textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 06z TAFs. Otherwise, no significant changes.

KEY MESSAGES

- 1. Above average temperatures and increased chances for showers and storms continue into early next week.

- 2. Cooler and drier air returns by the middle of next week but forecast uncertainty remains.

DISCUSSION

KEY MESSAGE 1: Above average temperatures and increased chances for showers and storms continue into early next week.

A cold front will continue its slow southward progression before stalling over the forecast area later today. Increasing moisture and weak forcing will support another chance of isolated to scattered showers and thunderstorms this afternoon. Convection should be highest across the southern and western portions of the area, where PWATs of 1.8-2 inches and ample diurnal heating will help maintain unsettled conditions. While a low-end threat for locally heavy rainfall and minor flooding remains, modest instability and weak deep-layer shear should limit the severe threat.

The remainder of the weekend looks similarly unsettled, with additional spotty showers and thunderstorms possible during the afternoon and evening. Deep-layer moisture persists into early next week, with PWATs remaining around 120-150% of normal. Despite limited large-scale forcing, the anomalously moist air mass, combined with unseasonable hot and humid conditions, will support diurnally driven showers and storms each afternoon through Tuesday.

KEY MESSAGE 2: Cooler and drier air returns by the middle of next week but forecast uncertainty remains.

Forecast confidence decreases by the middle of next week as uncertainty increases regarding the upper-level pattern across eastern North America. The aforementioned upper low is forecast to eject from the northeast Gulf and lift along the eastern seaboard Tuesday into Wednesday. This evolution will allow surface high pressure to strengthen over the northeast and ridge southward along the coast, potentially establishing a cold air damming wedge.

However, the classic southwest flow aloft and associated overrunning precipitation typically favored with this setup does not appear likely to develop until late in the week. Instead, drier air is expected to advect from the northwest, which should limit precipitation chances late next week. Regarding temperatures, blended guidance favors near- normal highs during this period; however, IQRs indicate substantial spread, with the distribution skewered toward cooler solutions. We will continue to monitor trends as the dominant summer pattern may finally begin to break down.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Other than brief mvfr visibility restrictions towards sunrise, expecting vfr conditions the remainder of the period.

Storm activity has pushed south of all taf locations for the 06z issuance, with only very light rainfall returns showing up on regional radars. Metars generally indicating those light returns are not causing any impacts at this time, so vfr to start off the period at all sites. Guidance not entirely bullish on widespread visibility issues overnight, especially with expected mid and upper level cloudiness persisting across the region through much of the night. Did included a tempo for 4sm br though due to lingering moisture and light winds. Clouds as stated will remain vfr, with broken mid-level clouds possible through the afternoon hours. Winds overnight will turn light and variable, then increase out of the northeast by late morning, with speeds between 5-8 knots anticipated. As a weak front sinks southward through the afternoon Saturday, can not completely rule out some isolated convection, and have included mention of prob30 for storms, although confidence remains on the lower side at this time. Any shower/storm activity should be weakening/dissipating by 03z.

EXTENDED AVIATION OUTLOOK...Chances for showers and/or storms will continue through early next week. Morning cig/vsby restrictions are possible as well.

CAE WATCHES/WARNINGS/ADVISORIES

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