SPC Mar 19, 2017 2000 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 19 Mar 2017

SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0223 PM CDT Sun Mar 19 2017 Valid 192000Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF IOWA AND ILLINOIS... ...SUMMARY... Marginally severe hail may occur tonight over parts of Iowa and northern Illinois. ...Discussion... Overall forecast reasoning below remains valid. Isolated/widely scattered thunderstorms should organize late tonight on the nose of a southwesterly low-level jet, with an attendant threat for a few instances of marginally severe hail. Only notable change is focusing Iowa portions of the marginal risk closer to the frontal boundary aloft, where ascent should be maximized. Recent convection-allowing guidance also suggests this corridor is favored for convective initiation late tonight. ..Picca.. 03/19/2017 .PREV DISCUSSION... /ISSUED 1105 AM CDT Sun Mar 19 2017/ ...IA/IL... Morning water vapor loop shows a mid-level shortwave trough over WY. This feature will track eastward across SD/NE today and into the midwest states tonight. Meanwhile, a strengthening southwesterly low level jet will nose into parts of IA/IL tonight. This will enhance low level warm advection and lift, promoting the development of scattered showers and thunderstorms (mainly after 10pm). Favorable deep-layer shear and steep mid level lapse rates suggest a conditional risk of hail over much of IA and northern/central IL tonight. However, the consensus of 12z CAM solutions suggest that vigorous thunderstorm activity is most likely along a corridor from northeast IA into parts of northern IL. Have therefore focused the Marginal risk area to that zone. Read more



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