A week into 2013 and we are still waiting on our first measurable rain (or snow) to fall. Fortunately, the wait is about over as a significant storm system, taking an unusual path, will bring plenty of moisture our way. The compact upper-level low is spinning its way into northern Mexico with only small amounts of rain or snow associated with it so far. As that low moves further east, it will tap into the Gulf of Mexico moisture and bring quite a rain event for the Southern Plains.
Before this storm system moves into Oklahoma, it will continue to dive deeper into Mexico. This will actually create a risk of severe weather for northern Mexico and Deep South Texas. As the system lifts back to the north, it will pick up a healthy fetch of Gulf moisture. Due to the compact nature of this system, the bulk of the heavy rain will be closer to its center, initially to the south of the Red River. Outside of a few showers late in the day, Tuesday should be dry. On Wednesday, that rain shield will spread north into Oklahoma and bring widespread rainfall to the region. Embedded thunderstorms are also possible Wednesday night. Some lingering showers are possible Thursday before the low pressure lifts to northeast of Green Country.
Through midweek between a half inch and two inches of rain are likely. The attached map shows the estimated rainfall distribution from this storm. As of now, it appears southern Oklahoma will see the heaviest rains. Even northern Oklahoma should at least get a nice soaking from the system. These are exactly the kind of rain events we need to battle our drought. Prolonged, steady rain events during cooler weather offer great relief!
Since this system dives so far south, it doesn't tap into any Arctic (or even modestly cold) air. Therefore, wintry weather is not a concern for us. A different scenario will play out this weekend where moisture may be lacking, but the Arctic chill won't be. A strong cold front will sweep through Oklahoma Saturday, allowing temperatures to go from the 60s on Friday, to the 30s for highs by Sunday. It'll be a nice, but brief reprieve from winter. From there, the pattern suggests the cold air settles in the central U.S. for quite awhile as a sustained trough in the jet stream sets up. Mid-January may bring us some of the coldest air of the season.