textproduct: Charleston

WHAT HAS CHANGED

The Key Messages have been updated.

KEY MESSAGES

- 1) Hot and humid conditions across coastal South Carolina and Georgia today.

- 2) A slow-moving front will drift into the area from the north and bring increased chances for showers and thunderstorms late this weekend and into the weekend. Locally heavy rainfall will be possible and could bring a risk of flooding to portions of the area.

DISCUSSION

KEY MESSAGE 1: Hot and humid conditions across coastal South Carolina and Georgia continues into the weekend.

One last day of hot and humid conditions expected to continue as deep southwesterly return flow continues. Deep moisture will continue to surge northward and pool along a slowly sagging boundary by the weekend. Guidance continues to slow the boundary approach and have it stall over the area by the weekend. As a result of the slower arrival time, high temperatures will continue to reach in the mid to upper 90s today. With some drier air aloft, interior areas will continue to mix out into the upper 60s to low 70s for dewpoints once again keeping heat indices into the low triple digits (100-105 range). Closer to the coast, the afternoon seabreeze will likely remained pinned to the coast until later in the afternoon moving inland around 17 to 18Z. Behind the boundary, dewpoints will likely climb into the upper 70s to near 80 degrees. The rising dewpoints combined with mid to upper 90s, heat index values right along the coast may range from 105 to 109 degrees. However, the higher heat indices would likely not last long enough to support an advisory at this time.

The slow moving front should provide some relief to the area, especially further north as rain should keep high temperatures in the low 90s to potentially upper 80s where the heaviest rain occurs. However, the front is expected to stall and washout over the area during the weekend. As a result, moisture will pool along and south of this boundary with many areas likely not seeing as much rain as originally expect. Deep moisture content throughout the column would likely result in dewpoints in the mid to upper 70s area wide. Despite temperatures maybe hanging a few degrees cooler than the last week, increased dewpoints should help sustain heat indices in the low 100s through the weekend, especially the further south into Georgia. Thus while some areas could see some temporary relief from the heat, others will continue to deal with the hot and humid conditions well into the weekend and possibly next week.

KEY MESSAGE 2: A slow-moving front will drift into the area from the north and bring increased chances for showers and thunderstorms on Friday and into the weekend. Locally heavy rainfall will be possible and could bring a risk of flooding to portions of the area.

A cold front will slowly drift southward towards the region, before reaching the area on Friday and stalling in the vicinity though the weekend. As moisture associated with Bertha combines with an already moist airmass across the Southeast, PWAT values will increase to around 2.2 inches on Friday and up to 2.5 inches this weekend. This deep moisture combined with the presence of the front will yield increased showers and thunderstorms. This environment will favor efficient rainfall production and an increased the potential for localized flooding. While most flooding impacts are expected to remain minor, repeated heavy downpours over urban areas such as the Charleston, or Savannah Metro areas could warrant Flood Advisories and/or even Flash Flood Warnings.

There remains some question regarding how far south the front will make it, and current model consensus suggests that it will mostly become aligned across our southeast South Carolina counties. The setup is expected to favor rounds of showers and thunderstorms for the Friday through Saturday time period, with drier conditions returning by Sunday.

Although still subject to change, rainfall totals of 1-3 inches appear likely, especially across parts of southeast South Carolina and lesser amounts across southeast Georgia. Additionally, locally higher totals will be possible where thunderstorms repeatedly train over the same location. The Weather Prediction Center (WPC) continues to highlight southeast South Carolina in a Marginal Risk for excessive rainfall for Friday and Friday night, and then the entire area in a Marginal Risk for excessive rainfall Saturday and Saturday night.

AVIATION /14Z THURSDAY THROUGH MONDAY/

VFR conditions are expected to prevail at CHS/JZI/SAV terminals. The sea breeze should move inland during the afternoon across all terminals resulting in a slight wind shift from southwesterly to more southerly around 10 kts.

Extended Aviation Outlook: Chances of flight restrictions increase later this week with a greater coverage of showers/thunderstorms.

MARINE

Thursday (today) through Monday: Light to moderate winds should continue across the local waters as a cold front approaches from the region. Small Craft Advisories are expected to end by this morning. This aforementioned front will stall in the vicinity on Friday through the weekend, yielding increased showers and thunderstorms. Expect marine conditions to remain rather benign throughout this period. Seas will range from 2 to 3 ft.

Rip Currents: There is also a Moderate Risk for rip currents for Charleston County beaches through this evening. Although surf is expected to subside a little bit, a longer-period swell of around 8 seconds should continue to support dangerous rip currents. There is a Low Risk of rip currents for all beaches on Friday.

CLIMATE

Record High Temperatures:

July 23: KCHS: 99/2015

Record High Minimum Temperatures:

July 22: KCHS: 81/2011 KCXM: 83/2011

July 23: KCHS: 80/1991 KCXM: 83/1952

July 24: KCHS: 81/2024

July 25: KCHS: 80/2011 KCXM: 82/2016 KSAV: 80/1893

July 26: KCHS: 78/2025

July 28: KCHS: 80/2025

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.