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Weather conditions on bar directly above are near Lakefront. Tabs under Moon Phases refer to O'Hare (official).

Archives for SPC Convective outlook are updated daily with a live map a the beginning of the article. Touch or click map to get possible update, and follow link at end of article for referral to NOAA/NWS Storm Prediction Center. Archives for Chicago's hourly weather data were updated 24-48 hours after end of each day prior to Dec. 2020.

Wednesday, August 17, 2022

SPC Aug 17, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0249 PM CDT Wed Aug 17 2022 Valid 172000Z - 181200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THROUGH THIS EVENING FROM EAST TX TO THE LOWER MS VALLEY AND NORTH FL...SOUTHERN AZ...AND THE WESTERN DAKOTAS...... ...SUMMARY... Isolated damaging winds will be possible through this evening from east Texas across the lower Mississippi Valley to north Florida, southern Arizona, and the western Dakotas. ...20z Update... Only minor adjustments have been made to the Marginal risk area across Florida based on latest convective trends. Otherwise, the previous outlook remains unchanged and on track. See discussion below for more forecast details. ..Leitman.. 08/17/2022 .PREV DISCUSSION... /ISSUED 1129 AM CDT Wed Aug 17 2022/ ...Lower MS Valley to north FL this afternoon/evening... A remnant MCV will move east-southeastward from AR to MS/AL this afternoon, roughly along and just north of an outflow-reinforced front from the AR/LA border across central MS to southern AL. Strong surface heating and boundary-layer dewpoints well into the 70s will boost MLCAPE to near 3000 J/kg this afternoon along and south of the front/outflow, and additional thunderstorm development is expected by mid afternoon. The surface boundaries that will focus storm initiation will lie along the southwest fringe of the 20-30 kt midlevel flow, which will support multicell clusters. Precipitation loading with the strong buoyancy, in combination with DCAPE near or above 1000 J/kg, will support isolated wind damage with downbursts this afternoon/evening. Otherwise, isolated strong storms will also be possible across north FL, primarily with sea breeze and outflow interactions. ...Southern AZ this afternoon/evening... To the west of a remnant tropical low over northern Mexico, midlevel east-northeast flow will strengthen some through this evening over southern AZ. This will favor convective clusters moving southwestward from the higher terrain to the lower deserts, where strong surface heating and boundary-layer dewpoints in the 60s will contribute to moderate buoyancy and weakening convective inhibition. Typical steep low-level lapse rates and substantial precipitation loading will favor hybrid microbursts capable of producing isolated strong-severe outflow winds. ...Western Dakotas this afternoon/evening... Some convection is ongoing late this morning over the northern High Plains, in advance of a weak midlevel trough moving over northeast MT. The convection is expected to increase some later this afternoon as it encounters a deeper mixed boundary layer, when there will be the potential for isolated strong-severe outflow gusts. Read more CHECK UPDATE ZOOM GRAPHIC

Tuesday, August 16, 2022

SPC Aug 16, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0233 PM CDT Tue Aug 16 2022 Valid 162000Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FROM THE LOWER MS VALLEY TO THE OZARKS AND SOUTHERN HIGH PLAINS...AND ACROSS NORTHERN MN INTO CENTRAL ND...... ...SUMMARY... Isolated damaging winds and marginally severe hail will be possible this afternoon/evening for parts of the Ozarks, lower Mississippi Valley, southern High Plains, and northern Minnesota vicinity. ...North Dakota... The Marginal risk has been expanded westward into parts of central ND with the 20z update. Isolated thunderstorms have developed near a weak surface boundary oriented west to east/northeast from central ND into northwest MN. Visible satellite imagery has shown an expanding cumulus field near the boundary this afternoon. Vertical shear will remain modest, but MLCAPE around 1500 J/kg and enhanced low-level shear along the boundary, coupled with steep low-level lapse rates, could support a few strong gusts with storms that develop through early evening. ...Southern High Plains to the Ozarks/Lower MS Valley... The ongoing outlook remains unchanged. Isolated strong to severe thunderstorms remain possible across parts of the southern High Plains to the Lower MS Valley through early evening. Reference MCDs 1686 and 1687 for more details regarding short term severe potential. ..Leitman.. 08/16/2022 .PREV DISCUSSION... /ISSUED 1126 AM CDT Tue Aug 16 2022/ ...Ozarks/lower MS Valley/southern Plains through this evening... A diffuse MCV over northern MO will move southeastward today, within a band of 30-40 kt midlevel flow (per regional VWPs). Elevated convection has persisted from overnight into this morning in a zone of warm advection over southern MO, and clouds/differential heating will reinforce a baroclinic zone across southern/western AR into southwestern MO. This baroclinic zone will serve to focus additional thunderstorm development later this afternoon near the MO/AR/OK border intersection, and storms will subsequently move southeastward through the evening. There will be a narrow corridor of overlap of moderate buoyancy and somewhat stronger vertical shear along the surface boundary where some low-end supercell potential will exist (at the northeast edge of the stronger surface heating and deeper mixing). Isolated wind damage and marginally severe hail will be possible with any supercells that form. Otherwise, a few cells/clusters may form along the slow-moving front farther southeast toward central MS, where MLCAPE of 2500-3000 J/kg and DCAPE near 1000 J/kg will support the potential for isolated strong/damaging downbursts. Buoyancy will be weaker in the warm sector farther west along the cold front in OK/eastern TX Panhandle and storm coverage is in question. If storms do form, deep inverted-v profiles and large DCAPE (> 1500 J/kg) will support the threat for isolated microbursts. ...Southeast CO/northeast NM vicinity this afternoon/evening... Low-level flow is expected to become weak upslope in a post-frontal environment from southeast CO into northeast NM by later this afternoon. Though midlevel lapse rates will not be particularly steep within the lingering monsoonal moisture plume, boundary-layer dewpoints in the upper 50s to lower 60s and surface heating will result in MLCAPE of 500-1000 J/kg with minimal convective inhibition. Scattered thunderstorm development is expected by mid afternoon along and just east of the higher terrain, and convection will spread east-southeastward onto the High Plains. Steepening low-level lapse rates and clustering/upscale growth may support isolated strong outflow gusts. ...Northern MN and vicinity this afternoon/evening... A convectively-enhanced shortwave trough near the MN/ON/MB border intersection will move slowly east-southeastward near the international border through the afternoon. An associated wind shift/weak cold front extends west-southwestward from northwest MN into eastern ND. Ascent along the wind shift, in combination with pockets of surface heating and boundary-layer dewpoints in the 60s, will support scattered thunderstorm development this afternoon/evening. MLCAPE of 1000-2000 J/kg and modest vertical shear will support isolated marginally severe hail and strong/damaging outflow gusts. Read more CHECK UPDATE ZOOM GRAPHIC

Sunday, August 14, 2022

SPC Aug 14, 2022 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0751 AM CDT Sun Aug 14 2022 Valid 141300Z - 151200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE CENTRAL HIGH PLAINS AND NORTH DAKOTA... ...SUMMARY... Scattered convection capable of isolated/marginally severe thunderstorms will spread across portions of the central High Plains region, as well as parts of North Dakota, this afternoon and evening. ...Central High Plains... Upper ridge-peripheral disturbances and moderately strong winds aloft will influence the eastern Great Basin/central Rockies into the central High Plains into this afternoon and tonight. Scattered convection will likely initially develop and increase across Wyoming/northern Colorado this afternoon as boundary layer warming aids destabilization. Weak deep-layer flow/shear suggest updrafts will struggle to organize; however, sufficiently steep lapse rates and adequate instability favor gusty winds and perhaps marginally severe hail with the strongest cores as storms develop east-northeastward. Model guidance suggests a notable increase to the low-level jet this evening across the central High Plains including western portions of Kansas/Nebraska, which should support eastward storm propagation after sunset. ...Western/northern North Dakota and vicinity... Have introduced low severe probabilities for the potential of a few strong/severe storms across the region, primarily late this afternoon and evening. In the wake of some early day cloud cover and isolated thunderstorms, a moist/potentially unstable air mass will persist near/east of a surface low/front-related triple point. Subsequent development toward/after peak heating may remain fairly isolated. Regardless, the environment would seemingly support some semi-sustained multicells and possibly a few slow-moving supercells particularly across western/northern Dakota if/where storms do develop. Localized severe-wind gusts and hail may occur. ...South Texas... Low-level southeasterly winds may modestly strengthen today in proximity to a westward drifting area of low pressure centered across Deep South Texas. A few weak/transient supercells are conceivable near the coast, but even so, destabilization inland should be hindered by cloud cover/precipitation and any low-level shear/SRH increase should remain modest overall. Thus, current thinking is the tornado/wind gust-related severe potential will remain negligible across the region. ..Guyer/Broyles.. 08/14/2022 Read more CHECK UPDATE ZOOM GRAPHIC

Saturday, August 13, 2022

SPC Aug 13, 2022 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0226 AM CDT Sat Aug 13 2022 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EASTERN GEORGIA INTO THE CAROLINAS AND SOUTHERN VIRGINIA... ...SUMMARY... Isolated strong to severe thunderstorms may occur Monday across parts of eastern Georgia into the Carolinas and southern Virginia. ...Eastern Georgia into the Carolinas and Southern Virginia... A large-scale upper trough should remain over much of the eastern CONUS and Canada on Monday. A belt of modestly enhanced mid-level northwesterly winds is forecast to persist from parts of the OH/TN Valleys into the Southeast. At the surface, low-level moisture should gradually increase ahead of a front that should move east-southeastward across the central Appalachians into the Southeast and southern Mid-Atlantic. Weak to moderate instability should develop ahead of this boundary by Monday afternoon as diurnal heating occurs. Low-level lapse rates are also forecast to steepen, especially ahead of convection that may be ongoing Monday morning. Deep-layer shear appears strong enough for organized updrafts, and most guidance shows the potential for one or more clusters of surface-based thunderstorms to develop along/ahead of the front and spread east-southeastward through Monday evening. A Marginal Risk has been included where the best signal for robust convection exists Monday afternoon, from parts of eastern GA into the Carolinas and southern VA. ...Central Plains... A surface low should be present over KS into southern NE on Monday, with rich low-level moisture extending in a narrow corridor from the Southeast into the Ozarks and central Plains. An upper ridge will likely remain prominent over much of the western CONUS into the southern Plains, with nebulous large-scale forcing aloft over the central Plains. Even so, a ribbon of moderate instability may develop across parts of NE/KS by late Monday afternoon along the axis of greater low-level moisture. A large degree of uncertainty remains regarding potential for surface-based thunderstorm development. But, if any convection can develop across the narrow warm sector, it would have the potential to become severe given the favorable instability and sufficient deep-layer shear forecast. Have opted to not include low severe probabilities for now, as the severe threat appears rather conditional on thunderstorms developing. ..Gleason.. 08/13/2022 Read more CHECK UPDATE ZOOM GRAPHIC