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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.

Wednesday, December 1, 2021

SPC Dec 1, 2021 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0243 AM CST Wed Dec 01 2021 Valid 041200Z - 091200Z ...DISCUSSION... Medium-range models indicate a significant amplification within the southern branch of a developing split flow across the eastern Pacific by late this week, leading to the evolution of a more amplified, blocked regime across the southern mid-latitude and subtropical eastern Pacific into southwestern portions of North America by early next week. It does appear, however, that much of the rest of the U.S. will remain under the influence of one prominent branch emanating from the northern mid-latitude Pacific, which probably will include a number of progressive embedded short wave troughs. The predictability of these perturbations remains unclear, but recent runs of the GFS/GEFS and ECWWF/ECENS suggest that one will rapidly dig east-southeast of the northern Rockies late this weekend, before turning eastward across the northern Atlantic coast early next week. It appears that this may be trailed by a similar perturbation at a somewhat lower latitude, which may support significant surface cyclogenesis from the lee of the southern Rockies into the lower Ohio Valley through the early to middle portion of next week. Of primary concern, as depicted by latest (01/00z) model output, this may be accompanied by substantive strengthening of low-level wind fields (including in excess of 50 kt around 850 mb) across parts of the southern Great Plains into the lower Ohio Valley. Although this is currently forecast to have a substantial southwesterly to westerly component, it might not be out of the question that an influx of moisture, off a modifying boundary layer over the northwestern Gulf of Mexico, could contribute to a corridor of weak boundary-layer destabilization across parts of the Mid South (particularly the southeastern Arkansas/northern Mississippi/western Tennessee vicinity). If this occurs, coincident with the very strong low-level (and deep-layer) shear, there appears at least some potential for the environment to become conducive to organized thunderstorm development capable of producing damaging wind gusts and a few tornadoes late next Tuesday into Wednesday. However, given the uncertainties concerning the evolving pattern (particularly at the Days 7/8 time frame) and the quality of return flow from the Gulf of Mexico, the probabilities for an organized severe weather event still seem relatively low. Read more LIVE: