Wednesday, June 19, 2013

Short Range Risk Analysis - June 19, 2013

This Short Range Risk Analysis, made on June 19th, covers the timeframe of now to 5-7 days from today. Confidence on this analysis is Above Average.

Overall Synopsis
Large closed low over the Pacific Northwest is enabling high pressure formation over the Northern Plains, advecting instability and conditions supportive for severe weather. Ridging pattern appears to be ongoing in this timeframe from the Ohio Valley eastward, allowing for a rather quiet period for the East.

Severe Weather Outlook: Medium/High Activity
Confidence: Average
Uncertainty in previous Short Range Risk Analysis has been greatly cleared up, allowing me to see the nature of the severe weather threats in the next 5-7 days. Model guidance is confirming pieces of energy from the closed low in the Pacific Northwest will slide east and interact with ridging high pressure over the Northern Plains to create multiple severe weather opportunities in that area. Progression of the severe weather threat moves east and south by the 3 day forecast mark, with the Storm Prediction Center placing a large portion of the Midwest and Upper Plains under the gun for severe weather. Threat should continue to the end of the 7 day mark in this short range analysis, leading the outlook to a Medium/High Activity level with Average confidence.

Flooding Outlook: Medium Activity
Confidence: Above Average
Ongoing severe weather events will span multiple days across the Upper Plains, particularly from North Dakota and Minnesota to Wisconsin. Current model guidance has multiple places in these states receiving up to 6.00 inches of rain in roughly 6 days. The multiple bouts of potentially strong storms will allow for multiple days of stress on rivers. While no major flooding is currently ongoing in the areas mentioned, 6 inches of rain in 6 days is enough to put at least considerable stress on some rivers.

Heat Outlook: Medium Activity
Confidence: Very Above Average
The presence of a closed low in the Pacific Northwest has led to some high pressure development in the Northern Plains. Amplification of this high pressure to include additional areas of the Plains and Midwest is expected, with more high pressure formation occurring in the Eastern US. Coagulation into a single high pressure system is expected over time, which will push the jet stream into a zonal flow and move it north. This zonal flow will allow warmer weather to shift north into the United States, and massive high pressure will enhance that job at the 7 day mark and a little bit beyond. Confidence is Very Above Average in the Medium Activity outlook for heat, as model guidance has been consistent on large high pressure formation for days.

Tropical Outlook: Low Activity
Confidence: Average
Tropical Depression TWO continues to shift towards Mexico, dumping heavy rain across the area. Redevelopment of this depression into a tropical storm was previously expected by the National Hurricane Center, and development into a tropical storm is now expected by the agency as soon as this afternoon. I remain skeptical on the idea considering how close to land the depression is, but as the depression slows down and seemed to get its act together in the evening hours last night, I can see how strengthening can be a possibility. However, Low Activity is listed for this outlook, as no development is anticipated following TD-TWO.