Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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246 FXUS62 KCHS 101923 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 323 PM EDT Fri May 10 2024 .SYNOPSIS... A cold front will push through the area tonight. 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 SATURDAY MORNING/... This evening and tonight: Satellite imagery shows cirrus steadily thinning and shifting to the east while a cumulus field is quickly filling in. Surface analysis shows that the cold front stretches from central Georgia through the South Carolina Midlands. This front will track to the southeast through the evening and shift offshore by the early morning hours. Along the front, we are seeing instability start to pool and this should be enough to trigger isolated to scattered convection this afternoon and into the evening. In fact, the first storms have already developed near the NC/SC state line. For our forecast area, the question is how much recover will there be over the next few hours and will these upstream storms along the front be able to move into portions of the area. Model guidance suggests that MLCAPE as high as 1,000-1,500 J/kg will be possible right along the front by early evening. The main area of concern for convection, and a couple of strong to marginally severe storms, will be for interior southeast South Carolina and especially inland Colleton, Dorchester, and Berkeley counties. This aligns with where the SPC Day 1 Marginal Risk is in place, and we will continue to highlight the threat in the Hazardous Weather Outlook. Flow in the mid-levels will be strong enough to yield 0-6km shear around 50 knots and 0-3km shear around 30 knots. So any storms that develop will have a damaging wind gust potential, as well as large hail potential. All convection should shift offshore by the mid to late evening hours, and the rest of the overnight will be dry. The front will shift offshore and northerly flow will usher in much cooler and drier air. Overnight lows are forecast to range from the mid 50s inland to the upper 50s and low 60s along the coast. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... Saturday and Sunday: A stout northwest flow will dominate aloft as surface high pressure builds in from the west. Quiet, dry conditions will prevail with forecast soundings showing modest capping aloft with low net moisture values (PWATs <1"). A modest west/northwest flow atop the boundary layer should delay/pin the afternoon resultant sea breeze both afternoons. Low-level thickness values support highs in the upper 70s/near 80 on Saturday warming into the lower 80s on Sunday. Lows Saturday night will drop into the mid- upper 50s inland with mid 60s at the beaches with upper 50s/lower 60s inland and upper 60s/near 70 at the beaches Sunday night. Monday: A warm front will begin to organize to the south and move north into the area as a storm system develops to the west. Isolated to scattered showers/tstms could develop near this feature in the afternoon, but the bulk of anything meaningful looks to remain south of the Altamaha River. Forecast soundings north of the warm front are not overly unstable with meager MLCAPE, positive LI`s with K- indices <30C noted, so conditions do not look overly favorable for deep convection despite highs warming into the upper 70s/lower 80s. Pops 20-30% look reasonable during this time with any mention of thunder being confined to mainly Southeast Georgia due to some uncertainty on location/timing of the developing warm front. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Monday Night and Tuesday: Rain chances will increase Monday night into Tuesday as a warm front lifts north and the region becomes fully embedded within the warm sector of an approaching storm system. Modest forcing for ascent ahead of a number of southern stream impulses embedded ahead of a shortwave that digs across the Tennessee and Ohio Valleys will steadily increase within an increasingly moist environment. There are a few model signals that a large convective complex along the northeast Gulf coast/Florida Panhandle could disrupt moisture transport into the area which could limit the amount of convection over Southeast South Carolina and Southeast Georgia Tuesday. These trends will have to be watched carefully. For now, a blend of the NBM with the drier SuperBlend consensus was used to construct pops. Pops 60-70% were highlighted for Monday night with 80% pops for Tuesday. Lows Monday night will range from the lower 60s well inland to the lower 70s at the beaches. Highs Tuesday will warm into the upper 70s/lower 80s, limited by extensive cloud cover and showers/tstms. Wednesday and Thursday: Overall, rain chances will be lower for Wednesday into Thursday, but some degree of convection can be expected as a series of weak fronts/troughs move through the Southeast States. Chance pops were highlighted during this time. Temperatures will be near to slightly above normal for both days. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... VFR conditions should prevail at KCHS, KJZI, and KSAV through 18z Saturday. The main forecast challenge will be the potential for isolated to scattered showers and thunderstorms late this afternoon and early this evening, primarily near KCHS and KJZI. We have added in a few hours of VCSH as the confidence of direct impacts at KCHS and KJZI remains low. A thunderstorm will be possible too, but chances aren`t high enough to include a mention of TSRA. Whatever activity does develop will shift offshore in the evening and the rest of the period will be dry. Skies will clear out overnight as well. Winds will turn northwesterly and then northerly overnight. Extended Aviation Outlook: Showers and thunderstorms could bring flight restrictions to the terminals Monday afternoon into the middle of next week. && .MARINE... Tonight: Elevated west-southwest flow will continue this evening, with a solid 15-20 knots and a few isolated gusts up to around 25 knots. An inland cold front will shift offshore by the early morning hours and winds will turn northwesterly and eventually northerly. Wind speeds will remain elevated into the 15-20 knot range. A few gusts up to around 25 knots will be possible, but we have opted to not issue any Small Craft Advisories at this time as winds should remain below criteria most of the time. Seas are forecast to average 2-4 feet through the night. Saturday through Wednesday: There are no concerns through Monday. The risk for Small Craft Advisory conditions will increase Monday night into Tuesday as a warm front lifts north and storm system approaches from the west. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM... LONG TERM... AVIATION...BSH MARINE...BSH