This Week in Weather

Rearview

The week's sharpest convective signal came out of the central plains on the evening of June 20 and into the early hours of June 21 (UTC), when six tornado warnings were issued across a corridor stretching from Weld County, Colorado to southwest Missouri. The Goodland, KS office (GLD) issued three of those warnings between 6:00 and 6:55 p.m. CDT on June 20, targeting Sheridan, Thomas, Rawlins, and Decatur counties in quick succession — a tight geographic cluster driven by discrete supercell activity along the dryline. By 9:55 p.m. CDT, the Springfield, MO office (SGF) had added warnings for Barton, Cedar, Dade, and Vernon counties, suggesting a system that tracked northeast and reorganized as it crossed the Missouri border.

NOAA SPC

Across the full seven-day period, SPC logged 77 tornado reports, 268 hail reports, and 1,713 wind reports. The wind-dominant ratio is notable: Georgia led all states with 168 total reports, followed by Pennsylvania (158), Kansas (153), West Virginia (147), and Illinois (130). That distribution — with Georgia and the mid-Atlantic well represented alongside the expected plains states — points to at least two distinct convective regimes operating during the period, not a single outbreak event.

The week's largest seismic event was a M6.7 strike near Palu, Indonesia on June 16 at 11:27 a.m. local time. Palu sits at the convergence of three tectonic plates and was the site of a catastrophic 2018 earthquake and tsunami; any significant event in this zone warrants attention. Two M6.6 events also occurred — one off Kamchatka, one along the central Mid-Atlantic Ridge — bringing the week's M6.0+ count to four within roughly 96 hours.

Wikimedia Commons

Space weather was quiet. The week's peak Kp index registered 0, and the lone notable solar event was an M2.7 flare at 2:46 a.m. UTC on June 21 — significant enough to note but well below the threshold for geomagnetic or HF communication impacts.

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Roadmap

USGS / Wikimedia Commons

The dominant pattern for the coming week is a strong, persistent ridge anchored over the southern tier of the country, with a flatter and more active flow regime across the northern plains and Great Lakes. The jet stream is positioned well north of its climatological average for late June, which keeps the most organized storm systems tracking through Canada while leaving the central U.S. exposed to diurnal convection along the ridge's western and northern flanks. There is no major trough in the picture for the eastern two-thirds of the country — what forcing exists comes from shortwave energy rotating around the base of the ridge and from the low-level jet pulsing moisture northward on successive nights.

Midwest and Great Lakes

Chicago's forecast shows the most aggressive precipitation signal of any region in the dataset: 1.59 inches of total precip for the week, with a 100% precipitation probability on June 21. That near-certain figure on a single day suggests a well-organized system — likely a mesoscale convective system or a squall line — rather than afternoon pop-up storms. Temperatures average 71°F for the week, which is notably cool relative to the southern tier; the same trough energy driving precipitation is suppressing the heat. Anyone in the I-90 corridor from the Quad Cities to South Bend should expect at least one significant rain event early in the week, with additional rounds possible as shortwave features continue to rotate through.

Northeast

New York City averages 82°F through the week with 0.70 inches of precipitation and a 75% probability peak on June 22. That timing aligns with the same synoptic feature pushing through the Midwest a day earlier, arriving in the mid-Atlantic and southern New England as a weakened but still moisture-rich system. The pattern is not a heat event for the Northeast — 82°F is seasonal — but the Monday-Tuesday window carries a meaningful convective threat, particularly for areas that can tap residual low-level moisture from the coastal plain.

South Plains and Mountain West

Dallas averages 96°F with zero measurable precipitation and a 13% peak probability on June 23. That number tells the story plainly: the ridge is in full control, the Gulf moisture feed is suppressed, and the region is in a heat consolidation phase rather than a severe weather phase. Denver averages 93°F with only 0.17 inches for the week, consistent with a ridge axis positioned to the south and west that limits afternoon storm development except on the highest terrain. The 40% probability on June 24 likely reflects orographic afternoon convection over the Front Range — localized, not synoptic.

International callout

London's forecast average high of 87°F for the week is striking for mid-to-late June. Long-term climatological averages for London in late June sit near 70°F. A reading 17 degrees above that average, sustained over a week, points to a persistent upper-level ridge over western Europe — a pattern that has recurred with increasing frequency in recent summers and that carries meaningful heat stress implications for a city with low air conditioning penetration.

The week's structure, then, is a two-speed country: an active northern tier where shortwave energy and a pulsing low-level jet keep convective chances elevated from the Rockies to the Appalachians, and a heat-locked southern tier where the main hazard is sustained high temperatures rather than storms.

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Eyes on the Sky

• The June 21-22 precipitation window for the Chicago-to-New York corridor is the week's highest-confidence severe weather threat — watch for NWS mesoscale discussions Sunday evening that will sharpen the timing and mode of any organized convection.
• Dallas residents should treat the 96°F average as a floor, not a ceiling, given the ridge's tendency to amplify on individual afternoons; heat index values in the 100-105°F range are plausible on multiple days this week.
• The M6.7 near Palu, Indonesia warrants continued monitoring — aftershock sequences in this tectonic environment can include secondary events above M6.0 in the days following the mainshock.