textproduct: Columbia

WHAT HAS CHANGED

Removed Saturday wording and updated first paragraph of Key Message 1 to reflect decreasing rain chances. Aviation discussion updated for 00Z forecast.

KEY MESSAGES

- 1. Scattered showers possible later tonight into early Sunday with more widespread rain chances Monday. Potential totals continue to trend down.

DISCUSSION

Key Message 1: Scattered showers possible later tonight into early Sunday with more widespread rain chances Monday. Potential totals continue to trend down.

A relatively unsettled patterns continues through Monday as deep troughing lingers over the eastern US and interacts with a reservoir of gulf moisture. However, the majority of the heavier showers and persistent rain chances are staying to our south as a series of strong convective systems have cut off some of the moisture advection. Model guidance continues to suggest the best rain chances tonight will be across the far southern CSRA into the southeastern Midlands, roughly from Burke to Clarendon counties. Even here, rainfall amounts are forecast to be under a tenth of an inch. General instability and high PWAT's could still pop scattered showers or an isolated thunderstorm Sunday afternoon, especially along and south of I-20, but overall a dry Mother's Day with clearing skies and warmer temperatures is favored.

More widespread showers and storms are expected Monday as a strong shortwave and associated surface front push through, but the potential for notable accumulations has trended down. LREF clusters and overall ensemble guidance has backed off considerably on potential totals from this slowing front for much of the area; generally 0.5-1.0" likely along I-95 and south of I-20, less than 0.25" expected to the north of I-20. Overall the down trend in totals is due to some offshore low pressure development and stronger convection to our south. These both prevent the strongest moisture advection and higher PWAT's from pushing into SC. So the best chances for heavier precip will be focused in the afternoon, closer to the coast and in the southern CSRA. Drier air fills in late Monday and Tuesday with another front moving through on Wednesday.

AVIATION /00Z SUNDAY THROUGH WEDNESDAY/

Generally VFR conditions expected through the evening hours as as the lower level clouds temporarily clear out in between weak upper level disturbances. Overnight, another weak shortwave will pass overhead, allowing the lower level moisture in the form of stratus to bump back northward. How far north they get is a bit of a question mark with hi-res models more aggressive with northward return than global models. For now, I won't stray far from the previous forecast for late tonight and early Sunday morning, but model means right now suggest the forecast may be a bit pessimistic, especially for the Columbia area TAFs.

The lower clouds that do develop should break by mid morning with VFR conditions returning for the rest of the day. There is a small chance of isolated afternoon shower, but too small to mention in the TAFs right now.

EXTENDED AVIATION OUTLOOK...Another system brings a chance for restrictions with widely scattered showers and thunderstorms Sunday Night and into Monday. Conditions will improve Tuesday with mainly VFR expected. Another front with more scattered showers and thunderstorms will approach the terminals later Wednesday.

CAE WATCHES/WARNINGS/ADVISORIES

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