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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.


Thursday, October 28, 2021

SPC Oct 28, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0248 PM CDT Thu Oct 28 2021 Valid 282000Z - 291200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE FLORIDA PENINSULA AND THE COASTAL CAROLINAS... ...SUMMARY... Isolated damaging winds and a couple of tornadoes will remain possible across parts of the Florida Peninsula this afternoon into the coastal Carolinas tonight. ...20Z Update... The only change to the prior outlook has been to reduce/remove severe probabilities behind ongoing convection across the FL Peninsula. Damaging winds and a couple of tornadoes will remain possible in the short term across the FL Peninsula this afternoon, but the overall severe threat should gradually lessen this evening across this region as low-level winds slowly veer and weaken. No changes have been made to the Slight Risk across coastal NC/SC for a conditional and isolated wind/tornado threat tonight. ..Gleason.. 10/28/2021 .PREV DISCUSSION... /ISSUED 1122 AM CDT Thu Oct 28 2021/ ...Central/north FL today to the coastal Carolinas tonight... A deep, occluded cyclone in MO/AR will move slowly eastward toward western TN/KY by tonight. Southeast of the cyclone, a cold front will move eastward across northern/central FL, and a weak secondary wave will move northeastward across coastal areas of GA/SC/NC as an embedded speed max aloft likewise rotates northeastward around the periphery of the deep, closed low. Thunderstorms are ongoing as of midday in a pre-frontal band from northwest of Tampa to near Jacksonville, with other storms in the warm advection zone farther to the east. Surface heating will be muted across north FL due to widespread clouds, but continued warm/moist advection from the south will still contribute to destabilization (MLCAPE up to 1000 J/kg) from central into northeast FL in advance of the pre-frontal convection. Deep-layer shear and low-level hodograph curvature will be sufficient for supercells and bowing segments with an attendant threat for damaging gusts and a couple of tornadoes through early-mid afternoon, especially near the north edge of the surface warm sector across north FL. The tendency will be for low-level shear to slowly weaken from southwest to northeast across central/north FL by this afternoon, with more unidirectional wind profiles expected. The stronger storms will tend to move the Atlantic coast by mid-late afternoon, aside from lingering convection across central and south FL into this evening/overnight. However, weakening vertical shear with time and southward extent suggests that any severe threat by then will be marginal damaging winds. Farther north, the inland extent of the warm sector is somewhat in question. Assuming boundary-layer dewpoints near or above 70 F can spread inland across the coastal Carolinas, there will be a conditional damaging wind/tornado threat tonight. Read more LIVE:
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