textproduct: Columbia

WHAT HAS CHANGED

Potential for cold air damming to develop by the middle of next week. Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Above average temperatures and increased chances for showers and storms continue into early next week.

- 2. More seasonably cooler and drier air returns by the middle of next week.

DISCUSSION

KEY MESSAGE 1: Above average temperatures and increased chances for showers and storms continue into early next week.

An upper ridge remains in place, centered to the west near the Mississippi Valley. Meanwhile, an upper low is visible in water vapor satellite imagery, just off the north Florida coast. The ridge is forecast to retrograde westward, driven by the upper low moving westward over Florida and into the Gulf. This will leave our area on the periphery of the upper ridge. Moisture expected to increase today, both around the axis of the ridge from the north and from onshore flow with the low to the south of the area. Temperatures will be well above average which is expected to persist into early next week before the ridge breaks down but today is expected to be the hottest day with the NAEFS mean indicating 850mb temps will exceed the 99th percentile. While most of the day will likely remain dry for much of the area, as a shortwave pushes in from the north, scattered showers and storms are likely to develop and begin to push into the area late afternoon and evening with the highest chance north of I-20. Moderate destabilization and strong low level lapse rates will support an isolated damaging wind gust threat in the strongest storms. While some hi-res models continue to sustain convection southward into the overnight hours, the severe threat will diminish. Unsettled pattern will continue into early next week with LREF probability of PWATs greater than 1.75 inch around 70-80%. While widespread forcing will likely be limited, this deep layer moisture and a unseasonably hot and humid air mass will support scattered showers and storms each afternoon through Tuesday.

KEY MESSAGE 2: More seasonably cooler and drier air returns by the middle of next week.

There remains uncertainty as to the exact pattern that evolves towards the middle of next week. Synoptically, with strengthening upper level confluence in the northeast and a developing and likely slow-moving upper low in the Mid- Atlantic, this would support cold air damming developing by the middle of next week. Blended guidance favors near normal temperatures for highs, although the distribution is skewed towards lower amounts. For now, highs have been adjusted a bit below the blend but will need to continue to monitor trends over the coming days.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

VFR conditions expected through the forecast period outside of possible convection.

The upper ridge will retrograde westward today and weak shortwave energy rotating around the ridge is expected to help initiate convection over the higher terrain and Piedmont region which then should drift south through the forecast area. Will continue a PROB30 group for possible convection during the 22z-03z time frame but confidence not as high at OGB so left out there. Higher clouds (over 10kft) moving over the terminals, visible on satellite this morning will likely dissipate later in the day and become replaced with diurnal cumulus. Winds increase out of the southwest by afternoon, although remain around 5 knots.

EXTENDED AVIATION OUTLOOK...Chances for showers and storms continue through the weekend. Morning cig/vsby restrictions are possible this weekend as well.

CAE WATCHES/WARNINGS/ADVISORIES

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