textproduct: Columbia

WHAT HAS CHANGED

Rain becoming widespread for much of the day Wednesday with amounts generally between a quarter and three quarters of an inch.

KEY MESSAGES

- 1) Cold front brings widespread rain to the area Wednesday morning, continuing through much of the day.

- 2) Temperatures near to slightly below average through the weekend.

DISCUSSION

KEY MESSAGE #1: Cold front brings widespread rain to the area Wednesday morning, continuing through much of the day.

A cold front that is currently moving through the Lower Mississippi Valley will continue to approach the forecast area. Surface high pressure over the area will shift offshore with increasing southwesterly flow leading to warm advection and increasing moisture with HREF mean indicating PWATs rise to 0.9-1 inch. This will lead to widespread rain developing across the area Wednesday morning. As an upper trough digs deeper over the Mississippi Valley during the day Wednesday, this will reinforce deep southwesterly flow aloft and cause the front to slow over the area. As a result, periods of rain will continue through much of the day for the area before the front clears, likely Wednesday night. Expect a beneficial rain as the entire area remains in drought. HREF members indicate rain rates won't be particularly high but generally favor rain amounts between a quarter to three quarters of an inch. Drier air expected to move in aloft Wednesday night and while the upper trough may lead to some lingering precipitation, it is expected to taper off and become light. A note that while some model guidance is indicating frozen precipitation at the end of this period, with moisture so shallow it is unlikely that there would be ice the cloud. While cannot rule out a brief period of freezing drizzle along the northernmost portion of the forecast area, impacts would be limited with temperatures above freezing until a short period just before sunrise Thursday.

KEY MESSAGE #2: Temperatures near to slightly below average through the weekend.

Overall expect temperatures to be near average through much of the period, quite the change from the significant cold spell for the Midlands and CSRA over the last week or so. The exception will be behind the front Thursday which likely be colder with an upper trough over the forecast area, with NAEFS mean indicating 500mb heights will be below the climatological 10th percentile. Upper ridging late this week into the weekend will begin to build over the central US with blended guidance favoring a quick return to near average temperatures.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR conditions expected into the early overnight hours, then deteriorating conditions and restrictions into Wednesday morning.

Another weather system will move through the region Wednesday. Ahead of this, vfr conditions will prevail at least into the early portions of the overnight hours tonight. Expecting thin cirrus to continue traversing the region, with those being the primary cloud type this afternoon. Low and mid level moisture will then begin to increase later tonight, with increasing cloud cover expected to really begin between 00z-06z tonight. Through that period though, vfr ceilings will still occur as light rain moves in from the west. Lowering ceiling into mvfr will occur towards 11z-12z, with a rapid drop to ifr or lower shortly there after at all sites. Wind light and out of the south to southwest around 5 knots for majority of the forecast period.

EXTENDED AVIATION OUTLOOK...Another system and front moving into the area late Tuesday night and into Wednesday likely to bring some restrictions back to the region.

CAE WATCHES/WARNINGS/ADVISORIES

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