textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

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

Isolated showers and thunderstorms have begun to develop across the area, limited only by the H5 592 dm ridge in place aloft. This has helped temperatures across most places climb to the mid 90s so far today. Dew points well into the 70s have resulted in heat indices 100+, with some spots along the coast already above 108F. Little cooling relief is expected through the evening with not much in the way of convective coverage this afternoon. Current Heat Advisories in effect across southeast South Carolina and southeast Georgia will continue until 8 PM tonight.

Sunday and Monday will see little change in the synoptic set up, with low pressure in the Northern Gulf and high pressure positioned over the Western Atlantic. This continued set up will allow temperatures to reach into the low to mid 90s each day, with heat index values around 100-105. The current forecast keeps heat index values just shy of Heat Advisory criteria (>108), however Heat Advisories cannot be ruled out, especially along the coastal corridor where the dew points will be highest. The pattern will begin to shift on Tuesday as an upper level trough swings eastward. This will yield greater coverage of afternoon showers/thunderstorms and limit the heat potential each afternoon.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

18/18Z TAFs: Isolated showers and thunderstorms will continue to develop this afternoon into the evening, initiating along the sea breeze. The best chance for a storm to have impacts on any of the terminals looks to be across southeast Georgia potentially near KSAV prior to sunset. However, due to their isolated nature, we keep the mention of PROB30. Gusty southerly winds will accompany the sea breeze this afternoon, before becoming lighter late this evening, and ramping up again Sunday afternoon. Otherwise, we anticipate VFR conditions to prevail through 18Z Sunday.

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 and tonight: As the local waters situate between an inland trough and a subtropical high to the east, this will allow for the pressure gradient to strengthen throughout the day. Expect wind speeds to range from 15 to 20 kts with gusts up to 25 kts (especially across the Charleston County nearshore waters). Thus, Small Craft Advisories has been issued for the nearshore South Carolina waters from 0-20 nm (not including the Charleston Harbor) starting at 8 PM and into tonight. Should see a slight downtrend in wind speeds late tonight, with winds ramping down just prior to sunrise Sunday. Expect seas to range from 2 to 3 ft, before increasing to 3 to 5 ft tonight.

Sunday through Wednesday: The marine waters will remain positioned between high pressure to the east and low pressure in the Northern Gulf into early next week. This will yield a pinched pressure gradient and SW winds gusting around 20 knots. Sunday will see gusts as high as 25 knots across the Charleston nearshore waters. A Small Craft Advisory is in effect for this marine zone through Sunday evening. Mid week a trough inland will shift offshore and again enhance the wind gusts. Small Craft Advisories could be needed mid- week, especially in the Charleston nearshore waters and the Charleston Harbor. The National Hurricane Center is monitoring a system in the Northern Gulf for possible tropical development, with a 40% chance of development in the next 7 days. If this system were to develop and track up the SE coastline there would be additional wind and wave concerns across the marine waters.

Rip Currents: The pinched gradient across the marine zones will yield SW wind gusts around 20 knots. Due to the enhanced winds along the coastline there is a Moderate Risk of rip currents at all area beaches tomorrow (Sunday).

CLIMATE

Record High Minimum Temperatures:

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...Heat Advisory until 8 PM EDT this evening for GAZ087-088- 099>101-114-115-137-216>219-238>241. SC...Heat Advisory until 8 PM EDT this evening for SCZ040-042>045- 147>152. MARINE...Small Craft Advisory from 8 PM this evening to 8 PM EDT Sunday for AMZ360. Small Craft Advisory from 8 PM this evening to 6 AM EDT Sunday for AMZ362.