Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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189 FXUS62 KCHS 300742 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 342 AM EDT Tue Apr 30 2024 .SYNOPSIS... High pressure will prevail through much of the week. A weak disturbance will move through today and Wednesday, then a weak cold front will stall in the vicinity this weekend. && .NEAR TERM /THROUGH TONIGHT/... Early this morning: We`re starting off a bit warmer than yesterday morning, but there are still a number of places down in the mid and upper 50s far inland. Closer to the coast it`ll be about 5-10F degrees warmer. Nothing more than a little light fog and patchy stratocumulus and cirrus. Today: The ridge aloft is forced east in advance of a short wave that crosses the Appalachians during midday, then moves into the local vicinity the second half of the afternoon. Meanwhile at the surface, a lee side trough will develop, as the western periphery of Atlantic high pressure originally over the area pulls to near the coast this afternoon. There will be some showers and storms in the ocean within the southerly flow on the back side of the offshore high. But the main convergence that generates this convection stays offshore, maybe coming close to the Charleston County coast for a brief time late morning /early afternoon. There`s a weak cap that holds in place into the early afternoon, before we reach our convective temperatures around 80F degrees. So there is little to no chance of any rain through 2 or 3 pm. However, with the approaching short wave, and PWat climbing to between 1.25 to 1.50 inches, we do look to get our first chance of rain in more than a week. While lapse rates are decent, the CAPE and shear isn`t anything significant. That along with the greater buoyancy staying to our west, suggests that convection will likely remain disorganize. Thus the severe risk is basically non-existent. However, it is non-zero, given dry air between about 700 and 500 mb, and the resulting DCAPE of 600-800 J/kg. So maybe a few strong wind gusts can occur where incoming convection collides with the sea breeze late in the day. There might also be a little hail in the stronger updrafts with WBZ less than 10K feet. The highest chances for convection will be near and west of I-95, where we have 30-40% PoPs late day. It is also those places that might see a couple of stronger storms. Despite increasing cirrus this morning, which lingers into the afternoon, there is good warm advection to allow for max temperatures to hit 80-85F degrees away from the beaches, where the sea breeze holds coastal communities down in the 70s. Tonight: the short wave passes through the forecast area, reaching near the coast or offshore by Wednesday morning. the lee side trough remains in place, while the western side of the Atlantic ridge pulls a bit further out to sea. There is just enough instability and ample moisture for the short wave to work with, so we do maintain chance PoPs much of the night. Although with the passage of the short wave, probabilities drop off across Georgia late. The nocturnal environment is not conducive for any severe storms after the early evening. There are indications of some fog forming across parts of Georgia after midnight. But with perhaps too much lingering cloud cover, we refrained from including in the forecast at this time. Given the cloud cover and dew points in the lower and middle 60s, that`s about as cool as it`ll get. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... A few showers could move through the Charleston Tri-County area Wednesday morning in association with the tail end of the upper shortwave. Weak upper level subsidence will develop during the afternoon as shortwave ridging occurs. However, moderate moisture will remain in place during the afternoon, and a decent sea breeze will develop, potentially popping isolated showers. Deep layered ridging Thursday into Friday should maintain dry weather with above normal temperatures. A shortwave could approach far western areas late Friday afternoon so it`s possible some convection could drift into those zones late in the day. Highs will reach the mid to upper 80s both days. && .LONG TERM /FRIDAY NIGHT THROUGH MONDAY/... A relatively zonal flow will develop Friday night and continue into early next week, with occasional shortwaves rippling through. A weak cold front is forecast to stall across far inland areas over the weekend. Tropical moisture will spread into the area with PWATs hovering around 1.7" much of the period. Isolated to scattered mainly diurnal convection is expected, along with above normal temperatures. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... KCHS/KJZI/KSAV: VFR will prevail at all sites through 06Z Wednesday. There will be a few showers off the coast of KJZI during the late morning and early afternoon, as they remain offshore. Upstream from all terminals, scattered SHRA/TSRA will occur during the mid and late afternoon, eventually progressing east tonight. While flight restrictions are possible should any directly impact a terminal, probabilities are too low to show anything in the latest TAFs. All airfields will experience some wind gusts of 15-20 kt in wake of the sea breeze after 18-19Z. Extended Aviation Outlook: VFR will generally prevail. && .MARINE... Today and tonight: While an inland trough develops and remains in place, it keeps the western edges of Atlantic high pressure close to the local waters through the period. This in turn causes southerly winds of 15 kt or less. The exception might be Charleston harbor this afternoon, where some gusts approach hing 20 kt will be possible at times. Seas in the Atlantic will be no more than 3 or 4 feet. Mariners should be alert for a few t-storms here and there, with a few potentially resulting in gusty winds and frequent lightning strikes. Wednesday through Sunday, no marine concerns expected. Atlantic high pressure will remain the dominant feature with a relatively weak gradient in the area. Wind speeds will generally stay below 10 kt except right along the coast in the afternoon sea breeze, and seas will mostly run 2-3 ft. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...JRL LONG TERM...JRL AVIATION... MARINE...