textproduct: Charleston

WHAT HAS CHANGED

Updated Key Message #1 and the Aviation section for the 18Z TAFs.

KEY MESSAGES

- 1) A fairly typical summertime pattern is forecast with daily shower and thunderstorm chances through the weekend.

DISCUSSION

KEY MESSAGE 1: A fairly typical summertime pattern is forecast with daily shower and thunderstorm chances through the weekend.

As the Atlantic high pressure remains well offshore, the westerly flow aloft will keep the afternoon seabreeze pinned to/near the immediate coastline through the late afternoon, before slowly tracking more inland (esp. along the South Carolina coastline). Afternoon temperatures will reach into the upper 80s to low 90s, with dewpoints remaining in the low to mid 70s (away from the coastline). This environment will be favorable of pulse-like convection in the absence of any meaningful synoptic forcing mechanisms. A couple showers and thunderstorms will likely keep initiating across southeast Georgia and the South Carolina Lowcountry through the afternoon, and then potentially become locally enhanced as the seabreeze pushes inland and/or collides with other boundary outflows. The primary hazards within these thunderstorms that develop will be wind gusts near 40 to 60 mph, frequent cloud-to- ground lightning, and locally heavy rainfall. Thereafter, convection will slowly wind down through the evening as diurnal instability wanes.

Ahead of an approaching cold front, southwesterly flow will likely keep the boundary well mixed for many areas overnight. This will yield temperatures in the low to mid 70s west of I-95 with upper 70s elsewhere. The record high minimums at all three climate sites could be challenged, assuming convection this afternoon does not drive temperatures below record levels prior to 1 AM Tuesday. See the climate section below for additional details.

A weak cold front will move towards the Carolina coastline and across central Georgia Tuesday morning and then stall, remaining nearly through the end of the week. Isolated to scattered showers and thunderstorms are possible Tuesday afternoon/evening, owing to the front in the vicinity, however deep westerly flow will advect drier air into the region and limit convection. Thereafter, isolated to scattered diurnally- driven convection will be possible in the afternoon/evening through the end of the week. A few stronger storms are possible each afternoon, but there is no apparent significant severe threat at this time.

AVIATION /20Z MONDAY THROUGH SATURDAY/

22/18z TAF Discussion: VFR conditions will prevail through the 18Z TAF period, however isolated showers and thunderstorms could impact the terminals this afternoon/evening (esp. KSAV). Therefore, a TEMPO was noted for KSAV between 18/21Z for thunderstorms, and then again between 21/00Z. Also, as southwesterly winds remain rather breezy, gusts of 18-22 kt were mentioned at all terminals through the evening. After the sunset, showers and thunderstorms should gradually wind down overnight.

Extended Aviation Outlook: Brief flight restrictions are possible with mainly afternoon showers and thunderstorms.

MARINE

Through tonight: Broad south-southwesterly flow will persist across the waters as high pressure holds well offshore. Expect winds to rang from 10 to 15 kt, then increasing to 15 to 25 kt across the nearshore Charleston waters late this afternoon. The afternoon seabreeze will likely remained pinned to/near the coastline as the westerly flow aloft delays the onset. As a cold front approaches overnight, expect the highest winds to center across the nearshore Charleston and offshore Charleston waters with the risk of reaching frequent gusts 25-30 kt. Thus, a Small Craft Advisory has been issued for the Charleston nearshore waters. At this time, Small Craft Advisories are not being currently issued for the offshore waters. Expect seas to range from 2 to 4 ft, then increasing to 4 to 5 ft across the offshore Charleston waters briefly after midnight.

Tuesday through Saturday: A weak cold front should approach the Carolina coastline Tuesday morning, and then stall nearby through the end of the week. Expect the pressure gradient to become pinched as the waters sit between the offshore high pressure and a low pressure located across the Mid-Atlantic. This will result in gusts reaching 25-27 kts at times Tuesday afternoon, especially across the Charleston nearshore waters. A brief Small Craft Advisory could be needed, mainly between the afternoon and evening hours. Thereafter, the pressure gradient will relax as high pressure gradually rebuilds over land. There are no additional marine concerns through the remainder of the period.

CLIMATE

Record High Minimum Temperatures:

June 23: KCHS: 78/2024 KSAV: 77/2017

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 6 AM EDT Tuesday for AMZ360.