April Outlook Update: Lingering Chill Possible in New England, Northwest as the Plains, Rockies Bake

Chris Dolce
Published: March 30,2017
Stubborn cool weather may hang on in parts of the U.S. in April, but warmth that will linger into early summer is still expected for most of the country, according to the latest three-month outlook from The Weather Company, an IBM Business.
New England is among the areas that may spend much of the month chillier than average, thanks to a pattern that largely took shape in March, punctuated by Winter Storm Stella.
"This minor pivot in the pattern, along with the copious late-season snowpack across New England and southeast Canada, have locked in a colder pattern that has been very difficult to break," said Dr. Todd Crawford, chief meteorologist with The Weather Company.

April 2017 temperature outlook.

Crawford said the reflecting influence of the New England snowpack has a greater influence in spring, and may help to keep the air mass colder at least through the first half of the month.
Conversely, the greatest chance of above-average April temperatures continues to be in the nation's heartland and Rockies.
(MORE: The U.S. Saw a Mild, Wet Winter)
While La Niña is officially over, the atmosphere still showing a hangover from La Niña.
"Anomalously warm sea-surface temperatures near and east of the Indonesia/Maritime Continent are still persisting, and since they drive the anomalous convection that has produced the La-Niña-like pattern this winter, we don’t see any clear reason why the atmospheric response to La Nina won’t hang around for a while," said Crawford, chief meteorologist with The Weather Company.
(MORE: When is the Last Freeze, Typically?)

May 2017 temperature outlook.

The start of summer in June could then usher in an intensification of the warmer-than-average conditions east of the Rockies given the transition from the La Niña event we just saw to the potential development of El Niño conditions later this year.
NOAA has placed the odds of El Niño developing at 50 to 55 percent in the July-December timeframe, though it mentions there is some chance it could begin to emerge earlier. El Niño is the warming of the equatorial central and eastern Pacific Ocean temperatures, which can have wide-reaching impacts on weather patterns across the globe depending on its strength.
"Typical transitions from La Niña to El Niño conditions result in cooler summers overall, especially late; our forecast reflects this warmest-early, coolest-late idea, but is not particularly cool given the recent pronounced global-scale warming after the last historically-strong El Nino event along with the expected negative NAO conditions driven by historically-low Arctic sea ice levels," said Crawford.
(MORE: El Niño Could Return During Hurricane Season)
June's forecast map reflects the potential for a hot start to summer with the potential for much above average warmth overall along the East Coast. Above-average temperatures are also favored throughout a large swath of the nation's southern tier plus the Ohio Valley and Great Lakes.
"We think any big eastern heat will be more likely to occur earlier in the summer," Crawford added.

June 2017 temperature outlook.

The only area where the start of summer may be near or slightly below average is in the northern Rockies and northern Plains.
(MAPS: Average Highs and Lows By Month)
This outlook is an overall trend for the three-month period April-June. An individual cold front or an upper ridge of high pressure could lead to a brief period of colder or warmer weather, respectively.

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