Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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079 FXUS62 KCAE 300741 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 341 AM EDT Mon Sep 30 2024 .SYNOPSIS... The remnants of Helene along with the upper level trough axis will be north of the area today while continuing to slide slowly eastward. The system will finally move off the coast on Tuesday as a weak cold front approaches. This will keep the area under southwesterly flow aloft with a few showers possible this afternoon and evening, especially in the Northern Midlands and Pee Dee. This will be followed by the passage of a weak cold front mid-week but the chance of precipitation is low. High pressure then builds in behind the front with continued dry conditions Thursday and Friday. Temperatures remain near or above seasonable values through Friday. && .NEAR TERM /THROUGH TONIGHT/... Key Message(s): - Heed road closures and DO NOT drive around barricades. - Avoid unnecessary travel as utility crews continue restoring power and clearing downed trees and powerlines. - Flooding on area river levels will continue with some locations at major flood level. - Isolated showers possible this afternoon and evening. Currently clouds blanket the the CSRA and much of the southern Midlands and will continue moving northward through daybreak. There is some potential for fog to develop mainly in the eastern Midlands and southern CSRA where skies remain mostly clear however fog which develops will generally be patchy with limited visibility restrictions. Low temperatures will be in the mid 60s to around 70. Synoptic situation will be slow to change today as the remains of Helene along with the upper level trough will be north of the area while gradually sliding eastward. By this evening the remains will have reached WV and by daybreak Tuesday be nearing the Delmarva region. This will keep the area under WSW to SW flow and with plenty of moisture across the area potential for a few showers this afternoon and evening. With forecast soundings again showing some dry air in the mid levels along with weak lapse rates expect mainly showers as the cumulus will be vertically limited. The exception will be in the northern Midlands and Pee Dee where there is a bit more instability and there could be a thunderstorm or two late this afternoon into this evening when the upper trough axis begins swinging through the region. Expect the thunderstorm threat to end with sunset. Overnight partly to mostly cloudy skies will again be over the area which will limit the fog and stratus potential. High temperatures this afternoon will generally be in the mid 80s along and north of I-20 and the upper 80s south of I-20. Low temperatures tonight will be in the low 60s in the far western Midlands with mid 60s elsewhere. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Key Messages: - Upper low continues eastward, moving offshore on Tuesday. - Low (10-30 percent) chance for showers on Tuesday, mainly in the Northern Midlands and Pee Dee. - A weak cold front approaches on Wednesday but rain is not expected. - Daytime temperatures above normal. There continues to be little change in the overall weather pattern during the mid-week period. The upper low will be located in the Mid-Atlantic region at daybreak on Tuesday, slowly moving east, passing offshore during the daytime hours. Southwesterly flow aloft keeps us warm and moist and there is a low (10-30 percent) of showers across the Northern Midlands, especially Chesterfield County. A cold front will follow behind the upper low on Wednesday but is not expected to produce precipitation in our forecast area. Temperatures during the period remain above normal. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Key Messages: - Warm and mainly dry conditions through Friday. - Uncertainty increases this weekend ahead of the next system. High pressure will be in control of the weather on Thursday while the axis of an upper ridge passes overhead. This will result in another warm and dry day with above normal temperatures favored once again. Forecast confidence decreases this weekend as model guidance has not come into agreement regarding a potential tropical cyclone in the Gulf of Mexico. Opted to favor the GFS solution with this forecast package which shows an upper trough and strong high pressure diverting any tropical moisture to our south. Having said that, the best rain chances in this scenario should be over our southern and eastern counties where there are Slight Chance PoPs on Friday and Sunday afternoons, though again confidence in any one solution is low at this time and will need to be refined as the week goes on. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... VFR conditions expected except for possible brief VIS/CIG restrictions around sunrise. Satellite imagery shows mid clouds continuing to move across the area with some clouds around 3.5 kft embedded with the mid clouds. Through daybreak the main concern will be potential for MVFR to IFR cigs and vsbys however with increasing clouds from AGS to CAE expect the threat to be lowering however have kept mention at prone AGS around daybreak fro MVFR vsbys. OGB remains clear and potential for sunrise restrictions remains possible however mid clouds moving toward the terminal may disrupt that and will continue to monitor. With sunrise any restrictions will mix out with the remainder of the period VFR with winds westerly to southwesterly at 8 knots or less. EXTENDED AVIATION OUTLOOK...No significant impacts to aviation expected through Friday. && .HYDROLOGY... Key Message: - Widespread moderate-major flooding underway and will continue over the next several days. Heavy rainfall associated the the pre-Helene event combined with rainfall associated with Helene has produced high flows and flooding on many of the streams and rivers across the Midlands and Central Savannah River Area. Rainfall amounts ranged from 3 to 6 inches across much of the area with some counties reporting rainfall amounts from 6 to 12 inches. Many of the area rivers continue to rise as rainfall across western NC and the Upstate of SC continues to move down the river basins. Most river forecast points will be reaching at least Moderate Flood, with several locations in the Major Flood Category. Stevens Creek at Modoc set a new crest record just over 43 ft. The pool elevation at Lake Wateree is expected to crest just under 107.0 feet which is approaching the record lake level height set back in 1989 with Hurricane Hugo. The Congaree river at Columbia is forecast to crest at 31.0 feet, near the 2015 level. It will take several days for the rivers across the Midlands and CSRA to return to more normal flows. Those working around area rivers and creeks are urged to monitor levels and use caution near flooded areas for underwater and unseen hazards. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$