So far this winter has thrown the entire kitchen sink at us. Record temperatures in December, a Roidzilla for most in January, and sub-zero temperatures earlier this month. These have been the highlights. I think most would agree this has been a divided winter. Areas N&W of NYC are well below their seasonal snowfall while those in and S&E of NYC reached or surpassed their seasonal snowfall. Only 1 more week of February is left. This means we're down to our last week of Meteorological Winter.
Light to moderate snow may be coming down Tuesday afternoon as a weak wave tracks up the coast. Snow should change to a mix then rain by late Tuesday. A minor 1 to 2 inches of snow is possible for those N&W and N&E of NYC. Some models are showing much more in the way of accumulation but I do not think the wave is strong enough to support high precipitation amounts. Wave 2 will be stronger but since it will be tracking well west of the area that means temps will go soaring into the 50's so rain will be the main concern. Rain may continue through Thursday morning. Overall, a soggy and overcast week.
Once the storm tracks into Canada, it will shift winds from the south to the north and help bring colder air back into the area.
To finish out the month the GEFS and EPS are in agreement the NW flow will return and below normal temps are likely the 27th-29th. The trough axis does not support the development of any major snowstorms. The PV is over the Hudson and the flow across the country is more zonal than meridonial. We'll see as we get closer to this time frame if models begin showing any southern stream energy eject out of the STJ and possibly interact with upper energy out of the polar jet. That would support at least a moderate snowfall. At this time, models do not show that but instead think it'll be mainly cold with possibly an arctic front bringing light snow to the area.
The March 1st-5th time frame looks more favorable for winter storm chances. The PV is east of the Hudson and the trough axis is sharper. Additionally, the NAO looks to be negative at this time. This is shown by the higher than normal heights across Greenland into Baffin Bay / Davis Strait. The PNA will remain positive thanks to the anomalous trough over the Aleutian Islands and the AO will also remain negative. The key will be to see how much staying power this pattern has. If it's transient, it will be difficult for a storm to get organized in time before it breaks down. The timing will be critical for whatever upper energy we have to work with. So, keep in mind the March 1st-5th time frame for a possible winter storm. At the very least, it should remain cold (dating back to the February 27th period).
According to the CFS OLR forecast, the last week of February will feature impressive negatives over the Dateline which supports a trough over the Aleutian Islands and a ridge up the west coast. As we just saw, the Ensembles do a nice job of depicting just that. Notice by the time we get into March, especially after the 6th, the negative OLR anomalies begin to shift east closer to 120W than 180. With forcing shifting east, this will also push the trough over the NPAC east and break down the +PNA. If you think back to December and early January, this was basically the same situation where tropical forcing was east of the International Dateline.
The CFS Weekly does a nice job showing the NPAC trough gradually shifting east week 1 to week 2 of March. Notice the negative anomalies beginning to show up over the western U.S. with the higher heights focused across Canada.
The CFS is not the only piece of guidance showing this pattern change. The GEFS and EPS agree negative heights will spread into the west coast by the 6th of March. The ridge will shift into Canada and the flow across the U.S. will be mainly progressive with little amplification. We will see how deep the trough gets over the western U.S. The deeper the trough, the more amplified the southeast ridge gets over the east and the warmer our temperatures get.
While the mean trough will try to stay confined to the Aleutian Islands, it looks like lobes of upper energy will break off it and come crashing into the west coast to prevent the PNA from going positive. Again, this is reminiscent of the pattern we saw in early January. In December, the PNA was very negative and the east was seeing temps way above normal. I do not see that type of pattern returning just yet, but even early January was a frustrating time for winter weather lovers located in the east.
In sum, I think February 27th-March 5th will be a cold period with 1-2 winter storm chances. Once the 2nd week of March rolls around, I think the unseasonable colder air will retreat north and our temps will hover around normal to slightly above depending on how deep the negatives get in the western U.S. Normal temps for CPK NY in early March are in the lower 50's. If the aforementioned pattern comes to fruition winter will be coming to a vast ending sooner than later.
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