SPC AC 190049
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0749 PM CDT Tue Sep 18 2018
Valid 190100Z - 191200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM A PORTION
OF THE CENTRAL AND NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY
Isolated large hail remains possible tonight from South Dakota,
Nebraska into Iowa.
...Central and northern Plains area through the upper Mississippi
Early this evening a quasi-stationary front (a portion of which has
been convectively reinforced) extends from the OH Valley westward
through northern MO to along the KS/NE border. A weakening cluster
of warm advection storms continues southeast through MO into IL.
Farther upstream across western NE new storms are in the process of
developing in response to the next in a series of vorticity maxima
moving through a low amplitude synoptic upper ridge. The low-level
jet will strengthen tonight, partly in response to this feature.
Increasing isentropic ascent north of the front will contribute to
fairly widespread thunderstorm development spreading eastward
through tonight. Updrafts will remain elevated, but given 7-7.5 C/km
mid-level lapse rates, moderate instability and 35-45 kt effective
bulk shear, a few storms may become capable of producing hail.
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