Prolonged Atmospheric River in the Pacific Northwest; Snow and High Winds from the Upper Midwest into the Northeast

A prolonged atmospheric river will continue to impact the Pacific Northwest into the Northern Rockies with heavy rainfall, areas of urban and river flooding, landslides, heavy mountain snow, and gusty winds into Thursday. A strong clipper system will bring the threat of heavy snow and high winds across the Upper Midwest/Great Lakes as well as portions of the interior Northeast and Appalachians. Read More >

Overview

On the morning of December 31, 2006 low pressure was located over south-central Iowa, which deepened over the next 12 hours and moved northeast into Wisconsin. Heavy snow fell in the afternoon from Cambridge through the western suburbs of the Twin Cities, as well as to Fairmont and Blue Earth. Snowfall rates were up to 2 inches per hour and total snowfall was 8-10 inches from the western suburbs of the Twin Cities through Mankato and Blue Earth. Snowfall decreased by early evening over eastern Minnesota.

Snowfall
Radar
Environment

Snowfall Totals

Total snowfall ranged from 8-10 inches from the western suburbs of the Twin Cities through Blue Earth.

Radar:


6 hr precip forecast from Dec 31 12Z NAM run	Reflectivity at 16:06Z on Dec 31	Reflectivity at 18:03Z on Dec 31	Reflectivity at 20:04Z on Dec 31

Environment

An area of low pressure was located over south-central Iowa at 12Z, which then deepened over the next 12 hours and moved northeast into Wisconsin. The region that received the heaviest snowfall was between the left exit region of a 250 mb jet in Illinois and the right entrance region of a 250 mb jet north of Minnesota. The December 31 12Z NAM run showed significant forcing and instability over south-central Minnesota. Also, the 12Z sounding showed a high precipitable water value and deep southerly flow, which provided ideal conditions for snowfall. The 0Z sounding showed a lower temperature profile and wind shift after the low had passed.


Mean Sea Level Pressure (mb) at 12Z	MSLP (mb) at 15Z	MSLP (mb) at 18Z


MSLP (mb) at 21Z	MPX 12Z sounding	MPX 0Z sounding


NAM differential layer divergence at 21Z	Satellite imagery showing deformation zone at 20:45Z

Media use of NWS Web News Stories is encouraged!
Please acknowledge the NWS as the source of any news information accessed from this site.

MPX RSS Feed

Prolonged Atmospheric River in the Pacific Northwest; Snow and High Winds from the Upper Midwest into the Northeast

Summary of December 31, 2006 Heavy Snowfall