textproduct: NWS Wilmington

WHAT HAS CHANGED

Snowfall totals decreased slightly over portions inland NC southward to the SC state line due to a potential dry slot while areas of South Carolina have seen a slight increase as the main shield of precipitation swings southeastward this afternoon and tonight. Confidence is a little less near coastal NC where some afternoon onshore-moving bands may compensate for any the central NC dry slot. Banding near the coast tonight will increase the potential for locally higher amounts.

Wind gusts have increased for later today and tonight. Wind chills were adjusted due to the stronger winds, but headlines remain unchanged. A Cold Weather Advisory remains in effect for parts of the CWA through this evening. An Extreme Cold Warning is then in effect for the entire CWA tonight into Sunday morning. Another may be needed Sunday night and Monday morning. The Winter Storm Warning remains in effect for the entire CWA.

KEY MESSAGES

1) A significant winter weather event will begin to impact the area today through Sunday morning. Expect impacts to travel and infrastructure, ranging from hazardous to dangerous conditions and closures.

2) A very cold air mass paired with snowfall will result in dangerous cold and record low temperatures this weekend. Wind chill temperatures below 15-20 degrees will linger through at least Monday night/Tuesday morning.

3) Dangerous marine conditions this weekend with a Gale Warning in effect.

DISCUSSION

KEY MESSAGE 1) A significant winter weather event will begin to impact the area today through Sunday morning. Expect impacts to travel and infrastructure, ranging from hazardous to dangerous conditions and closures.

Satellite and radar show a developing coastal low offshore. A vorticity maximum moving southeastward out of the mid- Mississippi River Valley will amplify this surface low later today and tonight. Deep arctic air in place over the Carolinas will produce light snow this afternoon, increasing in intensity as the low strengthens offshore and the deeper lift approaches the coast tonight. Snowfall accumulations of 5 to 8 inches are expected with locally higher amounts up to 10 inches possible in the Pee Dee and eastern NC.

The latest hi-res model suite continues to indicate that a dry slot will develop between the isentropic lift inland and convergent lift near the developing low in the vicinity of the Outer Banks later today. Pinpointing exactly where this dry slot develops has been a difficult task thus far and the location of this drier air is unlikely to resolve itself before these features can be identified on area radars. Generally, the potential presentation of the dry slot in our area looks to be bounded by I-40 to the east and US-501 to the west. However, slight wobbles in either direction will be similar to shifting trends in where thunderstorms develop during a summer afternoon; advanced prediction will be very difficult and snow totals will vary in some areas at the expense of stronger bands elsewhere.

It's worth noting that none of the hi-res guidance has initialized well and these features (as expected) are less prevalent in the global ensembles. For this reason, we have favored a mix of HREF and NBM in regards to QPF which depicts a little more uniformity and forecast consistency across the region.

Snowfall amounts remain generally similar to the previous forecast, around 5 to 8 inches across the region; minus the slight reduction in areas such as Robeson and northern Columbus County. Recent HREF trends show a potential for higher totals over South Carolina this evening as the main precip shield swings southeastward. On either side of the dry slot, isolated totals up to 10 inches are possible. The latest HREF favors the Pee Dee and extreme eastern NC as having the best chance at seeing snow totals near or just above the upper bound. Between these two extreme snow totals will be closer to 5 inches. Expect quite a bit of variance in the dry slotted area and near the coast where banding is possible. The dry slot which will likely exist in the vicinity of Robeson and Bladen County and extended southward into portions of northern Columbus and possible toward the southeastern NC/extreme northeastern SC coast. Banding near the coast will give a higher chance for locally higher variance in snowfall totals in both coastal SC and coastal NC.

We're already seeing light snow and sleet develop across the I-95 corridor. This is not associated with the main event, but has already made roads slick in portions of Florence, Dillon, northern Bladen, and Robeson County. Isolated snow showers are expected to continue in southeastern NC today. Heavier accumulating snow is expected to spread across the region during the afternoon inland and closer to evening at the coast.

KEY MESSAGE 2) A very cold air mass paired with snowfall will result in dangerous cold and record low temperatures this weekend. Wind chill temperatures below 15-20 degrees will linger through at least Monday night/Tuesday morning.

A Cold Weather Advisory remains in effect for inland areas this morning with wind chill values expected to bottom out in the 10-15 degree range. Even lower readings then for tonight (between 0 and 5 degrees on average areawide) when an Extreme Cold Warning is in effect. This due to the combo of low temps in the teens, gusty NW winds, and new snowpack from the anticipated snow later today. About a 50% chance of needing another Extreme Cold Warning Sunday night...winds will be diminishing, but lingering snow pack could make temps a few degrees lower than model predictions. A trend towards somewhat milder temps thereafter through midweek.

Several of our climate sites could see record lows during this weekend, and possibly even Monday night though with a bit more uncertainty due to snowpack. Record lows for Feb 1 and Feb 2 are in the climate section below for reference.

KEY MESSAGE 3...Dangerous marine conditions this weekend with a Gale Warning in effect.

Marine section below has more info on marine hazards.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR is generally trending toward MVFR, but dry low level air has made this a slow process. Once precipitation expands a little more, this process should proceed rather quickly. Precip becomes more widespread this afternoon, mainly inland, but also possibly near the NC coast where additional ocean moisture translates into isolated snow showers. Heavy snow is likely tonight as the main precip shield swings southeastward. IFR VIS will be likely during this transition. VFR returns near sunrise Sunday. Gusty NE to N winds are expected throughout the period. Some VIS issues are possible with strong winds and fresh snowpack. LLWS may be introduced with the deepening, departing low.

Extended Forecast... VFR will develop on Sunday in dry air advection. Remaining breezy as the coastal low moves off to the northeast. Light rain and lowered cigs could return on Wednesday.

MARINE

Through Tonight... Deepening coastal low offshore will lead to deteriorating conditions today, especially late this afternoon and this evening. Gale Warning remains in effect. Gusts up to 40 or 45 knots are possible through Sunday morning. Significant seas remain a little lower than what would be associated with such winds 5 to 8 feet, possibly up to 9 east of Cape Fear.

Sunday through Wednesday... Gale force gusts early Sunday will gradually diminish through the day as the sfc low pushes farther offshore, so the Gale Warning will eventually be replaced by a SCA. Sub-SCA conditions then expected for Monday through Wednesday with weak sfc high pressure moving through the area.

CLIMATE

Record Low Temperatures for Feb 1 & Feb 2 ILM: 14 in 1936; 17 in 1980 FLO: 20 in 2010; 18 in 1980 CRE: 20 in 1945; 20 in 1945 LBT: 4 in 1936; 11 in 1980

ILM WATCHES/WARNINGS/ADVISORIES

NC...Cold Weather Advisory until 6 PM EST this evening for NCZ087- 096-099-105. Winter Storm Warning until 4 PM EST Sunday for NCZ087-096-099- 105>110. Extreme Cold Warning from 6 PM this evening to 10 AM EST Sunday for NCZ087-096-099-105>110. SC...Cold Weather Advisory until 6 PM EST this evening for SCZ017- 023-024-032-033-059. Winter Storm Warning until 4 PM EST Sunday for SCZ017-023-024- 032-033-039-054>056-058-059. Extreme Cold Warning from 6 PM this evening to 10 AM EST Sunday for SCZ017-023-024-032-033-039-054>056-058-059. MARINE...Gale Warning until 7 PM EST Sunday for AMZ250-252-254-256.