Change in the weather coming soon?

We've been stuck in sort of a rut, with our typical January blocking holding on strong, coinciding with a deep upper-level low spinning over the Gulf of Alaska (GOA) and persistent troughing and advection of arctic air over the eastern US. The block has wavered between an omega/rex/split flow block since December. The block is bad for mountain snow: it keeps upper-level temperatures relatively high and limits the amount of precipitation.... what we are looking for is a change in the pattern that can break down the block or move it out of the area. There have been a number of decent jet streaks the past few weeks that formed in the west Pacific and showed promise for chipping away at the block, but energy was directed northward around the GOA trough. However, the next streak forming now shows more promise!



The streak looks to strengthen and stretch across the Pacific in the next  week or so, advecting energy into the east Pacific, helping to erode the block. This development is supported somewhat strongly by the ensembles.


If all goes well, the block will begin to smooth out and the jet stream can penetrate into and south of WWA, leading to cooler upper air and more moisture.











Although, the pattern change is quite a ways out (and therefore uncertainty is high), the GFS ensemble spread is fairly low for this event out to ~180 hours or so. The 180-hr GFS forecast (below) shows a decent jetstreak impacting the block (an atmospheric 'right hook' so to say) that could help get things moving and lead to a better pattern for mountain snow (ensemble spread is high after this features arrives, so cross your fingers).










In the near term, a short-lived pulse of winter weather should bring some mountain snow. Beginning Monday evening, the block tends to flatten in response to the passage of a 100+ knot jetlet and cold air advection aloft. 850 mb temps fall below freezing and remain so through Wednesday morning. Precip. arrives, giving the ski resorts some snow Monday-Wednesday morning. Unfortunately, it warms right back up with snow levels climbing to summer levels by the weekend as the ridge rebuilds... oh well.

There is not even a hint of a favorable pattern that could result in an arctic air intrusion into the lowlands, although the last few previous ensemble runs contained some members that favored weak intrusion from the ~1030mb high sliding into BC on Sunday... the odds of this are near zilch now. Our benign winter weather continues.