Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
805 ACUS02 KWNS 200518 SWODY2 SPC AC 200517 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1217 AM CDT Sun Apr 20 2025 Valid 211200Z - 221200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe thunderstorm potential appears low on Monday. ...Synopsis... An upper low/shortwave trough over the Upper Midwest on Monday morning will lift northeast across the Great Lakes into southern Ontario and western Quebec by Tuesday morning. Meanwhile, another upper shortwave trough over the northern Rockies will develop eastward to the northern Plains. ...Ohio Valley/Lower Great Lakes to the TN/Lower MS Valleys/Southeast TX... A belt of moderate southwesterly deep-layer flow associated with the Great Lakes upper trough will overspread much of the Ohio Valley into the Mid-Atlantic/Northeast. At the surface, low pressure will move in tandem with the upper trough from WI to western Quebec, with a trailing cold front developing east across the Ohio Valley to the north-central Appalachians/Mid-Atlantic vicinity. A narrow corridor of 250-500 J/kg MLCAPE may develop ahead of the front across the upper Ohio Valley vicinity. While instability and lapse rates and will remain poor, robust vertical shear may allow for a few stronger storms capable of producing locally strong wind gusts. The southern extent of the aforementioned cold front will stall over the TN/Lower MS Valley and into southeast TX. Better-quality boundary layer moisture will reside ahead of the boundary this far south, resulting in up to 1000 J/kg MLCAPE. However, vertical shear will be very modest. A couple of strong storms will be capable of locally strong gusts or small hail, but a lack of stronger vertical shear will likely limit longevity of any stronger/better organized updrafts, precluding severe probabilities. ...Northern Plains... Cold temperatures aloft with the upper shortwave trough will support steep midlevel lapse rates from MT into the northern Plains vicinity. This will support thunderstorm development during the afternoon into evening. While instability will remain weak, small hail may accompany stronger thunderstorm cores across MT into the western Dakotas. Additional thunderstorms may develop overnight eastern SD into southern MN/northern IA on the nose of a developing low-level jet. This activity also may produce small hail into early Tuesday morning. ..Leitman.. 04/20/2025 $$