textproduct: NWS Wilmington

SYNOPSIS

Mild conditions today and tonight ahead of an arctic cold front Sunday morning. Ahead of the front light showers will move across the region. Unseasonably cold temperatures arrive Sunday night and linger through Monday night. Temperatures will gradually warm up next week as high pressure moves overhead.

NEAR TERM /THROUGH TONIGHT/

Sill remaining under the longwave upper troff this period. Sfc high overhead this morning, will slide off the Carolina Coasts later this morning. This will leave a rather weak sfc pg across Southeast NC and Northeast SC, under mainly clear skies. The upper trof to amplify later today thru tonight, forcing the nearly 1050 mb arctic high S and SE ward. By the end of this period, later tonight, the Arctic high will be on the doorsteps of the FA along with the Arctic front. Increasing moisture, mainly during the pre-dawn Sun hrs, will result in clouds increasing and the threat for pcpn mainly far NW portions of the ILM CWA. Look for increasing temps this period that should actually run slightly above normal for this time of the year. Normal is generally in the mid to upper 50s for maxes and lows in the mid to upper 30s.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Main concern for the short term will be the unseasonably cold air, the coldest of this young season in fact. Strong cold front on the doorstep Sun morning which surges across the area and offshore by midday. Ahead of the front a narrow, but deep, stream of moisture will push precipitable water over 200% of normal. Low level convergence and limited dynamical forcing as weak low moves along the front should lead to a swath of showers moving across the forecast area during the morning. Widely scattered showers will likely be ongoing across the western half of the area at daybreak Sun. Strong cold advection will lead to temperatures falling through the day, even as skies clear out behind the front.

Highs will occur in the morning, making the high temp forecast tricky. Most areas will end up within sight of normal, but Sun morning is the last time temperatures will be within shouting distance of normal until the middle of next week, maybe. 850mb temperatures drop from 6 to 8C Sun morning to -6 to -10C just 12 hours later. Winds will be gusty Sun afternoon as the cold air announces its arrival, leading to a very raw day. Lows Sun night will approach records with mid teens across the area. However, the bigger concern will be the wind chill. Values will drop under 10 degrees in some areas. Cold advection ends by Mon morning, with even a hint of some warm advection later in the day. Not that it will do much against the dense cold air. Highs Mon end up right around 40, or just below it. Lows Mon night in the low to mid 20s with much less wind making it feel almost 20 degrees warmer than the night before.

As moist as the pre-frontal air is, the post front air mass will be extremely dry. Precipitable water drops to 10% of normal by Sun evening, under 0.10". Slight uptick in moisture for Mon with pwat around 0.20". The lack of moisture will keep skies clear through Mon night once clouds clear out in the post front regime. Afternoon humidity will drop to near 20% Mon afternoon and wouldn't be shocked to see values dip into the teens.

LONG TERM /TUESDAY THROUGH FRIDAY/

Arctic high from the beginning of the week will be overhead Tue morning. Temperatures will climb close to 30 degrees by afternoon, although highs will still fall several degrees short of normal. Weak warm advection continues through Thu with highs back near normal Wed and above normal Thu. Although low level moisture makes a quick return, dry air aloft hangs around through Wed night. Another cold front approaches from the northwest later Thu, bringing with it some scattered showers. The front end the week is the polar opposite of the one that starts the week. The incoming air mass has its origins in the Pacific Maritimes, not Arctic Canada. Much less cold air and little to no dry air. Temperatures will drop a bit Fri and Fri night, but the region will still be at or just above normal.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR conditions to prevail thru atleast 06Z Sun with the prevailing 6 hrs there-after to 12Z under the umbrella of potential MVFR conditions from ceilings/vsby associated with light rain ahead of an approaching Arctic front. Otherwise, looking at occasional thin/opaque cirrus during Sat aftn and evening, followed by ceilings slowly dropping thru the pre-dawn Sun hrs. Sfc high to push off the Carolina coasts today allowing winds to become SSW-SW around 6 kt thru this evening, then increasing to near 10 kt at all terminals during the 06Z-12Z time-line.

Extended Outlook...Low level wind shear remains possible late tonight. Surface wind gusts over 30 knots are possible Sunday afternoon and Sunday night in the wake of a strong arctic cold frontal passage. Otherwise VFR conditions should continue through the extended period.

MARINE

Through Tonight... Expect Light and variable (will identify a best direction in lieu of going variable) winds during the pre- dawn hrs into daylight Sat. The sfc high will slide off the Carolina Coasts later today, resulting in winds becoming SW 5 to 10 kt. As the Arctic front approaches the waters from the NW, look for SW winds to increase to possibly SCA levels late tonight. Seas will follow suit, at their lowest at the start of this period, building as sfc winds increase. Majority of the seas will result from short period wind waves. An underlying but small SE ground swell to remain present and accounted for.

Sunday through Wednesday... Strong cold front moves across the waters around midday Sun with offshore flow ramping up late Sun and Sun night as cold air surges into the region. Borderline SCA/Gale event, holding off for now on issuance of any headlines given the uncertainty/low confidence. Do have high confidence of almost 24 hours of nasty marine conditions, late Sun through midday Mon. However, once speeds drop under 10 kt Mon evening winds will remain 10 kt or less through Wed. Seas are quick to ramp up to 4-7 ft late Sun into Mon, but then rapidly fall later Mon, ending up 2-3 ft Mon night. A northerly wind wave will be the dominant wave Sun night and Mon. Seas 2 ft or less Tue and Wed with a weak southeast swell being dominant.

ILM WATCHES/WARNINGS/ADVISORIES

NC...Extreme Cold Watch from Sunday evening through Monday morning for NCZ087-096-099-105>110. SC...Extreme Cold Watch from Sunday evening through Monday morning for SCZ017-023-024-032-033-039-054>056-058-059. MARINE...None.