textproduct: Columbia

WHAT HAS CHANGED

Trend in above normal temps increasingly likely to remain above normal into the weekend. Aviation discussion updated for 18z TAF issuance.

KEY MESSAGES

- 1. Mostly dry weather and well above normal temperatures expected into the weekend with heat index values above 100F.

- 2. Active weather possible this weekend followed by decreasing temperatures.

DISCUSSION

KEY MESSAGE 1. Mostly dry weather and well above normal temperatures expected into the weekend with heat index values above 100F.

The forecast remains on track as the robust upper ridge currently centered just over the Tennessee Valley continues to slide its way overhead by Thursday before gradually retrograding this weekend. There remains solid deterministic and ensemble agreement that as this ridge shifts in, temperatures should top out in the upper 90s as 500mb heights near the climatological max with 850mb temperatures near the NAEFS 99.5th percentile. A slight difference in latest guidance suggests these well-above temps will continue into the first half of the weekend and there are hints it could continue into Sunday. The daily record at KCAE could still be challenged today (99F in 2014), considering the max temperature yesterday was 98F with the ridge positioned further west than it should be today. However, the current cumulus development in the area could keep us just shy of the record. The KAGS record will be tougher to near (101F in 1957), but values today could still fall near 2-5 degrees within this. With PWAT's remaining near 1.90" much of the week, surface dewpoints should stick toward the upper 60s to lower 70s, bringing widespread heat indices between 100-105F each day through Saturday, with a possibility of nearing those values into Sunday. A couple spots nearing Heat Advisory criteria (108F) could be possible, tomorrow through Saturday, but this will depend largely on how deep of mixing is seen each day. Overall, a anomalous period of heat and humidity will persist much of this week with an increased risk for heat- related illnesses so be sure to take heat safety precautions this week.

KEY MESSAGE 2. Active weather possible this weekend followed by decreasing temperatures.

There remains solid agreement across ensemble guidance that the upper ridge should gradually retrograde this weekend in response to a deep trough digging into the eastern CONUS. As this occurs, a front should near the area with accompanying shortwave energy, bringing back the chance for at least scattered convection each afternoon this weekend. With this said, timing differences remain for the front with the potential for a later passage on Saturday. Due to this, temperatures with the current NBM run remain warmer Saturday (in the upper 90s) before cooling toward normal on Sunday, but temps Sunday have trended slightly warmer than previous runs as well. Current trends suggests temperatures near normal could persist into early next week with isolated rain chances.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Early morning fog and stratus possible in the eastern and southern Midlands.

Ridging should limit convective coverage today and Thursday. Although an isolated shower or storm is possible it is unlikely that the TAF sites will experience anything other than diurnal cumulus. Winds will generally be out of the SE around 5 to 8 kts from 15Z to 00Z each day with light and variable winds outside this timeframe. SE low level winds tonight will help pull deeper moisture into SC overnight. With a LLJ of 10 to 20 kts, this may favor a brief period of stratus along the coastal plain around sunrise Thursday. The inland extent of the stratus remains uncertain with highest chances of restrictions at OGB. Similar to Wednesday morning we may see some patchy fog develop but AGS appears to be the most likely to experience MVFR vis.

EXTENDED AVIATION OUTLOOK...Chances for restrictions and thunderstorms increase this weekend as a cold front approaches.

CAE WATCHES/WARNINGS/ADVISORIES

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