NWS Columbia SC .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The main concern during the medium-range period is a possibility of a wintry precipitation mix. Surface high pressure will extend from the Midwest into the mid- Atlantic region over the weekend. this ridge of high pressure will direct a cold northerly flow into the forecast area. Low pressure along the western and central Gulf Coast Saturday will move northeast and be off the Southeast Coast Sunday and Monday. The GFS and ECMWF and most of the ensemble guidance exhibit this general pattern but with enough inconsistency in the surface and upper features for a low confidence precipitation-type forecast. Moisture ahead of the Gulf Coast system will be moving into the forecast area Friday night. The GFS and ECMWF show the significant lift remaining west of the area through the night. The airmass will be initially dry and it may take most of the night to saturate, so have continued a chance for rain late Friday night. Forecast soundings were consistent indicating liquid precipitation. The moisture should become deep Saturday ahead of the Gulf system. Isentropic lift will also be on the increase. The GFS and ECMWF MOS have trended higher with likely or categorical pops. The moisture will likely remain high through Monday. However, there may be a mid-level dry slot which the models have shown affecting the area mainly Sunday and Sunday night which further complicates the forecast. The deterministic GFS and ECMWF forecast soundings have generally indicated liquid precipitation throughout the area Saturday and Saturday night except the soundings indicate a rain and sleet mix in the extreme north part Saturday night into Sunday then some warming as the low nears the area. More cooling will likely occur as the low shifts eastward and the cold upper system moves into the area. We have forecasted a rain and snow mix in the northwest part Sunday night and Monday. A considerable number of GFS and ECMWF ensemble members support periods of frozen precipitation in the north. Most but not all members have liquid precipitation in the south. There have been differences with respect to the development of a mid-level cut- off low and in its position. A farther south track of a strong upper system would indicate a threat of winter precipitation even in the Central Savannah River Area. The threat in the south should hold off longer and depend on the upper system Monday. Based on the ensemble guidance at this time, we believe the threat of significant winter precipitation during the Saturday night to Monday time frame is about 40 percent in Lancaster County in the north to just 5 to 10 percent farther south in the Columbia to Augusta areas. High temperatures will be in the 40s Saturday through Monday. The storm system is expected to lift out of the area Monday night with dry conditions returning Tuesday. Highs Tuesday will moderate into the upper 40s and 50s. .