textproduct: Columbia

WHAT HAS CHANGED

Updated Key Message #1 to reflect current conditions. Aviation Discussion updated for 06z TAFs.

KEY MESSAGES

- 1. Gusty winds, heavy rainfall, and severe weather are possible this afternoon into Friday morning.

- 2. A more typical summer-like pattern returns for the weekend into next week.

DISCUSSION

Key Message 1: Gusty winds, heavy rainfall, and severe weather remain possible through Friday morning.

The remnants of Arthur will continue lifting northward across the forecast area as a cold front approaches from the northwest and pushes it offshore. The primary hazards and concerns remain locally heavy rainfall capable of producing isolated flash flooding and a few strong wind gusts. Earlier convection Thursday afternoon have helped limit current instability, although PWATs remain around 1.75-2.25" with continued southwest flow maintaining a rich moisture supply from the Gulf. A modest low-level jet and sufficient shear remain in place that a severe threat remains possible, but instability is lower than previously anticipated and is unlikely based on current mesoanalysis trends.

Additional showers and thunderstorms persist closer to the center of circulation over central GA. At this time, there is a bit of a dry slot overhead currently but a "third" line/cluster behind it shows the heaviest rainfall remaining just south of the area. However, Hi-res guidance and recent radar trends suggest light precipitation coverage should increase somewhat as the center tracks overhead over the next few hours. All activity should exit by mid-morning on Friday. A few gusty winds are also possible, mainly near convection as the pressure gradient increases but should diminish by midday.

Key Message 2: A more typical summer-like pattern returns for the weekend into next week.

After the remnants of Arthur move out of the area, a front is expected to slide through the FA Friday afternoon/evening, bringing isolated to scattered shower/storm chances. Slightly drier conditions are expected behind the front this weekend, but with warming temperatures into the low 90s. Multiple disturbances are forecast to move through upper zonal flow, bringing a more summer-like pattern of diurnal thunderstorm chances as we head into next week.

Looking further, the upper pattern becomes more amplified as troughing deepens over the Midwest and heights fall across the southeast. Ensemble guidance begins to diverge by that point, but the are indications that a shortwave may eject across the region, potentially supporting an uptick in convection and perhaps severe weather. However, confidence remains too low at this time for further details.

AVIATION /06Z FRIDAY THROUGH TUESDAY/

Flight restrictions due to low ceilings will persist at the terminals into midday, followed by improvement to VFR conditions for the remainder of the forecast period.

As the remnant low of former Tropical Cyclone Arthur passes through during the early morning hours today, one additional band of showers will accompany its passage, with the rain potentially reducing visibilities and at times mixing down some higher gusts upwards of about 20 kt. The rain should generally come to an end by mid-late morning based on the latest HREF guidance, but low ceilings will remain an issue, with MVFR or IFR ceilings persisting through about 16-17Z at the terminals. After that ceilings will rise to VFR levels, and eventually scatter out by this evening. Winds will generally be southerly at the start of the forecast period, but veer more westerly by late morning with sustained wind speeds of 8-12 kt. Winds should become rather light out of the west-southwest this evening.

EXTENDED AVIATION OUTLOOK...Diurnally driven convection can be anticipated heading into the weekend, although coverage will be isolated with higher coverage next week.

CAE WATCHES/WARNINGS/ADVISORIES

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