Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
030 FXUS62 KCHS 241449 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1049 AM EDT Fri May 24 2024 .SYNOPSIS... A series of weak disturbances will move through the area late week into the holiday weekend. A cold front could bring impacts to the region Monday night into Tuesday. && .NEAR TERM /THROUGH TONIGHT/... Today: Morning analysis indicates the Atlantic ridge across the Florida peninsula, while a lee side trough is also indicated to our northwest. there is also a weak warm front to our west that edges closer this afternoon. Upper air analysis reveals a weak MCV moving east through southern Georgia, with a stronger short wave heading east from western Tennessee and northern Mississippi. The first feature aloft will dampen further as it moves through our southern zones early afternoon. This will likely not have have any impacts on our convective potential. The further upstream wave will approach might take until very late or this evening until it gets close enough to aid in development of showers ands t-storms. Even so, our convective temperatures will be reached by early to mid afternoon, and with less of a cap than recent days, the sea breeze could become more active, as well as other micro and meso scale boundaries. Given PWat near 1.75 inches, plus sufficient SBCAPE around 2000-2500 J/kg, and only minimal CINH, we do foresee decent coverage of showers and t-storms during the mid and late afternoon. Some of the convective parameters are indicate of some strong or severe storms. This includes a K-Index of 38; Total Totals Index of 52; Lifted Index of -7. The DCAPE is around 1000-1200 J/kg, suggesting that damaging winds are possible in the strongest storms. While the hail potential is lower since Wet Bulb Zero is around 11-12K feet. But since the SPC outlook has a 5% chance, it is certainly a possibility. Guidance provides mixed solutions on where the greatest coverage and severe potential exists. But there are indications that the nearby warm front would help in getting activity going across central Georgia as it spreads east with the steering flow. Then it combines with the other small scale boundaries to produce as much as numerous showers and t-storms. We have numerous convective coverage over most of our South Carolina zones and Chatham County in Georgia. But adjustments will likely be required as more recent model data and trends become available. There is some risk for heavy rains and at least a minor to perhaps moderate flooding concern. the 00Z HREF shows high enough probabilities of 1" or greater in 3 hour periods from 18-21Z and again from 21-24Z that Flood Advisories are possible. This includes the areas in and near Charleston, Beaufort, and Savannah. It is certainly plausible that if the heavier rains are slower in ending this evening, that there is an additional concern about the 930 PM high tide in Charleston, as we are currently showing 6.8 ft MLLW around that time. Low level thickness supports temperatures in the lower and middle 90s. But given the convective rains, we didn`t go that hot. We kept the previous forecast which had highs a few degrees either side of 90F away from the beaches. Tonight: Convection will wind down during the course of the evening with loss of heating and exit of the MCV. But, another MCV/ripple in the flow may be right behind potentially bringing additional showers and thunderstorms into the area late. Again, each successive high resolution guidance run offers a differing scenario leading to low confidence. For now, we have precip chances starting to increase again toward Saturday morning. && .SHORT TERM /SATURDAY THROUGH MONDAY/... Northwest flow develops aloft on Saturday as a shortwave trough shifts offshore. There could be some convective activity moving through in the morning, with additional development expected in the afternoon during peak heating. Shear remains around 20 knots, so an organized severe threat is not expected, but a few stronger storms with gusty winds are possible with drier air in the mid levels and DCAPE progs approaching 1000 J/kg. Temperatures will peak around 90/lower 90s. Showers/thunderstorms should fade/shift offshore Saturday evening. Lows mainly in the upper 60s to lower 70s. Mid level heights continue to build overhead on Sunday. Convection will be limited with mainly just isolated diurnal showers and thunderstorms possible. The hot temperatures will continue with highs forecast to reach the low to mid 90s (this is 5 to even 10 degrees above climo). Low temperatures stay mild, only falling to the lower 70s. The ridge axis will get pushed offshore on Monday/Memorial Day as a mid level trough shifts into the eastern CONUS. Concurrently, a cold front will approach the region. Convection could stay pretty isolated through much of the daylight hours, before activity possibly moves in from the west later in the day and overnight. Forecast features just 20% rain chances through 00z. It will be another hot day with highs again in the lower to mid 90s. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... A cold front moves into the region Monday night into Tuesday. There should be an uptick in shower/thunderstorm coverage during this timeframe with larger scale forcing for ascent. Quieter weather looks to return mid week and beyond with deepest moisture exiting off the coast. Unseasonably warm temperatures will moderate back to normal through the period. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... VFR conditions are expected at the CHS/JZI/SAV terminals through at at least 18Z. Showers and/or thunderstorms may eventually impact the terminals mid-late afternoon for a few hours and produce flight restrictions. VCTS has been included at all terminals from 20Z through 00Z/01Z. Convection diminishes thereafter, although some additional convection might advance back into the region late overnight. However, confidence is too low to add any mention to the current terminal forecast. Extended Aviation Outlook: Brief flight restrictions are possible due to showers/thunderstorms each afternoon/evening. && .MARINE... Surface high pressure will remain off the southeast coast through tonight with south to southwest winds prevalent. Wind speeds of 10 to 15 knots will be common and seas 3 feet or less. A few strong or severe t-storms can occur during the late afternoon and early evening as they move offshore. Wind gusts could be enough to produce Special Marine Warnings for winds of 35 kt or greater. Saturday through Wednesday: Southerly flow prevails through early next week, until a cold front cross the waters late in the period. Conditions stay below Small Craft Advisory criteria, with winds generally 15 knots or less and seas 2-3 feet on average. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...