New England April Weather Outlook: Cooler Start

April remains a highly transitional month with spring trying to tighten its grip while winter tries its best to hold on for a bit longer. Average high temperatures rise about 10-12° through the month. The jet stream also slows down and migrates northward, creating prolonged stretches of cloudy and unsettled weather.

Summary: This April is starting off active with highly variable temperatures. A generally cooler and potentially unsettled pattern is likely to set up for the first half of the month. Up and down temperatures will likely continue with more down than up through the first half. A general warming trend may ensue for the second half of the month, but this is far from locked in. Read below for the in-depth discussion.

TEMPERATURES

For the rest of the first week of April and into this weekend, New England's overall pattern will remain in place. This pattern involves a ridge of high pressure offshore well south of New England with troughing to the north and west. This setup has the jet stream positioned through New England, setting up a baroclinic zone (which is an area where a temperature gradient exists in an area of constant pressure).

Moving into this weekend, a trough will be digging into the central United States with waves of energy. An elongated frontal boundary will extend across the Ohio Valley into the northeast. The ridge over the southeast will likely slow down the progress of this boundary through the weekend. All of this will lead to continued changeable temperatures and sharp temperature gradients across New England through the first week of the month.

Heading into next week, a more amplified flow is expected to develop (which is when the jet stream becomes more wavy in nature with more pronounced troughs and ridges, as opposed to flat). An expansive ridge looks to build over the western United States with troughing across the east. This will likely set up a divide with sustained milder temperatures remaining across the west with more persistent chill in the east.

Below: Euro average height anomaly for April 7th to the 14th, showing the ridge-in-the-west-trough-in-the-east setup:

New England may end up more on the edge of the trough (on average, troughs and ridges remain in motion and are never truly static), especially heading into the latter part of next week. This means that while cooler weather is currently favored for all the east, the probability of this outcome is highest to the southwest, across the Mississippi, Tennessee and Ohio Valleys. This can be seen on the Climate Prediction Center's 6-10 day outlook, which has the highest chances of below average temperatures from south Texas through southern Ohio. New England may be able to see some form of warm-up later next week.

Heading into the middle of the month, there is little indication of any major pattern shift. Overall, minimal eastward progression of the overall pattern is expected, meaning the ridge-in-the-west-trough-in-the-east pattern is expected to generally remain in place. With that said, the pattern may de-amplify, allowing the ridges and troughs to become less pronounced. A less amplified pattern makes for more difficult forecasting in the long term, so confidence begins to decrease significantly heading into the second half of the month.

With minimal eastward progress in the over pattern through the first half of the month, however, cooler temperatures remain generally favored for the east. This doesn't mean it will be constantly cool as it is the spring and small-scale factors will lead to some milder days, however, there are currently no major signals for any sustained heat (multiple 70 & 80° days strung together) for New England.

Heading toward the second half of the month, there is a large spread in potential outcomes. While forecasting confidence will always drop looking this far out, the end of this month is particularly difficult to predict at this point. Overall, a gradual evolution of the pattern from the middle of the month seems to be the most favored outcome right now. This would involve a continued general de-amplification of the pattern and potentially more mild weather spreading across much of the country off the Pacific. This is very far from being locked in, however.

Overall, April is trending toward a generally cooler first half with limited mild days. A general trend toward more mild days may come as the month progresses. Remember, this is relative to average. Average temperatures rise a good 10-15° from the start to the end of the month, so the end of the month is naturally warmer than the start.

PRECIPITATION

New England is currently in a rather active pattern. With the jet stream generally cutting through the region, waves of low pressure have been frequently moving through, bringing rounds of rain, ice and snow. This higher activity will continue through this weekend. A quick moving system will bring another round of showers and mixed precipitation tonight into Thursday. Heading into the weekend, the offshore ridge of high pressure will cause a frontal boundary to slow down and become stationary near New England, setting up another weekend with multiple rounds of precipitation.

This boundary will likely lead to a significant flood threat from Arkansas through southern Indiana in the coming days. With general troughing in place, it could help keep more unsettled weather around for much of April. Overall, there aren't any strong signals either way for New England, and when this happens, the best course of action to go with near average for total precipitation for the month as a whole.

While progress has been made on New England's drought over the past couple months, it does remain in place. A near to slightly below average March for precipitation occurred across areas where the drought is deepest. These areas still have a deficit of 5+" of precipitation since the fall, when the drought began.

Below: Current US drought monitor status:

LOOKING BACK

Overall, we predicted an up and down month with both winter and spring getting wins. We predicted a near average month temperature-wise due to warm spells and cold spells canceling each other out. The milder times generally won out more often than not with all major climate sites in New England recording a top 20 warmest March on record. We also stated that the best chance for warmer weather would be confined to New England's west. This did pan out, with more widespread warmer conditions across western New England and points west, as seen on the map below.