Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0400 AM CDT Tue Aug 29 2017 Valid 011200Z - 061200Z ...DISCUSSION... Medium-range models are in decent agreement through the first 24-48 hours of the period, though substantial differences are evident with respect to their handling of the remnants of Harvey. These differences eventually result in deviation solutions with respect to the larger-scale pattern as well, and thus forecast confidence diminishes Day 6 (Sunday 9-3) and beyond. In the mean time, some degree of tornado risk may continue to accompany Harvey, mainly Day 4 (Friday 9-1) while the system remains more well-defined. However, both degree and location of risk remain uncertain -- and definitely below 15% threshold required for a day 4-8 outlook area. Otherwise, a fairly substantial short-wave trough is progged to move east-southeast across the Canadian Prairies and adjacent north-central U.S. Day 4, with an accompanying cold front to shift across the Dakotas. At this time however, very limited CAPE is anticipated ahead of the front, which should substantially limit severe risk. Day 5, the system is progged to continue east across Ontario and the Great Lakes, with a weakening cold front to cross the Great Lakes area as well. Even less instability is indicated Day 5, thus suggesting little if any severe risk. Uncertainty prevailing through the remainder of the period precludes any assessment of longer-range severe risk.Read more
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