textproduct: Columbia

WHAT HAS CHANGED

Minimal change to Key Messages. Aviation discussion updated for 12z TAF issuance.

KEY MESSAGES

- 1. Mostly dry weather and well above normal temperatures expected this week with heat index values above 100F.

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

DISCUSSION

KEY MESSAGE 1. Mostly dry weather and well above normal temperatures expected this week with heat index values above 100F.

The forecast remains on track as the robust upper ridge currently centered just west of the FA continues to work 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. The daily record at KCAE could be challenged today (99F in 2014), considering the max temperature yesterday was 98F with the ridge positioned further west than it should be today. 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. A couple spots nearing Heat Advisory criteria (108F) could be possible, especially Thursday 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 and decreasing temperatures possible this weekend.

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 have trended warmer Saturday (in the upper 90s) before cooling toward normal on Sunday. Current trends suggests temperatures near normal could persist into early next week with isolated rain chances.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

VFR conditions generally expected outside of possible predawn fog at favored locations.

Some sunrise fog remains possible this morning but confidence is decreasing any notable IFR restrictions; tempo included at typically prone sites through 13z for MVFR vsby. Otherwise, typical summer day expected today but with little-no chance for precip. Cu field develops by late morning with winds developing first out of the east, then becoming southeasterly this afternoon with gusts up to 12 knots.

EXTENDED AVIATION OUTLOOK...Early morning restrictions still possible despite a drier outlook for the week. Increased chances of restrictions over the weekend with increased chances of convection with an approaching cold front.

CAE WATCHES/WARNINGS/ADVISORIES

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