textproduct: Columbia

WHAT HAS CHANGED

The slow moving cold front is expected to bring rain and thunderstorms to the northern forecast area today, eventually spreading south tonight and Friday. Aviation discussion updated for 12Z Update.

KEY MESSAGES

- 1. Rain chances increase across northern areas as a slow- moving front approaches. Unsettled weather continues into the upcoming weekend.

DISCUSSION

Key Message 1: Rain chances increase across northern areas as a slow-moving front approaches. Unsettled weather continues into the upcoming weekend.

The well advertised cold front has finally reached North Carolina tonight and will continue to sag south towards the forecast area, eventually stalling near or over the region. Rain chances increase tonight near the North Carolina border but most locations will remain dry tonight. Probabilities of seeing measurable precipitation before daybreak are highest in the finger of Lancaster County. Since the boundary continues to move slower than depicted in model guidance, most locations south of I-20 should have another hot, humid, and dry day. Today's heavy rain and flash flood risk will likely be confined to the northern Midlands, mainly Chesterfield and Lancaster counties.

This setup increases the risk for impactful flash flooding over the next few days as heavy thunderstorms train along the boundary with plenty of moisture available. Heavy rain chances will increase from north to south tonight into Friday with the flooding threat consequentially increasing each day along the I-20 corridor. PWATs are forecast to exceed 2" with deep SW flow, relatively skinny CAPE profiles, and deep warm cloud depths. With mean flow oriented almost perfectly parallel to the boundary, training and highly efficient rainfall producing cells remain likely. Showers and thunderstorms are possible this weekend but should be more scattered in nature as the front dissipates and drier air moves in next week.

While locations along and south of I-20 see another day with highs in the lower to mid 90s, the clouds and rain across the north should result in lower temperatures with forecast highs in the 80s. Below normal temperatures are expected across the FA on Friday as the clouds and rain spread south.

AVIATION /12Z THURSDAY THROUGH MONDAY/

VFR likely throughout the day with convection staying north of the TAF sites. IFR cigs and rain likely late in the period

Outside of a few showers, the frontal zone remains across NC with notable precip remaining north of CAE and CUB. As a result, no restrictions are expected overnight from any convection. This will continue into Thursday afternoon before the front starts to sag south, but even then precip chances are less than 50% at CAE and CUB, and even lower at the other TAF sites. So prob30 remains appropriate for CAE and CUB in the afternoon, no mentions elsewhere. Breezy southwest winds expected by mid- morning with gusts up to 20 knots after 18z through 00z. More widespread showers and storms will push southward towards the end of the period along with IFR cigs; IFR cigs should reach CAE and CUB by 06z and then near the end of the period for the other sites.

EXTENDED AVIATION OUTLOOK...Periodic restrictions from showers and thunderstorms likely into the weekend for all TAF sites.

CAE WATCHES/WARNINGS/ADVISORIES

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