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Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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912 FXUS62 KCAE 120620 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 220 AM EDT Mon Aug 12 2024 .SYNOPSIS... Temperatures cool off slightly this week with daily chances of afternoon showers and thunderstorms continuing. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Key Message(s): - Isolated showers and thunderstorms through daybreak, mainly north of Columbia. Forecast remains largely on track early this morning. Another shortwave upstream from the Carolinas is expected to continue to provide at least weak lift, with CAMs consistently showing enough instability to support convection across the northern half of the forecast area for much of the night. This has generally occurred, and thankfully precip is moving off to the northeast at a decent pace. Temps will be fairly similar to what they have been - generally mid 70s across the area. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... Key Message(s): - Showers and thunderstorms expected across the eastern half of the forecast area on Monday - Increasing chances of showers and thunderstorms Tuesday Zonal upper level flow will persist over the CONUS through much of the short term with some amplification noted late Tuesday and Tuesday night as ridging builds over the central US and weak troughing over the eastern US. At the surface the weak and diffuse boundary will be over the eastern Midlands on Monday continuing to act as a focusing mechanism. Instability will again be moderate to strong Monday afternoon with pwat values remaining in the 2.0 to 2.2 inch range over the central and eastern Midlands. This will again make for showers and thunderstorms during the afternoon and evening with much of the anticipated activity along and south of I-20. Wind gusts will be the main threat for severe thunderstorms as DCAPE values will again push toward 1000 J/Kg. The other concern remains the potential for locally heavy rainfall combining with already saturated or nearly saturated soils. WPC has much of the central and eastern Midlands in a marginal risk of excessive rainfall and with the anticipated convective coverage this seems reasonable. With sunset expect much of the activity to dissipate however with the instability and remaining outflow boundaries a few cells could develop into the early overnight hours. High temperatures Monday will range from the mid to upper 80s in the far northern Midlands to the low 90s in the southern Midlands and CSRA. Lows Monday night will be in the low to mid 70s. On Tuesday the pattern begins to shift as the upper levels amplify over the central and eastern US which will put the area under NW flow aloft. Although this will be ushering some drier air into the area models are indicating a short wave which will be moving through the northern portions of the forecast area which should trigger convection once again for the afternoon and evening hours. Much will depend on the location of the short wave as it moves through the region however with slightly drier air aloft DCAPE values during the afternoon will be rising to over 1000 J/Kg producing a wind threat from thunderstorms. With the lower pwat values Tuesday afternoon around 1.8-1.9 inches the threat of locally heavy rainfall will be slightly lower. High temperatures Tuesday afternoon will again be in the upper 80s north to low 90s south with overnight lows in the upper 60s to lower 70s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Key Message(s): - Slightly cooler temperatures but seasonably dry weather expected throughout the middle part of the week. The upper level pattern amplification will continue as the ridge builds over the central US with the trough digging along the Atlantic Coast. This will keep the forecast area under northwesterly flow and drier conditions for Wednesday and Thursday. By late in the week low pressure will be marching into the western Great Lakes with a frontal boundary extending into the central Gulf States. This system is expected to slow as it reaches the Great Lakes with the frontal boundary lingering over the SE US through the weekend. This will once again bring showers and thunderstorms back into the area however with the trough over the eastern US and expected cloud cover temperatures will be slightly lower. Afternoon high temperatures will be slightly below normal in the mid to upper 80s. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... Generally VFR conditions expected outside of brief restrictions in diurnally driven thunderstorms and early morning stratus/fog. Convection is north of the terminals early this morning with mainly mid and high level clouds across the area. With shallow low-level moisture, near calm winds overnight and decreasing high clouds, fog and low stratus may develop toward dawn. Have included a mention of restrictions in the TAFs, possibly as low as LIFR/IFR but improving by 12/14z. As the air mass becomes moderately to strongly unstable this afternoon, scattered thunderstorms are expected to develop once again. Outside of convection, sfc winds will be variable at 5 to 10 knots. EXTENDED AVIATION OUTLOOK...Afternoon and evening convection and associate restrictions will be possible through Friday. Early morning fog and stratus could occur, especially at fog- prone AGS/OGB. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$