textproduct: Columbia

WHAT HAS CHANGED

Updated aviation.

Higher resolution guidance highlights the potential for a brief snow band to set up over portion of the area Sunday morning into early afternoon. High end amounts continue to be below winter weather advisory criteria, however and much of the area likely will receive little to no snow accumulation.

KEY MESSAGES

1) A rain/snow mix is possible Sunday, but the potential for significant accumulation is low. Patchy black ice possible early Monday morning.

2) Arctic air mass moves into the Southeast early next week with temperatures well below normal. A Cold Weather Advisory may be needed.

DISCUSSION

Key Message 1: A rain/snow mix is possible Sunday, but the potential for significant accumulation is low. Patchy black ice possible Sunday night.

The overall synoptic pattern for the system Saturday night into Sunday remains the same with a deepening 500mb trough into the Mississippi Valley leading to cyclogenesis along the northern Gulf coast. Surface low pressure will move along the coast of GA/SC in what is a typically favorable setup for winter weather in our area. The issue we will run into is high confidence in temperatures in the 40s Saturday night and while a colder air mass will begin to push in and overrunning will lead to rain developing, allowing for evaporative cooling, climatologically it is difficult to get any kind of meaningful snow accumulation when the cold air is not already in place. Rain will likely transition to a rain/snow mix Sunday morning but light snow will struggle to accumulate with temperatures likely near freezing and ground temperatures likely above freezing.

HiRes models do still indicate the potential for mesoscale banding associated with warm advection and a strengthening band of frontogenesis leading to sufficient lift in the dendritic growth zone. This would lead to some higher snow rates which would likely be able to overcome marginal surface temps leading to some accumulating snow at the surface. Higher end amounts continue to remain around a half inch and much of the area would likely receive less than this (or no accumulation at all). With high confidence that total snowfall remains less than an inch, we will not be issuing a Winter Weather Advisory with this package. There may be some minor impacts for a brief period, likely late morning into early afternoon, if and where this band sets up but overall, widespread impactful winter weather is not expected over the forecast area.

Precipitation expected to push east of the area late Sunday afternoon with a colder air mass pushing into the forecast area as high pressure settles over the Deep South. Blended guidance shows about a quarter to a half inch of total liquid precipitation with this system and as temperatures drop below freezing Sunday night, there will be potential for black ice to develop on roads. This will likely not be a widespread issue as a lingering pressure gradient will lead to breezy winds into Sunday night which will help to dry out roads, but patchy black ice is possible.

Key Message 2: Arctic air mass moves into the Southeast early next week with temperatures well below normal. A Cold Weather Advisory may be needed.

Arctic air mass will settle into the Southern Plains tonight and slowly move eastward, into the Deep South. EC EFI highlights the area in potential for anomalously low temperatures Sun, Mon and Tue nights. As high pressure remains to the west of the area Sunday night, cold advection will likely push temperatures into the low to mid 20s Monday morning with a tight spread within the blended guidance. High pressure slowly moves eastward with a reinforcing cold front likely late Monday. Coldest night will likely be Tuesday night into Wednesday morning with higher probability in stronger radiational cooling as high pressure will likely be over the area. LREF indicates around a 30-50 percent probability of wind chills below 20F each night, indicating that a Cold Weather Advisory will at least need to be considered.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

MVFR ceilings will be overspreading the area at issuance time ahead of an approaching system. Rain showers will begin to approach the area after 00z Sunday.

A mixture of low and mid level cloudiness has surged eastward and will be overspreading all taf sites between issuance time and 13z with ceiling restrictions dropping to mvfr. Although there may be some improvement back to vfr by early afternoon with better mixing expected, ceiling will remain broken to overcast through the period. A return to mvfr should occur towards 06z tonight. A few light rain showers current moving slowly eastward across the upstate of SC and much of central GA. Coverage should diminish some this morning as it approaches the western forecast area, but can not rule out a brief light shower this morning. Additional and more widespread rainfall, and possibly a little snow mixed in, will occur later tonight and into Sunday morning as the main upper shortwave trough tracks through the region. Winds will be southwesterly and pick up to the 5-10 kt, with some terminals gusting to 15-20 kts at times before diminishing once again by sunset.

EXTENDED AVIATION OUTLOOK...The next system is expected to impact the region through the day on Sunday, and some restrictions are possible.

CAE WATCHES/WARNINGS/ADVISORIES

SC...None. GA...None.