textproduct: Charleston

WHAT HAS CHANGED

All Key Messages and sections were updated.

KEY MESSAGES

- 1) Temperatures are expected to rise through the weekend, likely approaching triple digits on Sunday. Heat Advisories could be needed this weekend and into early next week.

DISCUSSION

KEY MESSAGE 1: Temperatures are expected to rise through the weekend, likely approaching triple digits on Sunday. Heat Advisories could be needed this weekend and into early next week.

Saturday through Monday: The mid-levels will consist of ridging building over the Southern MS Valley on Saturday. It'll build north into the Great Lakes region and strengthen significantly into Monday. A roughly 596 dam 500 mb High will be centered over the Mid MS Valley on Monday. These heights will be about 2 standard deviations above normal per NAEFS. At the surface, High pressure will also be in the northern Gulf. Likewise, this pattern will support above normal moisture values across the region. The combination of all of these things will cause building heat and humidity this weekend into early next week.

High temperatures on Saturday will peak in the lower to middle 90s, except a few degrees cooler at the beaches. Sunday will be the hottest day of the summer so far. High temperatures should peak in the upper 90s to around the 100 degree mark across our entire area, with only slightly cooler temperatures at the beaches. High temperatures on Monday should be comparable to Saturday. Also to note, low temperatures will only fall into the mid to upper 70s Saturday night and Sunday night, with some locations possibly not falling below 80 degrees. This means there won't be significant relief from the daytime heat.

In addition to the hot temperatures, dew points well into the 70s will cause heat index values to rise into the triple digits. Saturday, heat index values will peak in the 100-105 degree range across our entire area with locally higher values possible, closer to the coast. Sunday we'll see the highest heat index values so far this summer. There should be a large swath of values in the 108-112 degree range stretching from the Charleston Tri-County and south along our coastal counties. A few locally higher values are certainly possible in these locations. The remaining locations should see heat indices in the 100-105 degree range. If this pans out, Heat Advisory criteria (108-112 degrees will be met). Heat indices on Monday should be comparable to Saturday.

The one challenge is the potential for showers and thunderstorms each afternoon. So it's possible these temperatures and heat index values could be briefly reached, only to tumble due to convection. So these details of the forecast will need to be refined each day.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

26/06z TAF Discussion: KCHS/KJZI/KSAV: VFR through 27/06z. Scattered showers/tstms are expected to develop inland this afternoon/evening. Most of this activity should remain west of KSAV and KCHS, but some data suggest activity may get close to either terminal at times. PROB30s were maintained, but adjusted slightly to 19-22z at KCHS and 00-03z at KSAV. KJZI looks to remain displaced from much of this activity, although will need to watch for a few showers making a run for that terminal daybreak through mid- morning.

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

MARINE

Through Tonight: A pretty standard surface pattern for summer will remain in place through tonight with the region positioned along the western flanks of Atlantic high pressure. A southerly flow regime will prevail localized sea breeze influences likely this afternoon along the land/sea interface and Charleston Harbor. Southwest winds 5-10 kt this morning will back to the south 10-15 kt this afternoon possibly 15 kt with gusts 20 kt along the beaches and Charleston Harbor. Overnight, nocturnal surging is likely to occur with the highest winds occurring over the South Carolina nearshore and offshore legs as well as the Georgia offshore leg. Here winds could surge as high as 15-20 kt with 15 kt over the Georgia nearshore waters. HREF probabilities for frequent gusts 25 kt or greater are running 20-40% so confidence is too low to justify a Small Craft Advisory, but this will need to be watched carefully. Seas 1-3 ft will build 2-4 ft tonight.

Saturday through Wednesday: A standard summertime wind pattern is forecasted through early next week. Expect backing of the winds each afternoon, especially 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. Each night, winds will veer. Though, they could be elevated at times if local jetting develops.

Rip Currents: Gusty winds with the sea breeze and a 8 ft/2 sec swell will result in a borderline low/moderate risk situation along the Charleston County beaches this afternoon. Local rip current calculations support a low risk while the latest rip current MOS output supports a moderate risk. Per coordination with WFO Wilmington, a low risk was maintained, but this will have to be monitored throughout the day, especially if the sea breeze ends up being a bit stronger than expected.

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.