textproduct: NWS Wilmington

WHAT HAS CHANGED

Updated 12Z TAF discussion.

Temperatures well below normal tonight will remain above Cold Weather Advisory criteria of 15F. Confidence in a significant winter storm this weekend is increasing, but confidence in the details remains lower. Rain, freezing rain, sleet and snow are all possible outcomes with the storm.

KEY MESSAGES

1) Unseasonable cold tonight. Cold Weather Advisory not expected.

2) Potential for a significant winter storm this weekend continues to increase. A combination of rain, freezing rain and snow could make travel hazardous.

3) Well-below normal temperatures and dangerous cold possible Saturday, Sunday and Monday nights.

DISCUSSION

KEY MESSAGE 1: Unseasonable cold tonight. Cold Weather Advisory not expected.

High pressure building in will lead to calm winds and clear skies through most of tonight. This should result in low temperatures colder than Monday, and I've deviated from the NBM slightly to account for widespread cooling. Lows largely in the lower 20s with some inland spots dipping into the teens. With the lack of wind, the only areas cold enough to reach near the 15F threshold for a Cold Weather Advisory are our typically colder spots (Holly Shelter, Green Swamp, etc), and even then it's only for a couple hours before sunrise. The high will start to slip offshore towards the end of the night, moderating the airmass and bringing in some clouds, but I think these shouldn't impact our cooling as they'll come in too late.

KEY MESSAGE 2: Potential for a significant winter storm this weekend continues to increase. A combination of rain, freezing rain and snow could make travel hazardous.

Confidence in a significant winter weather event occurring this weekend is increasing, but confidence in the details remains very low.

A cold front will slowly move into the region Friday, pushed south by an arctic air mass. Meanwhile the flow aloft will be relatively flat, spreading Pacific moisture over the Southeast. Isentropic lift along the front combined with deep moisture will lead to the development of light rain Fri, likely later in the day. As the arctic air mass settles south, Fri night into Sat, temperatures in the boundary layer will drop near freezing and by Sat morning there will be at least some potential for sleet and freezing rain across the forecast area, if precipitation is still occurring. The initial surge of moisture in the low levels is along the leading edge of the arctic air. It's quite possible rain comes to an early Sat before freezing temperatures arrive. However the dry stretch would be short lived, boundary layer moisture will increase Sat as evaporation and moisture transport help saturate the arctic air mass. Once this happens rain, freezing rain, sleet and snow will all be possible depending on location within the forecast area. Mixed precipitation will continue through Sat night ending later Sun or Sun evening. The shallow nature of the cold air continues to suggest that freezing rain and/or sleet are still likely the biggest threat with potential for significant ice accumulation in some areas.

The location of the quasi-stationary front and the strength and depth of the cold air will be key factors in the forecast. An additional forecast problem will be the presence of surface waves moving along the front(which itself will be shifting north and south). The timing of these waves and their strength as they pass will play a role in precipitation type, especially for coastal counties. These waves could result in transitions from frozen to liquid precipitation for a period of time before freezing precipitation returns. Depending on the timing of the waves coastal areas could end up with limited frozen precipitation for the event. Still too early to get into specific details or discuss possible amounts (which are likely to have a wide range across the area), but the key takeaway is that significant impacts to travel are likely across the region this weekend with potential for a period of extended impacts farther inland.

KEY MESSAGE 3...Well-below normal temperatures and dangerous cold possible Saturday, Sunday and Monday nights.

The combination of low temperatures well below normal, low to mid 20s Sat night and low to mid teens Sun and Mon nights, and northerly winds will create dangerously cold conditions for the end of the week and start of next week.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

No changes, VFR. North winds in the morning will become NW in the afternoon, speeds max ~8kts. Light NE winds once the sun goes down.

Extended Forecast...VFR likely through Wednesday. Restrictions may return as early as Thursday as a front remains in the area. A winter storm may impact the area into the weekend.

MARINE

Through Tonight... North winds ~15 kts will become NW in the afternoon ~10 kts as high pressure builds in. Seas 2-3 ft.

Wednesday through Saturday... Weak high pressure overhead Wed morning shifts east with a weak, dry cold front crossing the waters early Thu. Front leads to one surface high replacing another, although the overall result is a barely noticeable change, mainly light north- northwest winds instead of northeast. Another front arrives Fri, but stalls in the region, setting up an active weekend. Very cold air will build in from the north Fri into Sat with northerly winds increasing to at least SCA thresholds and possibly higher, especially as surface waves moving along the stalled front cross the waters. Confident headlines will be needed Sat, possibly as early as late Fri night, but have less confidence in the type of headline. Seas 2-3 ft through Fri ramp up Fri night and Sat, peaking 4-8 ft late Sat. A southeast wind wave will be dominant into Fri before increasing northeast winds will lead to development of a dominant northeast wind wave Sat.

ILM WATCHES/WARNINGS/ADVISORIES

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