Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
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730 FXUS62 KCAE 291816 CCA AFDCAE Area Forecast Discussion...CORRECTED National Weather Service Columbia SC 216 PM EDT Sat Jun 29 2024 .SYNOPSIS... Hot and humid conditions continue through the weekend. Afternoon and evening rain and storm chances increase Sunday afternoon and evening as a frontal boundary moves into the area. The cold front is expected to bring slightly cooler and drier conditions to start off the work week, but building high pressure will allow the return of temperatures near the century mark by mid- week. && .NEAR TERM /THROUGH TONIGHT/... KEY MESSAGES: - Warm and humid again, showers and thunderstorms expected mainly south and east of I-20 this afternoon and evening. - Heat index values pushing into the mid 100`s in many spots. A modestly unstable environment continues to develop across the Midlands and CSRA this afternoon. PWAT`s have climbed to near 2.0" and ML CAPE is rising to around 1000 J/kg by mid-afternoon. Some showers have pushed into the CSRA as of 18z, but lightning has been very isolated thus far. Hi-res guidance was a bit late with this initial initiation, but the overall progression, timing, and behavior of convection so far is following obs and showers-storms will spread eastward along the I-20 corridor and points eastward this afternoon. The severe threat looks to remain relatively low, in line with the last couple days, as we lack any sort of forcing mechanism, deep layer shear, or truly impressive thermodynamics. So a strong- severe thunderstorm is possible, again mainly in the CSRA and southern Midlands, but confidence is very low. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... KEY MESSAGES: - Heat Advisory in effect Sunday afternoon and early evening. Not as hot on Monday with a front entering the region. Sunday and Sunday night...Broad upper trough developing in the northeast CONUS and Mid Atlantic region. The upper ridge over the area will weaken with northwest flow aloft over SC. A weak cold front will move toward the region late in the day. Moisture will increase through the day with southwesterly low- level flow. Strong moisture flux expected with precipitable increasing to 2 inches or even higher ahead of the front. Models soundings suggest deep moisture. This will result in hot and muggy conditions by early afternoon. Heat indices in the 105-110 range are expected with high temperatures in the mid to upper 90s. So a heat advisory has been posted. So, as the front approaches, the air mass will become moderately unstable with ML CAPE 1500-2000 J/kg. CAM models are suggesting a few isolated showers in the morning, followed by scattered to numerous showers and thunderstorms late afternoon into the evening as a short wave trough approaches in northwest flow aloft. Highest pops appears to be across the north Midlands into the Pee Dee where lift is maximized due to approaching short wave and divergence aloft. Deep shear near the NC/SC border is only 20 knots but can`t rule out a severe pulse storm anywhere due to strong heating and moist conditions. Moist downburst wind gusts main threat. Muggy conditions overnight with showers diminishing but lingering as the front moves slowly to the southeast. Monday and Monday night...Although the deterministic pop guidance is suggesting low pops on Monday, the front is expected to stall near the area. The ensembles are suggesting relatively high pops, actually categorical across the southeast CWA through the day with lower/chance pops to the north. The air mass will likely remain weakly unstable and quite moist. Temperatures should be cooler with considerable clouds at least through the morning with some clearing northwest. && .LONG TERM /TUESDAY THROUGH SATURDAY/... KEY MESSAGES: - Brief break from excessive heat on Tuesday before the heat and humidity return later in the week. -Dry conditions may lead to increased fire danger mid to late week. The front should push a little further south on Tuesday with much drier air filtering into the central Midlands. Precipitable water expected to fall below 1 inch across a good portion of the area. So, a brief respite from the summer heat and humidity can be expected. With the front near the Savannah River area, kept chance pops there, but chance of rain should decrease by afternoon. Ensembles show high pressure building aloft again over the Southeast U.S. during the latter half of the week with temperatures once again well above normal. Moisture will slowly increase across the region through the period. Convective activity should be mostly limited to near the sea breeze front and small scale atmospheric interactions. Below normal rainfall during the past month has led to dry vegetation which increases the risk of fire starts, especially with upcoming Independence Day celebrations. Another front may approach the area by next weekend with an increase in showers/thunderstorms. But overall the period appears mainly dry and increasingly hot by mid to late week. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... VFR conditions generally expected through the period. Some showers and isolated thunderstorms are currently moving through AGS and DNL, with some brief associated restrictions likely through roughly 20z. Lightning has continued to remain fairly limited in any of this convection, but this will likely increase through the afternoon. These will continue to shift east over the afternoon, likely moving into CAE, CUB, and OGB by 20z. Given the coverage and timing uncertainties, went with a VCTS group at these sites from 20z through 00z. Winds this afternoon will remain fairly light, mainly out of the south, with gusts to 10-12 knots. Not expecting fog or stratus overnight tonight into Sunday. Confidence is fairly high in restrictions on Sunday as a front approaches. EXTENDED AVIATION OUTLOOK...Widespread showers and thunderstorms likely Sunday afternoon and evening. Chances of rain in the afternoon and evening continue Monday and Tuesday, with stratus and fog in the mornings. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...Heat Advisory from 2 PM to 6 PM EDT Sunday for SCZ016-018- 020>022-025>031-035-037-038-041-116-135>137. GA...Heat Advisory from 2 PM to 6 PM EDT Sunday for GAZ040-063>065- 077. && $$