textproduct: Charleston

WHAT HAS CHANGED

Removed Key Message 1 regarding the Dense Smoke Advisory.

KEY MESSAGES

- 1) Hot and humid conditions are expected across the area into midweek. Heat Advisories could be needed.

- 2) A shift in the synoptic pattern will likely bring higher precipitation chances towards the end of the week.

DISCUSSION

KEY MESSAGE 1: Hot and humid conditions are expected across the area into midweek. Heat Advisories could be needed. Very little change in the forecast is expect the next couple of days as the heat and humidity lingers through Wednesday. The overall players remain the same across the area with deep upper troughing across the Northeast, high pressure to our east over the Atlantic and a tropical depression over the northern Gulf. Monday and Tuesday, will see highs topping out in the low to mid 90s and dewpoints able to mix out into the low 70s. This should be enough to keep heat indices in the 100 to 105 range and while this is still hot, this is more in line with typical summertime conditions for the area. A few locations may be able to crack 108 to 110 along the immediate coastline especially across coastal south carolina as the seabreeze slowly moves inland. Confidence in reaching those values for a long enough period of time is too low at this time to support a Heat Advisory today. Nonetheless, the difference between 104/105 and 108/109 is not that noticeable and the key takeaway is that conditions still remain on the hotter side.

The bigger questions come on Wednesday as dewpoints should gradually increase as better moisture arrives. This will be aided by the depression in the Gulf as it slowly tracks westward. The usual trouble areas behind the seabreeze could approach advisory criteria come Wednesday as dewpoints climb into the upper 70s to near 80 resulting in heat indices of around 108 to 110. This could require Heat Advisories across portions of the area. The biggest question for Wednesday will be if convective coverage will be enough to limit the heat across the area. With better moisture usually comes more storms and more storms earlier in the day could limit how hot we are able to get.

KEY MESSAGE 2: A shift in the synoptic pattern will likely bring higher precipitation chances towards the end of the week.

As a low pressure in the northern Gulf (TD2) slowly shifts westward through the mid-week, a high pressure will remain centered over the western Atlantic. Simultaneously, a mid-lvl trough will situate itself over the eastern CONUS by mid-week. At the surface, an associated cold front will approach the region on Wednesday, likely stalling in the vicinity of the forecast area into the end of the week. This stalled front will likely bring increased precipitation chances to the region. The Weather Prediction Center (WPC) has the entire forecast area outlooked in a Marginal Risk for Excessive Rainfall on Thursday, with a Slight Risk over northern Charleston and Berkeley Counties.

AVIATION /15Z MONDAY THROUGH FRIDAY/

20/12Z TAFs: Expect VFR conditions to prevail at all terminals through the period. Light southwesterly flow should strengthen this afternoon as the seabreeze shifts inland between 18-19Z for KCHS/KJZI and ~20Z for KSAV. Winds should veer out of the south behind the seabreeze with gusts up to around 20 kts. Gusts should subside after 00Z, although sustained south- southwest winds around 10 kts will continue through the end of the period. An isolated shower or thunderstorm is possible this afternoon; however, any storms that do develop should be inland of all TAF sites.

Extended Aviation Outlook: Prevailing VFR through mid week. Chances of flight restrictions increase later this week with a greater coverage of showers/thunderstorms.

MARINE

Today: The gradient will remain pinched between a high pressure centered offshore and the Piedmont Trough throughout today. Expect wind speeds to range from 10 to 15 kts with gusts up to 20 kts. Thus, marine conditions remain under Small Craft Advisory (SCA) criteria. With little to no swell energy, seas will range from 2 to 3 ft through the evening, before increasing to 3 to 4 ft overnight.

Tuesday through Friday: As a mid-lvl trough slowly situates itself across the region through the period, an associated cold front will approach the local waters on Wednesday and then stall out in the vicinity. This will yield breezy south-southeasterly flow on Tuesday through Thursday. Also, southerly swell will briefly surge into the local waters on Tuesday night and allow for seas to increase from 4 to 6 ft (esp. across the South Carolina waters). Thus, SCAs will likely be needed Tuesday through Wednesday given the elevated winds and seas. Thereafter, seas should taper back on Wednesday afternoon through the rest of the period.

Rip Currents: A Moderate Risk of rip currents is in effect for our SE GA beaches through this evening, given enhanced winds along the coastline and wave periods up to 6 seconds. A Moderate Risk returns to all area beaches on Tuesday as 6 second swell and enhanced SSW/SW winds develop along the entire coastline.

CLIMATE

Record High Minimum Temperatures:

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