textproduct: Columbia

WHAT HAS CHANGED

Onset of precipitation today has trended later in the day. Precip chances have lowered for Wednesday and Thursday. Aviation discussion updated for 06z TAFs.

KEY MESSAGES

- 1. Unsettled weather returns for the rest of the work week.

DISCUSSION

Key Message 1: Unsettled weather returns for the rest of the work week. Unsettled weather is expected to return for the remainder of the week as the frontal boundary lingers across the southeast and multiple shortwaves move over the region. This pattern will help expand shower and thunderstorm coverage into the forecast area, particularly as a weak surface low attempts to develop along the stalled boundary Tuesday morning. However, latest trends suggest the precip associated with this moves into the area later than previous forecasts. The latest guidance trends keep the highest moisture transport and PWATs generally south of the area for much of the week, keeping the highest PoPs (and best chance for thunder) in the southern portions of the forecast area and locations south. A relative lull in precip chances then arrives for Wednesday and Thursday as the majority of rainfall stays south of the area. Instability appears relatively weak, so widespread severe weather is not anticipated at this time, but given the time of year, any stronger storm is capable of producing gusty winds.

Looking to the end of the week, most deterministic guidance remains in good agreement regarding a vigorous shortwave trough diving into the Upper Midwest while a weak tropical disturbance drifts across the western Gulf. The associated surface low is expected to lift into the northeast along the aforementioned boundary, helping to maintain a stalled front across the Deep South. Temperatures are forecast to gradually warm back to near-normal by midweek, while higher precipitation chances return Thursday night into Friday. Forecast confidence decreases late in the week as model solutions continue to diverge on the evolution of the low in the Gulf as it tracks inland along the stalled front. The ECMWF continues to depict a stronger and slower-moving system, while the GFS remains faster with the wave reaching the area by Thursday. Regardless, increasing rain chances appear likely late in the week as upper level winds pull moisture from the system to the north and east toward the forecast area. A heavy rainfall threat and isolated severe weather could be possible Friday, but confidence remains too low for greater detail at this time. By the weekend, drier air should return as the upper trough shifts eastward.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

VFR conditions expected through 18Z then possible restrictions arrive from south to north.

A weak surface boundary over the area combining with increasingly more southwesterly flow aloft should result in some weak isentropic lift supporting isolated showers developing around 12z in the CSRA and somewhat better coverage of showers and possible thunderstorms during the afternoon and evening hours as an upper disturbance approaches. Generally high clouds over the area will gradually lower through the period as moisture increases from south to north with low VFR cigs expected by this afternoon and possible MVFR cigs arriving late afternoon, with widespread MVFR cigs expected to overspread the region after 00z. Will keep a tempo group from 18z-00z for afternoon convection. Winds will pick up from the southwest after 14z and become gusty through the afternoon.

EXTENDED AVIATION OUTLOOK...Relatively high chances of restrictions predawn Wednesday with diurnally favored convection possible each afternoon. Breezy conditions expected Thu/Fri with increased chances of rain as a Gulf coast system approaches the area.

CAE WATCHES/WARNINGS/ADVISORIES

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