04/27/2026
There it is, they just updated to moderate risk, I had a feeling it was coming.
SPC AC 271245
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0745 AM CDT Mon Apr 27 2026
Valid 271300Z - 281200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF MISSOURI INTO ILLINOIS...
...SUMMARY... Numerous severe thunderstorms are expected from the mid Mississippi/lower Ohio Valleys into the Mid-South through this evening, with a threat for multiple strong to intense tornadoes (EF-3+), widespread severe/damaging wind gusts, and scattered large to very large hail.
...Mid Mississippi Valley/Midwest into the Mid-South/Lower Mississippi Valley... An active severe weather day is forecast for much of the mid MS Valley/lower OH Valleys into the Mid-South. Ongoing thunderstorms this morning complicate the overall scenario to some extent, but a very favorable corridor for intense supercells and strong tornadoes is apparent this afternoon/evening across parts of MO into IL, where a Moderate Risk (Level 4 of 5) has been introduced.
Elevated supercells with mainly a hail threat should persist for at least a couple more hours this morning across the mid MS Valley as strong low-level warm advection aids in continued influx of sufficient MUCAPE amid strong deep-layer shear. Multiple clusters/embedded supercells are also ongoing this morning across western into northern MO. This activity should pose a greater threat for scattered severe/damaging winds, along with some hail risk. The tornado threat in the short term (this morning) remains unclear, but it should eventually increase as the boundary-layer across central MO continues to gradually destabilize/moisten. See Mesoscale Discussion 565 for more details on the near-term severe risk with these ongoing thunderstorms.
Current expectations are for the greatest severe risk to focus south of these morning thunderstorms. A mid/upper-level trough will eject northeastward from the northern/central Plains into the Midwest and mid MS Valley through the period. Low-level mass response will encourage the primary surface low to consolidate across MN/WI by this evening, with an effective warm front delineated by the morning convection. Aided by daytime heating and steep mid-level lapse rates, a moderately to strongly unstable airmass is expected to be in place by early to mid afternoon across much of central MO/southern IL southward into the Mid-South and lower MS Valley.
Strengthening west-southwesterly flow aloft associated with a 50-70 kt mid-level jet will overspread much of the warm sector by peak heating, and a 35-45 kt south-southwesterly low-level jet will both provide ample low-level and deep-layer shear to support supercells. Initially discrete surface-based development appears likely to occur by 19-21Z across the mid MS Valley/Mid-South ahead of the surface cold front, and perhaps along weak low-level confluence zones in the open warm sector.
These supercells will exist in a very favorable environment for tornadoes through the afternoon and evening, and multiple strong to intense tornadoes (EF-2/3+) appear likely, especially from parts of MO into IL along/near the effective front. This strong tornado threat may also extend farther south into AR/TN, but confidence is somewhat lower with southward extent due to weaker large-scale forcing. Large to very large hail (2-3 inches in diameter) may also occur with any sustained supercells.
By early evening, convection will probably tend to consolidate into clusters capable of producing numerous to widespread damaging winds from the mid MS Valley eastward into the lower OH Valley, before eventually weakening tonight as instability gradually decreases. A threat for QLCS and embedded supercell tornadoes will persist through much of the evening and early overnight hours as well given strong low-level shear forecast.
To the north of the ongoing morning convection across IA/northern IL/WI, a lesser (but non-zero) severe risk is forecast. This region will have less instability this afternoon, but strong shear. Have maintained the Marginal/Slight Risks for the possibility of isolated to locally scattered hail/damaging winds, and perhaps a couple of tornadoes.
...ArkLaTex into Texas... Confidence in sustained convection occurring from the ArkLaTex southward into TX is lower compared to locations farther north. But, strong heating ahead of a surface dryline could support isolated to scattered supercells capable of producing large to very large hail and occasional damaging winds. Increasing low-level warm/moist advection tonight could foster additional robust thunderstorms along the retreating dryline and eventually the southward-moving cold front. Severe probabilities have been expanded across these regions to account for this potential.
..Gleason/Thornton.. 04/27/2026
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
