Day 80: The Ensuing Warm-Up Begins

Posted by pmarsh on 21 Mar 2010 | 0 comments

Yesterday, much of Oklahoma spent the day with temperatures in the 20s and 30s (F), dealing with strong northerly winds, and watching snow fall.  Today, snow is still falling across the eastern sections of the state, while the western half of the state enjoys a spring thaw.  As of 2:45 PM CDT, there was a 23F temperature change throughout the state!  56F in portions of the panhandle to 33F in several places in the east.

If we compare today’s temperatures to what was occurring yesterday at the same time, some areas are 20F warmer today (panhandle) whereas others are 5F cooler (far southeast).  So why such a rapid warm-up?

Normally, rapid warm-ups after snowfall is the result of strong southerly winds bringing the warm air northward.  However, as the image above indicates, northerly winds persist across almost the entire state.  So, southerly winds can’t be the reason for the warm-up across the southern plains.

The actual reason for such a rapid warm-up has to do with what time of year it is.  As we continue into the spring and summer months, the sun angle continues to increase in the sky, and is present longer than during the winter months.  The image above is a measure of how much sunlight is reaching the ground.  Warmer colors indicates areas where more sunlight is reaching the ground and cooler colors indicate less sunlight.  Notice the sharp gradient between western and central Oklahoma?  Also, notice how it matches up quite nicely the with sharpest temperature gradient in the first image?  This is where the edge of the clouds associated with the departing winter storm can be found.  Areas in western Oklahoma are free of clouds and are enjoying maximum sunlight, whereas places to the east have thick clouds and snow is still falling.

Tomorrow, the winter storm will be well to the east of the southern plains.  As such, the late March sun will act quickly to warm the area back to seasonable levels.  The exception to this will be in far eastern Oklahoma, where 12-18″ of snow will have fallen over the weekend.  Before all of the sun’s energy can go toward warming the atmosphere, in these places, it must first work to melt some of the snow.  Don’t get me wrong, these places will still be a lot warmer than they have been this weekend, but they won’t be as warm as they could have been.

So just how impressive is the warm-up across the southern plains?  Check out the following two visible satellite images from today.

The image above is valid this morning at 1545 UTC (10:45 AM CDT).  Notice the white areas that stretch from southwest Oklahoma and northwest Texas northeast into southcentral Iowa.  Most of this white is actually not clouds, but snow on the ground from the previous two days.  Now, take a look at the image below, which is valid this afternoon at 1945 UTC (2:45 PM CDT).  The white areas described previously have faded considerably or disappeared altogether.  In the span of four hours, most of the snow that fell yesterday has melted.  Eastern Oklahoma and western Arkansas will have this kind of rapid melting to look forward to in the coming days.

(PS…Look how classic this storm is!  Very clear comma shape, with the comma-head over eastern Oklahoma and western Arkansas and a very pronounced dry-slot extending from the Gulf of Mexico, northeast into the western Florida panhandle and southern Alabama!  If you look close enough, you can follow the dry-slot from southern Alabama, north then northwest then west then southwest all the way into eastern Arkansas!!)