textproduct: Columbia

WHAT HAS CHANGED

Sub freezing temperatures have remained locked in place through the forecast area. Moderate precipitation along a cold front will likely lead to additional ice amounts for at least the northern and western Midlands this afternoon and evening. Overnight temperatures will warm slowly with most locations returning to above freezing for Monday morning.

KEY MESSAGES

- 1) Subfreezing temps remain locked in for the northern FA. Additional freezing rain expected as the cold front approaches.

- 2) Cold arctic air moves in behind this system with well below normal temperatures expected through the week. Temperatures near Cold Weather Advisory criteria are expected multiple nights, especially Monday night into Tuesday morning.

DISCUSSION

KEY MESSAGE 1: Subfreezing temps remain locked in for the northern FA. Additional freezing rain expected as the cold front approaches

A cold front will work through the forecast area today and this evening. Along the front, moderate to periods of heavy precipitation are occurring. Since temperatures have remained in the low to mid 20s we expect additional, significant freezing rain accumulations from northern Saluda County north into Lancaster county which will almost certainly remain below freezing as the heavier precip begins to move through. Some of these more northern locations may receive an additional two to three tenths of an inch of ice accumulations. With additional freezing rain on the way for the northern Midlands we may see power outages increase.

There is also some concern for the central Midlands and the northern CSRA where temperatures may not recover to freezing. These locations could also see additional accumulations of around one tenth of an inch.

The heavier precip rates will not be the most efficient for ice accretion with much of the QPF becoming runoff. Although with all surfaces, including roadways, already saturated and below freezing, ice will form from the onset.

Following the front, temperatures will slowly rise through the night. As strong cold advection sets in around sunrise Monday, there could be a few spots, especially in Lancaster and Chesterfield counties which fall back below freezing. Although most locations will be in the mid to upper 30s we may need to issue an SPS for black ice for the most northern counties.

KEY MESSAGE 2: Cold arctic air moves in behind this system with well below normal temperatures expected through the week. Temperatures near Cold Weather Advisory criteria are expected multiple nights, especially Monday night into Tuesday morning.

The extended forecast remains largely unchanged with upper troughing in control of the weather across the Eastern United States and strong surface high pressure across our region. This will promote cold and dry conditions through at least Friday. High temperatures will be in the 30s and 40s, falling into the teens and 20s each night. These temperatures, combined with the wind, could produce wind chill values that approach or exceed Cold Weather Advisory criteria in spots. The first opportunity for this will be Monday night into Tuesday. Opted to not issue any cold weather products with this package as confidence in meeting criteria is not high enough at this time but trends will continue to be monitored.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

IFR and LIFR conditions will continue today, and a strong cold front will pass between 22Z and 00Z.

Currently ceilings are between 200 and 400 feet and will slowly improve to IFR over the next few hours ahead of a cold front. Freezing drizzle and very fine snow is becoming more of a light freezing rain as cloud layer near the ground slightly warms and precipitation intensifies a bit. These conditions will continue at all sites with surface temperatures remaining just below freezing ahead of said cold front, which will cross the area between about 22Z and 23Z at Augusta, 23Z and 00Z at Columbia, and around 00Z at Orangeburg. Significant freezing rain during this period is possible, especially at Columbia sites that will be a bit colder. A temporary gusty northwest wind is expected, with otherwise a several hour period of LLWS anticipated surrounding the front. Behind the front, ceilings should remain low with lingering IFR conditions for much of the TAF period, with low clouds finally scattered out towards 12Z Monday. Winds will become mainly westerly 5 to 10 knots overnight.

EXTENDED AVIATION OUTLOOK...Gusty northwest winds may increase above 20-25 knots at times late Monday, with VFR conditions as skies become mainly SKC through Thursday.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Ice Storm Warning until 1 PM EST Monday for SCZ016-018-020>022- 025>031-037-115-116. Winter Weather Advisory until 1 PM EST Monday for SCZ035-038- 041-135>137. GA...Ice Storm Warning until 1 PM EST Monday for GAZ040-063>065. Winter Weather Advisory until 1 PM EST Monday for GAZ077.