Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
403 ACUS02 KWNS 151732 SWODY2 SPC AC 151730 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1230 PM CDT Sat Jun 15 2024 Valid 161200Z - 171200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY LATE SUNDAY... ...SUMMARY... Scattered strong to severe storms are expected Sunday evening and overnight from parts of the northern Plains into the upper Mississippi Valley, with hail the primary risk. ...Synopsis... A low-amplitude shortwave will likely extend from the Upper Midwest southwestward into the Mid MO Valley early Sunday morning. This shortwave is expected to quickly move northeastward across Upper MI and into central Ontario. A stronger shortwave trough is forecast to extend from southern Saskatchewan into the central Rockies early Sunday morning, before then quickly progressing eastward/northeastward and maturing into a mid-latitude cyclone over Manitoba by Sunday evening. Surface low associated with this system will gradually shift eastward from central Saskatchewan into northern Manitoba, while an attendant cold front moves quickly eastward/southeastward from central portions of the northern/central Plains through the Upper Midwest. Northern/eastern portion of this front will remain progressive as it moves through MN and into WI, but the southern/western portion of the front is expected to stall over the northern NE vicinity during the evening. Lee troughing is expected to sharpen throughout the day as well, with surface cyclogenesis likely across eastern CO by Sunday evening. The surface pattern Sunday evening will likely feature a low over northeast CO, with the stationary front extending northeastward from this low across central NE to another weak low near the NE/SD/IA border intersection. A cold front will extend northeastward from this secondary low northeastward across southern MN into northwest WI and then more north-northwestward into far northwest Ontario. A lee trough will also extend southward from the northeast CO low through eastern NM and the TX Trans Pecos. Thunderstorm development is possible along all of these surface boundaries, with highest coverage along the stationary front across NE and SD into central/southern MN and northern WI. Additionally, a weak wave is expected to slowly track northward/northwestward across the Gulf of Mexico, bringing increased moisture to much of the Gulf Coast. Afternoon/evening thunderstorms are expected across the entire region, particularly across the central Gulf Coast closer to the track of the wave. ...Upper Midwest into Upper MI early Sunday... Elevated showers and thunderstorms will likely be ongoing early Sunday morning ahead of the low-amplitude shortwave trough mentioned in the synopsis. Expectation is for these storms to progress northeastward into upper MI during the morning as the wave (and associated warm-air advection) shift northeastward. Moderate elevated buoyancy and shear will be in place, so a few storms may become strong enough to produce isolated hail. ...Central High Plains across NE/SD into MN/WI Sunday afternoon into Sunday night... Temperatures along and south of the stationary front will likely range from the mid to upper 90s during the afternoon from northeast CO across southern and eastern NE. Dewpoints are expected to be in mid to upper 60s across much of that same area. Temperatures in the upper 80s/low 90s with dewpoints in the upper 60s to low 70s expected farther east across MN ahead of the cold front. Afternoon thunderstorm development appears unlikely along the stationary front, with warm mid-level temperatures and the lack of stronger large-scale ascent keeping the airmass capped. There is a low chance that initiation could occur along the cold front in MN, particularly across northern MN where greater large-scale ascent is anticipated. Any storms that do form along the cold front could produce large to very large hail. However, uncertainty regarding development precludes higher than 5% probabilities with this outlook. A strengthening low-level jet will likely aid in the development of predominantly elevated convection to the north of the stationary front after 00Z. Development is possible along the length of the front, but will likely begin in the eastern WY/western SD/NE Panhandle vicinity. Strong buoyancy and shear will support hail with these elevated storms. Despite the elevated character to these storms, a few stronger gusts may be able to reach the surface, particularly near the stationary front. ...Central/Southern High Plains Sunday afternoon into evening... Strong diurnal heating and deep boundary-layer mixing is anticipated along the lee trough from far eastern CO southward into the Texas Trans-Pecos. Isolated thunderstorm development is possible along this boundary amid low-level convergence and airmass destabilization. High cloud bases and relatively modest shear should support outflow-dominant structures, and strong gusts are possible with any deeper, more persistent updrafts. ..Mosier.. 06/15/2024 $$