textproduct: Columbia

WHAT HAS CHANGED

Aviation updated for 12z TAFs. Key messages updated. There is a low threat of strong thunderstorms in the southern Midlands and southern CSRA today.

KEY MESSAGES

- 1) Showers for much of the area but thunderstorms possible to the south today, followed by breezy NW winds through Monday.

- 2) Freezing temperatures likely Monday and Tuesday mornings.

DISCUSSION

KEY MESSAGE #1: Showers for much of the area but thunderstorms possible to the south today, followed by breezy NW winds through Monday.

A frontal boundary is draped over the Midlands and CSRA this morning and will waiver a little further north then back to south through the day as a low pressure develops in advance of an upper trough. Atmospheric moisture rises to well above normal with PWAT values exceeding 2 inches today. Showers will continue along the boundary through much of the day with intensity expected to pick up from mid- day into the afternoon as a shortwave moves over the region. CAMs suggest the bulk of the convection will remain south of I-20 with 50 to 75 percent of HREF and NBM members showing one half inch of rain or higher in this area.

Convection will be focused along the frontal boundary and should slip south of the area later in the afternoon. On the warm side of the boundary, we will see weak to moderate conditional instability in an environment with strong shear in the lowest 1 km. Although most 00Z model runs were quicker to push the front to our south more recent runs have kept it further north. This increases concern for severe weather from mid-day into the afternoon along the extreme southern FA including Burke, Barnwell, and Bamberg Counties. If the front is slower to move to our south then there would be potential for a severe thunderstorm to produce damaging winds. With 0 to 1 km shear around 20 kts and enhanced helicity along the front we also cannot rule out a tornado.

As the main area of convection shifts south of the area by this evening, we may see a break in the rainfall until another round of showers moves in ahead of a cold front on Sunday. Once the cold front moves through we can expect gusty NW winds through the remainder of the day. Winds should gust between 25 to 35 mph through the afternoon, with a Lake Wind Advisory or Wind Advisory will likely be needed. Winds are expected to be a little weaker on Monday as strong cold advection continues.

KEY MESSAGE #2: Freezing temperatures likely Monday and Tuesday mornings.

Temperatures are likely to drop below freezing Monday and Tuesday morning with temperatures as low as the low 20s possible for the latter. Models have come into better agreement for early next week with little spread in temperature guidance. This increases confidence in temperatures below 28 degrees. Given the warm up over recent days, any sensitive vegetation that has blossomed may be harmed if unprotected.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

Mix of MVFR-IFR conditions, heavier rain and thunder with MVFR- IFR restrictions expected Saturday morning into the afternoon.

A stalled front across the region will bring widespread showers and isolated thunderstorms throughout the TAF period. Starting around 12z, some scattered showers will steadily develop with cigs and vsby generally MVFR-IFR. This initial batch of showers will likely bring a period of -TSRA to CAE and CUB. After 14z, more persistent and heavier showers and thunderstorms will shift south and continue to impact AGS- DNL- OGB, with a mix of associated LIFR-IFR-MVFR restrictions. The heaviest precip period looks to be between 15-19z which is also when TSRA is most likely, again at DNL-AGS- OGB; tempo included there, with prob30 group included at CAE- CUB given the lower confidence as the heaviest precip shifts south. Showers should lighten up a bit in the afternoon and evening, before lowering cigs to IFR- LIFR moves in after 2200z and then throughout the remainder of the TAF period with additional rain expected towards the end of the TAF period.

EXTENDED AVIATION OUTLOOK...Restrictions likely into Sunday morning before drier air and windy conditions move in. No notable periods of restrictions expected through mid-week.

CAE WATCHES/WARNINGS/ADVISORIES

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