textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section was updated to reflect the 12Z TAFs.

KEY MESSAGES

- 1) Hot and humid conditions are expected across the area this weekend and through early next week. Heat Advisories could be needed.

DISCUSSION

KEY MESSAGE 1: Hot and humid conditions are expected across the area this weekend and through early next week. Heat Advisories could be needed.

Today: Aloft, a ridge will become more pronounced across the western Atlantic while low pressure slides across the eastern Gulf. At the sfc, a light southwesterly wind will prevail across the local area into mid-late morning between high pressure offshore and weak troughing inland. This should help temps warm into the mid-upper 90s away from the immediate coasts while some low-lvl mixing out of sfc dewpts into the lower 70s occurs across the interior with some drier air depicted on model soundings. The exception will remain along the coast, where the light southwest wind turns south/southeast with a sea breeze, causing a surge in dewpts (upper 70s to near 80). This should occur 1-2 hours quicker than the previous day, favoring a longer period of higher dewpts in spots where afternoon highs approach the mid-upper 90s prior to isolated/scattered convection. Heat index values should approach 108-110 degrees across Charleston and eastern Berkeley County where convection is more isolated, with a the surge of dewpts occurring for some 3-5 hours during peak heating hours. A Heat Advisory has been issued for Charleston and Berkeley Counties from 11 AM to 7 PM EDT as a result.

Late weekend into the middle of next week: Sfc high pressure will persist across the western Atlantic, favoring a southwest/south flow that brings slightly higher dewpts and warm afternoon temps in the mid-upper 90s. Widespread heat index values above 100 degrees across Southeast South Carolina and Southeast Georgia are likely, while a swath of 105-110 heat index values occurs for areas along and east of the I-95 corridor. Heat Advisories could be needed each afternoon during the weekend through the middle of next week. However, convective coverage could become more numerous with an inland trough nearby next week, followed by the approach of a front from the northwest heading into the middle of next week. This could limit overall heating potential if occurring during peak heating hours each day.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

17/12Z TAFs: VFR conditions will prevail through mid-day, accompanied by light SSW winds. In the early afternoon, hi-res guidance continues to hint that the seabreeze should develop and progress inland between 19-20Z. As this boundary pushes inland, isolated to scattered showers and thunderstorms should develop along with it, thus a TEMPO was mentioned at KCHS/KSAV and a PROB30 at KJZI for a -TSRA between 20-24Z. In addition to the convection, the winds should veer out of the south around 10 kts with gusts up to 15 kts as this boundary passes over each terminal. After 00Z, convection should diminish and VFR conditions are likely to prevail again.

Extended Aviation Outlook: Predominately VFR conditions through the period, however there is a low chance of brief flight restrictions each afternoon from showers and thunderstorms developing along the seabreeze.

MARINE

Today: As a subtropical high develops across the local waters, expect south-southwesterly winds at 5 to 10 kts with gusts up to 15 kts to persist through the majority of the day. Seas will range from 2 to 3 ft.

Saturday through Sunday: The pressure gradient will strengthen this weekend as the local waters become sandwiched between an inland trough and the aforementioned high developing to the east. This will yield strong south-southwesterly flow with wind speeds ranging from 15 to 20 kts with possible gusts up to 25 kts (esp. across the South Carolina waters + Charleston Harbor). Thus, there is a chance that we'll need Small Craft Advisories (SCAs) on Saturday evening through early Sunday morning. Expect seas to range from 2 to 3 ft, before increasing 2 to 4 ft in the nearshore waters and 4 to 6 ft in the offshore waters (highest across the 20-60nm out from South Santee, SC to Savannah, GA).

Monday and Tuesday: The aforementioned inland trough will likely shift offshore early next week, yielding the continuation of elevated winds with a low chance of additional SCAs on Tuesday. It's noteworthy to mention that there is a low chance (20%) for a low pressure system to develop across the northeastern Gulf this weekend and then shift slowly northeastward across our local waters on Monday/Tuesday, which could bring additional wind and wave concerns.

CLIMATE

Record High Temperatures:

July 17: KCHS: 99/1983 KCXM: 97/1925

Record High Minimum Temperatures:

July 17: KCHS: 79/2025

July 18: KCHS: 79/2007 KCXM: 81/2007

July 19: KCHS: 79/1986 KCXM: 83/1986

July 20: KCHS: 79/2025 KCXM: 83/2000 KSAV: 79/1942

July 21: KCHS: 80/1986 KCXM: 83/1998

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

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...Heat Advisory from 11 AM this morning to 7 PM EDT this evening for SCZ045-150-152. MARINE...None.