textproduct: Columbia

WHAT HAS CHANGED

Moisture has increased over the region lowering fire weather concerns slightly. However, due to continued drought conditions South Carolina Forestry Commission's State Foresters Burning Ban remains in effect until further notice. Updated aviation discussion for 18z update.

KEY MESSAGES

- 1. Scattered showers, low rain amounts this weekend.

- 2. Higher rain and thunderstorm chances mid-week.

DISCUSSION

Key Message 1: Scattered showers, low rain amounts this weekend.

Weak southerly flow will lead to increasing atmosphere moisture over the Southeast as a front approaches from the west. Although PWAT values may rise to 1.5 inches, or about 175 percent of normal, the low levels will remain quite dry through the afternoon with surface dewpoint depressions of 30 to 35 degrees. It will be difficult to get deep convection to develop this afternoon with high LCLs and warm mid-levels. We would expect to see only isolated showers until a shortwave moves over the area this evening and the frontal boundary draws closer. With surface dewpoints rising into the 60s tonight and colder air aloft we begin to see thermodynamic profiles more supportive of deep convection and possibly a few thunderstorms. Any thunderstorms would be weak and the environment does not support severe weather. Rainfall will be limited tonight with PMM QPF amounts from the REFS generally less than 0.1" across the FA, although a few deeper cells could allow for localized higher amounts.

A backdoor front will cross through the FA from the north on Sunday with isolated to scattered convection possibly forming along the boundary. Any showers or storms will be forming in an environment with dry air aloft so it's possible that entrainment could prevent sustained updrafts. So again we would not expect very much in the way of rainfall for much of the area.

Key Message 2: Higher rain and thunderstorm chances mid-week.

A more unsettled pattern develops next week as ridging gives way allowing a series of shortwave troughs to encroach on the Southeastern US mid-week. NAEFS PWAT values rise to the 90th percentile of climatology for Tuesday and Wednesday. This pattern of above normal atmospheric moisture and shortwave activity over the region supports at least a chance of rain mid- week. That said there remains a great deal of uncertainty for rainfall amounts with the NBM IQR from 0.1 to around 1 inch through the week. Thunderstorms will also be possible with the majority of GEFS and ECMWF ensemble members showing more than 500 J/kg of MUCAPE Wednesday and Thursday. With a potential frontal passage, moderate wind shear, and at least weak instability there may be a threat of severe weather that needs to be monitored. Some of the NCAR ML/AI severe probabilities are also beginning to pick up on low potential for severe weather.

AVIATION /18Z SATURDAY THROUGH WEDNESDAY/

VFR conditions continue into the afternoon. A cold front ushers in showers later today. Uncertainty as to whether restrictions develop tonight.

A cumulus field has developed across the area, with bases in the 7-9kft range at this time. Additionally a few showers have begun to develop across the region, but are currently well away from the terminals. A front to our west continues working its way eastward, bringing additional shower activity to the area. Some of these showers are likely to affect the terminals, but confidence is on the low side for any visibility restrictions with these showers. Given how dry the surface is, there could be gusty winds associated with any showers or storms near the terminals. After the shower activity subsides tonight, there is potential for low ceilings and/or fog, but there is a lot of spread between the various guidance, so confidence remains too low to include at this time. Will continue to monitor with future TAF issuances. Winds are generally from the southwest around 8 kts with isolated gusts up to 15 kts. Winds are expected to become light and variable to calm overnight, becoming northerly after about 15z.

EXTENDED AVIATION OUTLOOK...Some periodic vsby and cig restrictions are possible over the next week with a more unsettled pattern and chances for rain Sunday and Tuesday.

CAE WATCHES/WARNINGS/ADVISORIES

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