Posted: 8:08 am Thursday, February 22nd, 2018
By Kirk Mellish
If you follow me on a regular basis then you’ve had weeks of advanced notice of a cooler pattern change for March.
In several previous blog posts I’ve shown the crazy links to past extreme weather that has occurred following similar weather patterns to those evolving this year. Most recently here.
It is not unusual to have warm surges in the East part of the country in February in a La Nina. Over half of NYC record highs in February for example have occurred in La Nina winters.
It turns a little cooler by next week but still warmer than normal for this time of year.
Anything more dramatically colder will have to wait until we get further into March, even then it looks like a step-down process.
It is too early to tell if there will end up being any hard freeze or any precipitation type concerns, but it’s a worry on the table.
The jet stream patterns in the Atlantic (AO/NAO) are favorable for extreme weather in March, but importantly SO FAR anyway, the Pacific jet stream patterns (EPO/PNA) are not or are much less so.
At least that is what computer equations show. However, as discussed previously, more organic non-model methods are sounding the alarm for at least the potential for dramatic cold and some winter precipitation risk. The prospects of a March ‘Nor Easter snowstorm for Mid-Atlantic or New England is certainly present.
The NAO is projected to reach its lowest negative since 2010.
(Source: Commodity weather)
Looking back at history when Dateline-Greenland-NE Canada blocking of the jet stream this has been the past result on average:
But as of now signals conflict as to if that pattern will prevail for much of March and into April or if it would only last a couple weeks.
So when does it start? It’s a step-down process:
So a return to below-normal temperatures next month is likely. However, big questions remain unanswerable as to the magnitude and duration of any cold air mass and if the marginal lows in the 30s will be in place with any winter storm system that may form.
(Virginia Weatherman annotations)
Right now I’d ESTIMATE highs in the 50s if it’s sunny and highs in the 40s if cloudy, so no extreme cold foreseen yet. But IF much colder than that is coming I would NOT expect models to be able to pick up on it this far in advance given the abnormality of the jet stream patterns.
As I reminded in previous post, beyond March 10 any noteworthy winter precipitation is awfully rare although it has happened as late as April, and a TRACE of snow as late as June (1955).
I noticed that records show in all past March snows of 2 inches or more ALL but one had a high temperature the day before of about 50F or above. One had a high of 61F the day before with 52F just 12 hours before a 4.2 inch snow in the city (2009).
Mother nature followers her own calendar not ours, as we’ve seen with our May level temperatures here in February.
AVERAGE LAST FREEZE DATES:
FROST can occur at air temps above 32 Check here for LAST FROST DATES.
If you look at the ENSO region NINO 3.4 ONI to find analogs and combine them with the similarities discussed in the previous blog they too show similar results for March. This is what they show for April. Again, it’s a correlation from teleconnection analogs not a forecast but can be used as one guidepost:
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