SPC Mar 19, 2017 0600 UTC Day 1 Convective Outlook

By Newsroom America Feeds at 19 Mar 2017

SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1237 AM CDT Sun Mar 19 2017 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM PARTS OF IOWA AND NORTHERN MISSOURI EASTWARD TO NORTHWEST INDIANA... ...SUMMARY... A threat for marginally severe hail may organize across parts of Iowa, northern Missouri, and into the northern half of Illinois and possibly northwest Indiana Sunday night. Elsewhere, a few thunderstorms will be possible across the southern High Plains, as well as portions of the Pacific Northwest and northern Rockies. ...Synopsis... As an eastern U.S. upper trough shifts into the western Atlantic during the day and a second area of troughing lingers over the eastern Pacific, a broad area of long-wave ridging will prevail over much of the country. With that said, eastward advance of a large upper trough across central Canada will flatten the northern portion of the U.S. ridge, with flow even turning weakly cyclonic over far northern portions of the country. At the surface, the trailing portion of a Canadian cold front will move eastward across the northern U.S. and into the Great Lakes region late, while trailing westward across the northern Intermountain region. Elsewhere, aside from a weak lee cyclone which may drift into the central Plains with time, high pressure should prevail across much of the country. ...Parts of Iowa and northern Missouri east to northwest Indiana... Weak height falls and -- correspondingly -- increasing low-level warm advection at the nose of a strengthening southwesterly low-level jet should support development of elevated showers and scattered thunderstorms overnight. The convection will be fueled by moderate instability, as low-level moistening beneath steepening mid-level lapse rates yields elevated CAPE values in excess of 1000 to 1500 j/kg. Given this expected thermodynamic environment, and increasing westerly flow aloft associated with the advance of the short-wave impulse, a few stronger/locally severe storms may evolve after midnight -- capable of producing hail in excess of 1" in diameter. The storms will spread eastward with time, possibly as far east as northwest Indiana by the end of the period. ...Elsewhere... Showers and a few thunderstorms may be ongoing at the start of the period over the eastern Kansas/southern and central Missouri area, which should weaken through midday/early afternoon. In the West, a band of weak convection -- including the potential for a few embedded lightning strikes -- will linger through the period from northern California/southern Oregon eastward across the northern Intermountain region in the vicinity of a quasi-stationary front. Finally, a couple of storms may evolve across parts of southern New Mexico and western Texas during the afternoon hours. In each of these areas, appreciable severe risk is not expected. ..Goss/Smith.. 03/19/2017 Read more



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