You really need to watch these upper lows this time of the year. A closed off low doesn't have much influence from the main jet to push it along and therefore they are slow moving. This time of the year, these features are well known for producing flooding and some of it can be flash flooding. The atmosphere is juiced up with moisture and temperatures are quite warm. These slow moving systems have a ton of moisture to work with and can produce tremendous rainfall amounts. Due to the cut off nature to the low, projecting the exact path and timing can be difficult in the long range. Remember, low pressure has a counterclockwise spin to it in the northern hemisphere. This allows it to grab Gulf moisture and force it out in front of the storm system. The "lift" associated with these lows can produce heavy rain and storms just east of the center while the western side is drier, but not completely immune to rain and storms.
The time period we really need to watch is the beginning to middle of next week. Memorial Day? Yes, but most of the data points to the highest chance for rain starting next Tuesday.
|The European model valid next Wednesday morning has the low over Missouri so you can see the differences between the two long range models.|