Tuesday, April 2, 2013

Mild Pacific air in place across the Midwest while the south remains stormy

After the 11th coldest March on record in Rockford it appears that things may be changing - and for the better!

The southern branch of the jetstream will act as the focal point for thunderstorms this week as gulf moisture collides with a stationary boundary from the central/southern Plains to the southeast.  The northern branch of the jetstream will begin to shift more from the west allowing a mild, Pacific air mass to move across the High Plains and Midwest with temperatures trending up by Thursday.  A weak cool front will move within the northern branch but remain moisture starved as thunderstorms to the south will be in full force.  This front will only bring a few extra clouds to the Stateline and drop temperatures slightly by Friday.  As we get closer to the weekend temperatures will warm once again ahead of an approaching low pressure system that will likely bring showers and thunderstorms to parts of the Midwest. 

The weather pattern after the weekend may get a little more active as the overall jetstream pattern begins to shift to a warmer, and possibly wet, scenario.  We've discussed how the negative phase of both the AO (Arctic Oscillation) and NAO (North Atlantic Oscillation) have impacts on the weather in the Great Lakes by pulling down colder air from the north, but current forecasts suggest a change from the negative phase to more of a positive phase will begin sometime during the second or even third week of the month.  Each red line on the graph indicates a different forecast model for both of the AO and NAO.  And while the spread among the lines grows greater towards the second week of April, all models indicate that a possible warming trend isn't that far away! 

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