![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
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
971 FXUS62 KCHS 010602 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 202 AM EDT Mon Jul 1 2024 .SYNOPSIS... A cold front will impact the area Monday into Tuesday before dissipating offshore. High pressure will return for the latter half of the week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Tonight: Aloft, h5 shortwave energy will continue to nudge southeast across the local area along the eastern periphery of a weakened ridge extending across the Deep South. At the sfc, a weak trough will persist inland ahead of an approaching cold front. The pattern will continue to support scattered to numerous showers and a few thunderstorms across inland areas, mainly south of I-16 during the next few hours. Here, observed rainfall totals between 2-3 inches have been common, and an additional 1/2 inch of rainfall could occur as an outflow boundary nudges activity south and eventually beyond the Altamaha River during the next 1-3 hours. Outside of a temporary cooling from precip, temps will remain mild, with lows generally ranging in the mid 70s inland to upper 70s/near 80 near the coast. && .SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/... Monday: Models continue to advertise a heavy rain/flooding signal along parts of the Georgia and lower/middle South Carolina coast for Monday. Subtropical ridging aloft will quickly give way to broad troughing along much of the Eastern Seaboard during the day as pronounced shortwave energy embedded in the northwest flow aloft approaches the Carolina coast. This will help push a slow moving cold front south into southern South Carolina, propagating south of the Santee River by early afternoon. Modified soundings ahead of the front show solid mixed-layer instability (MLCAPE 1500-2000 J/kg with K-indices pushing 40C) developing by late morning embedded within a weak shear environment (0-6km bulk shear averaging ~15 kt). Moisture is also abundant with surface dewpoints progged to hold in the mid- upper 70s with PWATs nearing 2.50" at times (daily max for KCHS for July 1 is just over 2.30" per SPC sounding climatology). Expect convection to develop near the Santee River in the vicinity of the front by late morning, then slowly spread south through the rest of southern South Carolina into Southeast Georgia into the afternoon/evening hours in tandem with the front. Given the degree of instability and moisture coupled with surface moisture convergence values surpassing 50 g/kg/12hr at times near the front and some forcing aloft with approaching shortwave energy, the setup looks favorable of periods of extremely heavy rainfall with hourly rainfall rates potentially exceeding 3 in/hr. This is reinforced by the 30/12z HREF QPF progs showing an ~90% chance for 3+ inches to fall in 3 hours clustered in the Savannah-Charleston corridor. There are even some signals that a few spots could see localized amounts in excess of 6 inches (noted 12-hr probs of >5" averaging 70-75% over central Charleston County, including Downtown Charleston). Although antecedent conditions are fairly dry with D0 and D1 drought conditions in place, there is an increasing concern that pockets of significant flash flooding could occur given the intense hourly rainfall rates expected with the slow moving convection, especially in urban areas such as Beaufort and both the Charleston and Savannah Metro Areas. Complicating matters is heavy rains could be falling at the afternoon high tide which could enhanced the flood risk, especially in Downtown Charleston and nearby communities. A Flood Watch has been issued from Noon until 9 PM Monday for the South Carolina and Georgia coastal counties, including Effingham, Hampton, Inland Colleton, Dorchester and Inland Berkeley. Storm total QPF Monday into Monday night will run 2-4" with localized amounts in excess of 6". Categorical pops 80-100% look reasonable, which is a bit higher than the various 12z statistical guidance packages, but closer to the 30/13z NBM. Highs will warm into the upper 80s/lower 90s, warmest across Southeast Georgia. Convection will slowly wane through night, although elevated pops will hold through daybreak Tuesday as the front moves south and northeast onshore winds will keep moisture in place. This will be especially true for coastal Georgia. Lows will range from the upper 60s/lower 70s well inland to the near 80 along the Georgia and far southern South Carolina beaches. Tuesday and Wednesday: The front will slowly dissipate to the south and offshore through the period as subtropical ridging aloft builds back to the east. The pattern will return to more typical summer time convective regime with onshore winds supporting higher low- level moisture values across Southeast Georgia. Scattered to numerous shower/tstms are expected each afternoon and evening with activity diminishing during the overnight hours. Highs will only warm to the mid-upper 80s Tuesday with upper 80s/lower 90s for Wednesday. Lows Tuesday night will range from the lower 70s well inland to the upper 70s/near 80 at the beaches. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... An impressive upper-level anticyclone will setup across the Deep South and Southeast U.S. mid-late week. The risk for showers/tstms will generally average below climatological normals as a result. The heat will also steadily build with highs reaching the upper 90s/near 900 inland Friday into the weekend. Heat indices will push the 108 Heat Advisory criteria during this time as well. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... KCHS/KJZI/KSAV: Lingering showers across southeast Georgia and newly developed showers near the CHS/JZI has led to TEMPO MVFR cigs/vsbys being included between 06Z-08Z tonight. VFR conditions should then return late tonight and persist into late morning hours. However, the next chance for convection and prolonged flight restrictions will occur Monday afternoon as a cold front slowly moves over and/or stalls across the area. Showers and thunderstorms, some possibly moderate to heavy rain producers, are expected to impact all terminals by 19Z Monday, then persist for at least a few hours into early evening. TSRA remains at all terminals during this time frame, followed by SHRA Monday evening. Tempo IFR cigs/vsbys are possible during thunderstorms and will likely be added in future TAF issuances as timing of direct impacts becomes more clear. Precip should come to an end by 03-04Z Tuesday, but flight restrictions will remain at all terminals for at least MVFR cigs through 06Z Tuesday. Extended Aviation Outlook: Brief flight restrictions are possible in showers and thunderstorms, mainly in the afternoon and evenings through the period. && .MARINE... Tonight: There remains a fairly tight gradient between an inland cold front and Atlantic high pressure across Florida. This will produce S and SW winds as high as 15 to 20 kt, and perhaps a few gusts up to 25 kt along the coast during the next hour or two, but trends favor a gradually diminishing of winds late. The duration should fall just short of the need for a Small Craft Advisory across local waters overnight. Seas will range between 2-4 ft, largest across offshore Georgia waters. Monday through Friday: A cold front will drop south through the waters Monday with east/northwest winds prevailing all areas Monday night. Widespread showers/tstms with heavy rain could reduce vsbys to less than 1 NM at times and be accompanied by gusty winds and cloud- to-ground lightning. There will be a bit of a post-frontal surge Monday night into Tuesday with speeds increasing to 15-20 kt over the South Santee to Edisto Beach nearshore leg with 10-15 kt elsewhere. Northeast winds will gradually veer more southerly for Thursday and Friday. Seas will average 2-4 ft through the period, except up to 5 ft over portions of the South Carolina nearshore waters in the northeast flow behind the cold front. && .CLIMATE... Daily Rainfall Records for July 1: KCHS: 2.66 set in 1948 KCXM: 1.64 set in 1966 KSAV: 2.76 set in 1871 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Flood Watch from noon EDT today through this evening for GAZ101-116>119-137>141. SC...Flood Watch from noon EDT today through this evening for SCZ042>045-047>052. MARINE...None. && $$ NEAR TERM...DPB SHORT TERM... LONG TERM... AVIATION...DPB MARINE...DPB