textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 06Z forecast.

KEY MESSAGES

- 1. Increasing moisture this weekend leading to chances for rain and storms through Monday when a front moves through.

DISCUSSION

Key Message 1: Increasing moisture this weekend leading to chances for rain through Monday when a cold front moves through.

Strong convection has developed well to the west early this morning near Texarkana and will continue to shift into the Deep South through the day. This MCS to the west will likely continue to propogate southeasterly with highest instability along the Gulf coast which will likely limit significant convection occuring within the forecast area. Heaviest rain and highest thunderstorm coverage has trended southward for today among CAMs. However, moisture over the forecast area has gradually increased and is expected to continue to increase with HREF mean PWATs generally around an inch and a quarter to the north to an inch and a half in the south. With HREF probability of sbCAPE above 500 J/kg around 60-70% this afternoon, scattered convection still remains likely, favoring the southern portion of the forecast area. Models have generally trended stronger with a 500mb trough to the west for Sunday which may shift some drier air into the northern area and keep strongest forcing to the south. As a result, pops have trended downward for the day Sunday, although still have kept slight to chance pops in the southern portion of the forecast area. Highest confidence in widespread showers and storms continues to be Monday with an approaching cold front. Slightly slower timing of the front has led to blended guidance a bit more unstable with probability of sbCAPE greater than 1000 J/kg around 40-60%. Forecast soundings indicate profiles with long, skinny CAPE. This would favor moderate to potentially heavy rain at times, although likely limit the severe weather threat, although some ML guidance has indicated at least a low end threat so it is worth monitoring. Drier conditions arrive Tuesday has we eventually end up within the northwest flow regime of the persistent troughing.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

VFR conditions expected to deteriorate around sunrise with MVFR cigs developing.

Satellite imagery shows persistent stream of cirrus clouds over the region ahead of an approaching upper trough. Moisture advection expected to increase over the area during the predawn hours resulting in lower clouds developing and possible light showers moving in. Guidance is suggesting MVFR cigs beginning around 12z and continuing through around 18z-20z with possible IFR cigs, although confidence is lower in prolonged IFR cigs. Will include a tempo group for IFR cigs and lower vsbys in showers. Winds should be light from the south through sunrise then increase to around 5 to 8 knots shifting to the southwest as a frontal boundary approaches from the west.

Most precipitation should be light and ending from west to east during the early afternoon hours.

EXTENDED AVIATION OUTLOOK...Another system brings a chance for restrictions with showers and thunderstorms this weekend into Monday.

CAE WATCHES/WARNINGS/ADVISORIES

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