textproduct: Columbia

WHAT HAS CHANGED

Minor changes to the key message. Aviation discussion updated for the 12z 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 will gradually reorient itself 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 across the forecast area, with values falling below 1.5 inches today and Thursday. This 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 heat indices near criteria will increase with highs in the upper 90s to around 100 degrees and higher dewpoints. Regardless of whether advisory criteria is reached, conditions will exist that pose a risk for heat-related illnesses to those with outdoor plans, which will include many of the holiday weekend festivities. 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 /12Z WEDNESDAY THROUGH SUNDAY/

VFR conditions expected through the TAF period.

Through 12-13z, some typical morning MIFG may develop around CAE/AGS/OGB, though confidence remains low in any restrictions; included a tempo for VFR MIFG for the time being. A similar pattern is expected on Wednesday as Tuesday, with east winds increasing to 6-10 kts by mid- morning and gusts up to 12 knots in the afternoon. Dry conditions will persist, outside of a very isolated shower, with typical summer cu around 5-6k feet developing during the day and increasing cirrus moving in toward the end of the period.

EXTENDED AVIATION OUTLOOK...Convection unlikely for the remainder of the week as ridging builds overhead. Brief early morning restrictions possible. Rain chances and possible restrictions start to increase Saturday and especially Sunday.

CAE WATCHES/WARNINGS/ADVISORIES

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