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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.


Saturday, August 26, 2023

SPC Aug 26, 2023 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0252 PM CDT Sat Aug 26 2023 Valid 262000Z - 271200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING ACROSS THE SOUTHEAST MO/NORTHEAST AR VICINITY... ...SUMMARY... Occasional damaging gusts will be possible this afternoon and evening across southeast Missouri/northeast Arkansas and vicinity, with more isolated strong winds possible into the southern Appalachians and across parts of Idaho and Oregon. ...20Z Update... Overall, no changes are needed to the previous outlook. More forecast details provided below and in the appended outlook. ...Southeast MO/northeast AR area this afternoon/evening... As mentioned in recently issued MCD #2054, thunderstorms capable of producing isolated to scattered damaging winds will become increasingly possible later this afternoon across parts of southern MO/IL, northern AR, and western KY/TN. Strong heating and large PW will support a threat of at least isolated wet microbursts as these storms sag southward through the afternoon. ...Southern Appalachians into the Central Carolinas... As discussed in MCD #2055, strong heating ahead of an eastward-progressing MCV, along with typical diurnal terrain circulations should support additional thunderstorm development through this afternoon. Moderate buoyancy (1000-2000 J/kg of MLCAPE) and fairly steep low-level lapse rates should support occasional strong updrafts. As result, isolated strong to severe storms, with the potential for a few damaging downburst gusts, will be possible this afternoon and evening across the region. ...Southern ID/Eastern OR... Thunderstorm development has already be observed across the region ahead of the approaching speed max, with additional storm development still possible this afternoon/evening. Modest vertical shear could help organize updrafts, with high cloud bases and steep low-level lapse rates contributing to the potential for isolated strong/severe outflow. ..Mosier.. 08/26/2023 .PREV DISCUSSION... /ISSUED 1127 AM CDT Sat Aug 26 2023/ ...Southeast MO/northeast AR area this afternoon/evening... The persistent midlevel high continues to slowly weaken over the southern Plains, while a series of MCVs rotate around the northern and eastern periphery of the high, from KS to the southern Appalachians. The most pronounced MCV is now moving southeastward over northwest MO and will interact with the unstable warm sector this afternoon in the vicinity of southeast MO, where additional thunderstorm development is expected south of the ongoing convection near Saint Louis. Daytime heating in cloud breaks and boundary-layer dewpoints in the mid 70s will result in MLCAPE of 2500-3000 J/kg, and lapse rate profiles will also favor strong downdrafts (DCAPE of 1000-1500 J/kg). Primarily multicell clusters are expected as a result of weak vertical shear in the warm sector ahead of the MCV. Damaging outflow winds will be the main severe threat from mid-late afternoon into this evening. ...Southern ID/eastern OR this afternoon/evening... A weak mid-upper speed max is translating northward around the western periphery of the ridge from the southern Plains into the Rockies. A band of ascent and midlevel moisture, coincident with surface heating in cloud breaks, will support scattered thunderstorm development this afternoon into this evening. Typical inverted-V profiles and some modest enhancement to deep-layer vertical shear will support somewhat organized cells (and perhaps a low-end supercell) capable of producing isolated strong-severe outflow gusts. Read more CHECK UPDATE ZOOM GRAPHIC
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