aftn.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Air mass will continue to modify in southerly return flow as high pressure shifts farther offshore. Temps will reach near or just above 60 under December sunshine on Wed. A warming trend will continue until mid to upper trough pushes a cold front through Fri. Temps will reach into the 60s on Thurs and 70s on Friday ahead of the front. As it looks right now, best chance of pcp will be ahead of the front Friday morning. Temps will drop behind the front on Sat but may remain above normal.

AVIATION /09Z SUNDAY THROUGH THURSDAY/

Short window of MVFR bordering on IFR possible from 12Z to 16Z today, perhaps as late as 17Z along the NC coast, as a strong cold front moves across the region. Showers along the front will briefly lower ceilings under 2k ft and drop visibilities to 3-5 SM. Threat of MVFR/IFR rapidly decreases by midday with VFR quick to return. Bigger story will be strong, gusty winds. Ahead of the front, low level wind shear will be a concern, especially at inland terminals where surface winds are weaker. Once the front passes winds will quickly shift to west then northwest with speeds 15-20 kt and potential for gusts around 30 kt. Gusty winds will continue in the evening decreasing after midnight with gusts dropping out between 09Z and 12Z.

Extended Outlook...Predominantly VFR through the extended period.

MARINE

Through Tonight... Gale Warning remains in effect for all of the waters. A strong cold front will move offshore early this afternoon. Brief period of strong offshore flow in the wake of the front will lead to winds 30- 35kt with higher gusts. Duration of gale force winds may end up being a little shorter than the current warning, but whenever the gale does come down a small craft advisory will be needed. Although conditions will be improving the advisory is likely to run past daybreak Mon. Seas 3-5 ft today build to 4-7 ft tonight due to the strength of the northwest flow. Seas will be a mix of dominant wind waves and background swell from the southeast. Wind wave will be southwest into the afternoon but then a northerly wind wave develops and quickly becomes the dominant wave.

Monday through Thursday...Small Craft Advisory conditions will be coming to an end mid to late Mon morning as gradient relaxes as high pressure migrates across the Southeast reaching closer overhead by late Mon. The high will shift farther offshore and out into the Atlantic leaving the area waters in a light southerly return flow through midweek until next cold front moves through on friday. Seas will be down to 3 ft or less by Mon eve and will remain that way until cold front approaches on Fri.

CLIMATE

Record Low Temps for Dec 15: KILM: 17 / 2010 KLBT: 13 / 2010 KCRE: 17 / 1944 KFLO: 13 / 2010

Record Low High Temps for Dec 15: KILM: 34 / 1958 KLBT: 37 / 1949 KCRE: 40 / 2010 KFLO: 35 / 1958

ILM WATCHES/WARNINGS/ADVISORIES

NC...Cold Weather Advisory from 10 PM this evening to 9 AM EST Monday for NCZ087-096-099-105>110. SC...Cold Weather Advisory from 10 PM this evening to 9 AM EST Monday for SCZ017-023-024-032-033-039-054>056-058-059. MARINE...Gale Warning from 4 PM this afternoon to 7 AM EST Monday for AMZ250-252-254-256.