Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 210859 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 359 AM EST Tue Feb 21 2017 .SYNOPSIS... Above normal temperatures expected through the period. Today will be dry but cloudy as high pressure shifts offshore ahead of an approaching system. Increasing moisture and isentropic lift will bring a chance for showers tonight into Wednesday. The chance for a few showers will linger into Saturday. A cold front will cross the region Saturday with dry high pressure building into the area for the start of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High clouds will continue to increase as upper ridge axis shifts east and next weather system approaches. Mid and low clouds will also increase today as southeast flow brings low-level moisture and isentropic lift. By this evening, an upper low will be centered over the lower Mississippi valley, and pre-frontal showers could begin moving into the CSRA. Temperatures will once again be above normal with highs in the 70s. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... Upper and surface ridge will be located off off the coast tonight as an upper low tracks southeast across the Gulf of Mexico. An onshore flow...with increasing isentropic lift and moisture transport will bring a chance for showers. Have indicated the highest pops across the western part of the forecast area with slight chance pops east tonight through Wednesday. Most of the guidance indicate higher rainfall coverage and amounts to our north enhanced by orographic lift and a weak in situ edge, though some additional showers could develop in diurnal heating/differential heating across the forecast area Wednesday afternoon. With possibility of weak wedge affecting the North Midlands and Piedmont, kept daytime highs a little cooler...around 70. Should see high temperatures in the low to mid 70s for the remainder of the forecast area. Went near guidance consensus for overnight lows in the 50s tonight and Wednesday night. && .LONG TERM /THURSDAY THROUGH MONDAY/... The models take the closed low near the Florida Keys on Thu through the Bahamas on Friday. Surface high pressure off the Carolina coast will ridge into the region with building heights aloft. The weak in situ wedge may linger just to our north Thu. A moist E to SE low level flow to provide a continued chance of showers, enhanced by diurnal heating, Thu aftn. However, by Thursday, some drier air aloft may move into the region and cut down on overall shower chances. The next cold front will be crossing the MS River Valley Friday with a nearly zonal flow across the southern tier of states. The long term models are in agreement with this front crossing the area Saturday. Chance pops appear ok with the front. Surface high pressure and drier air will settle into our FA late Sat through Sun. Modified Pacific air mass with cooler temps but still projected to be above normal. Nearly zonal upper flow across the southern states expected to continue late in the forecast period as well, with systems moving rapidly. A quick moving trough will track east across the country, with it and the surface low staying to our north. Surface high to shift east ahead of it Sun night into Monday, with moisture return for our area Mon/Mon night into early Tue. Any chance for precipitation will be low. && .AVIATION /08Z TUESDAY THROUGH SATURDAY/... Expect mainly VFR conditions through Tuesday, with possible MVFR restrictions Tuesday evening. High pressure will remain over the area through morning. However, high clouds will continue to stream in from the west in advance of the next weather system. Nocturnal cooling may help support early morning fog, but it should be precluded by the dry air mass plus the high cloudiness limiting net radiational cooling. Also, a 20 kt low-level jet will provide boundary layer mixing. Expect light easterly surface winds. The high pressure ridge will shift east on Tuesday. Low-level moisture should increase with a southeast onshore flow. The models also indicate isentropic lift which will allow stratocumulus to develop during the day. The clouds will increase and lower during the late afternoon and evening, causing MVFR conditions by the end of the TAF period. Also, some light showers may move into the area and especially the CSRA around 22/00Z. EXTENDED AVIATION OUTLOOK....Moisture associated with an onshore flow may help bring widespread MVFR or IFR conditions through Friday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$

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