Jesse Risley
Staff member
Just to dust off the archives I've been watching a local 'gentleperson's' chase here in the upper Mississippi Valley for later today. As of this writing a strong mid-level 90kt H5 jet streak is traversing the region on the basal side of a mid-level low currently centered over the Dakotas. A 990 mb surface low is situated over C MN with an attendant cold front pushing into W IA. As the system treks east this afternoon mediocre moisture is returning into the risk area ahead of the main surface low, with Tds in the mid to upper-40s already pushing north towards the I-80 corridor. Some doubt remains about the further extent or depth of moisture return, with some models previously showing low-50s Tds but that does not look to be realized based on current surface obs. A prefrontal trough appears poised to geospatially enter the region early this evening coterminous with the left entrance region of main H5 perturbation aloft, serving as a focal point for scattered convection with MLCAPE values AOA 800 J/KG. Of note, 500 hPA near -30F suggest cold core potential with favorable low-level (>7 C/km) and mid-level (>8 C/km) lapse rates owed to the steep temperature drops with height yielding deeper mixing and eventual erosion of CINH. Modest 0-3km CAPE levels have been noted by guidance over the last several days as well, with this morning's 12z HRRR being particularly magnanimous. Any discrete storms that are able to take advantage of the narrow tongues of moisture would have the potential to produce damaging winds, some hail and a tornado or two (Td profiles yielding unfavorable LCLs and more unidirectional shear profiles may limit TOR potential). CAMs do indicated an evolution to a more cluster-like mode as convection pushes closer to the western Chicago metropolitan region. It's something worth watching as I'd expect a few SVR reports later.
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