Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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094 FXUS62 KCAE 300549 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 149 AM EDT Tue Apr 30 2024 .SYNOPSIS... On Tuesday there will be a chance of thunderstorms in the afternoon with a low threat of severe weather. Broad ridging aloft will develop for the rest of the week limiting the extent of convection and allowing temps to rise above normal, then precip chances increase over the weekend. && .NEAR TERM /UNTIL 8 AM THIS MORNING/... Cumulus clouds over the area are dissipating as the sun sets this evening leading to mostly clear skies to begin tonight. As the upper ridge shifts to the east and moisture increases with southwesterly winds aloft. A line of showers and storms remains well to the west of the area as of 8pm, entering western Alabama. This line will continue to advance through the Deep South into tonight with forcing provided by an upper shortwave. All indications from HiRes guidance is our area remains dry through tonight with increasing clouds over the area downstream of these showers and storms to the west. Low temperatures remain a bit warmer tonight with the increasing clouds with lows in the upper 50s. && .SHORT TERM /8 AM THIS MORNING THROUGH 6 AM WEDNESDAY/... The axis of an upper level ridge will shift further offshore on Tuesday. As the ridge shifts east, an upper trough will move across the Deep South. Convection associated with the trough is expected to weaken through the early morning hours Tuesday. Virtually no SREF members bring the convection into the forecast area before dissipating so we have kept PoPs out of the forecast. However it would not be the first time that overnight convection has held together despite no model guidance showing it. Either way the upper level trough will cross the forecast area on Tuesday. Divergence aloft, moisture advection through SW low level flow, and convergence along the previous day`s outflow boundary should promote convective development in the after noon hours. Low and mid-level lapse rates are supportive of thunderstorms but are not very steep. The interquartile range of sbCAPE values from the SPC HREF range between 400 to 1000 J/kg. Deep layer (0-6km Shear) values are around 20 kts with weak 850mb wind fields. This may limit the threat of organized convection. Thunderstorms should develop in the afternoon either scattered or focused along a possible remnant outflow boundary. There`s a low threat of severe weather given the modest lapse rates and wind fields. A slot of mid-level dry air in the afternoon suggests the biggest threat would be isolated downburst winds or small hail. As the trough shifts east in the evening expect the bulk of the thunderstorm activity to move out of the forecast area with some lingering convection possible into the night. Highs will be in the low to mid 80s Tuesday with lows in the upper 50s to around 60 degrees. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Drier air will move into the area for Wednesday as an upper level trough moves east of the area. PWAT values will still be around 1 inch and there may still be a few showers along the coastal regions where low level moisture is higher. But overall, convection should be suppressed by the dry air and warmer temps aloft. Global ensemble means favor ridging aloft over the Southeast through much of the long term. This along with generally southerly flow favors temperatures above normal with highs on Thursday and Friday in the mid to upper 80s with some locations possibly breaking 90 degrees. Over the weekend and into early next week, the overall pattern supports flattening the ridge. This could lead to a series of shortwaves moving over the forecast area. This in combination with PWAT values from 1.5 to 1.75 inches supports a chance of showers and thunderstorms each day through the remainder of the long term. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... VFR conditions expected through the early afternoon. Restrictions possible late this afternoon into the evening as convection moves through the area. High pressure offshore is extending into the area. The ridge will weaken this afternoon as an upper trough approaches the area. Satellite indicating mid and high level clouds will increase across the area through the morning. Some mixing in the boundary layer and less nocturnal cooling expected so fog not expected early this morning. The air mass will become weakly to moderately unstable by this afternoon. Scattered to broken cumulus possible late morning through the afternoon but should remain VFR. Ceilings more likely to be mid level. Convective models show scattered convection developing ahead of the upper trough late this afternoon into the evening. Brief restrictions possible mainly 20z-01z time period. Patchy light showers possible through 06z Wednesday. EXTENDED AVIATION OUTLOOK...Restrictions possible Tuesday night. Additional restrictions become possible again by Saturday ahead of a frontal boundary. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$