Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 211110 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 610 AM EST Mon Jan 21 2019 .SYNOPSIS... A cold and dry pressure ridge approaching from the west will extend through the forecast area today, then move offshore Tuesday. Moisture will begin to return Tuesday night and Wednesday with some spotty light showers and increasing clouds. A cold front will approach on Wednesday and move through Wednesday night, bringing more showers. High pressure will move in for Friday, with a reinforcing high behind a dry cold front moving in on Saturday. && .NEAR TERM /THROUGH TONIGHT/... The cold surface pressure ridge will approach from the west today and be in the region tonight. There will be much less wind today compared to yesterday with the ridge axis nearing the area. Satellite trends support just high thin cloudiness at times. We leaned toward the lower temperature guidance today because of the cold air mass. Used the guidance consensus tonight. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... Tuesday...the arctic air mass will slowly start to moderate as the high pressure area moves to the outer banks and low level southeasterly flow from off the Atlantic begins. Afternoon high temps will still be several degrees below normal, with only the southern part of the FA expected to crack 50. Tuesday night...the low level return flow strengthens, bringing enough low level moisture to produce clouds and some very light precipitation in the form of light rain or drizzle. Precipitation type looks to potentially be an issue in far northern areas of the FA close to the Charlotte Metro. 00Z NAM forecast soundings indicate a possible period of light freezing drizzle, mainly between 06Z and 12Z, whereas 00Z GFS is too warm. Normally I would tend to side with the NAM when it comes to handling the slower erosion of the arctic wedge, but it has been too aggressive with holding on to cold air in the couple of systems we have had already this winter. Therefore, I am going with a mix of ZR-/R- for northern Lancaster County Tuesday night with no ice accumulation for now, hoping that future model runs will clear up the issue a little bit. Min temps will not be as cold given the cloud cover and gradual warming, with min temps ranging from around freezing in the far north to around 40 in the far south. Wednesday...Skies will be generally cloudy, but significant warming will occur as winds turn around to the south ahead of the next low pressure area and associated cold front. There will still be a chance of some light rain, but I expect the more significant rain will hold off until Wednesday night. Temps will almost feel tropical-like after Monday and Tuesday, with highs from around 60 in the far north to around 70 in the far south. Winds will be increasing on Wednesday as well. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Rain will come in earnest Wednesday night and Thursday morning as the cold front and associated low move into the region. A surge in PWs to 1.5 inches and above, along with a very favorable jet location providing significant diffluence aloft, support a period of moderate to heavy rain. The models do have timing differences, with the GFS running about 6 hours faster than the ECMWF, so there will still likely need to be some future adjustments in that regard, but I have high confidence the entire FA will get wet. An area of high pressure will move in behind the front for Thursday afternoon and Thursday night, but the air mass will not be of arctic origin, so expect more normal late-January temps. A weak, dry cold front may move through on Friday with a reinforcement of somewhat colder air. High pressure should continue to dominate on Saturday, and after a chilly start we should be up to normal temps in the 50s. Another area of low pressure will be approaching from the west on Sunday, but the models really begin to diverge at this point, so I have just gone with a blend of everything for now. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... We have high confidence of continued VFR conditions through the 24-hour TAF period. Dry high pressure moving into the region will dominate. There will be diminished wind with the ridge axis nearing the area. Followed the GFS LAMP with wind north to northeast at 5 to 10 knots. Satellite trends support just periods of thin high cloudiness at times. It should remain too dry for fog. EXTENDED AVIATION OUTLOOK...MVFR or IFR cigs are expected to return Tuesday night into Wednesday morning due to low clouds. We may see a break for a little while Wednesday afternoon, but low cigs/vsbys will likely return Wednesday night, maybe stretching into Thursday morning, as a low pressure area and cold front move through from the west. VFR conditions dominate the later half of the week. && .HYDROLOGY... Rainfall totals ranged from 1 to 1.25 inches across the Upstate and headwaters of the area rivers to .75 to 1 inch across much of the Midlands and CSRA. This will produce rises on the area rivers early this week. Some minor flooding is forecast along the Congaree River south of Columbia as the water moves down the Broad and Saluda River basins. && .EQUIPMENT... The Columbia, SC (KCAE) WSR-88D is out of service due to a faulty voltage regulator. The part will be ordered but an estimated time of arrival is unknown at this time. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99 HYDROLOGY...99 EQUIPMENT...99

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