Interesting Day Today, Gradual Warm-Up Ahead.

Sunday, March 2nd 2014, 3:41 pm
By: News On 6

One of the more interesting aspects of this winter weather event is the precipitation type and the occurrence of thunder with the sleet, snow, freezing rain, and even hail that we have been experiencing from time to time through the day today. The chart on the right is an attempt to explain what is going on using my limited graphic skills.

This type of chart is commonly used in meteorology to show how temperature and moisture vary in the vertical. The X axis is temperature and the units are in degrees Celsius. The Y axis is elevation measured in units of pressure and also meters. By the way, the temperature is skewed to the right and I have shown the freezing line as it slopes upward to the right by the black line and label. The actual temperature as measured by weather balloons is the red curved line which is also labeled and the moisture line is the green curved line which is also labeled.

Now for the details. Notice that at the surface, the temperature and moisture lines are both well to the left of the freezing line, in other words well below freezing. I have filled that in and labeled it cold and wet. Also, they are pretty much on top of each other indicating a basically saturated atmosphere which extends upward to an elevation of 1901 meters at which point they diverge. That indicates the presence of drier air above that level. That also happens to be the warmest point on the sounding with a temperature of about 8 degrees Celsius which corresponds to the mid 40s Fahrenheit.

Notice also that the temperature/moisture traces are below freezing from the surface up to an elevation of about 1300 meters or about 4000 feet. From there the temperature warms into the mid 40s as mentioned above before dropping back to below freezing at an elevation around 3200 meters or about 10,000 feet. I have filled that area in and labeled it warm & moist. This chart therefore shows the depth and magnitude of the cold, wet air near the surface as well as the depth and magnitude of the warm, moist layer aloft. By the way that warm, moist layer aloft is also unstable which is why thunder is occurring along with the sleet and freezing rain.

It is this vertical distribution of temperature and moisture that is most difficult to forecast as a difference of just a few hundred feet in the elevation of the freezing line can make a huge difference regarding whether we get sleet, freezing rain, snow, or some combination. Thus, the devil is really in the details. By the way, that vertical distribution of temperature and moisture is only measured twice a day with weather balloons contributing another source of uncertainty.

Hopefully, that helps explain what has happened so far today. Now for what is expected to happen for the rest of the day and overnight. All indications are that colder air will be moving in aloft replacing the layer of warm, moist air currently over us. That means the sleet/freezing rain will make a transition over to snow for at least a brief time for the evening and early night time hours. By Monday morning, much drier air will also be spreading over the state which should allow for at least some partial clearing and at least some sunshine. However, temperatures will still be brutally cold as we will stay in the low teens today, drop into single digits tonight, and will struggle to get above 20 on Monday. By the way, that will be a record for coldest daytime high on that particular date.

After that, the cold air will begin to shift further eastward allowing for some modification, although it will be rather slow. Tuesday morning will be in the teens, that afternoon only near 40. But, Thursday should be into the 50s and even some 60s by Friday so things will be moderating later in the week.

Notice the second and third maps on the right which are the 8-14 day projections. As you can see, temperatures will be gradually moderating and trending closer to normal by then. However, the moisture that we are receiving now is not going to help much with the ongoing drought situation and the opportunity for additional moisture of any significance over the next two weeks appears very limited as well.

So, hang in there and stay warm.

Dick Faurot