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Published March 31, 2011, 04:59 PM

Updated Spring Melt Outlook from the NWS

The following is the updated outlook of expected weather conditions over the next one to four weeks from the National Weather Service in Grand Forks. That time period constitutes a critical melting period

Information presented is based on data and forecasts generated by the Grand Forks NWS and the Climate Prediction Center (CPC).

Synopsis:

The blocking pattern that developed after the March 22-23 snow storm continues, but has begun to decay and shift eastward. Unseasonably cold high pressure will continue to dominate the regions weather, with a continuation of the very slow melt conditions. The liquid precipitation that was generated during the March 23rd storm and in prior melt cycle periods has made its way into the river systems. As a result many area rivers continue to rise with several points on the main-stem Red above flood stage. Meanwhile, the snow that fell has been slow to melt, making only minor contributions to the developing flood.

Near term outlook: April 1 -7

Refer to NWS Grand Forks forecast products for updates. A potent storm system will move across the plains this first weekend of April. This system has the potential to produce significant snows across the Red River Valley region Sunday and Monday April 3rd/4th. Some rain is also likely, but the exact rain/snow ratio is unknown at this time. Precipitation forecasts from the NWS Hydrologic Prediction Center suggest 0.75 to 1.00 inches of liquid possible. Updates are issued twice daily and are available on the web here.

As of this writing, much of the precipitation in the Red River Basin is forecast to fall as snow. This will help keep runoff to a minimum as well as add extra, unneeded moisture to the snow pack. Stay tuned for updates.

Beyond the early April storm, there are indications of another storm impacting the northern plains late in the first week of April. Based on data from the Climate Prediction Center (CPC) these two storms are, in part, being fueled by the Madden-Julian Oscillation (MJO) which is moving slowly into the western Pacific. As the MJO continues it eastward track, storm systems moving across the Pacific have the potential to be energized, increasing the threat for significant precipitation over the plains. Satellite imagery shows a series of storms lined up across the Pacific into the Eurasian region that will move east toward the United States. Based on data from the CPC, this pattern of enhanced storminess across the Pacific towards the northwest U.S. and northern plains is typical of La Nina winters and springs.

8 to 14 day Outlook: April 8 - 14

During the first two weeks of April, the threat for increased storminess exists, as a slow pattern change continues to develop. As is typical of Aprils that follow a La Nina, a broad trough of low pressure in the upper atmosphere is expected to form in the western half of the United States, as high pressure develops over the southeast US. This will gradually make the upper level flow turn more west-southwest over the plains. This favors increased storminess over the region, which is becoming more apparent in the short term.

Long range outlook: April 15 - 30

Based on the CPC outlook for April, the pattern of below normal temperatures and above normal precipitation will continue beyond mid month.

Flood Risk Assessment:

See the bi-weekly NWS Grand Forks product BISESFFGF titled Spring Thaw Progress for the Red River of the North. This product will be issued on Mondays and Thursdays until the spring snowmelt flood begins in earnest.

Flooding is expected to continue and increase, with the risk for local river variations of 1 to 3 feet due to ice jams. A few forecast points will reach moderate flood stage. Depending on the state of drainage systems – ditches, culverts, etc. overland flooding will likely increase as well. As indicated, below normal temperatures and above normal precipitation the next week is expected. The below normal temperatures will maintain a gradual melt process, with the new precipitation replacing what has been melted into the river system the past few weeks.

Through April 7th, continued below normal temperatures would favor a mix of rain and snow as the primary precipitation threat. The overall climate/weather pattern suggests a series of storm systems will traverse the plains, maintaining an enhanced risk of above normal precipitation through the period. As is typical of the spring years with a weakening La Nina, increased storminess is not uncommon. There are indications that a period of warmer weather may develop in association with a potential storm in the April 8 - 10 time period. This could re-initiate a more vigorous melt pattern.

In the April 10 to 15 time frame a period of more normal precipitation pattern is expected with continued below normal temperatures.

At this time it is impossible to make Quantitative Precipitation Forecasts beyond about day 5, therefore we refer to the three categories of below, near normal or above to describe the precipitation threat. The overall pattern should continue transitioning to the above normal precipitation category into the second week of April as described above. It is important to remember that April is a transition period, when weather systems can develop and intensity rapidly. Due to the technological limitations, the NWS in Grand Forks can only relay trends of major storm systems beyond the 7 to 10 day period.

As the overall pattern transitions from relative quiet to a more stormy pattern, your NWS will update this Hazards Outlook.

Mark Ewens

Climate Services Focal Point

NWS Grand Forks

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