textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section has been updated for the 00Z TAF issuance.

KEY MESSAGES

- 1) This weekend will feature hot and humid conditions, with temperatures Sunday approaching triple digits in some spots. Heat Advisories may be needed Saturday and likely required Sunday.

- 2) Temperatures decrease slightly into the middle of next week, with hot conditions building into the weekend. Rainfall chances decrease throughout the week.

DISCUSSION

KEY MESSAGE 1: This weekend will feature hot and humid conditions, with temperatures Sunday approaching triple digits in some spots. Heat Advisories may be needed Saturday and likely required Sunday.

500 mb ridging across the southeastern states will build into Sunday, with a 594 dam high located over Mississippi by Sunday evening. High pressure will also be the dominant synoptic feature at the surface, with high pressure anchored over the northern Gulf. This synoptic pattern will support building temperatures and above normal moisture values. The combination of the heat and humidity will yield heat index values 100-105 on Saturday and 103-109 on Sunday. At this juncture, heat index values for Saturday appear to be just shy of Heat Advisory criteria. Conditions Sunday will be slightly warmer and a Heat Advisory may be required along areas east of I-95. Temperatures on Sunday could challenge the records at the local climate sites, see the Climate Section for details.

It is worth noting that in addition to the hot and humid daytime conditions, overnight lows will also challenge record high minimum temperatures at the local climate sites. Overnight temperatures will only dip into the mid to upper 70s, with some low 70s further inland. These lows will provide little relief from the daytime heat. Afternoon convection will be limited both Saturday and Sunday, given the plentiful dry air aloft and the dominating high pressure.

KEY MESSAGE 2: Temperatures decrease slightly into the middle of next week, with hot conditions building into the weekend. Rainfall chances decrease throughout the week.

A weak prefrontal surface trough moves through during the Monday morning hours, with some "cooler" temperatures lagging behind. As some weak shortwaves move down the eastern periphery of the ridge amidst decent low-mid level moisture, scattered showers and isolated thunderstorms activity is expected to build throughout the morning hours. Chances for severe weather can't be ruled out given soundings showing 1500-2500 J/kg CAPE, but details are unclear. With additional rainfall chances due to the expected afternoon sea- breeze, the temperature forecast may be running a touch on the warm side. Heat indices into the lower to mid 100s may still occur in between rounds of rainfall, with isolated spots along the coast possibly making it into the upper 100s given higher dewpoints in the mid/upper 70s.

As the aforementioned ridge slow shifts eastwards Tuesday, slightly cooler temperatures work their way through the 850mb flow across the region, resulting in afternoon highs in the upper 80s along the coast to lower 90s for inland areas. Isolated showers/storms can't be ruled out, though the subsidence from the high pressure throughout the column will likely keep any such activity rather short-lived. Expect much of the same for Wednesday.

Ridging aloft continues to shift towards the east coast into the end of the week, further decreasing chances for showers/storms as the subsidence aloft intensifies. The already warm/hot air mass will continue to warm into the weekend, with upper 80s to lower 90s expected along the coast and up into the mid/upper 90s for inland areas. The need for a Heat Advisory will be closely monitored as heat index values begin to reach up into the upper 100s Thursday/Friday, with chances continuing into the weekend.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

VFR conditions are expected to prevail at CHS/JZI/SAV terminals through 00Z Sunday. However, an isolated shower can not be ruled out at the terminals overnight, then again during peak heating along/near a sea breeze Saturday afternoon. Winds should top out around 14-17 kt Saturday afternoon.

Extended Aviation Outlook: Brief flight restrictions are possible due to showers and thunderstorms, mainly each afternoon.

MARINE

Through Tonight: Southerly wind gusts will remain 15 to 20 knots through the overnight across the nearshore waters. Conditions should remain below Small Craft Advisory criteria, however there is a chance that some 25 knot gusts could occur in the nearshore Charleston County waters in the early morning hours Saturday.

Saturday and Sunday: Surface high pressure over the Atlantic will keep winds predominately out of the southwest through the weekend. During the afternoon hours however, expect more of a southerly direction behind the expected sea breeze, which is when wind speeds will increase into the evening hours with winds sustained in the teens to lower 20s and gusts into the mid 20s before decreasing into the overnight hours. Can't rule out brief Small Craft Advisory (SCA) level winds, but widespread SCA criteria are not expected at this time.

Monday and Tuesday: Expect weak winds on Monday as a prefrontal trough moves into the area bringing variable winds. Breezy northeasterly winds develop as an inland surface high pressure moves towards east coast, though currently looking to remain sub-SCA criteria.

Rip Currents: Gusty winds with the sea breeze and 2-3 ft/8 sec swells will continue to result in a borderline low/moderate rip risk forecast across all southeast South Carolina and southeast Georgia beaches through the weekend. Local rip current calculations support a low risk while the latest rip current MOS output supports a moderate risk.

CLIMATE

Record High Temperatures:

June 28: KCHS: 99/1998 KCXM: 100/1959 KSAV: 100/1998

July 2: KCHS: 99/1996

Record High Minimum Temperatures:

June 27: KCHS: 77/2015

June 28: KCHS: 78/2013 KCXM: 81/1998 KSAV: 80/1880

June 29: KCHS: 79/1977

July 1: KCHS: 77/2024

July 2: KCHS: 78/2025

CHS WATCHES/WARNINGS/ADVISORIES

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