Tuesday, May 13, 2014

Another Slow Moving Weather System

The first two weeks of May have seen almost the entire spectrum of weather from snow to record heat to severe thunderstorms and tornadoes. The upper level weather pattern has been amplified since late April, and this week another large trough is making its way across the country.  This started out as a double-headed low, with one low center over the Canadian Rockies and a second that came ashore in the Pacific Northwest on Friday.

500 millibar map for 7:00 a.m. CDT May 11, 2014

The Pacific center dropped southeast into the Four Corners region on Sunday. Sunday morning's surface weather map had one long frontal system extending east from southern California through the central U.S. to off the New Jersey coast.

Surface map for 7:00 a.m. Sunday, May 11, 2014

Snow falling in Walden, CO (Jackson County) on Sunday,
where about 10 inches accumulated. Photo by Peg Brocker.
Heavy snow fell on the cold side of this system on both sides of the Continental Divide, but the heaviest snow fell from southern Wyoming south through central Colorado.  Two to three feet of snow was reported in Wyoming, with 43 inches west of Encampment, WY. 20 to 30 inches fell in northern Colorado, with 6 to 8 inches in Fort Collins and 3 to 5 inches in Denver. 12 inches of snow fell in parts of the Nebraska Panhandle.

72-hour snowfall ending the morning of Tuesday, May 13.
Meanwhile, south of the front temperatures soared to summer like readings in the 80s and 90s from Texas north to Kansas and east to southern Michigan and Ohio on Sunday. The warm weather was also accompanied by dewpoints in the 60s.

Temperature (L) and dew point (R) at 4:00 p.m. CDT Sunday, May 11.
The warm, unstable air and the frontal boundary produced conditions ripe for severe weather, and the worst storms occurred along the front in an arc from southwestern Kansas to southeastern Nebraska, southern Iowa and northern Illinois.  Severe weather continued along the system Monday and today, but severe weather reports were far fewer in number.

24-hour precipitation ending at 7:00 CDT 5/13/2014
Thunderstorms also dropped heavy rain in many areas. Some of the more impressive totals were found in eastern Texas, where there were numerous reports of 24-hour amounts of 4 to 6 inches of rain and one report of 8.30 inches in Colorado County. Unfortunately the rain produced by this system missed the bone-dry areas of central and western Texas and Oklahoma.

The slow-moving upper trough and the associated surface front will spend the next three days moving through the eastern half of the country. Showers and thunderstorms weill continue to develop in the warm humid air ahaead of the front, while showers will occur in the cool air behind the front beneath the upper level low.

Quantitative precipitation forecast for the 3-day period ending Friday at 7:00 p.m. CDT

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