textproduct: Columbia

WHAT HAS CHANGED

Additional rain is moving into the area with latest trends limiting severe and flooding rain threat today. Aviation discussion updated for 12Z TAFs.

KEY MESSAGES

- 1. Additional moderate to heavy rain and isolated storms moving into the area this morning.

- 2. Rain chances increase again this weekend into early next week.

DISCUSSION

Key Message 1: Additional moderate to heavy rain and isolated storms moving into the area this morning.

Significant deep layer moisture remains in place early this morning and while there was a break in the widespread rain after midnight, a shortwave moving through the Deep South currently will lead to stronger low level moisture transport with PWATs greater than 2 inch moving towards the area. This will lead to widespread rain continuing through the morning hours. The most significant thunderstorm activity with the coldest cloud tops observed on satellite will likely continue through southern AL/GA and may just brush our southern portion of the forecast area. There does remain some elevated instability across the Upstate and Piedmont where there remains some more significant height falls but thunderstorm coverage over the Midlands and CSRA will likely be limited, at least through daybreak. Severe threat has diminished through the early morning as the area remains significantly worked over from the convection that occurred several hours ago and not sufficient time for air mass recovery. CAMs still show some spread of the evolution as the convection through the morning as there may be another break after sunrise. A few CAMs favor weak destabilization at the surface later this morning, mainly in the southern area. While the severe threat will remain limited, strong winds aloft with HREF mean 850 mb jet around 45 knots, will lead to a conditional threat for damaging wind gusts in any strong storms that can develop. As far as the heavy rain threat is concerned, will likely require more significant training convection to see flooding over the area. Rainfall rates are generally maxing out around a quarter to a half inch to the west moving in. While these rates may increase as PWATs increase, it remains unlikely that flooding will be a concern outside of any poor drainage areas.

As the shortwave pushes east into the afternoon, convection will shift to the east as well and shower and thunderstorm coverage will diminish. There could be some isolated convection along the front late in the afternoon into the evening mainly in the northern area but with the strongest low level jet shifting east, severe weather is not expected.

Key Message 2: Rain chances increase again this weekend into early next week.

Surface high pressure will lead to a drier Friday. As an upper low over the Gulf of California will move eastward and a northern stream trough deepens over the Mississippi Valley, southwesterly flow will likely lead to increasing moisture this weekend. LREF probability of PWATs above 1.5 inches will be around 40-60% by Sunday as a series of weak shortwaves embedded in the southwesterly flow will likely lead to chances for rain each day Saturday through Monday, although widespread hazardous weather remains unlikely.

AVIATION /12Z THURSDAY THROUGH MONDAY/

Conditions expected to deteriorate quickly after the forecast period begins and persist through early afternoon with periods of showers and possible thunderstorms ahead of a front.

Upper trough axis remains to our west with axis of deepest moisture expected to move through this morning bringing intermittent showers and possible thunderstorms. Instability is weak and best in the CSRA through the day so left the mention of thunderstorms at AGS/DNL/OGB/AIK while keeping thunderstorms out of CAE/CUB. Ceilings just west of the terminals are MVFR/IFR and expect these to arrive around 12z-14z time frame all but OGB and by 15z at OGB. Vsbys are more difficult to anticipate but could fall to IFR through late morning with any persistent and heavy showers. Showers should come to an end as the cold front crosses the region this afternoon with winds initially from the southwest around 10 knots gusting up to 20 knots shifts to the west and eventually northwest by this evening and weakening below 10 knots. There is some potential for stratus redevelopment late tonight but confidence is low at this time. EXTENDED AVIATION OUTLOOK...Another system brings a chance for restrictions once again with showers and thunderstorms this weekend.

CAE WATCHES/WARNINGS/ADVISORIES

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