Area Forecast Discussion
Issued by NWS Columbia, SC

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000 FXUS62 KCAE 150747 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 347 AM EDT Mon Oct 15 2018 .SYNOPSIS... An approaching cold front will be in the forecast area Tuesday and Wednesday. High pressure will extend into the area from the north and northeast Thursday and Friday. Another cold front will be in the region Saturday. && .NEAR TERM /THROUGH TONIGHT/... Low-level moisture has increased in an onshore flow directed into the forecast area south of the pressure ridge off the mid- Atlantic Coast. The moisture should remain shallow because of upper ridging through today. The MOS was consistent with pops less than 20 percent. Moisture should become a bit deeper tonight associated with convergence close to the front nearing the north part late. We forecasted slight chance pops in the north section. Farther from the front and closer to stronger upper ridging the shower chance should be less in the southeast section. The increased low-level moisture combined with nocturnal cooling will likely lead to stratus and fog during the early morning hours. We leaned toward the higher maximum temperature guidance south of the front today. Used the guidance consensus tonight. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... Little change made during this period. The upper ridge over the southeastern states will flatten Tuesday in response to a digging upper trough moving across the Great Lakes region into New England. This will allow a cold front to sink southward across the region Tuesday night into Wednesday. As the front crosses the region, the best chance for showers across the Midlands and CSRA will be Wednesday. Precipitable water values will rise to around 1.8 inches along and just ahead of the front on Wednesday. However, the best forcing will remain to our north across VA/NC. MET/MAV pops have trended lower over the past few runs, but will continue with slight chance/chance pops Tuesday into Wednesday. Temperatures will continue to average above normal through the period. The best chances for rain will be across the northern Midlands along the NC border. Rainfall amounts will around/less than one quarter of an inch. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... The cold front is forecast to push east of the area by Wednesday evening as strong high pressure builds in from the north. Fall weather will return to the region Thu/Fri as cool and dry high pressure settles over the region. However by Friday afternoon/night, surface high pressure will quickly move eastward off the Mid-Atlantic coast. This will shift the low level flow to a more east/southeast flow over the area by Saturday. A trough will once again dig across the Great Lakes into New England Saturday into Sunday. The GFS/ECMWF have continued to disagree slightly timing with frontal boundary as it moves into the Midlands and CSRA. However, the best chance for showers, maybe an isolated thunderstorm, will be on Saturday. The front will push south of the region Saturday night and high pressure will once again move over the region. Temperatures during this period will be near or slightly below normal Thu/Fri and remain near normal over the weekend. Could see our coolest morning of the Fall season by Thursday night with high pressure over the region. Guidance temperatures in the 40s for many locations. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... Expect a period MVFR or IFR conditions during the early morning hours. Low-level moisture has increased in an onshore flow directed into the forecast area south of the pressure ridge off the mid- Atlantic Coast. This moisture combined with nocturnal cooling should lead to areas of stratus and fog during the early morning hours. There was inconsistency with the guidance with the NAM MOS most pessimistic. We leaned toward the NAM MOS because of the low-level moisture and drying aloft associated with the upper ridging. Heating and mixing of the shallow moisture should result in mainly VFR conditions later in the morning and during the afternoon and evening. The NAM and GFS MOS support wind mainly southwest less than 10 knots during the day, and light and variable at night. EXTENDED AVIATION OUTLOOK... Widespread mainly late night and early morning MVFR or IFR conditions associated with a front may occur Tuesday and Wednesday. Dry ridging should dominate Thursday and Friday. && .HYDROLOGY... The Congaree River continues to gradually fall and should fall below flood stage at the Congaree National Park this morning. Additionally, the Great Pee Dee River is gradually diminishing and has fallen from moderate flood stage to minor flood stage. It should fall below flood stage by late tonight or early Tuesday. Please refer to the latest observations, forecasts, and flood statements. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99 HYDROLOGY...

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