Storm Updates: Oklahoma and High Plains Slight Risk, Midwest Flood Leftovers — Sunday, September 20, 2026 (Morning)

This is the Sunday morning Storm Tracker for September 20, 2026. Overnight Severe Thunderstorm Watches 670, 671, and 672 have all expired. The Storm Prediction Center’s 1300 UTC Day 1 outlook holds a Slight Risk of severe thunderstorms this afternoon and evening across parts of Oklahoma and from eastern Colorado into far western Kansas. Isolated severe gusts and hail remain possible in a broader Marginal Risk from the southern Plains across the Ozarks into the Ohio Valley.

The flood story is leftover water, not a new Moderate Risk. Weather Prediction Center’s current Day 1 Excessive Rainfall Outlook is a Slight Risk over portions of the Midwest and Ohio Valley, plus a separate Slight over the northern High Plains focused on southwest South Dakota. Flash Flood Warnings fired overnight into this morning from eastern Iowa and the Quad Cities through southeast Ohio and the Charleston–Huntington corridor in West Virginia.

These are county-scale thunderstorms and flash-flood polygons. There is no U.S. landfalling tropical cyclone. Tropical Storm Fay is well southwest of the Azores. Tropical Storm Odalys is well southwest of Baja California. Verify the county warning at weather.gov before you roll.

What expired overnight vs what is live

Watch 670, issued Saturday afternoon over Kansas into Oklahoma and the Texas Panhandle, expired at 0400 UTC Sunday (11:00 p.m. CDT Saturday). Watch 671 expired at the same hour. Watch 672, issued after 8:00 p.m. CDT Saturday, expired at 0600 UTC Sunday (1:00 a.m. CDT). No convective watch is in effect as of this morning desk.

NWS warning text from Saturday evening still shows the pulse that those watches covered: a 61 mph gust at Childress, Texas; Severe Thunderstorm Warnings over Childress and Collingsworth Counties in the Texas Panhandle; western Oklahoma counties including Harmon, Greer, and Beckham; west-central Kansas around Wichita, Wallace, Logan, and Greeley Counties with radar-indicated golf-ball hail; and a line that warned St. Joseph, Atchison, and neighboring Kansas–Missouri counties. Those products have expired. They are last night’s just-hit list, not today’s watch board.

SPC’s storm-report table for the new convective day (1200 UTC Sunday onward) showed no tornado, hail, or wind LSRs at the time of this desk. That is consistent with a quiet pre-dawn after the watches died. Afternoon initiation is the next check.

Hotspot 1 — Oklahoma Slight Risk, afternoon and evening

SPC: thunderstorms with severe wind gusts and large hail this afternoon and evening across parts of Oklahoma. A frontal zone that convection modulated overnight over the eastern Texas Panhandle and Oklahoma will sag south. Mid-to-upper 60s dewpoints and heating support moderate buoyancy by mid-afternoon. Deep-layer shear is enough for organization.

The 1300 UTC outlook added an intensity Level-1 wind corridor over parts of southern Oklahoma where HREF/REFS guidance clustered 60–80 mph gusts on very steep 0–3 km lapse rates. Cities in or next to the Slight: Oklahoma City, Tulsa, Norman, Lawton, Wichita Falls. Storms are expected to develop from the Low Rolling Plains and Red River Valley and move northeast into central and eastern Oklahoma. Mixed mode early, with a chance the wind threat maximizes if a line segment organizes toward evening.

Restoration read: wind and hail first. Stage tarps, glass, and tree crews for late afternoon, not after dark. Southern Oklahoma is the gust corridor if the Level-1 language verifies. Photograph roofs in remaining daylight only if it is safe.

Hotspot 2 — Eastern Colorado into far western Kansas

A mid-level shortwave moves into the central High Plains today. Easterly low-level flow north of the front holds 50s dewpoints. Heating should remove inhibition by mid-to-late afternoon. Forecast soundings show straight hodographs and sizable CAPE in the hail-growth layer. A few supercells are the favored mode. Primary hazard is large hail, 1 to 2.5 inches, plus isolated severe gusts. Some lingering severe risk may drift into southeast Colorado late this evening and the Oklahoma Panhandle overnight.

Lamar sits inside the tighter probabilistic contour. Watch the I-70 and High Plains county warning areas from late afternoon. Restoration read: hail and isolated wind. Vehicle and roof claims, not a flood headline, unless a cell trains on a burn scar or a small basin.

Hotspot 3 — Midwest and Ohio Valley flood leftovers

Yesterday’s WPC Moderate Risk over eastern Iowa, northern Illinois, and northern Indiana has been stepped down. The current Day 1 ERO, updated 0819 UTC Sunday and valid 12Z Sunday through 12Z Monday, is a Slight Risk from southeastern Iowa and northern Missouri east into the Ohio Valley, with a second Slight over southwest South Dakota. Overnight convection is why Flash Flood Warnings were still live into Sunday morning for the Quad Cities, Cedar Rapids and eastern Iowa, Parkersburg–Athens, Hocking–Pickaway–Ross, and the Charleston–Huntington counties.

WPC language: the threat wanes from west to east this morning into early afternoon as the back edge of the rain moves off. Farther east, overnight convection near the Ohio River toward West Virginia terrain lowered flash-flood guidance. Some guidance rebuilds moderate-to-heavy rain later. Valley moisture supports locally 2–5 inch totals where cells train.

SPC also keeps a Marginal Risk from the Ozarks east into the Ohio Valley for isolated severe gusts and hail this afternoon south of a front near the I-70 corridor. That is a secondary wind desk, not the Slight.

Restoration read: Iowa, northern Missouri, Illinois, Indiana, southeast Ohio, and northwest West Virginia are extraction and drying work from last night. Check which county still has a warning. Do not treat the whole corridor as a new Moderate flood day.

Just hit

Saturday night’s organized pulse was the Kansas–Oklahoma–Texas Panhandle watch complex plus the Midwest and Ohio Valley rain. Documented hits in official warning text include the Childress airport gust near 61 mph and severe-warned storms over the eastern Panhandle, western Oklahoma, west-central Kansas hail cores, and the St. Joseph–Atchison line. Flood polygons stacked from eastern Iowa through the Ohio River counties overnight. Those tickets are already on the books.

Today’s new work, if it verifies, is the Oklahoma afternoon Slight and the High Plains hail corridor. The Midwest is aftermath plus a declining Slight flood overlay.

Pulse table

What this means for restoration teams

Oklahoma this afternoon is a wind-and-hail stage. If the southern Oklahoma Level-1 gust corridor verifies, expect roofs, siding, and trees in a relatively small footprint — staff it as county work, not a regional event. The High Plains Slight is hail first. Midwest and Ohio Valley crews already have water in buildings from Saturday night. The mold clock on those interiors started last night, not this afternoon.

Do not send the same crew to Tulsa hail and Cedar Rapids extraction without checking which county actually has a warning now. Property owners should photograph damage in daylight if it is safe, call the carrier, and start extraction the same day if water is inside.

What this is not

This is not a U.S. mainland hurricane landfall and not a Moderate flood day on the current WPC map. Fay and Odalys are named and far from U.S. land. Last night’s watches are closed. Today’s organized severe risk is two compact Slight areas plus a wide Marginal. That is the local-storm pattern this desk should staff.

Looking ahead

The next official Day 1 convective update is scheduled by 1630 UTC. The front continues south through Oklahoma tonight. Isolated severe risk may linger into the Oklahoma Panhandle after dark. WPC flood risk over the Midwest should keep easing from west to east unless new training rebuilds on the Ohio Valley side. Watch the afternoon Storm Tracker rather than assuming the 1300 UTC Slight is the last line of the day.

Sources and how to verify

Primary sources: NOAA Storm Prediction Center Sep 20, 2026 1300 UTC Day 1 Convective Outlook; SPC current convective watches page (Watches 670, 671, 672 expired); SPC storm reports for 19–20 September 2026; Weather Prediction Center Day 1 Excessive Rainfall Outlook updated 0819 UTC Sunday; National Weather Service watch/warning text; National Hurricane Center public advisories for Tropical Storm Fay and Tropical Storm Odalys.

Check weather.gov for the county warning, spc.noaa.gov for the outlook, watches, and LSRs, and WPC excessive rainfall for the flood overlay. Prior desk: Saturday, September 19 afternoon Storm Updates. Local flood polygons posted overnight live under the same Storm Tracker category.

Informational only — not an official weather warning. Follow local authorities and the National Weather Service. Turn around, don’t drown.