textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 12z TAF issuance.

KEY MESSAGES

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

Upper level ridging along the Gulf Coast will gradually build northward across the Deep South and MS Valley through Sunday. At the surface, subtropical high pressure will mostly drive the pattern with daily southwest flow giving way to the sea breeze in the afternoon and evening. Model consensus supports mid 90s for high temperatures today, followed by mid to upper 90s (and right around 100 in some locations) for Sunday. The slightly higher values on Sunday will be aided by surface winds taking on a bit more of a westerly component and pinning the sea breeze closer to the coast for a bit longer in the day. Perhaps the bigger and more important question revolves around dewpoints and the resulting heat index values. Dewpoints in the low to mid 70s, and upper 70s along the coast, will be sufficient to produce widespread coverage of 100-105 degree heat indices Saturday with values up to around 108 along the coast. Sunday continues to look like the better chances of seeing a tier of 108-112 degree heat indices, still primarily along the coast where dewpoints will be highest. So for now, no Heat Advisories today but a better chance coming on Sunday.

As forecast, Sunday's highs will likely approach daily records. Also of note, this period of hot conditions will also come with well above normal overnight temperatures as much of the area will only fall into the mid to upper 70s each morning. This will bring into play daily record high minimum temperatures as well. For record details, see the Climate section below.

Of course, thunderstorms could be a complicating factor each afternoon. However, most model solutions only support isolated coverage both days. As is typical for summer, it isn't out of the question to have one or two marginally severe storms especially where boundary collisions occur.

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.

Strong ridging will persist over the eastern half of the country, with a roughly 596 dam 500 mb High over the TN Valley on Tuesday, shifting to our north on Wednesday. This will cause slightly lower heights overhead, along with slightly lower 850 mb temperatures. The result will be high temperatures near normal Tuesday and Wednesday, generally the lower 90s.

Ridging continues to shift towards the East Coast towards the end of next week, with a large dome of hot temperatures expanding and following it. This will cause temperatures to again rise above normal. Highs should again be in the mid to upper 90s for the end of next week. Combined with dew points in the 70s, and we could have heat indices well into the 100s across portions of our area. So we may need Heat Advisories for portions of our area the towards the end of next week.

The changing location of the ridge next week will cause rainfall chances to gradually decrease throughout next week. Any convection this time of year will still have the potential to be strong to borderline severe, along with having locally heavy rainfall.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

The 12z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. Overall, VFR conditions are expected to prevail through the period at all 3 sites with no significant concerns for flight restrictions. The one potential issue continues to be afternoon thunderstorms. The best chance should be around KSAV, but even that currently looks too low to include in the TAF and will be handled with amendments if needed.

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

MARINE

Today and tonight: A pretty typical summertime pattern will persist across the local waters. Southwest flow will prevail for the most part, with winds turning more southerly along the land/sea interface this afternoon and evening with the sea breeze. Winds early this morning will be a bit stronger in a nocturnal surge and a few gusts to 25 knots will be possible in the Charleston County waters. Gusts this afternoon and evening should mostly be around 20 knots, continuing into the overnight. Seas should mostly average 2-3 feet, except up to 4 feet in the Charleston County waters.

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.