The weather across much of the country will remain rather quiet and low impact over the next week or so, mainly due to zonal flow setting up across the northern tier of the country. Zonal flow occurs when the jet stream is in a more stable state, lying "flat" across the United States. This allows for a strong west-to-east motion when it comes to weather events moving across the country.
A strong west-to-east motion allows for weather systems to move across the country fairly quickly. This also prevents large-scale, strong storms from crossing the country as the motion of the jet stream moves systems quickly across the country without stalling or gaining too much strength. Systems have trouble gaining much strength in this setup since they are moved through so fast, they simply don't have the time to organize.
A zonal flow is the opposite of what's called meridional flow, which is a stronger north-to-south motion. This is the pattern that is synonymous with larger-scale, more impactful storm systems. This is when the jet stream takes on much more of a wavy pattern, allowing for blocking of systems. In the winter, this pattern also allows for more extreme temperature contrasts, an important factor for (non-tropical) storms to strengthen. This becomes more important as we get later in the season.
The jet stream setup through much of the next week will be pretty close to the zonal flow image above, with some minor fluctuations (the jet stream is always moving and is never truly static in one place for extended periods of time). This will lend New England continued low-impact weather in what has been a very quiet stretch for a few weeks now.
Flow at 500mb (about 20,000 feet or jet stream level) late this week showing a quick, zonal flow:
While this setup does lend itself to low impact weather, it doesn't mean it will be perfectly quiet. As stated above, zonal flow lends itself to disturbances moving quickly through the area. In this case, a few quick shortwave disturbances will trickle through the region. The first of these comes today as a cold front weakens and eventually falls apart over New England. This could lead to a couple showers this afternoon and evening across western areas.
After this front, the next fast moving system will zip through Friday night into Saturday, delivering a better chance for a few showers across New England. Saturday doesn't look washed out by any means, but some shower activity will be around as the system quickly moves through the region. The afternoon may trend drier after a more unsettled morning.
CMC showing some wet weather around Saturday morning:
After that, the next frontal system looks to approach around Sunday night or Monday, bringing another chance for wet weather. At this time, generally zonal flow may begin to break down, allowing for a trough to hang around New England into next week. This would allow for cool air to push into New England and remain in place after the system with some true mid-fall temperatures by the middle of next week.
Weather map for Monday (October 7):
Zonal flow often pushes these systems to the north of New England. This naturally gives northern New England a better chance to see more in the way of wet weather. This can be seen in the current five day rainfall forecast (seen below). In between these systems, shortwave ridging and high pressure will set up, leading to nice and very quiet days. These days will be Thursday, Friday and Sunday. Zonal flow often leads to high and low pressure changing places over New England with neither dominating for an extended period of time.
Weather Prediction Center five day rainfall forecast. You can see generally more across northern New England, but still not much:
Temperatures will be around seasonable levels for the most part during this time, which is often the case with zonal flow. The exception will be Thursday and especially Friday, when a mini warm-up is expected. Widespread 70s are likely across New England with portions of southern New England making a run toward 80° on Friday. This will come as the persistent onshore flow gets replaced with a more southwest flow. Temperatures will gradually drop after Friday before the noticeably cooler air mass arrives next week.
Again, this zonal flow is looking to break down next week as an expansive ridge begins to take shape across the western United States, as mentioned in our monthly outlook yesterday. This will allow for at least cooler, fall-like air to move into New England with some seeing their first real taste of the new season amid potential troughing over the east.
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