textproduct: Columbia

WHAT HAS CHANGED

No significant changes to the forecast. Aviation discussion updated for 18Z TAF issuance.

KEY MESSAGES

- 1. Thunderstorms expected each day through the weekend with seasonable temperatures. Drier conditions and above normal temperatures are expected to start next week.

DISCUSSION

KEY MESSAGE 1: Thunderstorms expected each day through the weekend with seasonable temperatures. Drier conditions and above normal temperatures are expected to start next week.

The forecast remains on track compared to what we have been advertising the past few days. We did have some surprise convection this morning which has diminished across the area. Cumulus has replaced stratus from earlier, and within a warming and very moist atmosphere, expecting scattered to numerous showers and storms to develop this afternoon. Troughing to our west should help be a weak forcing mechanism, and >2" PWs should yield heavy, efficient rainfall in the strongest storms. Not really expecting severe weather today as DCAPE and TEI values are unimpressive in a very moisture rich atmosphere. Will be relying primarily on moisture loading for any severe storms. The persistent trough is forecast to hang around through about Saturday, with a deep plume of moisture atop the area on Friday and Saturday still. As a result, scattered to numerous showers and thunderstorms are expected both days across the forecast area. High PWs can and should result in continued heavy rainfall across the area, which has result in parts of the area being included in a Marginal and Slight Risk for Excessive Rainfall through Saturday. Flash flooding likely won't be a widespread issue but storms should be efficient enough at producing rainfall to make any training or slow movers capable of flash flooding.

As we get later into the weekend and early next week, confidence continues to increase in anomalous upper level ridging building overhead and persisting. This 500 hPa ridge should yield above normal temperatures beginning Monday and persisting through the end of the forecast period. It is unlikely that we will see widespread precipitation to help keep temps down during this period as upper level subsidence beneath the ridge center should hold convection mostly at bay. Given this, the potential for anomalous heat is rising. Highs in the mid to upper 90s appear possible, as signaled by a pretty robust EFI signal at this timeframe. Given consistent dewpoints in the 70s, dangerous heat index values are again forecast to return to the forecast area during this period, especially Tuesday through Thursday of next week.

AVIATION /18Z THURSDAY THROUGH MONDAY/

Showers and thunderstorms will continue to increase this afternoon, becoming numerous in coverage into this evening across the area. TAFs continue to indicate vicinity thunderstorms through 02Z, with either a PROB30 or TEMPO group for thunderstorms with some flight restrictions through the afternoon/early evening. Isolated showers are possible once again overnight, but confidence is not great enough to include mention in the TAFs at this time. Another round of ceiling restrictions and possibly some visibility restrictions will be possible again later tonight due to the moist low level airmass and nearby stalled front, so have a period of IFR conditions at all terminals from about 09-14Z.

EXTENDED AVIATION OUTLOOK... Restrictions possible from showers and thunderstorms each afternoon through this weekend.

CAE WATCHES/WARNINGS/ADVISORIES

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