Wednesday, May 29, 2013

Sloshing Into June

The last seven days have been a wet period from the Pacific Northwest to New England and for parts of Texas.  CoCoRaHS observers have been busy measuring inches of rain in many areas. The first map below shows the accumulated precipitation for the past seven days.  The second map shows the percent of normal precipitation.

Map compiled by the NWS Advanced Hydrologic Prediction Service

The greens to blue and violet colors depict normal to much above normal precipitation.
Map compiled by the NWS Advanced Hydrologic Prediction Service
The heavy rainfall, particularly in the Midwest, has been due to a frontal boundary that has extended from the western U.S. to the east coast. Since the weekend this boundary has been oscillating north and south as upper level waves have moved across the country. South of this boundary the air is warm and humid with dewpoints in the 60s. The warm humid air has fueled showers and thunderstorms along and north of the boundary.

Surface map for 7:00 a.m. CDT Tuesday, May 28, 2013
Over the next few days a much stronger upper level low will slowly move across the northern U.S.

500 millibar forecast map for 7:00 a.m. CDT Friday, May 31, 2013.

Heavy showers and thunderstorms are likely along this boundary once again, with from 2 to 4 inches of rain possible across the northern Plains and the Midwest.

Quantitative precipitation forecast for the 3-day period from 7:00 p.m. CDT May 29 to 7:00 p.m. CDT June 1, 2013.
This will prolong and worsen flooding along rivers in the Midwest. The Mississippi River from Burlington, Iowa south to St. Louis is mostly in moderate flooding at the present time, but with the expected rainfall the river is forecast to be in major flood during the first week of June at most river gauges along that reach.

 This map shows the Maximum Forecast Flood Category through June 7, 2013. 0

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