Jan 7, 2017 Winter Weather Event Decision Support Briefing # 5 Assessment for northeast South Carolina & southeast North Carolina National Weather Service Wilmington NC 4 PM EST Friday January 6, 2017 Steven Pfaff, WCM Steven.Pfaff@noaa.gov Weather Forecast Office Wilmington, NC weather.gov/ilm @NWSWilmingtonNC 1
New Information A Winter Weather Advisory now in effect to replace the Winter Storm Watch & the advisory has been expanded east & south to account for some freezing rain, sleet, & light snow. Snow/sleet accumulations have been shifted farther northwest. Minor accumulations from freezing rain/drizzle are possible with a few hundredths of an inch across northwest and northern areas with a slight glaze possible slightly farther south and east. Regarding impacts, included mention of the potential for some downed trees (those previously weakened or partially uprooted by Hurricane Matthew) with gusty north winds during Sat. 2
Impact Summary Greatest expected impacts Snow/Sleet None Elevated Moderate High Extreme -Highest far northwest areas Ice None Elevated Moderate High Extreme -Highest far northwest and northern areas Wind Surge/ Inundation None Elevated Moderate High Extreme -Gusts to 30 to 35 mph possible None Elevated Moderate High Extreme Marine None Elevated Moderate High Extreme -Gale conditions expected *These impacts do not apply to all areas of southeast NC or northeast SC, check the following slides for details on where impacts will be greatest. 3
Potential Impacts and Approximate Timing Approximate Timing Potential Impacts Hazardous driving conditions expected, especially bridges, overpasses, & elevated road surfaces, especially across inland areas Black ice possible on area roadways and sidewalks Sat night into Sun morning as arctic air arrives in force Some trees previously weakened by Matthew may fall from gusty northerly winds Sat Isolated power outages possible Sat Dangerously cold weather Sun and Monday with arctic air-mass over the region 4
Storm Total Snow/Sleet Accumulations Highest snow accumulations remain across northwest areas but a dusting is possible farther east and slightly southward as the system exists the area during Saturday. Any minor accumulations will primarily be on grassy and elevated surfaces. 5
Probability of Snow Accumulating 1 WPC Probability of Snowfall Accumulating 1 valid 7 PM EST Today through 7 PM EST Saturday The axis of highest probabilities has shifted slightly farther north and is now focused just north of a Greenville, SC to Greensboro, NC line. This implies the potential for less snow across inland portions of the NWS Wilmington NC forecast area. 6
Ice Accumulation Total Highest ice accumulations are expected to occur across northwest areas, while a light glaze is possible across remaining areas. Freezing rain will accumulate more efficiently on elevated surfaces. 7
Probability of Freezing Rain Accumulating 0.01 WPC Probability of Freezing Rain Accumulating 0.01 valid 7 PM EST Today through 7 PM EST Saturday The axis of highest freezing rain accumulating to 0.01 probabilities has shifted farther north as well from north of Columbia, SC toward Fayetteville, NC and Greenville, NC. 8
Wind Chill Period of Coldest Wind Chill Wind Chill Advisory is possible early Sunday morning and Monday morning for portions of the area. 9
Arctic Temperatures Arctic air-mass in place into Tuesday morning Coldest temperatures Monday morning, temperatures recovering beginning Tuesday 10
Peak Wind Gusts and Seas Gale Warning in effect for the adjacent coastal and offshore waters Conditions will deteriorate tonight with the worst maritime weather Saturday, then slow improvement Sunday. 11
Key Points This event is expected to have limited impacts in our area; however, people expected to travel farther inland portions of the Carolinas could encounter hazards driving conditions. Primary impacts will mainly be for elevated surfaces, bridges, overpasses as the wintry precipitation is falling. Other roadways and sidewalks could develop black ice Saturday night into Sunday morning as any water draining onto roadways/walkways could become frozen. Gusts up to 30 to 35 mph during Saturday could down some trees previously weakened by Hurricane Matthew. Very cold temperatures and single digit wind chill values (combination of wind and temperature) are expected Sunday morning and again during Monday morning. The arctic air-mass will begin to modify and exit the area beginning Tuesday with a significant warm up by mid-week. NEXT PDF BRIEFING: Not scheduled unless significant changes warrant 12