textproduct: Columbia

WHAT HAS CHANGED

Lowered temperatures Saturday with potential for CAD developing especially in the northwestern portion of the area. Aviation discussion updated for 00z TAFs.

KEY MESSAGES

- 1. Dry conditions with above normal temperatures are expected through Friday.

- 2. Increasing chances for rain associated with a front approaching this weekend.

DISCUSSION

KEY MESSAGE 1: Dry conditions with above normal temperatures are expected through Friday.

Upper level ridge axis remains to the west of the area and will gradually shift eastward towards the end of the week leading to above average temperatures as 500 mb heights will rise to near 1.5 to 2 standard deviations above normal based on ensemble means. This will likely lead to highs nearly 10 degrees above normal, in the low 90s as October begins unseasonable warm. With surface high pressure shifting offshore, low level moisture will gradually increase, although forecast soundings indicate a layer of substantial dry air in place that will preclude any rain today and tomorrow. While deep layer moisture begins to increase Friday with southwesterly flow beginning to develop, there will be a substantial PWAT gradient across the area. While an isolated shower or thunderstorm remains possible in the far southern area where moisture increases fastest, most of the area expected to remain dry Friday.

KEY MESSAGE 2: Increasing chances for rain associated with a front approaching this weekend.

Guidance appears to continue to converge on a generally slower solution with the arrival and progression of the front through the area this weekend with LREF PWATS greater than 2 inches showing a 60-80% chance Saturday night and increasing into Sunday. Once the cold front moves through Sunday into Monday, temperatures drop to more fall-like with lows in the 50s and highs in the 70s. Although, temperatures are uncertain this weekend into next week as medium range guidance is favoring cold air damming developing Saturday especially in the Upstate. Temperatures look cooler to the northwest, although there is potential for a substantial temperature gradient over the area from northwest to southeast. While forcing will be limited, especially early, isentropic lift will lead to developing rain over the area with highest chance for storms in the southeast. Stronger forcing likely late Saturday into Sunday which may lead to heavier rain. LREF is also showing an increase in a soaking rain potential with now a 30-40% of seeing totals over 2 inches through Monday night. Cold air damming likely lingers into Sunday and while blended guidance favors much cooler temperatures, there still remains the possibility that they are too high, especially in the northwest. Drier air likely filters into the area Monday as the front is pushed southeast with a deepening trough moving into the Great Lakes.

AVIATION /00Z THURSDAY THROUGH MONDAY/

VFR conditions expected through the evening. Restrictions in stratus/fog appear more likely Thursday morning with increasing low level moisture.

Another beautiful day has come and gone across the midlands, with few clouds to be seen throughout the day. Clear skies are present across the area right now, with low-level southeasterly flow forecast to possibly change that by daybreak. Moisture is forecast to increase overnight, coinciding with clear skies and light winds. Guidance is fairly bullish on showing an area of fog and low clouds developing between 09z and 12 across the coastal plain and into central SC and GA. This should result in shallow fog and stratus across the sites, with all sites forecast to see LIFR ceilings for some period of time tonight. AGS/OGB will probably see the lowest visibility restrictions but its possible that all sites see these. A rinse and repeat forecast is expected tomorrow, with more cumulus in the afternoon hours.

EXTENDED AVIATION OUTLOOK...Increasing chances of precipitation this weekend may lead to additional restrictions.

CAE WATCHES/WARNINGS/ADVISORIES

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