textproduct: Columbia

WHAT HAS CHANGED

Southward shift in potential for heavy rain this evening and tonight. Aviation discussion updated for 18z TAFs.

KEY MESSAGES

- 1. Scattered to widespread moderate rain expected this evening into early Monday, mainly south of I-20. Cannot rule out an instance of flash flooding.

- 2. Temperatures just below to near normal are expected the remainder of the week with mostly dry conditions.

DISCUSSION

KEY MESSAGE 1: Scattered to widespread moderate rain expected this evening into early Monday, mainly south of I-20. Cannot rule out an instance of flash flooding.

The surface front has sank toward the southern CSRA and far southeastern Midlands, with dewpoints along/south of the front in the low 70s, quickly dropping northward into the low to mid 60s. Behind the front, in-situ wedge conditions have been in place much of the morning with low stratus and periods of drizzle, keeping temperatures toward the mid to upper 60s. Stratus has appeared to thin a bit, but overall, a much more stable environment is seen north of the front. Due to this, mostly dry conditions are expected to continue for much of the CWA through this afternoon ahead of a shortwave moving into the southern Tennessee Valley. As this nears, a batch of scattered to widespread rain developing across western AL and GA should push toward the area, moving in during the evening hours and continuing overnight into Monday morning as PWAT's along and south of the front remain near 2". Periods of moderate to heavy rainfall remain possible, but with the front already further south than was forecast 24 hours ago, this risk has also shifted south, mainly confined toward our southern tier of counties (Burke, Barnwell, Bamberg, and southern Orangeburg). Cannot rule out an isolated instance of flash flooding here tonight with a few CAM's supporting localized amounts between 2-4", but this will be highly depending on if training of weak convection can occur. With the more stable air mass north of here, any rainfall across the central/northern Midlands is expected to be fairly light. A push of much drier air is expected through the day Monday, gradually bringing an end to rain chances by the afternoon hours.

Key Message 2: Temperatures just below to near normal are expected the remainder of the week with mostly dry conditions.

There is solid model consensus that behind the cold front, PWAT's should drop toward 0.50" Tuesday as surface high pressure builds into the Mid Atlantic. Persistent northeasterly low level flow into the mid week should keep temperatures near to just below normal with dry weather expected. Weak surface ridging is expected to continue into the late week before moisture may gradually uptick toward the end of the forecast period, possibly bringing back rain chances early next weekend.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Restrictions expected today and into Monday.

Ceilings have risen a bit this afternoon with low MVFR restrictions in place at all terminals (likely to return to DNL shortly). This will likely continue for the next several hours with chances for rain increasing this evening with lowering ceilings and visibility restrictions with highest confidence at the Augusta terminals. Guidance shows the potential for developing LIFR ceilings tonight which seems reasonable with lingering low level moisture and the front near the area. For now have included the mention of sct003 to account for this possibility along with visibility restrictions, although ceilings expected to be the predominant restriction. Improvement expected into the day tomorrow as drier air slowly filters into the area.

EXTENDED AVIATION OUTLOOK...Improvement expected late Monday with restrictions unlikely this week.

CAE WATCHES/WARNINGS/ADVISORIES

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