textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12Z TAF.

KEY MESSAGES

- 1. A typical summer pattern expected this week with increasing moisture.

- 2. Warming temperatures during the mid to late week time frame may lead to a period of dangerously hot temperatures.

DISCUSSION

Key Message 1: A typical summer pattern expected this week with increasing moisture.

Ridging and surface high pressure remain in place early this week. A plume of higher moisture shifts east today and brings better precip chances particularly for the western portion of the forecast area. While high pressure will work to limit convective coverage, elevated atmospheric moisture, generally 100-120% of normal PWAT values and strong heating are still expected to lead to isolated to scattered afternoon showers and thunderstorms as a few very weak shortwaves move through. The summer-like pattern persists into this weekend as PWAT values approach 2" and upper level support becomes stronger, leading to higher confidence in organized convection by Saturday and Sunday.

Key Message 2: Warming temperatures during the mid to late week time frame may lead to a period of dangerously hot temperatures.

Anomalously strong ridging over the area late this week is expected to lead to H85 temperatures around 20C, or about 4-6C above normal Thursday through Saturday during peak daytime heating. At the surface, this should bring high temperatures reaching the mid to upper 90s, or 10-15F above normal. At the same time, surface dewpoints remain in the mid to upper 60s in the afternoons. The combination of heat and above normal moisture could result in heat index values reaching the upper 90s to low 100s Thursday and Friday. At the moment, this would remain just shy of any headline criteria, but we'll be keeping a close eye on apparent temperatures with subsequent forecasts, as this would be the first significant heat wave of the season.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

Brief restrictions possible this morning; showers/storms possible in the afternoon and evening.

Mid to high level clouds continue at the terminals this morning. With lingering low level moisture (dew points over 70F), guidance has been indicating the potential for brief restrictions near sunrise, with most likely restrictions being MVFR. Given the current trends and observations, included a MVFR tempo for all sites around sunrise Tuesday morning. Restrictions clear out by mid-morning with a typical summer day following. Some scattered showers and storms likely in the afternoon, so included a Prob30 for the most likely terminals. Light and variable to calm winds return to the terminals overnight.

EXTENDED AVIATION OUTLOOK...Isolated, mainly diurnal, showers and thunderstorms.

CAE WATCHES/WARNINGS/ADVISORIES

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