Thu 09:30 AM Update — What had been expected to be a colder, active pattern next week (title of original post) is unfolding to be a seasonably cold, uneventful pattern. A flat and zonal flow as depicted in the “540 thickness” line (RED) of the Canadian Global model captures the uneventful flow and is NOT conducive to storm development—
Canadian Global model forecast for next Friday, Jan 22nd. Red line (“540 thickness line”) couldn’t be much flatter and it’s not conducive to storm development. (Click on image for a larger view.)
We’ll have a dip in the jet this weekend with an upper low affecting our area, but the original expectation for a continued amplified pattern next week has faded. As for the very cold weather, temperatures in Canada have significantly chilled, but there’s no indication at this time that it will move down to affect our area.
Addendum: Here’s the current day temperature deviation compared to the period 1979-2000—
GFS temperature anomaly Dec 14th compared to seasonal average 1979-2000. (ºC) As cold as things are getting in northern Canada, temperatures are relatively warmer than average. (Click on image for a larger view.)
Wed 09:48 AM Update — After looking at the latest GEFS (statistical ensemble) model as far out as it predicts -384 hours in the future – I don’t really see any intrusion of extremely cold air showing except in the far northwestern US. In fact, the jet flow is looking rather ‘flat’, (not amplified) so previous expectations of an active pattern next week may be incorrect. The flat pattern does not lend itself towards storm development. Cold air starts building in as shown below in the forecast for Sat, Jan 23rd below, but that’s a ways off—
GEFS forecast Saturday Jan 23rd showing high pressure building in. (Click on image for a larger view.)
Tue 10:52 AM Update — A plunge of cold air will cause low pressure development over our area Saturday. It looks like RAIN for our area on Saturday. Despite talk about displacement of the”the polar vortex” as suggested by signs of “stratospheric warming”, current statistical models have deep cold in Canada, but not deep or cold enough to extend into the US at this time. Current minimum temperatures from the statistical ensemble model (GEFS)—
Minimum Temps GEFS model for Monday 7 AM EST (Click on image for a larger view.)
This morning’s models are beginning to show an outbreak of very cold air around the last week of January.
Mon 06:22 PM Update — The pattern change expected over the weekend is still showing in the models. It appears it will be too warm for snow here, but there’s high uncertainty about Saturday’s forecast. Low pressure is expected to develop along the coast or slightly inland, keeping us in the warm sector, maybe with a brief changeover to snow before ending Saturday. Stay tuned.
This winter has been relatively quiet with average to above average temperatures, and with the exception of one storm, not much snow.
As mentioned in several posts over recent days, the models having been showing a strong signal towards a pattern change during the period January 16th through January 20th.
Colder air has been building in Canada and it appears that a southward plunge in this cold air will start occurring during the above timeframe, forcing a dip in the jet stream as a jet streak (1) causes the development of low pressure—
GFS version 16 forecast for Friday- 10 PM (Click on image for a larger view.)
The models have not come together with exact timing and placement of this plunge. The GFS (version 16) has rain, changing to snow for this first impulse: not a big storm.
GFS 16 forecast Saturday, 1 AM (Click on image for a larger view.)
The Canadian global model is similar to the GFS 16, with snow developing Saturday morning.
I should add that the current, operational GFS (version 15.2) is faster and does NOT have this storm form until the impulse is north of us—
Current Operational GFS version 15.2 Forecast for 1 PM Friday
Either way, colder temperatures are expected next weekend.
On the horizon is another impulse (#2 above), which depending upon the model, shows the possibility of a significant nor’easter a few days later.
It’s way too early to really know specifics, but the take-away is that colder temperatures are on the way next weekend and a more active winter weather pattern likely follows.
