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Advertised cold weather pattern should commence around December 6 and work in here well by Dec 7-8. I would like to limit precipitation charts to within 5 days. The exception is NWFS for the Mountains and Plateau, which is more skillful because it does not require an exact storm track. Discussion of favorable pattern (odds) is OK and even encouraged past Day 5, just no charts please. The good news is SER intrusions have departed recent model runs. Oh there is always a trade-off in the South. Northwest flow in the Plains gets as close as the Mississippi Valley at times, which opens the door for mild interludes within the cold pattern. Even with some variability the cold 6-15 day period carries high confidence. I put it near 85% in the 6-10 day; better than 50% in the 11-15 day. Still a slight risk that Day 10 mild interlude is the end, but I think cold reloads for the 11-15 day. Near textbook upper level pattern really lacks surface source region support though. Alaska and most of Canada cold is not strong. Manitoba and Ontario will get cold but it barely gets colder points north. Quebec looks strong but it's not our trajectory. Sustained cross polar flow from Siberia is required for impressive cold this time. A few days would not be enough since temps are AN in Alaska. Northern US snowpack deficit is a gaping hole in the equation for record or even just strong cold. So I think the 6-15 day will be cold enough to put one in the Holiday mood, but not particularly impressive. First front (6-10 day) may under-achieve as usual coming into a warm regime. Second front (11-15 day) should verify so long as it actually gets in here (>50% chance). If the upper level pattern holds through weeks 3-4, we might be able to talk about stronger cold anomalies. Right now looks like some lows in the 20s first half of Dec. If looking for teens or colder, more time in the cold pattern is required. A minority of ensemble members show a decent pattern for winter precipitation in the 11-15 day. Others are cold but dry. A smaller minority is too warm. I am looking for an active southern branch through the Deep South, not NW flow and zero SER attempts.
For the Tuesday update I would lift the slight into West Kentucky and get the ENH into northern Mississippi - perhaps Memphis. Warm front WF will probably get into West Tenn. Might make it to West Ky. Severe parameters including a screaming low level jet will augment the squall line from the WF south. Upper winds may be less backed than forecast if a lead wave can eject ahead of the bowling ball. A couple leading edge tornadoes would not surprise me. Unfortunately it may be after dark east of the Mississippi River. I'm expecting several to numerous damaging straight line reports, esp if some line echo wave patterns LEWPs can establish. Looks like a set-up favorable to LEWPs esp after dark. Good news farther east is relatively more stable air should keep Alabama, Mid and East Tennessee safe.
Could be severe weather dinner theater from Memphis north to Paducah this evening. Couple isolated cells may develop ahead of the main line. While Illinois may enjoy more turning winds with height, and a lovely retreating boundary, heating is better in the Mid South. Looks like some sort of differential heating boundary or moisture surge from eastern Arkansas into far western Tennessee. While it could be a focus for cells ahead of the line, most hi-res guidance just shows a big cluster of storms developing. Very latest 15Z HRRR shows a cluster in the Delta actually cutting off flow into the main line and even the above boundary. Previous HRRR and 12Z hi-res NAM had better inflow for the main line of storms. Looks like mainly wind and hail to me. I agree with the low tor probs from SPC for the Mid South. Maybe we will see nice photos of a shelf cloud over downtown Memphis this evening.
The 6-10 day forecast is hinting at another severe weather sequence from the southern Plains into the Southeast US. Just like last time the models seem to be trending from a Plains highlight to a Dixie Alley highlight. South severe is still 8-10 days away so uncertainty is high. Though one cannot pinpoint details or target areas, in May one can assume severe weather will verify at least 2-3 days out of the 6-10 day period.