FXUS64 KMEG 291141 AFDMEG Area Forecast Discussion National Weather Service Memphis TN 641 AM CDT Wed Jun 29 2022 .UPDATE... Updated for 12Z Aviation Discussion below. && .PREV DISCUSSION... /issued 233 AM CDT Wed Jun 29 2022/ DISCUSSION... The air mass across the Mid-South is rather subsident in the wake of the shortwave trough moving across the Upper OH Valley. A strong 595 dam ridge remains in place over the Desert Southwest, extending poleward into Alberta and Saskatchewan with northwesterly flow aloft feeding across the Midwest into the trough over the eastern CONUS. Meanwhile, a disturbance continues to meander over the northwest Gulf of Mexico, but it won't move much for a few days. At the surface, a quasi-stationary front extends from central TX, through central MS, into the Carolinas. This boundary will be a player the next couple of days as it lifts slowly to the north. The synoptic pattern will deamplify through midweek as the shortwave trough over Vancouver helps flatten the ridge eastward which nudges the east CONUS trough out to sea. As the trough moves east along the US/Canada border, attendant surface pressure falls will follow suit. This will enhance return flow and help lift the quasi-stationary front to our south into north MS today, eventually washing out tomorrow. Column moisture remains anomalously low at this time, especially north of I-40 where Total Blended Precipitable Water is near 0.5-0.7 inches. That is quite the contrast to the southern extent of the CWA where PWAT is closer to 1.5 inches. As the warm front lifts into the area today, isolated showers and thunderstorms are expected, mainly across north MS. Coverage doesn't look all that great and most areas will stay dry with highs near 90F. A few cells could persist beyond 00z but aren't expected to last much beyond sunset given the weak forcing aloft. Similar conditions are anticipated Thursday and Friday, though greater moisture across the Mid-South should yield an uptick in convective coverage, especially during the afternoon and early evening. Medium-range guidance is in pretty fair agreement that the wave over the northwest Gulf will move onshore over southeast TX by Friday, likely remaining poorly organized. What we will be watching is the potential for much deeper moisture to lift up the delta over the weekend. NAEFS and EPS guidance indicate PWAT increasing to 2.0" by Sunday which is in the 90th percentile of climatology. Concurrently, a cold front will sag south into the OH Valley late Friday. This boundary looks to remain north of the CWA through the work week, but there is a potential this front could shift a bit farther south over the weekend if convection is able to provide enough of a push. A moist, unstable air mass will reside over the CWA this weekend. NAEFS indicates a fairly strong probability for SBCAPE exceeding 2000 J/kg but the presence of the subtropical ridge axis will result in very weak vertical shear. This will limit the potential for organized severe weather, though a strong storm is certainly possible given the instability loading and potential for precipitation loading. Given the low confidence, will leave mention out of the HWO at this time. Otherwise, should the surface front move south into the CWA, the potential for localized heavy rainfall will increase. We'll be watching this closely over the coming days to see how this pattern evolves. Temperatures will be within a few degrees of climatology the next several days but are expected to increase slightly early next week as the ridge builds over the Lower MS Valley. MJ && .AVIATION... 12Z TAFs VFR to prevail again today and tonight. More humid air will settle into TUP this morning, supportive a cumulus field. Isolated afternoon SHRA expected around TUP, around the periphery of greater TSRA chances to the south, over west central AL and central MS. TSRA chances at TUP will be non-zero, but sufficiently low to preclude mention in the 12Z TAF. PWB && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$