Our first significant and possibly heavy rainfall looks to be on the way by Thursday night and Friday. This will really help the plants to shoot up after the long and hot dry spell we have been having. Here's what's going on: currently a weak shortwave trough is located over the western portions of North and South Dakota.
This shortwave will amplify and strengthen rapidly during the overnight hours, as the jet streak, a region of stronger winds in the jet stream, enters and "digs" into the trough. By tomorrow morning, widespread high and mid level clouds will enter into the region from the west, bringing the first signs of the storm system. As it strengthens tonight, it will slow its quick pace due to several processes occurring within the storm's structure. One of these processes is the latent heat release from the large area of convection currently located over South Dakota. Latent heat release slows the system's pace, due to processes that occur near the tropopause, which are so complex, is it not entirely understood by most operational meteorologist. In response, a low pressure system will begin to form and move along the frontal boundary that is currently located over the Ohio Valley region. This will cause the front to strengthen rapidly, first strengthening the storm system, but also causing a low level jet to form, which will cause the front to move northward as a warm front into the region. Increasing isentropic lift and frontogenetical forcing will foretell the coming of rain by late afternoon on Thursday. This is where model differences come into play. As the upper level wave strengthens, the low pressure system will deepen rapidly, drawing moisture northward above the warm front. This, combined with strong upper level forcing and frontogenesis will cause the development of heavy rain bands over the area by 9-11 p.m. Thursday night. Some of the models, such as the NAM, are too weak with the storm system, causing less rainfall, less moisture transport, and an obvious impact on the precipitation patterns. The GFS on the otherhand (this is kind of surprising), is much stronger with the storm system, has much more intense moisture transport into the region, which positively impacts the storm system, making it stronger. Usually, computer models do not have a good handle on rapidly developing storm systems in positive feedback processes. Actually it is kind of surprising that the GFS is stronger with the entire storm system, due to the fact that it does not have a good handle on convective development (thunderstorms, heavy rain, etc.). Therefore, my forecast will call for a stronger storm system, stronger moisture transport, and thus heavy rainbands, and much heavy rainfall. In fact, if the forecast goes as predicted, I would expect rainfall amounts in excess of an inch, especially west of Defiance. After the system moves out of the region by Friday afternoon, clouds will prevail, along with gusty winds and cool temperatures. By Saturday, clouds will still persist, but will allow some sunshine through. Temperatures will also moderate into the lower 70's.
This shortwave will amplify and strengthen rapidly during the overnight hours, as the jet streak, a region of stronger winds in the jet stream, enters and "digs" into the trough. By tomorrow morning, widespread high and mid level clouds will enter into the region from the west, bringing the first signs of the storm system. As it strengthens tonight, it will slow its quick pace due to several processes occurring within the storm's structure. One of these processes is the latent heat release from the large area of convection currently located over South Dakota. Latent heat release slows the system's pace, due to processes that occur near the tropopause, which are so complex, is it not entirely understood by most operational meteorologist. In response, a low pressure system will begin to form and move along the frontal boundary that is currently located over the Ohio Valley region. This will cause the front to strengthen rapidly, first strengthening the storm system, but also causing a low level jet to form, which will cause the front to move northward as a warm front into the region. Increasing isentropic lift and frontogenetical forcing will foretell the coming of rain by late afternoon on Thursday. This is where model differences come into play. As the upper level wave strengthens, the low pressure system will deepen rapidly, drawing moisture northward above the warm front. This, combined with strong upper level forcing and frontogenesis will cause the development of heavy rain bands over the area by 9-11 p.m. Thursday night. Some of the models, such as the NAM, are too weak with the storm system, causing less rainfall, less moisture transport, and an obvious impact on the precipitation patterns. The GFS on the otherhand (this is kind of surprising), is much stronger with the storm system, has much more intense moisture transport into the region, which positively impacts the storm system, making it stronger. Usually, computer models do not have a good handle on rapidly developing storm systems in positive feedback processes. Actually it is kind of surprising that the GFS is stronger with the entire storm system, due to the fact that it does not have a good handle on convective development (thunderstorms, heavy rain, etc.). Therefore, my forecast will call for a stronger storm system, stronger moisture transport, and thus heavy rainbands, and much heavy rainfall. In fact, if the forecast goes as predicted, I would expect rainfall amounts in excess of an inch, especially west of Defiance. After the system moves out of the region by Friday afternoon, clouds will prevail, along with gusty winds and cool temperatures. By Saturday, clouds will still persist, but will allow some sunshine through. Temperatures will also moderate into the lower 70's.
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