textproduct: Columbia

WHAT HAS CHANGED

Forecast remains on track for the next several days. Aviation discussion updated for 06z TAFs.

KEY MESSAGES

- 1. Above normal temperatures continue this weekend into early next week.

- 2. Chances for scattered diurnal showers and thunderstorms beginning today and continuing into next week. Strong storms are possible each afternoon and evening.

DISCUSSION

Key Message 1: Above normal temperatures continue this weekend into early next week.

This is basically a broken record of a key message but long duration heat episodes like this are the most dangerous. We have seen several days in a row of high temperatures in the upper 90s at this point, and the streak is forecast to continue over the next several days. Though the upper ridge will begin to break down today and be replaced with a trough to our west, 850 hPa temps are still forecast to remain above normal in the 19C-22C range through mid-week. High humidity is expected to return beginning today, with dewpoints back up into the 70s daily. Heat index values, despite "lower" afternoon highs, are expected to be quite high and may approach heat advisory criteria multiple times this upcoming week. This will be highly dependent on daily convection, as showers and thunderstorms are expected much of the week. But if these don't materialize one day for whatever reason, we may end up needing a Heat Advisory again.

Key Message 2: Chances for scattered diurnal showers and thunderstorms beginning today and continuing into next week. Strong storms are possible each afternoon and evening.

A fairly good setup for summertime convection is forecast to develop over the next couple of days as the strong ridge that has plagued the eastern US breaks down and shifts westward. General & somewhat persistent trough is forecast to develop in its wake, with southwesterly flow across our area causing moisture values to return back to near or above normal values. PWs of 110-120% of normal are expected beginning today and lasting at least the next couple of days. There is some uncertainty with respect to the pattern evolution by midweek, with a return to some level of confidence that higher rain chances return next weekend. Along with summertime storms comes the possibility for strong to severe convection, with today and Monday expected to have favorable environments for downbursts. Mean HREF soundings reveal 1500-2000 j/kg of CAPE, >1000 j/kg of DCAPE, and >25 TEI both afternoons. Forcing won't be particularly focused, but convective temps are forecast to only be in the mid 90s. This will likely result in storms popping up pretty quickly by early afternoon both days and continuing into the evening hours. ML guidance continues to show elevated probabilities for severe weather, specifically severe winds, the next couple of days and this is now backed up by environments that hi-res guidance is showing. Overall, the threat won't be widespread or anything but expect a severe thunderstorm or two every day across the forecast area over at least the next couple of days. As mentioned before, there is some uncertainty with respect to precip coverage midweek but it does seem more likely than not that we will see some unsettled weather continue for the majority of the forecast period. Its pretty difficult to get less unsettled than we have been lately!

AVIATION /06Z SUNDAY THROUGH THURSDAY/

VFR should dominate through the TAF period, though increased convective coverage this afternoon may lead to brief restrictions.

VFR conditions through this morning with low confidence in any restrictions through dawn. Winds light and variable through midday. Scattered storms develop this afternoon with better coverage and slightly higher confidence in impacts at the TAF sites. This may include some brief VSBY restrictions in the stronger storms, so have continued with a prob30 group at all terminals for -TSRA. There may be additional impacts with gusty convective winds. Otherwise, winds this afternoon should shift to the southwest at 5-10 kts. A few lingering showers are then possible this evening, though conditions should improve with the loss of daytime heating and winds return to light and variable.

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

CAE WATCHES/WARNINGS/ADVISORIES

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