textproduct: Columbia

WHAT HAS CHANGED

Minimal change to Key Messages. Aviation discussion updated for 00z TAF.

KEY MESSAGES

- 1. A more typical summer pattern is expected through Wednesday before drier conditions move in for the late week.

DISCUSSION

- 1. A more typical summer pattern is expected through Wednesday before drier conditions move in for the late week.

Drier air is expected to work in Monday with PWATs falling toward 1.60-1.80" as low level flow becomes a bit more northerly, especially early in the day. Overall, this should bring a mostly dry day across the CWA outside of possibly an isolated shower or two. The pattern becomes a bit more amplified heading into Tuesday and Wednesday as the robust upper ridge centered over the Rockies gradually retrogrades westward with a deeper trough digging into the Mid-Atlantic with 500mb heights near the LREF 2nd percentile. A shortwave pushing out of the base of this trough is expected to help drag a surface front into the region by late Tuesday into Wednesday, but ahead of this, moisture transport is expected to increase again with EC Ensemble and GEFS PWAT's reaching back near 2". Southwesterly low level flow should also aid in bringing hot/humid conditions Tuesday. The stronger kinematics with this system still appear to keep north of the FA in 12z guidance, overall limiting the severe risk. At least modest effective shear values toward the Pee Dee could bring an isolated strong to severe storm Tuesday evening, but confidence in this is low. The front then is shown working through the area on Wednesday with northwesterly flow behind it ushering in drier air. Rainfall expectations in the Tuesday- Wednesday timeframe have not changed all too much with any activity likely being fairly scattered at best and mainly in the Tuesday evening into Wednesday morning window.

Some of the driest air in at least the last 3-4 weeks is progged to move in behind the front thanks to the deep upper trough with mean LREF PWATs dropping to under 1.50" and perhaps even under 1.25" at times Thursday and Friday. This is further supported looking across members in the EC Ensemble and GEFS. Due to this, near normal temperatures with dry conditions are expected. Global models are hinting that as the upper ridge continues to retrograde toward the Four Corners region into the weekend, another shortwave could begin nearing the Southeast in this northwest flow regime. This could bring back rain chances, but it is worth noting there remains considerable spread in LREF clusters in the progression of this shortwave.

AVIATION /00Z MONDAY THROUGH FRIDAY/

Fog and stratus expected to develop early Monday morning.

VFR conditions currently in place at all terminals as showers and storms have diminished this evening. Northwest deep layer flow will lead to increasing dry air pushing into the region tonight with PWATs likely dropping below an inch and a half. With lingering surface moisture, this will create a favorable setup for fog development early Monday morning. Recent runs of guidance are consistent in widespread visibility restrictions, especially at Columbia, OGB, and AIK. A bit of uncertainty remains at AGS and DNL, mainly owing to the potential for lingering cloud coverage as a MCS moves into north Georgia from the Midwest. While fairly high confidence that associated showers and storms from this system will remain west of the Augusta terminals, debris cloudiness may interfere with fog development. Have continued visibility restrictions at all terminals with this TAF issuance. Improving conditions to VFR expected by mid to late Monday morning with scattered cumulus but low chances for showers or storms. Winds generally light and variable, favoring a northwesterly direction Monday.

EXTENDED AVIATION OUTLOOK...By late Tuesday and into Wednesday, rain chances begin to increase again with associated restrictions possible. Drier air moves in for the second half of the week.

CAE WATCHES/WARNINGS/ADVISORIES

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