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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, June 18, 2022

SPC Jun 18, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0237 PM CDT Sat Jun 18 2022 Valid 182000Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS NORTHWEST TO NORTH-CENTRAL MONTANA...AND THE FLORIDA PENINSULA... ...SUMMARY... Significant severe hail is possible across portions of northwest and north-central Montana through this afternoon. Scattered damaging winds are possible across parts of the Florida peninsula through early evening. ...20z Update... Only minor adjustments have been made to the 10 percent general thunderstorm lines based on convective trends. The Slight and Marginal risk areas across MT, the south-central states, and the FL Peninsula remain unchanged. Reference MCD 1215 and 1217 for short term information, and the previous outlook discussion below for more forecast details. ..Leitman.. 06/18/2022 .PREV DISCUSSION... /ISSUED 1115 AM CDT Sat Jun 18 2022/ ...Northwest/north-central MT... Large-scale ascent tied to a shortwave impulse ejecting north from the ID/NV/UT border area should aid in isolated to scattered thunderstorm development this afternoon along and to the cool side of a quasi-stationary front extending from southwest to north-central MT. Boundary-layer dew points holding in the 50s beneath steep mid-level lapse rates will support a confined plume of MLCAPE from 750-1500 J/kg near the MT/Alberta/Saskatchewan border area. Strong deep-layer speed shear yielding a rather elongated, straight-line hodograph will foster potential for a few discrete splitting supercells with a primary threat of large hail before convection crosses into Canada. ...FL Peninsula... Remnants of decaying morning pre-frontal convection persist across north FL. Scattered thunderstorms are expected to develop this afternoon ahead of this activity as surface temperatures warm through the 90s. Large MLCAPE in excess of 3000 J/kg supported by relatively steep mid-level lapse rates has already developed across the west-central portion of the peninsula. While deep-layer shear will be weak, northerly mid-level winds will support southward-propagating cold pools in pulse to loosely organized multicell clusters. A series of damaging downburst winds, especially along outflow intersections, is possible along with isolated severe hail. ...Central Gulf Coast and South-Central States... Isolated to scattered thunderstorms are expected this afternoon along and west of a backdoor cold front pushing southwest across the Lower MS Valley. Owing to close proximity of a stout mid-level anticyclone over eastern KS, deep-layer shear will remain weak, yielding predominately pulse convection. With the largest MLCAPE near the frontal zone, localized microbursts are most probable in this corridor yielding isolated damaging winds. ...Southwest to central Rockies/High Plains... The Southwest monsoon is underway with a plume of PW near or above 1 inch across eastern AZ/western NM, between the upper trough along the Pacific coast and the ridge over the Great Plains. Locally gusty outflow winds will be possible in scattered to numerous thunderstorms where pockets of stronger surface heating and steeper low-level lapse rates coincide with convective clusters. The threat for very isolated severe wind gusts while non-zero does not appear likely to be greater than 5 percent coverage over such a broad area. Read more CHECK UPDATE ZOOM GRAPHIC