A fast, zonal flow over the United States this week will lead to an active pattern that will see high and low pressure continue to trade places every couple days. This flow will bring a variety of precipitation types and variable temperatures across the region. As we mentioned in our monthly outlook yesterday, cold and mild air masses will be battling across the region over the next week or so, at least. This will lead to up and down temperatures and unsettled weather.
MONDAY & TUESDAY
Clouds will likely be stubborn to break apart for today after last night's clipper system, though some breaks in sun will be possible at times. As quickly as one system exits eastern Maine this morning, another enters western New England this afternoon. An area of low pressure will pass to the north of New England, dragging its cold front across the region overnight tonight into Tuesday morning.
Snow showers will likely break out across northernmost New England late this afternoon or early evening and gradually drop south through the evening. The southern edge of precipitation will likely be right near the northern and southern New England border, with only spotty rain showers potentially reaching northern Massachusetts. Warm air advection will keep this precipitation as a mix, or plain rain across southern New Hampshire and coastal Maine while farther north will see all snow.
Below: HRRR showing potential weather late this evening:
An additional 1-3 inches of snow will be likely tonight across the northern third of New England with 3-6 inches in the cards for northern Vermont and New Hampshire. Mixing and plain rain will keep snowfall limited significantly farther south in Vermont, New Hampshire and Maine. Snow and rain will dry up quickly in the early morning hours Tuesday as the cold front pushes southward.
Temperatures will need to be watched Monday afternoon as the day is starting out colder than anticipated. Temperatures should still reach the upper 30s to maybe low 40s in southern and central areas this evening, but it may end up taking much of the day to get there. The cold front will likely clear New England by Tuesday morning, bringing a very quick end to a little warm-up. This will lead to another day with a morning high and falling temperatures in the afternoon along with windy conditions.
WEDNESDAY
Wednesday will see a dome of high pressure move across the region, bringing quiet and cold weather to the region. Highs will likely range from the teens in the mountains to the upper 20s in southern New England. Both Tuesday night and Wednesday will be very cold, with sub-zero lows possible across the north.
THURSDAY
The region's next storm in this active streak will arrive by Wednesday night or early Thursday morning. This storm will involve a frontal system moving out of the Great Lakes and to New England's north while a smaller, secondary system moves to the south of New England, near the coast. These two systems will create a messy and raw day Thursday with multiple precipitation types on the table.
The exact timing and impacts of this system will come down to the strength of the secondary low off the coast. If this low is weaker and slower to develop, a warmer solution would occur with temperatures quickly rising and more by way of mixing and rainfall well inland. Should the coastal low become strong enough and develop quickly enough, it would keep colder air around longer, resulting in more snow across the north and a wintry mix across the south.
The current forecast represents a middle ground between the warmest and coldest scenario. This would bring a period of snow to just about everyone in New England at the onset Wednesday night into the start of Thursday. This would gradually change to a mix and possibly eventually plain rain from south to north during the day Thursday. The northern tier (including most of Maine) will likely remain mainly snow for the storm, although the exact northward extent of the mix line will be determined by the factor discussed above.
The timing of a changeover to a mix or rain across southern and central areas is uncertain. This will come down to the timing and placement of the secondary low. Should this low remain weak and slow to develop, it would allow milder air to rush into the region quicker. With that said, the storm will initially start out cold and cold air can be very stubborn to erode away, so it wouldn't be surprising to see the colder temperatures and wintry weather last into much of Thursday for those in the pink area above. It won't get truly warm on Thursday, with temperatures unlikely to make it out of the 30s for most.
Below: Model roundup (Euro, GFS, CMC and ICON) for Thursday afternoon:
With uncertainty surrounding precipitation types and timing, it's hard to give estimates on how much of any given precipitation will fall. Areas that do see mainly snow will have the chance for at least advisory-level snow (a few to several inches). Outside of that, estimates on snowfall farther south before a changeover can't be said at this time.
Below: Current probability of impactful winter weather Thursday:
The storm is a quick-mover and will likely be moving away from the region by Thursday evening and night with drying conditions. Typical upslope precipitation will likely continue for the mountains through the night.
FRIDAY
Thursday's system will have cleared out by Friday. New England will likely be caught between the departing low and incoming high, so it will likely be breezy, if not windy, amid the tight pressure gradient. Seasonable temperatures and variable clouds are expected.
WEEKEND
Zonal flow supports low and high pressure systems trading places with neither dominating for an extended period of time. This continues as high pressure builds in for Friday night and much of Saturday, bringing quiet weather and gradually calming winds for Saturday. The next bout of low pressure will move in for Saturday night and Sunday. This system may follow a similar setup to the Wednesday night to Thursday system, except this one will likely be stronger and have more moisture with which to work.
This storm is currently looking like it will track farther south than the Thursday storm. This would result in a colder scenario than Thursday with more snowfall farther south. A stronger storm would also allow for heavier precipitation rates. With that said, there remains a large spread in tracks among ensemble members, so uncertainty is very high with this one.
BEYOND
This general pattern we're in for this week will likely carry over into much of next week as well. Colder air will likely return after the Sunday storm, though temperatures may remain variable. We'll watch another storm around early to mid next week. Obviously there is much uncertainty, but the timing fits with the current pattern of a storm system nearby every few days.
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