Thursday, May 1, 2014
A ridge currently centered along the west coast is moving east towards our area and will bring warm and dry conditions that will persist into the new workweek. Several waves spinning around the Hudson Bay vortex will stay well to our north and east tomorrow and Saturday, but flatten the ridge, keeping temperatures around seasonal levels. There may be enough moisture and instability for afternoon clouds and a few thunderstorms, though this activity will be isolated. The ridge regains some of its lost amplitude by Sunday after these waves pass leading to unseasonably warm temperatures that will last at least through Monday.
However, this warm and dry weather will end around midweek when another wave forecast to make landfall in the Pacific northwest on Sunday begins to influence our area. The European ECWMF now agrees with the American GFS model with the early evolution of the storm, leading to warm and windy conditions ahead of this storm for Tuesday. Both models now have cold air from the Hudson Bay vortex entering the storm on Tuesday, but the American GFS continues to pour cold air into the backside of the storm leading to another prolonged cool and wet period from Wednesday through at least part of next weekend. The European ECMWF currently does not show this additional energy entering the storm and keeps it fast moving and through the area by Thursday.
Confidence that a storm will be over our area around midweek is high, but the details are uncertain. My inclination is to believe the cool and wet pattern advertised by the GFS as that model seems to be better handling the Hudson Bay vortex and its interaction with energy entering the west coast from the Pacific.