Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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913 FXUS62 KCHS 031715 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 115 PM EDT Mon Jun 3 2024 .SYNOPSIS... High pressure will extend across the area through Wednesday. A cold front will slowly move through on Friday, followed by high pressure. && .NEAR TERM /THROUGH TONIGHT/... Showers and t-storms that are developing on the sea breeze (located near US-17 as of early afternoon) and along a differential heating boundary from morning convection to our west will continue this afternoon. Since the overall thermodynamics are fairly mundane, we don`t expect anything more than scattered showers and general t-storms. The DCAPE is the only concerning factor from some gusty winds in a few storms. But nothing severe given weak updrafts. For now we maintain 20/30 PoPs, but pending later trends we might need t increase PoPs due to boundary interactions. Little to no chance in max temperatures. Today: In wake of a short wave pulling further offshore, a weak short wave ridge will prevail aloft. At the surface, the local region lies under the western portion of the Bermuda-Azores High, with some indications of a lee side trough developing late. The overall environment is not especially favorable for convection given weak lapse rates, only 1000 J/kg to maybe 1500 J/kg of MLCAPE, a TTI of 45 at best, and a 3-4C cap that needs to be overcome. However, guidance is not doing a good job of the convection in the Central Savannah River Valley region to parts of the South Carolina Upstate. This seems to be generated by a subtle impulse aloft, that should weaken as it trends further east. That activity though will likely leave a boundary for afternoon development. Even so, other than that, the sea breeze and daytime heating, there isn`t expected to be more than scattered coverage. The greatest chances are inland where boundary interactions will transpire. One item of note is the DCAPE which will peak around 1000-1200 J/kg. Given the lack of any substantial strength to the updrafts, this wouldn`t be able to produce anything more than some gusty winds in a few t-storms. Both the 00Z and 06Z HREF have backed off on the risk of any heavy rain concerns near and west of I-95 like it showed from yesterday. Our 850 mb temperatures are 2C warmer than yesterday, and that along with temperatures running several degrees warmer than 24 hours ago will produce highs well into the 80s away from the immediate coast. Tonight: Any ongoing convection should quickly end during the early evening hours with the loss of diurnal heating. The rest of the overnight will be quiet and dry, with no notable fog concerns. Lows are forecast to fall into the mid to upper 60s away from the immediate coast. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... A potent shortwave is forecast to move in from the west Tuesday afternoon. PWATs above 1.8" and moderate instability should be in place during the afternoon. Meanwhile, the seabreeze will eventually shift inland later in the afternoon. Decent convective coverage expected farther inland in the afternoon, with more isolated activity closer to the coast. Slightly higher surface dewpoints on Wednesday are expected to result in considerably greater instability. Southerly prevailing flow should allow for a more progressive sea breeze in the afternoon. A few weak vort maxima expected to move through during the day. Scattered convection expected mainly during the daytime. Model DCAPE values exceed 1000 J/kg over inland areas so we could see some gusty winds in some storms. Thursday could be the most active day this week due to upper levels transitioning to a broad upper trough and a pronounced shortwave moving through in the afternoon. PWATs expected to rise to near 2" during the day, providing plenty of moisture for showers and thunderstorms to develop. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... A cold front drops through the area on Friday, however convective coverage is uncertain since mid-level subsidence seems likely given the quasi-zonal flow. Compressional heating looks to push highs into the low to mid 90s. A noticeable airmass change is expected this weekend as high pressure builds from the northwest. Downslope flow should still keep highs above 90 in most spots, but dewpoints should mix down into the upper 50s to lower 60s. && .AVIATION /17Z MONDAY THROUGH FRIDAY/... VFR will prevail at KCHS, KJZI, and KSAV with the 18Z forecast. No more than a brief -SHRA or SHRA at KCHS and KSAV on the sea breeze this afternoon. We`ll show VCSH as a result. Otherwise, any TSRA will be inland from the terminals. For Tuesday the risk of SHRA/TSRA is too low or occurs after 18Z. So no mention in the latest TAFs. Extended Aviation Outlook: Outside of any convection, conditions will be VFR through the period. && .MARINE... This afternoon and tonight: High pressure to the east will remain the primary feature controlling winds and seas across the local waters. Winds are expected to be southerly to south- southeasterly through the period with speeds topping out in the 10-15 knot range. Some enhancement along the land/sea interface can be expected in the afternoon and early evening thanks to the sea breeze. Seas are expected to average 2-3 feet. Tuesday through Saturday: High pressure will remain over the western Atlantic Tuesday through Thursday night, maintaining southerly flow at or below 15 kt, seas at or below 4 ft, and a daily sea breeze circulation along the coast. A cold front will move through on Friday, briefly shifting winds to the NW before they turn back E by Saturday. && .TIDES/COASTAL FLOODING... Astronomical tides are on the rise this week. Although wind direction is not particularly favorable for surge, we continue to see a positive tidal anomaly of 0.5 to 0.7 ft. The evening high tides Tuesday through Thursday could reach at least 7.0 ft MLLW in Charleston, necessitating Coastal Flood Advisories. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...JRL LONG TERM...JRL AVIATION... MARINE...