textproduct: Columbia

WHAT HAS CHANGED

A northward shift in guidance may allow an area of showers and storms to move into the western FA tonight. Temperatures Thursday continue to trend a bit warmer with the slower front. Aviation discussion updated for 18z TAFs.

DISCUSSION

KEY MESSAGE #1: Batch of showers/storms could move into western FA tonight.

A shortwave is currently moving into Arkansas, sparking convection in a moist airmass along a diffuse boundary. This shortwave will continue eastward through the day, leading to upscale growth of convective clusters into a more organized MCS that moves through AL and north central GA this evening. Recent HRRR and RRFS runs have trended the MCS a bit further north, but still have it decaying as it approaches east central GA. Forecast soundings show PWAT's raising to near 1.25" as the shortwave nears the western FA thanks to modest moisture transport with around 30-40 kts of deep layer shear. Instability will likely be waning as the MCS nears after 05- 07z with soundings indicating less than 400 J/kg of elevated instability. Overall, thinking is that a batch of showers and storms should reach the western FA after 05-07z tonight as majority of high- res guidance is now showing this. The MCS is expected to be weaker and more elevated as it near the FA thus severe weather chances are low but an isolated stronger segment with gusts up to 35-50 mph cannot be ruled out before it continues to weaken with eastward extent.

KEY MESSAGE #2: Well above normal temperatures continue through the midweek with near record highs on Wednesday.

Another afternoon with temperatures into the upper 70s to low 80s is occurring today as a unseasonably warm airmass remains in place. Continuing through the week, a Baja Low will continue to drift eastward, leading to strong upper ridging over the region with this ridge nearing 1.5 standard deviations above normal. This should aid in bringing warming temperatures Tuesday and especially Wednesday where near record temperatures will be possible. This warm period is highlighted in the most recent and impressive EC EFI run with values between 0.9-0.95 each day with a SOT of 1 over the whole CWA. The latest ensemble/AI guidance has continued to generally slow the progression of the Baja low and its interaction with a northern stream trough, leading to temperatures closer to normal. Temperatures then are expected to cool behind the system on Friday before warming again this weekend.

KEY MESSAGE #3: The next storm system moves in Thursday with drier weather expected on Friday and into the start of the weekend.

As mentioned in Key Message #2, the interaction between the Baja low and northern stream trough has generally been slowed across guidance. This shift now favors the trough and surface front nearing the region closer to the Thursday afternoon timeframe rather than early Thursday morning into the early afternoon. With this said, timing differences still exist across LREF clusters so shifts are still possible. As the trough and cold front near, PWAT's should raise to 200-220% of normal with majority of each the EC Ensemble and GEFS members showing at least meager instability. AI/ML guidance such as CSU, the Pangu, and FengWu ensembles show at least some potential for more organized convection, but high uncertainty in this exists. Behind this system, there is fairly good agreement that a quick shot of slightly cooler/drier air will move in, bringing dry weather Friday and into the start of the weekend.

AVIATION /18Z MONDAY THROUGH SATURDAY/

VFR conditions are prevailing at all sites, and this is expected through the majority of the period. However, there is a wrinkle in there overnight tonight as a decaying convective system approaches from the west.

The weather is truly beautiful this afternoon at the TAF sites, with this expected to persist into this evening. Scattered cumulus dots the sky, remaining VFR after another morning of visibility and ceiling restrictions. The biggest issue at this point is some breezy winds that are oscillating from southwesterly to westerly. These should generally be in the 8-15 knot range for much of the afternoon, settling down this evening. Clear skies are expected to persist for the first part of the night tonight. However, hi-res guidance is increasingly bullish on a decaying convective system pushing into the area after 06z, especially nearest the Augusta sites. Increased clouds and rain chances exist in the 06z-15z timeframe because of this as the shortwave driving it pushes north of the area. WHile global models are not up to speed on this, the hi-res guidance has trended towards a more northern track along a remnant warm front draped across the area. Have VCSH at all sites, with a TEMPO group at AGS/DNL to account for this as it approaches the area tonight. There is still a chance that it remains to our south but that looks increasingly unlikely. So expect rain at all sites at some point tonight, with AGS/DNL most likely to see visibility restrictions. By the end of this TAF period, southwesterly winds are likely to kick back up again with drier conditions.

EXTENDED AVIATION OUTLOOK...The next good chance of rain is expected Wednesday night and into Thursday.

CAE WATCHES/WARNINGS/ADVISORIES

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