Heavy precipitation is expected along the west coast of Canada and in the central-eastern United States

It is forecasted that from September 21 to 26, influenced by the eastward movement of an upper-level trough and a low vortex system (Figure 1), a significant precipitation event will occur in the western coastal regions of Canada, the central and eastern United States, and the southern parts of Alaska. In these areas, moderate to heavy rain is expected, with a notable transition to snow in high-altitude regions. Localized heavy downpours, accompanied by short-term intense rainfall and thunderstorms, are also anticipated. The cumulative precipitation is expected to range from 40 to 80 mm. Specifically, regions such as British Columbia in Canada, eastern Oklahoma, southern Missouri, northern Arkansas, southern Indiana, and Kentucky in the United States could see accumulations exceeding 120 mm (Figure 2). Additionally, these areas will experience winds of 4 to 6 on the Beaufort scale, with gusts exceeding 8, and coastal regions may face winds reaching up to 10 on the scale. Precautions should be taken to mitigate the risks of urban flooding, landslides, and other secondary disasters that may be triggered by the heavy rainfall.

Figure 1  Forecast of 500 hPa Geopotential Height Field and 850 hPa Wind Field at 12 UTC on September 22

Figure 2  Forecasted Accumulated Precipitation from 12 UTC on September 21 to 12 UTC on September 26 (Unit: mm)

Author: Hu Yingying                                 Reviewer: Ma Jie 

English reviewer:Wang Yi                                                                       Issue approver:Dai Kan