Administrators NorthGeorgiaWX Posted July 25 Administrators Posted July 25 SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1224 AM CDT Thu Jul 25 2024 Valid 261200Z - 271200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS FAR SOUTHEAST MONTANA AND NORTHEAST WYOMING INTO WESTERN SOUTH DAKOTA...AND ACROSS FAR EASTERN NORTH DAKOTA INTO NORTHWEST MINNESOTA... ...SUMMARY... Isolated severe thunderstorms are possible across parts of the northern High Plains and far eastern North Dakota into northwest Minnesota on Friday. ...Synopsis... A more progressive upper pattern in expected on Friday as an upper trough develops westward across the western U.S. This will shunt the Plains upper ridge east, extending from the Great Lakes, southward to the Gulf Coast states. While the upper trough envelops much of the western U.S., an upper anticyclone will remain centered over northern Baja, and extend northeast into AZ/NM. At the surface, a cold front will extend southward across the western Dakotas early in the day. The northern extent of the front will develop east toward the ND/MN border by 00z, while the SD portion of the front stalls and becomes diffuse. Surface high pressure over the Great Lakes will maintain a mostly dry airmass from the Ohio Valley into the Northeast in the wake of a prior cold frontal passage. Meanwhile, a baroclinic zone over the Upper Midwest will allow for rich boundary layer moisture beneath the eastward-develop upper ridge. Southwesterly low-level flow across northwest Mexico into AZ will bring modest boundary-layer moisture into the southern AZ deserts as well. ...WY into western SD and Vicinity... Boundary-layer moisture is expected to modestly return in the wake of the morning cold front as the boundary stalls over western/central SD. Low-level flow is expected to become east/southeasterly during the afternoon, allowing for modest moisture return and destabilization in this post-frontal upslope flow regime. Forecast guidance suggests at least isolated thunderstorms will develop as large-scale ascent increases in response to a shortwave impulse migrating through southwesterly flow, generating modest height falls across the region. Forecast soundings indicate a deeply mixed boundary layer with inverted-v thermodynamic sub-cloud profiles amid 25 kt effective shear magnitudes. Isolated strong/severe gusts may accompany thunderstorm activity during the evening, especially if clustering/outflow consolidation occurs. ...Eastern ND into MN... Thunderstorms are expected to develop ahead of the eastward-advancing cold front by late Friday afternoon as the boundary impinges on richer boundary layer moisture. Initial capping should erode as the upper ridge shifts east toward the Great Lakes, resulting in falling heights/cooling aloft while warm advection continues in the low-levels. Even if weak capping is maintained, elevated convection is still expected. A narrow corridor of MLCAPE up to 2500 J/kg is forecast amid effective shear magnitudes around 35 kt, supporting robust updrafts and marginal supercells. Isolated hail will be possible in addition locally strong gusts. ...AZ... Modest boundary layer moisture and steep lapse rates will support around 500-1000 J/kg MLCAPE. Thunderstorms will once again develop over higher terrain and move south during the evening. Mid and upper-level flow will be a bit more northerly compared to the prior few days and fairly weak (generally less than 15 kt). Nevertheless, deep mixing and inverted-v thermodynamic profiles will support sporadic strong gusts. Given somewhat less favorable flow compared to recent days, will hold off on marginal wind probabilities at this time. ..Leitman.. 07/25/2024 Read more View the full article Quote
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