textproduct: Columbia

WHAT HAS CHANGED

Key message 1 updated. Not much change to the overall forecast with isolated to scattered showers and thunderstorms expected this afternoon, favoring the southern Midlands and CSRA. A few thunderstorms may become strong with damaging wind gusts as the primary severe hazard. Aviation discussion updated for 18z TAFs.

KEY MESSAGES

- 1. Hot and breezy conditions continue through the end of the week with isolated thunderstorms possible today and tomorrow.

- 2. A frontal boundary brings higher rain chances for the weekend followed by increasingly likely cooler temps.

DISCUSSION

Key Message 1: Hot and breezy conditions continue through the end of the week with isolated thunderstorms possible today and tomorrow.

The mid to upper ridge axis is centered along the east coast this afternoon moving eastward in response to an approaching trough over the Tennessee Valley. The ridge is expected to flatten out over the next couple of days. Expect hot and breezy conditions to persist this afternoon and again on Friday with high temperatures in the upper 90s to around 100 degrees and heat index values between 100 and 105 degrees. While below our Heat Advisory criteria, continue to exercise caution if spending an extended period of time outdoors during peak heating.

In terms of thunderstorm coverage, convection should once again favor the southern half of the forecast area. Radar is already detecting a few small showers in the CSRA with more robust thunderstorm activity over central Georgia. The SPC has upgraded the forecast area to a Marginal (1/5) risk for severe weather today, citing damaging wind gusts as the primary severe hazard. This is due to the presence of an Inverted-V signature on modeled soundings in addition to ample CAPE and DCAPE. PWATs remain high this afternoon but storm motion should be sufficient to limit the threat for flash flooding. Convective coverage may be higher Friday afternoon based on the latest hi- res guidance.

Key Message 2: A frontal boundary brings higher rain chances for the weekend followed by increasingly likely cooler temps.

A frontal boundary draped over the Upper Midwest early this afternoon is forecast to move southward in response to a shortwave moving from the Great Lakes into the Southeast through the weekend. As the front and associated upper trough approach the area, more widespread shower and thunderstorm activity can be anticipated for the weekend. This activity could linger into early next week as latest guidance indicates that the front stalls out near the area. In addition to the increased rain chances, it looks increasingly likely that we'll see cooler temperatures. The NBM interquartile range (IQR) on Monday ranges from the low to mid 80s to around 90F for the area. Given the recent hot weather, the NBM takes that into account and will likely have a warm bias. So, I would not be surprised if we end up toward the cooler end of the IQR.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

VFR conditions expected through the TAF period.

VFR conditions in place at all terminals with scattered cumulus clouds around 5kft. A bit more vertical growth in the clouds in southern Georgia with thunderstorms developing and slowly drifting towards the Augusta terminals. Isolated storms may approach and have continued the prob30 to account for this convective activity, although coverage is expected to remain limited through the afternoon. Convective activity will diminish this evening into tonight with winds diminishing as well. Similar conditions expected tomorrow with scattered cumulus and convective development possible but after 18z.

EXTENDED AVIATION OUTLOOK...Increasing chances for afternoon storms this weekend and into early next week.

CAE WATCHES/WARNINGS/ADVISORIES

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