Highly Amplified Weather Pattern Across the United States

Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 304 AM EST Fri Feb 13 2015 Valid 12Z Fri Feb 13 2015 - 12Z Sun Feb 15 2015 ***Highly amplified weather pattern across the United States*** ***Very cold weather continues east of the Rocky Mountains*** ***Warm and dry conditions for California and the Desert Southwest*** The overall weather pattern over the next couple of days will be featured with a pronounced upper level trough over the eastern half of the country, and a big upper level ridge for the western states. The result is that upper level winds are blowing from northwest to southeast, with low pressure systems dropping southward out of Canada towards the East Coast. This will keep the West Coast and into the Intermountain West warmer and drier than normal, and the central and eastern parts of the U.S. much colder and unsettled. The warmest temperatures are expected over southern California and southern Arizona, where more 80+ degree weather is expected.

Within this flow from Canada will be a potent shortwave disturbance aloft tracking southward from the Nunavut province of northern Canada. A surface low and strong cold front will accompany this feature as it tracks over the Great Lakes and then to the Northeast U.S., with a massive surface high pressure area settling in behind it. This low will then undergo what meteorologists call Miller-B type cyclogenesis near the New England coast, and this occurs when a low pressure system approaching from the west transfers its energy to a coastal low that rapidly intensifies and deepens. This coastal low is forecast to become an intense nor'easter with heavy snow and blizzard conditions for eastern New England by Sunday morning.

This same storm will usher in a truly arctic airmass behind it, with some of the coldest weather of the season for parts of the Mid-Atlantic and Northeast U.S. for this weekend. High temperatures are expected to be 20 to 30 degrees below normal by February standards, with afternoon readings in the single digits and teens, and 20s extending into Virginia and North Carolina. The strong winds will combine with these frigid temperatures to produce brutal subzero wind chills. D. Hamrick Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php