Released: February 27, 2003

Weird Winter Weather Signaling It’s Still Dry

MANHATTAN, Kan. – Last weekend’s snowfall may have protected Kansas wheat fields and lawns, but it didn’t bring much moisture.

"The blanket of snow provided some protection from our sudden change to frigid temperatures. At the same time, it continued a trend that’s been confusing weather watchers since 2003 began," said Mary Knapp, State of Kansas climatologist, based at Kansas State University Research and Extension.

The High Plains area has been getting some extremely cold air masses – weather fronts – which also are extremely dry.

"They’ve been proving the fact that snow and ice don’t always translate into soil moisture," Knapp said.

Dodge City provided an extreme example Feb. 23-24 with the 4.8 inches of snow it received. That snowfall translated into just .04 inch of moisture.

"At that level of dryness, Dodge City would’ve needed 120 inches of snow to get 1 inch of moisture," Knapp said. "The Manhattan and Parsons stations reported similar results."

Areas receiving greater amounts of snow also got more moisture – not only because of the volume but also because that part of the system contained more moisture and thus was able to produce more snow.

Even so, none of the 57 stations in Kansas that report to the National Weather Service received enough snow to get a liquid equivalent of 1 inch in rainfall. Bluff City’s 14.8 inches of snow equaled .83 inch of rain. Caney’s 10 inches of white brought .93 inch of moisture – the highest reported equivalent.

The dryness of this year’s weather systems has been the open door for winter’s abrupt, see-saw temperatures, Knapp said. It’s why 2003 has brought so many days with temperatures in the single digits or teens, followed by days in the 40s or 50s. And it’s why Kansans have experienced:

* A number of frosty mornings with an odd-seeming lack of frost on landscapes and car windows.

* Snowy sidewalks that generally have seemed slicker when the temperature is in the 20s (F) than when it drops into the single digits.

* A notable snowfall in January when some meteorologists actually had to revise their official moisture reports for a storm – to zero.

The coldness and dryness both are why storm watchers can get a better idea of what to expect if they pay attention to the reported dew-point temperature and size of snowflakes, Knapp said.

Those factors are important clues because water has "restless" molecules – always shifting among three forms: water vapor (gas), water (liquid) and ice (solid). And the dew point is the "signal" temperature for one of those changes, she said. It’s the temperature at which the balance shifts toward the liquid form.

How high or low the dew point is depends on other factors. Recent weeks have brought dew point temperatures in the 60s F, as well as near 0 F.

Even so, it’s the temperature at which water vapor will "condense."

"When the dew point is 5 degrees [F] and the current temperature is 10 [F], you don’t have to worry about scraping your car windows. The available water vapor won’t be condensing into frost or ice unless the air temperature drops," Knapp said.

When the air temperature reaches a dew point that’s above freezing, the available water vapor turns into fog, dew or rain (a liquid). When the "shift" temperature is below freezing, water vapor becomes frost, ice crystals or snow (a solid).

"Clouds are simply condensed water vapor, too," the climatologist said. "To a degree, when we get rain or snow, we’re simply benefiting from the fact that the upper atmosphere has reached dew-point levels."

In general, the smaller and "icier" the snow that falls from those clouds, the less moisture it contains, she said. And, the smaller and colder the flake or ice crystal, the more likely its molecules are to "escape" as a gas, rather than take the more typical route of melting into liquid first as has happened several times so far this year.

The Kansas Weather Data Library’s paper and computer archives include Kansas’ official weather records – which not only evolve from statewide weather stations’ daily reports, but also date back into the 1800s. As part of that, Knapp maintains a Website where Kansans can access current and historical weather information (http://www.oznet.ksu.edu/wdl).

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward, Communications Specialist
kward@oznet.ksu.edu
K-State Research& Extension News