textproduct: Columbia

WHAT HAS CHANGED

Minimal change to Key Messages. Aviation discussion updated for 18z TAFs.

KEY MESSAGES

- 1. Above normal temperatures likely continue this week as heat indices exceed 100F multiple days.

- 2. Chances for scattered diurnal showers and thunderstorms continue into the work week. Strong to marginally severe storms possible the next couple afternoons.

DISCUSSION

Key Message 1: Above normal temperatures likely continue this week as heat indices exceed 100F multiple days.

The stage for the first half of the week is already setting up with the axis of the upper ridge shifting a bit offshore in response to the trough currently extending from the northern Great Lakes toward the lower Mississippi Valley. This pattern will allow warm/moist advection from the southwest, keeping 850mb temps near 20C and generally keeping 1000-850mb thickness values above 1425m. Temperatures in the mid to upper 90s remain likely with LREF probabilities for max temperatures above 95F between 40-60% through the midweek before increasing toward 50-70% late this week. While generous mixing is expected each afternoon, 925mb dewpoints are expected to creep toward 19-21C, maintaining moist conditions with surface dewpoints sticking to the upper 60s to low 70s. This combination brings high LREF probabilities (above 60-70%) for heat indices to exceed 100F each day this week. As has been discussed, scattered diurnal convection that is expected each day complicates this a bit, but if drier conditions trend for any one day, additional heat products could be needed.

Due to the prolonged nature of this heat, be sure to check on those without adequate indoor cooling and take heat safety precautions this week.

Key Message 2: Chances for scattered diurnal showers and thunderstorms continue into the work week. Strong to marginally severe storms possible the next couple afternoons.

A similar strong to severe pulse environment is expected the next 2-4 days, but weak synoptic forcing in the form of pieces of shortwave energy that move over the FA as we remained wedged between the trough and the upper ridge could aid in initiation. The latest EC Ensemble mean solution keeps MUCAPE over 2000 J/kg in the area through at least Tuesday, and high atmospheric moisture content combined with generous mixing should yield impressive DCAPE values. As has been discussed, damaging downburst winds in the strongest storms will be the main risk considering the environment and the latest CSU ML probabilities maintain this elevated risk. The most recent NBM run and global models show slightly "drier" air (PWAT's near 1.60-1.80") could push into the region during the midweek, possibly limiting convective coverage a bit, but there remains some uncertainty in this. Overall, expect a couple strong to severe thunderstorms or two the next couple days across the area with diurnal convection chances continuing into the mid to late week, but with a bit more uncertainty at that point.

AVIATION /00Z MONDAY THROUGH FRIDAY/

VFR Conditions expected through the TAF period with scattered afternoon storms Monday.

VFR conditions in place at all the terminals as convection has shifted north of the terminals this evening. VFR conditions expected to continue into tonight with winds becoming light and variable. Expect similar conditions tomorrow, although winds will likely be more southwesterly between 5 to 10 knots. Scattered thunderstorms developing Monday afternoon and evening so have included a prob30 group for tsra at all terminals expect OGB, where coverage is expected to be more limited.

EXTENDED AVIATION OUTLOOK...Daily rain chances and possible restrictions continue through at least midweek.

CAE WATCHES/WARNINGS/ADVISORIES

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