textproduct: Columbia

WHAT HAS CHANGED

Still expecting rain chances to increase late tonight. Updated aviation discussion for 00z TAFs.

KEY MESSAGES

- 1. A few showers still possible this evening, then a better chance of more widespread rain late tonight into Thursday morning.

- 2. Confidence increasing in moderate rainfall for portions of the forecast area Friday night and Saturday.

DISCUSSION

Key Message 1: A few showers still possible this evening, then a better chance of more widespread rain late tonight into Thursday morning.

Partly cloudy skies being indicated this evening ahead of an approaching frontal boundary. Cloud cover should increase through the evening as increasing moisture in mid and upper levels moves in from the west. Radars not indicating much in the way of precip in the area, with the best coverage in the mountains ahead of the front, and across southern Alabama in association with a larger scale complex.

The main frontal boundary should move through the region overnight and there could be scattered showers and even an isolated storm as it moves through. However instability will remain somewhat limited, and do not expect much of a severe threat. With that being said, guidance is still showing the larger complex that is moving through the Gulf region this evening will continue tracking eastward overnight. It should weaken somewhat as it nears our southwestern forecast area late tonight, but a good chance of showers and isolated convection is expected beginning around 08z across the southwestern counties. As with previous guidance, the CSRA seems to be more favored than further to the north and highest pops will continue to be concentrated along and south of the I-20 corridor. Instability looks to be more elevated in nature but there will be shortwave energy providing upper support as it moves through. Any rainfall at this point will continue to be beneficial given our drought conditions.

Key Message 2: Confidence increasing in moderate rainfall for portions of the forecast area Friday night and Saturday.

Chances of the most significant rainfall we have seen in a while continue to look pretty good for Friday night into Saturday. Northern stream energy digging into the upper Midwest is expected to phase with southern stream energy moving across the southern Plains into the MS Valley on Friday before swinging through the Carolinas and off the Mid-Atlantic coast Saturday night. This will induce low pressure development along the Gulf Coast which then lifts northeastward off the Carolina coast on Saturday. While it appears the heaviest rainfall and highest totals likely remain south of our area, there should be reasonable chances for much needed rainfall with NAEFS IVT above the 97th percentile. The CSRA and southeast Midlands are more favored for highest rainfall given a gradient in PWATs with higher values from north to south. There is little instability available with this system as it looks like an overrunning event with the surface low to our southeast. LREF Probabilities for 24hr rainfall amounts greater than 0.5 inches are in the 50-75 percent range for Friday night through Saturday and probabilities of greater than 1 inch are near 50 percent in the southeast Midlands. 48hr QPF from the NBM is a bit more bullish with precipitation with the 50th percentile showing much of the forecast area receiving at least one inch of rainfall.

AVIATION /00Z THURSDAY THROUGH MONDAY/

VFR conditions are generally expected this evening, with increasing chances for showers toward early Thursday morning.

Lingering low stratus has diminished across most terminals this evening, though typical SCT strato-cu remain across the area. A weak cold front to our west will continue to support a few isolated showers and thunderstorms across northern SC, but confidence remains low to include any impacts at the terminals. More organized and widespread shower activity, and possibly a few thunderstorms, are expected early Thursday morning after 06Z from a decaying storm complex to our west. The greatest potential for restrictions appears to be more likely for OGB, AIK, and the Augusta terminals as activity advances from the SW to NW. Maintained the TEMPO groups there, with PROB30 mentioned for Columbia area terminals. Some brief gusty winds are possible with these showers and storms but generally should remain elevated. Some stratus may linger into Thursday afternoon before gradually diminishing after 20Z, with improving conditions expected Thursday night.

EXTENDED AVIATION OUTLOOK...Periods of restrictions are possible late this week into the weekend with more rain chances, especially Friday night and throughout Saturday.

CAE WATCHES/WARNINGS/ADVISORIES

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