textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Unseasonably hot weather will continue through Monday.

- 2) Showers and thunderstorms expected to continue into early next week with a persistent summertime pattern. Isolated strong-severe thunderstorm possible today.

- 3) Minor coastal flooding possible along Charleston and Colleton County coasts during evening high tides tonight and Monday evening.

DISCUSSION

KEY MESSAGE 1: Unseasonably hot weather will continue through Monday.

The strong upper ridge will persist today while a weak surface trough lingers just inland. Low-level thicknesses support high temps in the upper 90s over most of the area. The only negating factor will be scattered mid and upper level clouds this morning, then pop-up convection in the afternoon. High-res guidance shows very little convective development through mid- afternoon which should allow heat indices to steadily climb. WSW low-level flow will prevent much of a sea breeze from developing along the GA coast, though it should slowly creep inland over coastal SC by early to mid afternoon. A corridor of mid to upper 70s dewpoints will again occur in coastal counties this afternoon, producing a ribbon of 105-110 degree heat indices for several hours. We issued another Heat Advisory for coastal areas as a result.

Monday will remain relatively hot, but upper heights will slightly decrease, and convection/cloud cover may be greater, so heat indices may remain below advisory criteria.

KEY MESSAGE 2: Showers and thunderstorms expected to continue into early next week with a persistent summertime pattern. Isolated strong-severe thunderstorm possible today.

As the Atlantic surface high pressure lingers south of Bermuda, weak surface troughing across the southeast will continue the warm and moist surface conditions into early next week. Aloft, weak zonal flow will persist today, with the expected afternoon sea-breeze again leading to shower and thunderstorm chances, though some shower/storm activity will come from reaching convective temperatures.

Similar to the past couple of days, 1500-3000 J/kg of SBCAPE is expected to develop throughout the morning and early afternoon hours, though bulk shear values continue to remain poor. DCAPE values are a little lower today, mostly below 1000 J/kg, but still high enough to lead to an isolated strong/severe wind gust from a stronger storm. Previous round of convection allowing models (CAMs) hinted at a more organized storm complex developing out west of the area, becoming cold pool driven before pushing into the region this evening, though most recent guidance has backed off on that. SPC maintains their marginal risk to cover that possibility, though a strong-severe wind gust can't be ruled out from the pulse-storms as mentioned previously. With precipitable water values remaining near 2 inches (near the 90th percentile for mid-June) locally heavy rainfall will continue to be possible today from slow moving/repeating storms. Probabilities are near 70% for an inch of rain between the I- 95 corridor and the coast, where the sea-breeze will likely be pinned producing scattered showers/storms, with additional storms possible from subsequent outflow boundaries.

As we head into the early and middle part of next week, large and broad mid-level troughing is expected to encompass the eastern half of the CONUS. At the surface, a weak cold front will approach the region on Monday, and then move on Tuesday pushing offshore by Tuesday evening. Convection coverage will likely increase from late morning near the coastline before expanding more inland in the afternoons. Highest chances for rain will likely occur along and west of I-95 corridor where seabreeze interactions maximize, with additional forcing provided by periodic shortwaves moving through the trough.

The pattern looks to remain active into the end of the week as broad troughing continues aloft, with another cold front moving towards the area by late week/early weekend.

KEY MESSAGE 3: Minor coastal flooding possible along Charleston and Colleton County coasts during evening high tides tonight and Monday evening.

Breezy south-southwesterly winds each day along with the upcoming lunar Perigee (June 14th) and New Moon (June 15th) should result in elevated tidal departures above 1/2 ft today into early next week, setting the stage for minor coastal flooding along the Charleston and Colleton County coasts during evening high tide cycles. The latest TWL forecast calls for 6.9 - 7.1 ft MLLW in the Charleston Harbor this evening, and 7.0 - 7.2 ft MLLW are possible during evening high tides Monday night as astronomical influences peak and breezy onshore winds persist. Coastal Flood Advisories may again be needed for the Charleston and Colleton county coastlines.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

12Z TAFs: VFR conditions expected to continue into the afternoon hours, though scattered convection will likely lead to TEMPO flight restrictions at times, and have thus transitioned the PROB30 groups to TEMPO groups at CHS/JZI/SAV TAF sites. Strong damaging winds are the primary threat with the strongest storms this afternoon. Southwest winds will become breezy early this afternoon, lingering into the evening hours.

Extended Aviation Outlook: VFR conditions expected to prevail at CHS/JZI/SAV terminals. However, brief flight restrictions are possible with afternoon showers and/or thunderstorms into the middle of next week.

MARINE

Expect generally south-southwesterly winds with speeds ranging from 10 to 15 kts as Atlantic high pressure persists across the local waters. A pre-frontal trough will develop throughout the day, increasing the surface pressure gradient leading to wind gusts up into the lower 20s, possibly reaching/exceeding 25 kt overnight into Monday and overnight into Tuesday. Therefore, there could be need for Small Craft Advisories for portions of Monday and Tuesday, though probabilities are currently highest (near 50%) in the offshore zones from South Santee, SC to Savannah, GA, dropping towards 10-20% along the coast, so have held off on issuance. The cold front looks to push offshore by Tuesday evening, and then rapidly move further away across the Atlantic. Seas should remain below 6 feet throughout the period.

Rip Currents: A Moderate Risk of rip currents is forecast for Sunday along the southeast South Carolina and southeast Georgia beaches given the combination of elevated winds and a lingering south- southwesterly swell. Moderate rip risk continues for the Charleston county beaches on Monday given continued similar conditions.

CLIMATE

Record High Temperatures:

June 14 KCHS: 99/2010 KCXM: 97/1981

June 15 KCHS: 98/2015

Record High Minimum Temperatures:

June 14 KCHS: 79/2010 KCXM: 81/2010

June 15 KCHS: 80/2010

June 18 KCHS: 78/2015

June 19 KCHS: 79/2025 KCXM: 81/2025 KSAV: 79/1881

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from 11 AM this morning to 6 PM EDT this evening for GAZ217-219-239-241. SC...Heat Advisory from 11 AM this morning to 6 PM EDT this evening for SCZ045-148>152. MARINE...None.