The two time frames to watch for the threat of additional snowfall are March 28th-29th and March 31st-April 1st:
(Click on image to enlarge and read text at the bottom)
This 500mb heights/vorticity graphic from today's 12z GFS valid March 27th shows the ridge-trough combo with a potent piece of H5 energy digging into the mid-section of the country. There is some confluent energy leftover northern New England (which will be responsible to bringing us some rain this Thursday) that is keeping heights along the east coast flat. The mid-level trough is positively tilted and the overall flow across the country is progressive.
(Click on the image to enlarge and read text)
This graphic is now valid for March 29th and you'll notice the mid-level trough is no longer positively tilted, however, the H5 energy is very strung out. There are 2 main reasons why this trough de-amplifies:
- Western ridge retrogrades to connect with another mid-level ridge near the EPO region and the flow turns progressive for a period of time
2. An even stronger piece of H5 energy (circled) is about to dig into the eastern CONUS which disturbs the flow ahead of it.
Here is a look at just the 500mb height anomalies valid March 29th. The full latitude ridge in the west is impressive, but it's too little too late for the March 29th east coast storm as it's already well off the coast at this time. What I am interested in is whether the next piece of energy (notice the kink in the flow around North Dakota) digs into the eastern U.S. in response to the -EPO/+PNA and brings a Miller B storm to the area around April 1st.
Getting back to the March 29th, you can see the GFS shows an impressive system but it's well offshore.
(Click on the image to enlarge and read text)
The 12z EURO also keeps the March 29th system offshore. The mid-level trough is simply too positive and the flow is too progressive to get anything going off the coast. Notice it also has a very potent piece of H5 energy entering the country in the upper Midwest. With all that ridging in the west, I would be surprised it that energy does not trend further south and east over the next few days and show a sizable storm off the east coast around April 1st of the Miller B variety. There may not be enough blocking to get a Miller B system to work out for our area, but if the -EPO/+PNA amplification is real I do feel we still have a shot. Obviously New England is in better position than we are, but you never know.
The 12z GGEM is more robust with the east coast storm bringing rain to I-95 and snow to the interior northeast. Its evolution aloft is very ugly. The mid-level trough broadens out and the energy elongates over the east coast. It's basically just a wave of low pressure riding up the coast.
CONCLUSION - MARCH 28TH-29TH STORM
Remember this scenario the GGEM was showing last week with a closed off H5 and a sub 980mb storm at the surface? I doubt very much guidance trends back to this solution. As I just explained, the lack of blocking and the retrograde of the western ridge is keeping the overall flow too progressive.
What needs to happen to get a coastal storm:
- Get better consolidation of H5 energy within the mid-level trough instead of seeing it escape out to sea.
- Maintain ridge amplification in the western U.S. to prevent the overall flow from becoming too progressive.
- Get a piece of northern stream energy to phase into the trough to help reamplify it and possibly turn neutral-negative in time.
Will it happen? It could, but at this time I am not confident. We'll see how things trend through the course of this week. I kind of like the April Fool's Day time frame a little better. As long as the -EPO/+PNA couplet maintains amplification beyond March 30th, I think that set-up could produce a Miller B for someone in the northeast region.
COLD TEMPERATURES
The intrusion of both those mid-level trough's (March 27th and April 1st) means colder than normal temperatures yet again for the area.
The MJO is currently in phase 8 and heading into octant 1.
Composite's of an MJO in phase 1 for early April show negative heights anomalies over the east coast. The evolution shown aloft by guidance to keep the area colder than normal from the end of March into the 1st week of April makes sense.
Temp. departures will range anywhere from -5*F to as much as -10*F below normal for the NYC Metro area during the aforementioned time period.
If neither the March 29th nor April 1st storms work out, I do feel it would be awfully difficult to see accumulating snowfall again this season given that the MJO would likely be headed into phase 2 by then. Long range guidance is already suggestion the western ridge to spread east by April 6th or so. We'll see what happens!
Enjoy the rest of your Sunday evening!
-Francesco Paparatto
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