textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Isolated to widely scattered convection possible today and Tuesday with hot/humid conditions continuing.

- 2. A more active pattern is expected during the mid to late week with slightly cooler temperatures and chances for stronger thunderstorms Wednesday.

DISCUSSION

Key Message 1: Isolated to widely scattered convection possible today and Tuesday with hot/humid conditions continuing.

TD Two is expected to begin slowly drifting NNW across the Gulf through the day today as low level flow over the FA becomes increasingly southerly. The plume of deepest moisture associated with this system is expected to remain confined toward the Gulf Coast, but PWAT's between 1.85-2" are expected to remain over the region. Surface troughing is expected to gradually weaken through the day, but pieces of shortwave energy from the troughing pattern over the eastern CONUS are expected to pass near the Pee Dee this afternoon/evening. Surface dewpoints are expected to remain in the upper 60s to low 70s with mean HREF MUCAPE values nearing 2000 J/kg through the day with lingering cloud layer shear values near 20-30 kts. With the subtle nature of forcing, expect convective coverage this afternoon/evening to be fairly isolated with the best chances along and east of the I-26 corridor. Generous mixing should once again yield DCAPE values that could close in on 1000 J/kg so a stronger storm cannot be ruled out with this activity. Tuesday likely acts as a transition day where surface troughing and any upper support exit the CWA, but hot/humid conditions should still yield seasonable instability and isolated diurnal shower/storm chances. Temperatures today and Tuesday are expected to once again push the mid to upper 90s with heat indices up to 100-106F expected, remaining just under Heat Advisory criteria.

Key Message 2: A more active pattern is expected during the mid to late week with slightly cooler temperatures and chances for stronger thunderstorms Wednesday.

The upper pattern is expected to amplify a bit through the day Wednesday and into the late week as both the EC Ensemble and GEFS mean solutions show a strong trough (500mb heights 2-2.5 standard deviations below normal) extending from the eastern Great Lakes down into the Mid-Atlantic. This trough is expected to push a cold front down into the region which could near the FA by late Wednesday where IVT ahead of the front could reach the NAEFS 90th to 99th percentile and PWAT's exceed 2". LREF cluster analysis shows uncertainty in the depth of the upper trough exists, but even weaker solutions show decent PVA and kinematics reaching the FA with deep layer shear nearing 20-30 kts and a 20-25 kt LLJ in place. With seasonable to moderate instability likely in place, this trough and front could bring a chance for more widespread shower/storm chances by the evening where strong to severe storms could be possible. Global models depict the frontal boundary stalling near/within the FA on Thursday as another shortwave likely moves in. With anomalous IVT continuing, scattered to widespread rain chances could continue where heavy rainfall will be possible as EC Ensemble and NBM probabilities for greater than 1" of QPF near 50-60%. With the region remaining in northwest flow into the weekend, a series of shortwaves are expected to continue pushing through, bringing more rain chances.

Due to upper troughing and increased rain chances, Temperatures that start near normal Wednesday are expected to cool to slightly below normal during the late week. Fairly large 6-8 degree IQR ranges remain during this time period, but even the blends 75th percentile brings temperatures right around normal.

AVIATION /12Z MONDAY THROUGH FRIDAY/

VFR Conditions Expected to Continue.

VFR conditions at all terminals with some passing high clouds early this morning. Winds will generally be out of the SSW, increasing during the afternoon with gusts generally in the mid to upper teens. While guidance generally indicates a bit of a deep layer moisture increase associated with a tropical depression along the Gulf Coast, convection coverage will likely be somewhat limited again today. Confidence remains low in thunderstorms impacting the terminals with limited coverage in high resolution models. There may be some isolated storms along the sea breeze this evening but have left out the mention of tsra with low confidence.

EXTENDED AVIATION OUTLOOK...Potential for restrictions from showers and thunderstorms continues with the threat increasing later in the week.

CAE WATCHES/WARNINGS/ADVISORIES

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