textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Hot and humid conditions will occur this weekend and into Monday, with Sunday temperatures near 100 degrees in some locations. Heat Advisories could be needed on Sunday.

- 2) Temperatures will decrease to near normal for the middle of next week, then the heat returns for the end of next week. Rainfall chances gradually decrease throughout next week.

DISCUSSION

KEY MESSAGE 1: Hot and humid conditions will occur this weekend and into Monday, with Sunday temperatures near 100 degrees in some locations. Heat Advisories could be needed on Sunday.

Today: The synoptic setup today features ridging aloft centered over the northern Gulf, with high pressure at the surface centered over the western Atlantic. The combination of ridging aloft and high pressure at the surface has allowed temperatures to soar into the low to mid 90s across the region with several coastal locations reporting heat index values between 100-105. While shy of Heat Advisory criteria, dangerous heat will prevail through the remainder of the afternoon. CAMs are unimpressive with coverage of afternoon convection, leading to no real relief from the heat. Isolated showers and thunderstorms are possible along the sea breeze this afternoon. DCAPE values and shear are meager at best this afternoon, however a strong to marginally severe thunderstorm can't be ruled out along boundary interactions.

Overnight lows tonight will challenge record high minimums at some of the local climate sites, only dropping into the 70s. This will provide little relief from the heat heading into Sunday, which is forecast to be the warmer of the days this weekend.

Sunday: The only synoptic change on Sunday is a slight shift in the surface high pressure which will yield a more westerly surface wind across the local area. This will likely keep the sea breeze pinned along the coastline until later in the afternoon allowing temperatures to warm into the upper 90s and maybe even touch 100 in a few spots. A pinned sea breeze will allow lower the chances of afternoon convection, with only isolated coverage anticipated. Given the humid airmass in place along with the warm temperatures, heat index values will likely reach to 100-105 west of I-95 and 105-110 along the coastal corridor. At this juncture a Heat Advisory has not been issued for the coastal counties as confidence is too low that criteria (>108 heat index values) will be reached for 2 hours or more. The need for a Heat Advisory will be reevaluated with future forecast updates.

Monday: The ridging aloft will persist into Monday while at the surface a weak front will stall off the southeast coastline. Another hot day is forecast, with temperatures reaching into the mid 90s once again. Combined with dewpoints in the 70s heat index values will be in the 103-110 range. With the stalled front off the southeast coast an increase in shower/thunderstorm coverage is anticipated, with the forecast featuring scattered to widespread PoPs in the afternoon. Given the higher coverage of convection a Heat Advisory is unlikely, as the showers/thunderstorms will inhibit temperatures from reaching their full potential. While widespread severe weather is not anticipated, strong to marginally severe storms are possible especially along boundary interactions.

KEY MESSAGE 2: Temperatures will decrease to near normal for the middle of next week, then the heat returns for the end of next week. Rainfall chances gradually decrease throughout next week.

Ridging aloft will remain the dominant synoptic feature next week. Initially centered over the TN Valley early in the week and then shifting eastward towards the East Coast by the end of the week. Temperatures are forecast to moderate to near normal values in the middle of the week before warming to above normal as the ridge shifts eastward towards the end of the week. High temperatures could again reach into the mid to upper 90s, which combined with dewpoint values in the 70s will likely yield heat index values in the 100-110 range. Heat Advisories could be required for portions of the forecast area at the end of the week and into the holiday weekend.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

A brief shower or thunderstorm cannot be ruled out this afternoon, especially at KSAV, with mainly VFR conditions prevailing at KCHS/KJZI. Diurnal cumulus will continue to lead to TEMPO BKN conditions, but the bases should remain above any flight restrictions and coverage will diminish with the loss of heating this evening. Otherwise, winds will back as the sea breeze front moves inland during the afternoon. The flow will weaken as it veers back to a Wly direction overnight into Sunday morning.

Extended Aviation Outlook: Showers and thunderstorms may lead to flight restrictions, especially from late Sunday afternoon into Sunday night as a front moves toward the area. Some flight restrictions are possible due to these storms. Brief restrictions are also possible due to convection Monday and Tuesday afternoons.

MARINE

Through Tonight: A typical summertime pattern will persist across the marine waters through the remainder of this afternoon and into tonight. Southerly gusts along the coast/land interface will reach around 20 knots with a few higher gusts possible with the afternoon sea breeze. Winds will remain elevated along the coastline overnight, with gusts in the 15 to 20 knot range.

Sunday: Surface High pressure over the Atlantic will cause backing of the winds during the afternoon. The highest winds will be along the land/sea interface with the formation of the sea breeze. Gusts to 20 or briefly 25 kt will be possible, especially as the sea breeze crosses through the Charleston Harbor. At night, winds will veer and gradually ease.

Monday through Wednesday: Expect weak winds on Monday as a prefrontal trough moves into our area. Winds then shift to the NE by early Tuesday, where they'll prevail into Wednesday.

Rip Currents: Gusty winds with the afternoon sea breeze and a 2-3 ft swell at 8-9 seconds will generate a Moderate Risk of rip currents at all of our beaches this weekend.

CLIMATE

Record High Temperatures:

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

July 3: KCHS: 98/2019

Record High Minimum Temperatures:

June 27: KCHS: 77/2015

June 28: KCHS: 78/2013 KCXM: 81/1998

June 29: KCHS: 79/1977

July 1: KCHS: 77/2024

July 3: KCHS: 78/2016

CHS WATCHES/WARNINGS/ADVISORIES

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