textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12`z 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 continues 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 70-90% chance Saturday into Sunday with deeper moisture more southeast. While forcing is limited, especially early, isentropic lift will lead to developing rain over the area with the highest chance of storms in the southeast. Stronger forcing with an approaching shortwave and surface cold front will likely aid in the heavier rain occurring on Sunday. LREF continues to show a 30-40% chance of seeing rain totals over 2 inches with a spread of 1 to 3 inches between the 25th and 75th percentiles through early next week. In terms of temperatures, it remains uncertain in how high they become Saturday and Sunday. This is due to southwesterly flow at the surface and a strong high- pressure system over New England possibly hinting at a cold air damming setup this weekend. Confidence is higher in the Upstate in the development of a wedge with cooler temperatures to the northwest and a sharp gradient along the upstate. 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. 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 likely clearing out the CAD 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 /12Z THURSDAY THROUGH MONDAY/

Brief morning restrictions in stratus/fog then VFR conditions expected through the day.

Stratus clouds have developed over the Coastal Plain and moving into the eastern Midlands impacting mainly OGB but could reach the other terminals for an hour or so before lower clouds dissipate and are replaced by fair weather cumulus. Winds should remain light and variable under high pressure today. Concern for restrictions in stratus and possible fog again tonight.

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

CAE WATCHES/WARNINGS/ADVISORIES

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