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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.

Monday, June 28, 2021

SPC Jun 28, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0240 PM CDT Mon Jun 28 2021 Valid 282000Z - 291200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL IL INTO SOUTHERN LOWER MI...ACROSS PARTS OF NORTHERN NEW ENGLAND...AND ACROSS THE SC COAST... ...SUMMARY... Isolated thunderstorm wind damage may occur through this evening across northern New England and from central Illinois to southern Lower Michigan. An isolated/brief tornado will be possible along the South Carolina coast in association with Tropical Depression Four. ...20z Update... The ongoing forecast remains unchanged from the previous outlook. Scattered storms, some producing gusts of 30-40 mph, are ongoing across parts of central IL into southern lower MI. This activity will continue into early evening. Additional storms also are shifting eastward across northern New England, though these storms have struggled to intensify so far this afternoon. Additional showers and storms are moving westward across the Carolinas and GA as the center of T.D. Four approaches the SC coast. For short-term severe potential related to T.D. Four, see MCD 1122. ..Leitman.. 06/28/2021 .PREV DISCUSSION... /ISSUED 1129 AM CDT Mon Jun 28 2021/ ...Central IL to southern Lower MI this afternoon/evening... The large-scale pattern will change little through tomorrow morning, with dominant midlevel highs expected to persist near the Mid-Atlantic and the northern Rockies, and a weak trough over the northern Plains. Much of the convection this forecast period will be focused around the periphery of the Mid-Atlantic upper high, along a weak frontal zone from OK to MO/IL and southern Lower MI. Some enhancement to mid-upper flow will occur along and to the cool side of this frontal zone, and regional 12z soundings show only modest downdraft potential with relatively moist profiles. However, stronger surface heating and slightly stronger flow from IL to Lower MI could support storms capable of producing isolated wind damage this afternoon/evening. ...Northern New England this afternoon/evening... Northern New England will be on the southern fringe of somewhat stronger (40-50 kt) mid-upper flow, which will contribute to effective bulk shear of 30-40 kt. Scattered thunderstorm development is expected this afternoon/evening along and south of the weak front across northern New England, where the north edge of the 1000 J/kg MLCAPE and straight hodographs will support a low-end threat for splitting supercells. Given steep low-level lapse rates this afternoon, the strongest storms could produce isolated wind damage. ...SC coast this afternoon... The tropical disturbance off the SC coast has been upgraded to a tropical depression, and this depression is expected to move inland across SC by tonight. The lack of deep convection near the tropical cyclone core suggests little opportunity for strengthening with associated increases in the wind field/vertical shear. However, convergence along the coast could support some deep convection this afternoon in the zone of slightly enhanced vertical shear/hodograph curvature, where a brief tornado cannot be ruled out. Read more LIVE: