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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.

Sunday, December 5, 2021

SPC Dec 5, 2021 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1127 AM CST Sun Dec 05 2021 Valid 061200Z - 071200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF THE UPPER TX COAST/EAST TX INTO THE TN VALLEY AND SOUTHEAST.... ...SUMMARY... Isolated strong to severe thunderstorms may occur Monday from parts of coastal/east Texas into the lower Mississippi Valley and Southeast. Damaging winds should be the main threat. ...Synopsis... A strong northern-stream shortwave trough is forecast to extend from the Upper Great Lakes southwestward through the mid/lower MO Valley early Monday morning. This shortwave will be accompanied by a belt of very strong mid-level flow, with 100+ kt at 500-mb stretching from central MO through Lower MI Monday morning. Expectation is for this shortwave and attendant mid-level flow to progress eastward throughout the day, across the OH Valley, Mid-Atlantic, and Northeast. Surface low associated with this system is forecast to occlude further as it moves from northeastern Ontario northeastward into central Quebec. The cold front attendant to this low will extend from central OH southwestward to the TX Edwards Plateau early Monday, before moving southeastward/eastward throughout the day. By early Tuesday morning, the front is forecast to stretch from well off the Northeast coast southwestward through the central FL Peninsula into the central Gulf of Mexico. Within the southern stream, a closed low initially over the central Gulf of California is forecast to become a bit more progressive, moving across central Mexico into central/south TX, while devolving into an open wave. ...Coastal/East Texas into the Lower Mississippi Valley and Southeast... A broad warm sector will be in place ahead of the front mentioned in the synopsis. Dewpoints are expected to range from the upper 60s/low 70s across the middle TX coast to upper 50s/low 60s across middle TN. Warm mid-level temperatures associated with low to mid-level southwesterly flow will temper buoyancy throughout the warm sector, but modest buoyancy is still expected. The strongest buoyancy is anticipated across TX, where steep mid-level lapse rates will be in place early, with gradually reducing buoyancy with northeastward extent. Closer proximity to the stronger ascent will result in better mass response from the mid-South into the TN Valley, which will also result in stronger convergence along the front throughout the morning. Thereafter, further displacement from the main shortwave trough will result in weaker/more veered low-level flow and gradually diminishing convergence over time. Displacement from shortwave will also reduce vertical shear. The dissociation between the better forcing and shear (north) and the better low-level moisture and buoyancy (south) will likely limit overall severe coverage. However, enough overlap will exist early in the day for isolated severe storm potential from the TN Valley into Mid-South/Lower MS Valley. Potential for some more cellular, pre-frontal storms also exists across southeast TX into west-central/central LA. These will likely be elevated, with marginal hail as the main threat, but some potential for wind damage and/or a brief tornado exists if these storms are able to persist and mature. ...Northeast... Very strong low/mid-level flow is expected to overspread much of the Northeast on Monday as the upper trough progresses over this region. Buoyancy will be limited but there may still be enough instability to support isolated lighting flashes with elevated convection. The potential for surface-based thunderstorms with any appreciable strong/gusty wind threat appears low due to the limited low-level moisture and related lack of boundary-layer instability. ..Mosier.. 12/05/2021 Read more LIVE: