Annual rainfall record set to fall

One rainfall record for the Minot area is certain to fall. Another remains within reach. And there are still four months remaining in 2013.

At the North Central Research and Extension Center located immediately south of the city 1.56 inches of rain was recorded in the 24-hour period ending at 8 a.m. Thursday. The total for the year at that reporting point is now 26.47 inches of rain. The all-time record of 26.99 inches set in 1975 should soon be broken. When that occurs 2013 will claim the soggy distinction of being the wettest year in recorded history south of the city. Precipitation totals are read manually each day at the Research Center.

An automated system is in place at the Minot International Airport on the city’s north side. That gauge recorded .60 inches of rain early Thursday morning, pushing the yearly total at that location to 20.17 inches. The airport precipitation record for a single year is 26.99 inches set in 1975.

According to historical data compiled by the National Weather Service, Minot’s average precipitation for the final four months of the year is 3.75 inches. That means that average precipitation over the next 120 days, in a year that has seen nothing but average in terms of rainfall, would push the yearly total to nearly 24 inches, sixth greatest in history at the airport.

If average rainfall should occur at the Research Center the next four months, it would completely obliterate the existing record.

“The area has had a lot of rain, almost seven inches ahead of normal” said Bill Abeling, Bismarck NWS meteorologist. “Thunderstorms will produce a lot of variability in rainfall events.”

This year the amount of rain on Minot’s south edge has consistently run higher than what has fallen on the north side of Minot. That difference held true Thursday morning when the Research Center recorded almost a full inch more rain than did the airport.

“It’s not unusual. It really complicates things for forecasters,” said Allen Schlag, Bismarck NWS hydrologist. “I suspect ground water levels in those areas are healthy. Seeing water problems in basements is to be expected.”

With the wet conditions that preceded the historic flood of 2011 still entrenched in victim’s minds, rainfall approaching all-time record levels are certain to attract significant attention. However, says Schlag, wet soil conditions now may or may not influence the amount of runoff next spring.

“It’s still too early in the fall to make that determination. I’m most interested in the moisture conditions in the top six to 10 inches of soil right before freeze-up,” explained Schlag. “That’s where solid ice will develop in the ground and develop a nearly impermeable ground surface. Right now you still have vegetation doing everything it can to pull up that moisture. There’s still a lot of time.”

While the amount of soil moisture, or lack of soil moisture, is considered an important factor in compiling spring runoff forecasts, it is just one of several factors that must be considered in issuing runoff outlooks.

“It is one piece of many in a very complicated soup of ingredients,” said Schlag. “No one factor, other than no rainfall or snowfall, will guarantee or eliminate runoff. You have a lot of factors to consider in any given year.”

For now the NWS will continue to closely monitor rainfall and soil moisture conditions until freeze-up. While predicting what next spring’s runoff season will bring is not yet possible, 2013 rainfall has already secured its place in the record books.