textproduct: NWS Wilmington

WHAT HAS CHANGED

No major changes with this update. 18Z TAF discussion updated below.

KEY MESSAGES

1) Temperatures well below normal through at least the next seven days will result in periods of dangerously low wind chill temperatures.

2) Developing low pressure off the Southeast coast this weekend will likely bring snow and hazardous travel conditions to the area.

DISCUSSION

KEY MESSAGE 1: Temperatures well below normal through at least the next seven days will result in periods of dangerously low wind chill temperatures.

A series of arctic air masses moving over the Southeast over the next several days will keep temperatures 10-20 degrees below normal. A Cold Weather Advisory may be needed for a portion of the area Fri night. Extreme Cold Warnings are likely this weekend, especially Saturday night, for wind chill values as low as around zero degrees.

KEY MESSAGE 2: Developing low pressure off the Southeast coast this weekend will likely bring snow and hazardous travel conditions to the area.

Confidence in the presence of a system off the Southeast coast this weekend continues to slowly increase, but the finer details remain in question so there's no large changes with this forecast update. Very cold air will be in place, with temperatures 10-20 degrees below normal. A southern stream shortwave helps develop a surface low along the Gulf coast late this week, which then moves across northern Florida before heading northeast off the coast. Meanwhile a 5h trough dropping south from the Great Lakes will interact with the offshore low. The timing of the interaction and the location of these 2 features at that time will determine if the local area gets precipitation (mainly in the form of snow given thermal profiles) and how much falls. There are several key differences in the way the 5h trough is being handled by the guidance. It's speed, tilt, strength will all be factors in determining where the snow falls and where the accumulation gradients set up.

This is likely to be a system where snow totals could range several inches across county. So needless to say, confidence with respect to the finer points of the forecast remains quite low given the event is still several days out. Do have high confidence in snow vs sleet/freezing rain, where precipitation falls, and do have high confidence in the presence of the surface and 5h lows. This will allow for rapid strengthening of the low offshore, with the general consensus suggesting this will happen north of the area. Dry air wrapping around the 5h low is another source of forecast uncertainty. If the dry slot is stronger and faster than the guidance is depicting, total QPF could end up lower. Considering all the sources of uncertainty and looking at the ensemble data and the probabilistic data sets of the NBM can make a few educated guesses. Best chance for any snow would be Sat into Sat night. Likely total QPF is on the order of 0.20"-0.50", however if everything lines up perfect QPF could be 2 or 3 times higher. Winter weather headlines will likely be issued at some point per coordination with surrounding offices.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

VFR conditions are expected through the period.

Extended Forecast...Some flight restrictions are expected to develop with a storm system this weekend.

MARINE

Through Thursday... Winds will maintain a northerly component through the period. Speeds currently in the 10-15 knot range will increase a bit overnight and become a little gusty. While the gusts may reach 25 knots only isolated observations are expected to reach this threshold and a headline is not warranted. Significant seas will be 2-4 feet.

Thursday Night through Monday... Sub-SCA conditions continue early this period with sfc high pressure off to the north. Sfc low pressure then develops offshore Friday night, leading to increasing winds and seas through the weekend. At least gales, and possibly storm warning criteria, are a good bet starting Sat night in the N to NW flow on the back side of the low with it strengthening considerably as it slides off to the NE. Meanwhile, wind waves will rise to 7-9 ft out 20nm. May take until Monday for lingering SCA conditions to subside as the low pushes farther offshore.

ILM WATCHES/WARNINGS/ADVISORIES

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