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Severe Threat n the Mid-Atlantic; Fall Storm in the West to Plains

Showers and thunderstorms, isolated severe with damaging winds and large hail, can be expected across the Mid-Atlantic. A fall storm will bring showers and mountain snow in the Great Basin and Rockies. Locally heavy rain in the 4-Corners and South Plains could produce flash flooding. Gusty winds from the system will produce critical fire weather conditions in California and the north Plains. Read More >

Overview

From Saturday, June 16 through early morning Tuesday, June 19, a slow-moving upper-level low pressure system across the Northwest United States coupled with anomalously high moisture (precipitable water values upwards of 150-175% of normal) led to a long-duration rainfall event across northeastern Wyoming and western South Dakota. Much of this moisture was advected into the area via the remnants of Hurricane Bud (thanks Bud-dy!) in the Pacific. Many places saw more rainfall in these three days than they had seen for the rest of June.

In addition to the widespread rainfall, ample cloud cover helped keep much of the region much cooler than normal with highs in the 50s and 60s. The temperature at the NWS Rapid City office only deviated by 6 degrees from midnight June 17 through 6 AM June 19 -- with a high of 57 degrees and a low of 51 in that time frame. Only once the low clouds broke and the sun made it's presence known (albeit briefly) through after 830 AM MDT did the temperature finally begin to climb out of the 50s in downtown Rapid City.

See images below for temperatures at NWS Rapid City June 17-19.

Temperature at NWS Rapid City June 17, 2018 Temperature at NWS Rapid City June 18, 2018Temperature at NWS Rapid City June 19, 2018

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