textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Active weather increasingly likely to end the work week due to system from the Gulf moving across the region, with potential for locally heavy rainfall and isolated damaging winds.

- 2. Scattered showers this morning move out and dry conditions return into Thursday ahead of the active weather from Key Message 1.

DISCUSSION

Key Message 1: Active weather increasingly likely to end the work week due to system from the Gulf moving across the region, with potential for locally heavy rainfall and isolated damaging winds.

Potential Tropical Cyclone 1 (PTC 1) has moved off the TX coast and into the northwest Gulf. While over the warm waters, it is forecast to intensify briefly before making landfall in the lower Mississippi Valley and weakening. Guidance continues to show that the upper wave associated with this system moves along a stalled boundary over the Gulf Coast states and toward the Southeast. Although there is better agreement in timing, there is still some discrepancy between model solutions, with the ECMWF still being the strongest with the associated surface low. Regardless of how the upper wave and surface low evolve, confidence is increasing that we'll see active weather Thursday afternoon/evening into Friday.

In addition to the upper wave along the Gulf coast, a cold front is forecast to start moving southward from the Midwest late in the week. As a result, the pressure gradient is expected to tighten, causing breezy to gusty winds Thursday afternoon. There is a moderate chance (50-60%) of wind gusts exceeding 25 mph. Increased moisture is also expected as the upper wave pulls Gulf moisture into the region, with PWATs over 2" likely everywhere in the forecast area. Forecast soundings also look moist adiabatic Thursday evening into the overnight hours. Latest QPF amounts have increased as well, so the combination of these factors indicate the threat for locally heavy rainfall is increasing. Despite the increased threat for locally heavy rain, confidence isn't high enough that it will be widespread enough to warrant a Flood Watch at this time. The heaviest rain from this system is forecast to remain to our southwest. Lastly, ahead of the heavy rain, there should be sufficient CAPE (~1000 J/kg or greater) and 0-6 km shear (~20-25 kts) to support an isolated strong to severe storm or two with damaging winds being the main threat.

Key Message 2: Scattered showers this morning move out and dry conditions return into Thursday ahead of the active weather from Key Message 1.

A weak shortwave translating across the South is bringing scattered showers to the forecast area early this morning. Expect shower chances to continue ahead of this shortwave, which is weaker than forecast, leading to less activity than anticipated previously. Once this shortwave passes, dry conditions can be expected for the rest of today and into Thursday ahead of the system discussed in Key Message 1. Temperatures are expected to rebound to near average for today and tomorrow as well.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Widespread restrictions to start the forecast with improvement expected by afternoon.

Radar still showing some lingering showers moving through the region keeping the possibility of some vsbys restrictions in rain through 15z or so. Widespread MVFR/IFR cigs currently in place with abundant low level moisture and isentropic lift associated with an approaching upper trough. Restrictions expected to persist through 16z or so then gradual improvement back to VFR by 18z. Winds expected to be southwesterly 5 to 10 knots then pick up to around 10 knots after 15z with some afternoon gusts to 20 knots.

EXTENDED AVIATION OUTLOOK...Diurnally favored convection possible each afternoon, favoring the southern Midlands and CSRA. 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.