textproduct: Columbia

WHAT HAS CHANGED

Precipitation chances for diurnally driven convection today have decreased. Aviation discussion updated for 12z TAFs.

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 few clusters of showers and thunderstorms continue to our west and drifting southward early this morning along remnant outflows. Activity should remain limited, though heavy downpours cannot be completely ruled out.

Unsettled weather remains over the area the next few days, with isolated to scattered convection expected today through early next week. Above normal temperatures and PWATs over 1.75 inches will support seasonable instability. Given the relatively weak forcing, convection today and Monday should remain limited and diurnal in nature. Better chances for precipitation is expected Tuesday into Wednesday as the upper-air pattern evolves and a front nears. A mid- level low currently over the far eastern Gulf is forecast to lift northward along the Eastern Seaboard, while developing troughing moves in from the Midwest. These features will provide increasing synoptic forcing and support greater coverage of showers and storms. Overall, the severe threat remains low. However locally heavy rain will remain possible, with the potential increasing Tuesday and Wednesday as coverage becomes more widespread.

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

Troughing over the Midwest will shift eastward through the week, supporting the development of a robust area of high pressure that builds southward into the Mid-Atlantic. However, considerable uncertainty remains regarding the extent of surface ridging, as reflected by the spread among ensemble members and LREF clusters. The degree of moisture advection atop the potential surface wedge will likely depend on the timing and strength of the aformentioned troughing. The ECMWF remains weaker and showers, maintaining a more southwesterly flow aloft allowing greater moisture to overrun the surface wedge. The GFS and NAM favor a stronger trough with more northwesterly to northerly flow resulting in direr air.

Given the continued spread, confidence remains low from Wednesday through late week, particularly regarding temperatures and PoPs. Widespread precipitation appears unlikely, but should sufficient moisture and isentropic lift develop over the potential wedge, typical CAD precipitation cannot be ruled out, including periods of light stratiform rain/drizzle.

AVIATION /12Z SUNDAY THROUGH THURSDAY/

Possible MVFR/IFR restrictions towards sunrise, then VFR conditions for the remainder of the day.

Showers have finally dissipated this morning across the area. In their wake, some areas of low clouds and patchy fog have developed, mainly where there's been some thinning out of high level cloudiness from the early shower/storm activity. Confidence has increase somewhat that many areas should see at least some mvfr restrictions developing by 12z. Any low cigs and/or vis should lift/improve between 14z-15z, with a return to primarily vfr conditions by late morning. Winds generally light and from the east. As for afternoon convection, blended guidance showing mostly a dry forecast this upcoming afternoon, so for now no mention of any rainfall. Even so, with numerous surface boundaries around from yesterday and last night's round of showers and storms, can not completely rule out some isolated activity development this afternoon.

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

CAE WATCHES/WARNINGS/ADVISORIES

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