Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jun 06 2023 09:01:43 ACUS48 KWNS 060901 SWOD48 SPC AC 060900 Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Tue Jun 06 2023 Valid 091200Z - 141200Z ....DISCUSSION... Upper troughing over the eastern states should move into the western Atlantic on Day 4/Friday, with upper ridging remaining prominent from western Canada into the Rockies and much of the Plains. Some guidance indicates that a low-amplitude shortwave trough embedded within a southern-stream mid/upper-level jet may advance eastward from the Southwest and northern Mexico across the southern High Plains by Friday evening. Isolated thunderstorms will probably develop along a sharpening dryline across the southern High Plains in response. Instability and shear appear adequate for some severe threat with any convection that can form. However, confidence in thunderstorm coverage is not high enough to include a 15% severe area at this time. Isolated severe thunderstorms also appear possible Friday across parts of north FL along/south of a weak front, and across parts of the northern/central Plains as a separate cold front advances southward. An upper trough/low should approach the West Coast on Day 5/Saturday, and move slowly eastward across the western CONUS through Day 6/Sunday. While upper ridging will likely be maintained over the Rockies and High Plains, mid-level flow is forecast to gradually strengthen this upcoming weekend across the southern Plains. Rich low-level moisture should also return northward over the southern/central Plains in this time frame. In general, upper ridging will prevail over the warm sector; but, weaknesses in the ridging associated with weak mid-level perturbations are evident in model guidance across the southern Plains through the weekend. Any thunderstorms that can develop along the length of the dryline, or perhaps near a front/dryline intersection, should be capable of producing severe hail/winds. Due to nebulous large-scale forcing, too much uncertainty currently exists in the placement and coverage of robust convection to include any severe areas this weekend across the southern Plains, but model trends will be closely monitored. Differences in the synoptic-scale pattern across the CONUS become more substantial in medium-range guidance from Day 7/Monday onward. Regardless, upper troughing should advance slowly eastward from the western to central CONUS early next week. As this occurs, strengthening mid/upper-level flow should overlap the warm sector and pose a risk for severe thunderstorms. Exactly where the greatest threat will develop remains highly uncertain given current model spread. But, an increasing threat for severe thunderstorms is evident across parts of the southern/central Plains to the MS Valley early next week. ...Gleason.. 06/06/2023 = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .