textproduct: Columbia

WHAT HAS CHANGED

Another Heat Advisory issued Tuesday for areas generally along and south of I-20. Aviation discussion updated for 18z update.

KEY MESSAGES

- 1. Dangerous heat continues into this week with highest temperatures expected today.

- 2. Storm coverage more limited today and tomorrow, with increasing potential late week into the weekend.

DISCUSSION

KEY MESSAGE 1: Dangerous heat continues into this week with highest temperatures expected today.

Upper ridging hangs on today with heat indices continuing between 105-110 through the afternoon. A bit lower dew points compared to yesterday has been offset by higher air temperatures with improved mixing. A Heat Advisory remains in effect until 8pm tonight for the entire area. Tomorrow a weak front will move into the area and while overall temperatures will remain similar, it will likely usher in some slightly drier low level air into the western portion of the forecast area. Heat indices will likely still remain elevated, although higher confidence that areas north of I-20 remain below Heat Advisory criteria so have left them out of any heat products with this package. Blended guidance continues to favor max heat indices around 105F each day through Friday so will need to evaluate each day the need for a potential Heat Advisory through the end of the week. Regardless, significant relief from the heat remains unlikely until the weekend when the ridge finally breaks down and there will be increased chances for precipitation.

KEY MESSAGE 2: Storm coverage more limited today and tomorrow, with increasing potential late week into the weekend.

Convection will likely be limited this afternoon, even with a hot and humid air mass as a warm nose aloft will keep the area capped with limited forcing. Will have to monitor an MCS that will likely develop upstream in eastern TN/north GA but most hires models have this activity diminishing as it approaches the forecast area. Similar capping is expected tomorrow which will limit any convection even with some weak convergence along a surface front. Isolated afternoon storms will be possible each afternoon Wednesday and Thursday as moisture begins to increase with widespread convection Friday through the weekend with a robust mid-level trough moving into the eastern CONUS and deep layer southwest flow leading to increased moisture.

AVIATION /18Z MONDAY THROUGH SATURDAY/

VFR conditions are expected to continue through the TAF period. An isolated shower or storm cannot be ruled out this afternoon.

A SCT cumulus deck has developed early this afternoon across the area with 6-8 kt winds out of the west to northwest generally. Continuing the remainder of the afternoon and into this evening, a stray shower or storm cannot be ruled out but overall probabilities for impacts at the terminals remains quite low. A 20-25 kt LLJ is expected to develop tonight, keeping surface winds elevated out of the west. FEW to SCT cirrus could pass through the region tonight and chances for stratus/fog seems lower with elevated surface winds and slightly drier soundings. Winds pick up after 15-17z Tuesday out of the northwest with more cumulus expected to develop into the afternoon hours.

EXTENDED AVIATION OUTLOOK...Diurnal chances for thunderstorms continue through the end of the week.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Heat Advisory until 8 PM EDT this evening for SCZ016-018- 020>022-025>031-035-037-038-041-115-116-135>137. Heat Advisory from 11 AM to 8 PM EDT Tuesday for SCZ016-022- 027>031-035-037-038-041-135>137. GA...Heat Advisory until 8 PM EDT this evening for GAZ040-063>065- 077. Heat Advisory from 11 AM to 8 PM EDT Tuesday for GAZ064-065- 077.