textproduct: Columbia

WHAT HAS CHANGED

Forecast remains largely on track with locally heavy rainfall and flash flooding possible through the evening. Aviation discussion updated for 00z TAF.

KEY MESSAGES

- 1. Widespread showers and a few thunderstorms continue into the first half of the night. Heavy rain will be the main threat with the potential for areal and/or flash flooding. Lingering moisture leading to scattered to widespread afternoon storms Tuesday and Wednesday.

DISCUSSION

Key Message 1: Scattered to widespread showers and storms expected this afternoon, continuing into the early overnight. A couple strong to marginally severe storms will be possible along with isolated spots of flash flooding. Lingering moisture leading to scattered to widespread afternoon storms Tuesday and Wednesday.

A slow moving surface front is stalled across the I-20 corridor and CSRA. The heavy rainfall potential came to fruition for several areas, with multiple flash flood warnings issued in the CSRA. Radar precip estimates and rain gauge measurements indicated between 1-4" and in a few spots up to 4.5" of rainfall with very efficient rain rates (>5" per hour at times)!

As of this writing, activity has mainly transitioned away from any severe threat, but with ongoing showers across the forecast area, we continue to be diligent watching additional rainfall amounts. CAM guidance has done fairly well thus far, so we note the is potential for the Columbia area to get in on some of the rainfall here in the next couple of hours as storms spread south and west along the I-20 corridor. Outflow boundaries have been a bit more indicative of development today, so we are watching any collisions closely. After that, guidance generally has any lingering activity wrapping up around 07z tonight.

Scattered shower and thunderstorm chances will likely continue Tuesday and Wednesday as ensemble meteograms indicate PWAT's near to over 2" remain in place through at least the first half of Wednesday. As the mid level low slowly retrogrades, drier air may begin pushing into the Pee Dee and northern Midlands Wednesday, bringing lower rain chances here. Cooler than normal temperatures are also expected to persist through Wednesday before gradually warming during the second half of the week back to near normal. Typical diurnal rain chances could make an appearance late in the week into next weekend, but there is generous spread in LREF cluster analysis at this point.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

A mix of conditions are expected this evening and overnight, with widespread showers and storms causing MVFR and IFR restrictions. Widespread MVFR and IFR ceiling restrictions are then expected early Tuesday morning as precipitation tapers off.

Widespread showers will affect the terminals through the next TAF issuance with occasional TSRA. Heavy rain and reduced CIGS/VSBYS are likely. Winds should be light and variable or easterly/northeasterly, though some thunderstorm gusts could approach 20 kts briefly. Given the coverage of rain over the last 6 hours plus an already moisture rich airmass in place, guidance is quite aggressive with IFR CIGS at all the TAF sites through much of the night. This makes sense from a pattern recognition standpoint and have the forecast reflecting such. Expecting that MVFR/IFR cigs will hold on into the midday on Tuesday with northeast winds around 5-8 kts persisting. A few showers are possible Tuesday afternoon at the southern terminals, AGS/DNL/OBG in particular. Less confidence at CAE/CUB.

EXTENDED AVIATION OUTLOOK...A good chance for afternoon showers and thunderstorms with associated restrictions is expected through at least Tuesday.

CAE WATCHES/WARNINGS/ADVISORIES

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