Saturday, June 7, 2014

Mid-June Severe Weather Outbreak Still Looking Possible

The mid-June severe weather outbreak we first discussed in the middle of May still looks to pose a threat to the United States.

500mb forecast heights from forecast Day 3 (top right) across and down to Day 7 (bottom middle).
Long range guidance from the Weather Prediction Center shows troughing developing in the Pacific Northwest beginning on forecast Day 4 (top-middle panel), and continuing through Day 7 (bottom middle panel). This troughing along the West Coast then forces a dome of high pressure to rise up in the Central and East US, a feature that was predicted in the linked post above with the help of the Bering Sea Rule. It is this dome of high pressure that I believe may very well allow for this/these severe weather episode(s).

Instability forecast for June 16th
The GFS model has been showing vast expanses of very high amounts of instability overspreading portions of the Central US for multiple forecast runs now, with the most recent forecast shown above. The gist of this scenario is that a large plume of instability would be pulled north into the southern and central Plains, likely kicking off what might be a multi-day severe weather event. From there, guidance tends to shift that body of instability east, like the image above shows. However, with location of this instability plume and timing concerns raising uncertainty, we will need more time to see just how extensive this potential event may be.