textproduct: Columbia

WHAT HAS CHANGED

Hot and humid conditions continue with temperatures, likely peaking on Monday before Aviation discussion updated for 06z update.

KEY MESSAGES

- 1. The high heat and humidity continues with temperatures likely peaking on Monday.

- 2. Isolated to scattered afternoon and evening convection expected this weekend.

DISCUSSION

1. The high heat and humidity continues with temperatures likely peaking on Monday.

The high heat and humidity is expected to continue this weekend despite weakening upper ridging. High temperatures on Saturday should generally rise into the mid-90s which will combine with high humidity to produce max heat index values between 105 and 110 in most locations. A Heat Advisory remains in effect through 8pm Saturday and could be extended once again based on guidance for Sunday which suggests more widespread heat index values exceeding criteria. On Monday, model guidance shows anomalously high 850mb temperatures perhaps exceeding 10 degrees above normal yielding surface temperatures in the upper 90s and lower 100s. The humidity is unlikely to relent meaning another day or dangerous heat index values to start the new work week. A trough during the mid to late portion of next week may finally break the threat of extreme heat with daytime temperatures closer to seasonal values. The bottom line is whether you are outdoors for work or play, take appropriate precautions and limit time in direct sunlight during peak heating hours.

2. Isolated to scattered afternoon and evening convection expected this weekend.

The flattening ridge should result in isolated to scattered convection during the afternoon and evening hours this weekend. As has been the case during the last few days, any robust convection has the potential to produce damaging wind gusts. The lack of winds aloft means that localized flooding is also possible, primarily if rain falls over normally flood prone areas. Guidance once again removed the chance for precipitation on Monday and this appears to be due to the highly anomalous 850mb temperatures mentioned in the previous section. This would result in sufficient capping over the forecast area for Monday, with any rain arriving towards evening as a shortwave moves in from the northwest potentially eroding the cap. More typical August rain chances are then anticipated, perhaps increasing during the mid to late portion of next week when a trough may set up over the eastern CONUS.

AVIATION /03Z SATURDAY THROUGH WEDNESDAY/

VFR conditions likely outside of scattered convection this afternoon and evening.

Through Saturday morning, convection has dissipated and only some MIFG is expected with limited impacts on any restrictions for vsby. Throughout the rest of Saturday, typical summer cu will develop by late morning with light and variable winds varying from southwest to southeast. Scattered convection will develop after 18z with coverage increasing by late afternoon and evening, a bit more widespread than Friday. Prob30 groups for -tsra currently cover the potential for TAF sites, but a tempo or predominant group is expected to be needed as timing and location confidence increases. Convection will wind down after 00z Sunday, with fog-stratus potential contingent on rainfall amounts and footprint.

EXTENDED AVIATION OUTLOOK...Diurnal chances for thunderstorms continue each day through the weekend.

CAE WATCHES/WARNINGS/ADVISORIES

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