textproduct: Columbia

WHAT HAS CHANGED

Little change to the key message. Aviation discussion updated for the 18z TAFs.

KEY MESSAGES

- 1. Temperatures warm through the week, peaking during the Independence Day weekend.

DISCUSSION

Key Message 1: Temperatures warm through the week, peaking during the Independence Day weekend.

Strong upper level ridging continues to be the dominant atmospheric feature that will dictate the weather over the next several days. An anomalously strong (99th percentile) upper ridge over Tennessee will gradually reorient itself over the Ohio Valley on Wednesday and then over the Mid-Atlantic by the end of the week before breaking down late in the holiday weekend. Ensembles continue to indicate PWAT values lowering (at or below the 50th percentile) across the forecast area with values falling below 1.5 inches Wed/Thu which should significantly limit precipitation chances. Forecast soundings also show a strong subsidence inversion with large inverted-V signatures resulting from deep mixing further supporting suppressed convective chances.

While temperatures will be hot with highs expected in the mid to upper 90s, the drier air and deep mixing should result in lower dewpoints and therefore lower humidity resulting in heat indices well below our advisory criteria the next few days. As we move into the holiday weekend, moisture will be increasing and the probability of near criteria heat indices will increase with highs in the upper 90s to around 100 degrees and higher dewpoints. Whether or not we reach advisory criteria, conditions will exist that pose a heat risk threat to those with outdoor plans which will include many of the holiday weekend festivities and everyone should prepare accordingly and be alert to the heat and stay hydrated. The increasing moisture will increase instability and chances of convection late in the weekend into early next week as the upper ridge begins to break down.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR conditions expected through the TAF period.

Northeast winds will continue this afternoon at 6-10 kts, with occasional low-end gusts up to 15 kts at times under VFR cumulus. Winds will diminish to light and variable after sunset. Toward daybreak, some typical morning MIFG may develop around AGS/OGB, though confidence remains low at this time.

A similar pattern is expected on Wednesday, with east winds increasing to 6-10 kts by mid-morning. Dry conditions will persist, with fair weather cumulus clouds developing during the day and increasing cirrus moving in toward the end of the period.

EXTENDED AVIATION OUTLOOK...Afternoon convection is less likely for the remainder of the week as ridging builds overhead. Brief early morning restrictions also possible this week.

CAE WATCHES/WARNINGS/ADVISORIES

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