textproduct: Columbia

WHAT HAS CHANGED

Uncertainty remains in convection evolution later today into this evening. Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Storms with strong downburst winds possible through Thursday before additional shower/storm chances possible Friday and Saturday. - 2. Above normal temperatures likely, Heat Advisories possible, through early next week.

DISCUSSION

- 1. Storms with strong downburst winds possible through Thursday before additional shower/storm chances possible Friday and Saturday.

As of writing this, a weakening MCS that has become more outflow dominant is pushing into northern GA with the far eastern end of this well behind the outflow. This is forcing a few weak storms and additional showers in the Upstate that could gradually push into the CWA into the early morning hours, but the overall severe risk continues to diminish as MLCAPE falls under 1000 J/kg with more stable conditions setting up. The upper ridge remains off to the west and additional pieces of shortwave energy are sparking new convection in the Midwest. Large spread exists across individual CAM's in the progression of this convection, but the mean HREF solution depicts this reaching the western slopes of the Appalachians by the late morning hours. As heating and deep mixing occur, SBCAPE values could approach 2000 J/kg, but with drier air in the mid levels, PWAT's remain clos, but for now hedged with VCSH until the timing becomes better defined. er to 1.50-1.75". Overall, high uncertainty in convection evolution exists today, but if outflow from this convection reaches the FA with mild shortwave energy, it is not unreasonable to think additional semi-organized storms during the afternoon will be possible with the main threat of damaging straight line wind gusts. Outside of this, any isolated pulse variety convection could bring the risk of strong-damaging downburst winds with DCAPE values likely exceeding 1000 J/kg.

A similar setup in this northwest flow regime is expected Thursday, where a weak shortwave could aid in sparking additional isolated convection during the afternoon. A diffuse frontal boundary then is expected to near the area Friday and Saturday, where additional shower/storm chances will be possible, mainly Saturday as the front could stall in the CWA.

- 2. Above normal temperatures likely, Heat Advisories possible, through early next week.

Minimal change to the temperature forecast is seen as northwest, downsloping flow and rising 500mb heights favor above normal temperatures persisting into early next week. If convection does not keep high temperatures in check, it will be reasonable to see max temperatures in the mid to upper 90s the coming days. Deeper mixing should allow dewpoints to mix out slightly better, toward the upper 60s to lower 70s, but nonetheless, hot/humid conditions are very likely. Heat indices up to near 105F are expected today before they could top out between 105-110F Thursday through Saturday. LREF probabilities for reaching Heat Advisory criteria are highest (between 40-50%) Friday and Saturday and are a bit lower Thursday (around 30-40%), but with the expectation of at least isolated convection each afternoon, confidence in a widespread area reaching Advisory criteria is low. These trends will continue to be monitored over the coming days, but even if heat products are not issued, a prolonged period of heat is likely over the coming 7 days so precautions should still be taken.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

VFR conditions expected to dominate the TAF period, with occasional SHRA this morning in the CSRA. Additional TSRA expected this afternoon but timing remains uncertain.

A small area of showers will move through the CSRA and near the AGS/DNL terminals over the next couple of hours. Otherwise, a broad area of debris cloudiness will move overhead around 12-18kft MSL, largely hindering any stratus or fog development this morning. Light surface winds pick up again around 15z out of the west near 5-10 kts. Scattered cumulus should develop through the day with isolated storm chances possible through the afternoon. Timing and location is still a bit uncertain, so left VCSH. Wind gusts in the stronger storms could approach 30 kts with brief heavy downpours and associated restrictions. Unsettled conditions may persist into the evening but overall showers and storms should diminish tonight.

EXTENDED AVIATION OUTLOOK...A hot and drier weather pattern develops through the week. Convective coverage will likely be low and restrictions limited.

CAE WATCHES/WARNINGS/ADVISORIES

SC...None. GA...None.