textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAFs. Lee County has been added to the Heat Advisory for today.

KEY MESSAGES

- 1. Above normal temperatures continue, peaking this weekend. Another Heat Advisory will be in effect along and north of I-20 from 12pm-8pm Saturday with heat indices up to 105F possible.

- 2. Increasing chances for showers and thunderstorms late this weekend into next week. Strong storms are possible each afternoon and evening.

DISCUSSION

Key Message 1: Above normal temperatures continue, peaking this weekend. Another Heat Advisory will be in effect along and north of I-20 from 12pm-8pm Saturday with heat indices up to 105F possible.

Happy Independence Day! Hot weather is again expected out there, with dangerous heat likely this afternoon. Similar to the past few days, a strong 500 hPa ridge remains centered to our north over the Mid-Atlantic. 00z upper air analysis reveals this a bit further southeast and more sprawling than previously expected. Dry air, augmented by subsidence beneath this ridge, remains in place across the area. PWs this afternoon are forecast to remain below 1.5" which should help keep the dewpoints manageable at the surface. This deep mixing is expected to allow temps to make a run at 100F today. The axis of the upper ridge has allowed the hottest and most anomalous 850 hPa temps remain to our north and this likely will be the case today. Still, with 850 hPa temps of 20C-22C, highs this afternoon should range from 99F-101F across the area. Given the outdoor events taking place, went ahead with a Heat Advisory along and north of I20 where the hottest temps are generally forecast this afternoon. We won't be at our specific criteria but this advisory is focused on the impacts with the holiday. The heat, especially as it pertains to high temperatures, is forecast to begin taking a step back beginning Sunday. The ridge that has dominated the weather across the eastern CONUS for several days now is expected to rapidly break down as we get into the second half of the weekend and early next week, resulting in cooler day time highs. However, southwesterly flow aloft will help to usher in more seasonal to slightly higher than normal moisture values. So more heat products may be needed as we get into next week but it'll likely be dependent on daily convective coverage.

Be diligent to take appropriate heat safety measures this holiday weekend. The elderly, young children, pets, and those without indoor cooling will be at particular risk this weekend and over the coming week.

Key Message 2: Increasing chances for showers and thunderstorms late this weekend into next week. Strong storms are possible each afternoon and evening.

Isolated showers/storms are possible as we approach our convective temperatures this afternoon but it is unlikely that we see anymore than a storm or two. Coverage of convection is likely to increase beginning on Sunday and persisting through much of the week. The ridge will break down (as previously mentioned) and allow for persistent troughing and shortwaves to pass over the area through much of the next week. Given PWs approaching 2" again & ensembles showing CAPE of 1000-2000 j/kg each afternoon, strong to marginally severe storms are possible. ML guidance has been persistent with the signal for daily strong to marginally severe storms and do expect that to be the case with afternoon and evening convection. Damaging winds are the most likely threat with any strong storm that does get going. Rainfall will likely be hit and miss as is typically for this time of year; however, wouldn't be too surprised to see one of these days over-perform coverage wise and yield a decent shot of rainfall.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR conditions expected through the TAF period.

Light and variable winds this morning with some high clouds. Brief visibility restrictions associated with smoke from fireworks is also possible. Southeasterly winds around 5-10 kts should start around midday along with a few cumulus clouds. High clouds return tonight as winds return to light and variable, or perhaps favoring a southerly direction around 5 kts.

EXTENDED AVIATION OUTLOOK...Daily rain chances and possible restrictions start to increase Sunday into early next week.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Heat Advisory from noon today to 8 PM EDT this evening for SCZ016-018-020>022-025>030-115-116. GA...Heat Advisory from noon today to 8 PM EDT this evening for GAZ040-063>065.