textproduct: Columbia

WHAT HAS CHANGED

Cold air damming today is trending a bit weaker with less confidence in a wedge for the southern forecast area, leading to a large temperature gradient over the forecast area. Pops late this week trending lower with stronger upper ridging. Aviation discussion updated for 06z TAFs.

KEY MESSAGES

1. Backdoor cold front leading to cooler temperatures today.

2. Well above normal temperatures with showers and isolated thunderstorms possible later this week.

DISCUSSION

KEY MESSAGE #1: Backdoor cold front leading to cooler temperatures today.

A backdoor cold front is moving into southern NC early this morning and will continue to drop into the area through Monday morning. This will lead to cooler temperatures today, although significant uncertainty remains as to the evolution of temperatures owing to the uncertainty of where this front sets up. In general, cold air damming has trended weaker with flow aloft trending more westerly, indicating that the low cloud layer from developing low level onshore flow will likely be shallow. In addition, strongest isentropic lift likely remains north of the area and has trended later, which would have helped to strengthen the wedge over the forecast area. Overall, hires models seem to have a relatively good handle with a tight temperature gradient but uncertainty remains as to exactly where this sets up. This favors high temperatures in the low 50s in the northernmost area to around 70 in the southern area.

KEY MESSAGE #2: Well above normal temperatures with showers and isolated thunderstorms possible later this week.

High pressure expected to shift offshore midweek with upper ridging strengthening. This will lead to well above average temperatures with a relatively high confidence temperature forecast with limited spread among blended guidance with highs generally in the upper 70s to low 80s and lows in the upper 50s to low 60s. Moisture also expected to increase, with a noticeable rise in humidity and increasing PWATs with southwesterly flow aloft. GEFS and EC ensemble means general favor PWATs rising to around 150-200% of normal. The overall flow pattern has trended more amplified with strengthening troughing over the western CONUS leading to a stronger downstream ridge over the forecast area late week into the weekend. This will limit forcing and as a result, blended guidance has trended lower with pops for the second half of the week and into the weekend. With a relatively hot and humid air mass for this time of year, diurnal showers and possibly isolated thunderstorms will be possible each day Thursday through the weekend.

AVIATION /06Z MONDAY THROUGH FRIDAY/

VFR conditions start the forecast but increasing probabilities of MVFR cigs at CAE/CUB/OGB during the day....

High clouds continue to traverse the region ahead of a shortwave moving into the Ohio Valley but a backdoor front is sinking south through NC at this time. Satellite imagery showing some stratus developing across eastern NC and spreading southwestward behind the front. Most guidance suggests these lower clouds will build into the forecast area and impact CAE/CUB/OGB around 12z but likely not reach AGS/DNL. There is uncertainty in whether or not restrictions will persist through the day today as HRRR and other guidance shows cigs returning to VFR during the afternoon into early evening hours. Will opt to keep MVFR cigs at CAE/CUB/OGB where confidence is higher but also include a tempo group for a return to VFR cigs 19z-23z. Expect stratus to rebuild over the area all locations tonight beginning near the end of the forecast period.

EXTENDED AVIATION OUTLOOK...MVFR and possible IFR ceilings are expected tonight into Tuesday with weak cold air damming. Low end risk for a few showers on Tuesday with higher rainfall chances starting on Thursday.

CAE WATCHES/WARNINGS/ADVISORIES

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