Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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597 FXUS62 KCHS 100617 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 217 AM EDT Fri May 10 2024 .SYNOPSIS... A cold front will approach the area tonight, then move offshore Friday. High pressure will prevail for the weekend into early next week. A storm system could affect the area by the middle of next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 215 AM, IR satellite indicated widespread debris clouds across the region. Regional radar indicated a cluster of thunderstorms over south central GA, tracking to the southeast. This activity is expected to gradually dissipate over the next couple of hours. However, the updated forecast will feature SCHC PoPs across portions of SE GA early this morning. Temperatures really won`t move much through rest of the night, with actual lows in the mid 60s to lower 70s. && .SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/... The forecast for Friday is quite tricky. A quasi-zonal flow will persist aloft, though we will see several potent shortwaves ripple through the area during the day. Given the high theta-e airmass across the Southeast, ample instability should be in place to support convective development with these upper vort maxima. Furthermore, the presence of 50-60 kt of 0-6 km bulk shear will favor organization of the convection once it become established. Most of the guidance continues to indicate the most impressive shortwave will move through southeast SC/GA between 15Z and 18Z. There is surprising agreement between the synoptic models and the CAMs that a large area of showers and thunderstorms will move across the forecast area between 9am and 3pm Friday. It appears that an MCS could be ongoing across south central GA at daybreak that then pushes east through our area. Thus, the greatest coverage of convection would occur over our southeast GA zones. This is also where the strongest convective indices are expected, so our primary focus for severe weather potential is in southeast GA and extreme southern SC. Damaging winds appear to be the primary threat assuming the convection becomes organized into a line. Isolated large hail or tornadoes can never be completely ruled out. Farther to the north in SC, at least scattered showers and thunderstorms will move through, but extensive cloud cover in the morning and less available instability should reduce the overall severe weather potential. Rainfall totals on Friday will range from 1-1.5" in southeast GA and 0.5-1.0" in southeast SC. The brunt of the convection is expected to be off the coast by 3pm. A secondary shortwave will drop into SC early Friday evening, pushing the cold front into the area. A big question mark is what convection, if any, develops out ahead of the front. It will heavily depend on what happens in southern SC with the first batch of convection and whether or not the airmass gets worked-over as a result. If convective coverage is limited during the early afternoon activity, a greater degree of destabilization could occur in southern SC, allowing for a more conducive airmass for convective development late Friday afternoon or early evening. For now we penciled in scattered PoPs across eastern Berkeley/Charleston Counties late afternoon and early evening. Saturday will be dry and noticeably cooler with highs in the upper 70s. Sunday will warm up a bit due to upper ridging, with highs in the mid 80s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Early next week will briefly start off quiet before a warm front extending across the Deep South lifts north. Conditions look quite unsettled beginning late Monday night into Wednesday due to plentiful upper forcing and deep moisture building in. Several rounds of showers and thunderstorms are expected. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... Prior to the 6Z TAFs, IR satellite indicated widespread debris clouds across the terminals. Regional radar indicated a cluster of thunderstorms over south central GA, tracking to the southeast. This activity is expected to dissipate before reaching KSAV. However, a period of MVFR ceilings may develop over KSAV from 9-13Z. The main challenge will be the timing and intensity of MCS, located over southern AL and MS before 6Z TAFs. Based on the majority of the CAMs, the core of the MCS track along the FL/GA this morning. A band of showers and thunderstorms on the north side of the MCS is timed to pass over KSAV, expected between 13-16Z. The KSAV TAF will feature a mention of SHRA with VCTS between 13-16Z. KCHS and KJZI, the coverage TSRA will remain limited, the TAFs will indicate SHRA between 14-19Z. Late in the afternoon, a narrow band of showers and thunderstorms will develop along a cold front west of the terminals. After sunset, the coverage of showers and thunderstorms will decrease as the front approaches the terminals. The cold front is time to pass over the terminals between 3-4Z, turning winds from the NW at 10kts. Extended Aviation Outlook: VFR conditions will return for the weekend into early next week. Scattered convection expected Monday night and Tuesday. && .MARINE... Tonight: Expect winds to be mainly S-SW 10-20 kt. A few gusts up to 25 kt are possible at times, but not enough to justify a Small Craft Advisory. Seas will be in the 2-4 ft range. Low stratus and maybe some fog will develop overnight. Likely not enough fore an advisory, but possibly a Marine Weather Statement for Charleston Harbor. Friday: A decent SW gradient expected in advance of a cold front, though winds will be quite variable once convection moves offshore midday. Late in the afternoon and early evening, wind gusts could approach 25 kt, so it`s not out of the realm of possibility that a short-duration Small Craft Advisory is needed. Due to the low confidence we will hold off on any issuance with this package. Marine conditions will improve Saturday morning as high pressure builds in from the west. Winds/seas expected to increase Monday night into Tuesday ahead of the next storm system. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM...JRL LONG TERM...JRL AVIATION...NED MARINE...