Stepping Down Process...

November Pattern Thoughts For The Rest Of The Month..


Stepping Down Process...


There are two ways that we can get colder weather into the east & the northeast. The first would essentially be if there was a cold air supply to our north that has been building up ..The Arctic Oscillation crashes and essentially the rubber band snaps and the colder air drops down south and east into the USA. First entering the plains and then moving eastwards. That is not going to happen this time around. Why? At this present time there is no colder air to the north.
The 2nd way to get colder air into the region would be by a pattern change in which we get a - EPO ridge, -NAO & + PNA.
You see this occurring in the 00z GFS last night ( above)
When you get a negative EPO ridge this allows the colder air to filter across into Canada. Then when the AO crashes this colder air can then be filtered into the USA. This will probably happen in a step down process. This step down process has essentially already started with temperatures this week being back into the 50s instead of in the 60s & 70s. So consider this a transition period.
The most likely scenario that will occur is you will have a frontal passage with an area of low pressure that will head across the lakes. This will cause a cold front to come thru around Nov 25-27th period and this will then cause temperatures to step down some more. Temperatures will shift from seasonal to slightly above to seasonal to slightly below. A day or two in modification before the next FROPA come thru and we take another step down to below normal temperature regime. That then would lead us into the first week of December.
The ensembles have been consistent with this pattern change upcoming as well as the operational , though timing has been going back and forth. This has to be expected on the models whenever a pattern change occurs. The GFS for example has been showing a FROPA at times or a FROPA that develops a secondary or even some runs a coastal storm around Thanksgiving. During this time period will be a frontal passage that will bring the much anticipated pattern change.

So to sum things up:

Week #1 (current week) Seasonal to slightly above seasonal temperatures.
Week #2 (last week of November) Seasonal to slightly below normal temperatures