textproduct: Columbia

WHAT HAS CHANGED

Increasing confidence in hot, humid, and dry conditions this week. Aviation discussion updated for 12z TAF issuance.

KEY MESSAGES

- 1. Generally dry weather and well above normal temperatures expected with dangerous heat index values possible this week.

- 2. Active weather and decreasing temperatures possible next weekend.

DISCUSSION

KEY MESSAGE 1. Generally dry weather and well above normal temperatures expected with dangerous heat index values possible this week.

Ensemble guidance remains consistent in depicting a strong upper- level ridge building eastward across the region through the week, supporting a period of intense late-summer heat. This pattern will promote strong subsidence, with ensemble mean 700mb temperatures forecast near the 99th percentiles at around +10C. The anomalously warm temperatures, combined with a pronounced inversion will increase the overall lack of convection through the period. This combination will support highs climbing into the mid to upper 90s (or around 10 degrees higher than normal). Overnight temperatures will also remain anomalously warm, with EC EFI values around 0.7-0.8 and a nonzero shift of tails (similar to the max temperatures) with values about 5 to 10 degrees above normal. Persistent southeast to southwest flow will maintain ample low-level moisture across the region resulting in heat indices to exceed 100F throughout the week. Some values have the potential to approach heat advisory criteria by the mid to latter part of the week.

KEY MESSAGE 2. Active weather and decreasing temperatures possible next weekend.

Global models remain in good agreement depicting the strong ridge to retrograde westward across the Plains by next weekend. This evolution will favor the development of upper troughing along the East Coast and support a gradual cooling trend across the region. Shortwave energy is expected to drive southeastward along its backside, bringing increasing chances for rainfall back to the FA. This pattern should provide some relief from the heat starting next week.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Restrictions possible again towards the morning hours.

Although skies have been mostly clear on satellite, some patchy areas of low stratus/fog appear to be developing across the region, especially over the eastern Midlands near ogb. Do expect some of this to potentially impact other taf locations through 13-14z. Guidance is somewhat variable on widespread coverage, so will start off with continuation of either low end vfr or mvfr conditions, and have a tempo group through 14z for ifr or lifr visibilities. Conditions should be improving by 14z as slightly better mixing starts, with vfr expected through the late morning and the afternoon. Winds will be light, around 5 kts, through the day and out of the east, but could also be variable for large portions of the day. Showers and thunderstorms should be limited in coverage once again so we have left out mention of afternoon convection for the time being. Another bout of mvfr/ifr restrictions can not be ruled out for Tuesday morning near the end of the current taf period.

EXTENDED AVIATION OUTLOOK...Early morning restrictions still possible despite a drier outlook for the week.

CAE WATCHES/WARNINGS/ADVISORIES

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