SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0725 AM CDT Thu May 20 2021 Valid 201300Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF THE NORTHERN HIGH PLAINS... ...SUMMARY... Severe thunderstorms capable of large hail and wind damage will be possible across parts of the northern and central High Plains. ...Northern Plains... Morning water vapor loop shows an upper trough deepening over the northwest states. Increasingly strong south-southwesterly flow will be present across the northern Plains this afternoon and evening, along with steep mid-level lapse rates and strong daytime heating. Low-level moisture is forecast to be modest, and CAPE values are forecast to be mainly less than 1500 J/kg. But given the extent of heating, thunderstorms are expected to develop along the dryline over eastern WY/CO and build eastward through the evening. Mid-level heights are forecast to rise through the afternoon, and given the relatively weak instability fields, overall coverage of severe is likely to be limited. Nevertheless, the strongest cells will pose a risk of damaging wind gusts and large hail. ...MN/WI southward to LA... A plume of considerable low-level moisture will extend from WI southward into LA today. This will be coincident with a low-level jet axis of 30-40 knots. Several weak MCVs are noted within this corridor this morning, including one over northern IA, one over northeast TX, and one moving ashore in LA. Each of these features (and other weaker ones) will be accompanied by a mesoscale region of backed surface winds and enhanced low-level shear as they track northward today. While consistent model signals for strong convection are not apparent this morning with any of these features, have opted to extend the MRGL risk across the entire corridor including a 2% tornado probability area. ..Hart/Leitman.. 05/20/2021 Read more LIVE: spc.noaa.gov
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