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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.


Thursday, June 30, 2022

SPC Jun 30, 2022 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Thu Jun 30 2022 Valid 021200Z - 031200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SATURDAY ACROSS MUCH OF EASTERN PENNSYLVANIA...NORTHERN NEW JERSEY...SOUTHEASTERN NEW YORK AND MUCH OF LONG ISLAND...CONNECTICUT...RHODE ISLAND AND MUCH OF MASSACHUSETTS... ...SUMMARY... Strong thunderstorms are expected to develop and overspread much of the Northeast urban corridor Saturday afternoon, accompanied by a risk for damaging winds and hail. A cluster of strong thunderstorms might also develop across parts of the northern Great Plains late Saturday afternoon and evening, and pose at least some risk for severe weather. ...Synopsis... Little appreciable change to the large-scale flow is forecast through this period. Blocking with amplified split flow appears likely to remain prominent across the eastern Pacific into western North America. To the southeast of the persistent mid/upper high over the Canadian Yukon and Northwest Territories, broad troughing will remain entrenched across much of Canada and the adjacent northern tier of the U.S. to the east of the Rockies. However, the deep embedded mid-level low of Canadian Arctic origins is forecast to slowly progress east of the southern Hudson/James Bay vicinity, while several less prominent trailing perturbations dig across the Canadian Prairies and south of the central Canadian Arctic latitudes. Farther south, lower/mid tropospheric ridging extending from the southwestern Atlantic through the southern Rockies likely will be maintained. ...Northeast... Associated with the deep mid-level low shifting into Quebec, a cold front probably will already be advancing southward across northern New England and to the east of the lower Great Lakes by 12Z Saturday, before slowly continuing into southern New England and northern Mid Atlantic coastal areas by the end of the period. In advance of the front, it appears that a pre-frontal surface trough will become a focus for stronger boundary-layer heating and mixing across and just inland of much of the Northeast urban corridor, where surface dew points in the mid 60s to near 70F may contribute to moderate mixed-layer CAPE up to 1500-2000 J/kg. Thunderstorm activity likely to develop along or ahead of the cold front probably will intensify as it advances east-southeastward and encounters increasing inflow of this air mass. It appears this may occur coincident with 30-50 kt flow in the 700-500 mb layer, on the southern fringe of the stronger westerlies, with associated shear providing support for convective organization and potential for damaging wind gusts and hail. ...Northern Great Plains... A short wave impulse rounding the crest of the mid-level ridging across the northern Rockies, in advance of a stronger impulse digging within the cyclonic flow across the Canadian Prairies, may contribute to forcing for convective development across eastern Montana into the Dakotas by Saturday evening. Spread among the various model output remains sizable, but boundary-layer moistening beneath at least modestly steep mid-level lapse rates may contribute to CAPE on the order of 1000-2000 J/kg within the lee surface troughing across the northern Great Plains. Although it currently may be an outlier, the 30/00Z NAM indicates a rather substantive convective signal, suggestive of potential for the evolution of a rather strong, organized and progressive convective system capable of producing strong wind gusts. ..Kerr.. 06/30/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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