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Premium: Another ULL next week, warm temperatures follow

It’s May 11th, which means it’s getting in the late meteorological Spring season. Many of us often look forward to even warmer weather as we approach Memorial Day weekend and the beginning of meteorological summer. But the seasonal trends with blocking causing cool air intrusions are continuing over the last couple weeks, with omega blocking becoming a dominant presence. Now some high-latitude blocking is returning again for another cooler week of weather. But how cool will it actually be? And when will warmer weather return? We discuss more details on the overall pattern evolution for the rest of this month.

We start with a -EPO blocking ridge over Alaska. Shortwave energy coming downstream of this ridge will phase into a closed upper-level low over the Great Lakes later this week. Initially, this will cause heights to build over the Northeast. At the surface, high pressure will build over the Western Atlantic. More southerly flow around this high pressure will cause temperatures to rise near or slightly above normal for this coming Wednesday and Thursday.

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Premium: Warmer than normal temperatures by late May

The news many have awaited for several weeks is finally here: We are forecasting the return of above average temperatures by the end of May. For the past few weeks, the hemispheric pattern has been stuck in a bit of a rut. High latitude blocking has maintained its control over the pattern, on both the Pacific and the Atlantic sides, forcing the development of anomalous cutoff lows and troughs into the Northern 1/3 of the United States. Colder than normal air with unsettled weather has been the dominant sensible weather in our area.

The transition out of this pattern is already underway. While high latitude blocking on the Pacific side (a -EPO) will again flex its muscles late this week, it will be more of a parting shot than anything else. An upper level low will form, as a response to the -EPO ridging, and push into the Great Lakes. But its presence will be mainly progressive, as a front swings through our area and the upper level trough elongates and moves to our northeast.

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(Premium) Long Range: Is the End of Winter in Sight?

In the world of meteorology, Spring begins on March 1st. While the calendar doesn’t turn until the end of the month, meteorologists end winter statistics on the last day of February. Some winters, however, have featured major cold or snowstorms well into March and even April. Remember last year? Still, a year makes a big difference, as they say, and there are growing signs that after this week, cold and snow will become increasingly unlikely.

Looking back at February, temperatures will likely average above normal throughout the area. While we saw the first below zero temperatures in New York City in over two decades on Valentines Day, much of this month featured near or above average temperatures. Artic cold airmasses didn’t hang around for more than a few days. A couple of winter storms we saw earlier in the month tracked too far east to give the entire region of significant snowfall. And in the past two weeks, we have seen a storm track farther west with warmer air and heavy rainfall, as cold air moves in behind the storms.

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(Premium) Winter storm threat next week

Forecast models continue to show a classic pattern progression across the Northern Hemisphere over the next several days, with a continuation of a wave progression that favors the development of a Western USA ridge and Eastern USA trough by the beginning of next week. The redevelopment of this large ridge in the Western USA, extending northward into British Columbia, is expected to be the focal point for the potential development of a storm system in the Eastern USA between February 24th and 28th.

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