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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.

Saturday, June 19, 2021

SPC Jun 19, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0251 PM CDT Sat Jun 19 2021 Valid 192000Z - 201200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR NORTHEAST CO INTO SOUTH-CENTRAL NE AND NORTH-CENTRAL KS... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL HIGH PLAINS EASTWARD TO THE MID-ATLANTIC REGION...AS WELL AS OVER PARTS OF THE SOUTHEAST STATES... ...SUMMARY... Damaging thunderstorm wind and isolated large hail are possible from portions of the central High Plains to the Mid-Atlantic. A tornado threat also exists over parts of the central Gulf Coast States to southwestern Georgia, east of the inland track of Tropical Storm Claudette. ...20Z Update... ...Central High Plains into the Central Plains... As mentioned in MCD #1012, storms are beginning to develop over the Front Range where upwards of 2000 J/kg SBCAPE in the greater Denver area by RAP forecast soundings. Guidance continues to show that numerous storms will develop, before then moving off the higher terrain into the more moist and unstable air mass over the CO Plains. Additionally, southeasterly low-level flow veering to southwesterly then westerly aloft supports moderate effective bulk shear (30-40 kt) and the expectation is for relatively strong and organized updrafts. Severe Thunderstorm Watch #286 was recent issued over this area. Upscale growth is anticipated later this afternoon/evening, with the stationary boundary likely acting as a corridor for propagation. Numerous CAMs develop a rear-inflow jet with this convective line, and expected coverage of severe winds is now high enough to introduce 30%/Enhanced wind probabilities from far northeast CO eastward along the western and central NE/KS border. ...MO/IL... Thunderstorms have quickly developed in the vicinity of central MO/IL border. Strong instability and moderate vertical shear will likely result in strong updrafts capable of large hail and damaging wind gusts. Severe threat in this region could last for several hours and Severe Thunderstorm Watch #287 was recently issued to cover this threat. ...Downeast/Eastern ME... As mentioned in MCD #1014 a line of storms which had previously struggled to organize has strengthened in the last 15 to 30 minutes. This line of storms is a combination of both bowing segments and embedded supercells. The thermodynamic environment will likely limit the overall threat, but isolated large hail, damaging wind, or even a tornado remains possible as these storms move eastward over the next few hours. ..Mosier.. 06/19/2021 .PREV DISCUSSION... /ISSUED 1131 AM CDT Sat Jun 19 2021/ ...AL/GA/FL... Strong low-mid level wind fields in the southeastern quadrant of TS Claudette will continue to result in favorable vertical shear profiles for rotating storms through the afternoon and evening over parts of AL, GA, and the FL Panhandle. Please refer to WW 285 for further details. ...OH to Mid Atlantic Region... Overnight convection has resulted in a large canopy of mid/high clouds across portions of eastern OH and western/central PA. This will significantly limit daytime heating and destabilization later today. Therefore, have adjusted the SLGT risk area farther south into parts of OH/WV/MD where stronger heating is expected, and where CAM guidance in is better agreement regarding thunderstorm development. A shortwave trough currently over Lower MI will help to initiate storms across northern OH by mid-afternoon, with storms tracking southeastward through the evening. Other more isolated clusters of activity are expected from WV into the Chesapeake Valley this afternoon. All of these storms will pose some risk of locally damaging wind gusts and hail. ...Central High Plains... Strong daytime heating and ample low-level moisture will lead to scattered thunderstorms by mid/late afternoon over the foothills and adjacent plains of central CO and southeast WY. Storms will spread eastward and intensify by early evening, with several CAM solutions suggesting congealing cold-pools and the risk of significant damaging winds across parts of southwest NE and northeast KS. Considered an upgrade to ENH, but will maintain SLGT due to lack of a well-defined shortwave trough and relatively weak midlevel winds. Nevertheless, will re-evaluate the risk category at 20z. ...MO/IL/IN... Visible satellite imagery shows a large area of ACCAS and isolated thunderstorms from portions of northeast MO into central IL. Ample low-level moisture and strong heating in this region will yield afternoon MLCAPE values over 3500 J/kg and the potential for intense thunderstorms. 12z CAMs differ in their convective solutions over this area, but it is likely that one or more clusters of severe storms will develop this afternoon and evening. Storms that develop will pose a risk of large hail, damaging winds, and perhaps a tornado. Please refer to MCD #1009 for details on one particular cluster of ongoing storms. Read more LIVE: spc.noaa.gov