textproduct: Columbia

WHAT HAS CHANGED

Heat Advisory has been extended until 8pm Monday with heat indices expected between 105 to 110F. Aviation discussion updated for 18z update.

KEY MESSAGES

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

- 2. Scattered showers and thunderstorms continue into this evening.

DISCUSSION

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

Upper ridging is expected to persist into early next week with continued above average temperatures expected. Today, temperatures have risen into the mid-90s and with significant moisture as PWATs remain around 2 and a quarter inches across most of the area, there is not really much dry air aloft to mix to the surface, keeping dew points in the mid 70s. This is leading to heat indices between 105 to 110F which is expected to continue through the afternoon. Have gone ahead and extended the Heat Advisory through 8pm Monday. A bit stronger mixing tomorrow with some (relatively) drier air moving in aloft will likely lead to lower dew points. This will likely be offset with high temperatures likely as HREF mean 850mb temps will be a couple degrees higher, around 23C. Highs Monday as a result will top out around 100F with heat indices similar to today. While today and Monday will likely be the hottest days, HeatRisk will remain high, likely through Thursday as blended guidance continues to favor above average temperatures, although there is a bit more uncertainty for the second half of the week as the ridge begins to break down. Bottom line, significant heat relief is not expected until the end of the week.

KEY MESSAGE 2: Scattered showers and thunderstorms continue into this evening.

Isolated to scattered storms continue across the area, building off of outflows with a very moist air mass in place and very high instability with mlCAPE values approaching 3000 J/kg. This is leading to a very typical pulse thunderstorm day with weak forcing and shear. While the overall severe threat is low, a localized strong to marginally severe downburst remains possible in this highly unstable environment. Some drier air aloft will shift into the area tonight with northwest flow strengthening as storm coverage expected to be more limited tomorrow and favoring the eastern area Tuesday and Wednesday. The ridge will begin to break down for the second half of the week which will lead to increased chances for shortwaves to move into the area with blended guidance favoring higher chances for precip late week into the weekend.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

VFR conditions outside of afternoon and evening storms.

Afternoon cumulus has developed area-wide amid light and variable winds. Scattered convection is expected to continue through this evening, with most of the activity south and east of I-20. Coverage should remain isolated; however, any storms that develop could bring brief restrictions. PROB30 groups have been maintained at CAE/CUB, with TEMPO groups elsewhere due to ongoing vicinity storms. Activity should diminish after sunset with light winds. Low stratus and fog will be possible, mainly to our north and east. Given the limited support in guidance, vsby restrictions have not bee included at this time. Winds should gradually increase from the west on Monday as drier air moves in. A pop-up shower or thunderstorm cannot be completely ruled out in the afternoon, but activity should remain sparse.

EXTENDED AVIATION OUTLOOK...Diurnal chances for thunderstorms continue each day this week.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Heat Advisory until 8 PM EDT Monday for SCZ016-018-020>022- 025>031-035-037-038-041-115-116-135>137. GA...Heat Advisory until 8 PM EDT Monday for GAZ040-063>065-077.