Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 AM CDT Thu Apr 06 2017 Valid 071200Z - 081200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FRIDAY ACROSS PARTS OF THE NORTHERN INTERMOUNTAIN WEST... ...SUMMARY... Strong thunderstorms may impact portions of the northern Intermountain West Friday, with at least some risk for severe weather. ...Synopsis... Mid/upper flow to the east of the Rockies appears likely to remain amplified, but slowly progressive through this period. The axis of large-scale troughing across the Atlantic Seaboard at 12Z Friday is forecast to shift east of the coast by late Friday night, while the upstream ridge axis shifts east of the Plains into the Mississippi Valley. In lower levels, models indicate that surface troughing will slowly develop/deepen across the Plains, but substantive moistening in the wake of the prior frontal passage (east of the Atlantic coast and deep into the Gulf of Mexico) appears unlikely through at least 12Z Saturday. Across the west, the remnants of a strong mid-latitude Pacific jet are forecast to continue nosing inland across the Pacific coast, accompanied by a transition to a more zonal and progressive regime. A couple of short wave perturbations emanating from the jet may contribute to sufficient destabilization for scattered thunderstorm development Friday into Friday night, across northern Pacific coastal areas through the northern Intermountain region and northern Rockies. ...Northern Intermountain region.. Considerable weakening of an initially 70-90+ cyclonic 500 mb jet streak is forecast as it propagates inland across northern California into the northern Intermountain region. However, mid-level height falls on the order of 90-120 meters may still overspread the region during the day Friday. And model output continues to indicate that mid-level cooling and lift may contribute to considerable steepening of lower/mid tropospheric lapse rates within a corridor across eastern Oregon/Washington through northern Idaho and far western Montana by Friday afternoon. Coinciding with strengthening of deep layer southwesterly mean flow to at least 30-50 kt, it appears that the environment could become conducive to scattered vigorous thunderstorm development, some of which may be accompanied by a risk for marginally severe wind and/or hail. ..Kerr.. 04/06/2017Read more
from SPC Forecast Products http://ift.tt/GB0aDL
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