Very Warm Tuesday But a Chilly End to the Week
April 23, 2012 7:21 PM
The roller coaster of spring returns this week as we saw temperatures rise some 10 to 20 degrees on Monday from just a day earlier, and we aren’t going to end there. Another 10 to 20 degree jump in temperatures can be expected Tuesday as highs could top 90 in a couple locations across the west; to the left are the forecasted high temperatures for your Tuesday. But after Tuesday, we begin to slide back down the hill. Many areas stay warm Wednesday but then our next trough and associated storm rolls into the Midwest by the end of the week and temperatures could drop some 50 degrees from our peak with plenty of clouds and rain to go along with the cold, which will make it feel just that much colder. So as much as you would like to put your spring jackets and pants away, don’t do it just yet.
So why the big swing?? Well, as unusual as this may seem, for South Dakota, its nothing new. Spring can bring wild temperatures swings to the Plains because of the really cold airmass hanging on just to our north in Canada and the really warm airmass that’s building just to our south in parts of Texas and Oklahoma. This combination can lead to a drastic temperature contrast across the central U.S. Well, that contrast in temperatures can get even larger when a storm system rolls through it and draws in additional cold air on the north side and warm air on the south side as winds funnel into the storm. Let me show you…… for Tuesday, a ridge will be sliding through the Plains allowing warm desert air in the southwest to get catapulted to the northern Plains and bring our area plenty of warm weather. This can be seen in the image below.
(The white line represents the jet stream which shows you the ridge trough pattern. The white arrow shows you where the air in South Dakota is coming from.)
But once that ridge breaks down and shifts east, and a trough moves in (along with the impending storm) temperatures cool as cold air gets pulled southward by the developing storm system. Combine the cooler air with clouds and rain and that cool air just gets colder thanks to evaporation.
(The white line and white arrow represent the same items as the first picture; the jet stream and where South Dakota air is originating.)
As for the rain toward the end of the week, signs point to another beneficial soaker for the area. But the heaviest of the rain may fall in areas that don’t need the water nearly as much. Remember that even after the beneficial rains of last week, areas of the east are still dealing with a pretty substantial drought, but it may be the west that gets the most water from the heavens this go around. Here is a look at the forecast rainfall from Thursday evening through Saturday evening from the Hydrological Prediction Center.
Pretty easy to see that the heaviest rain may fall west river, however, notice that the entire area could get more then three quarters of an inch which would prevent almost every location from experiencing a below average April when it comes to precipitation, although some will be close.
Lets be honest though, this is South Dakota. All of us know that the weather you experience today may be gone as quickly as tomorrow so just enjoy it while it lasts, no matter what kind of weather you consider nice.