New England Weather Discussion

Current Temperature: 59.3°F (0.9) 
High Temperature for the day: 59.3°F
Rainfall Today: 0.00 inches
Current Dewpoint: 57.9°F (0.9)
Find all of my instrument readings here.

Last update: 7/28 - 5:53 PM

Skies will clear out tonight and will cool air in place, temps will drop into the 50s here in Southern NH.  A complicated set up for Thursday with mutiple waves of low pressure crossing New England. Some will bring showers and the threat of a thunderstorm or two. At the moment it looks like the most severe weather remains south of the Monadnocks. If you were expecting, or hoping, for some hot summer weather, you won’t be seeing any for the rest of July. The hot summer air has been bottled up in the mid west and west for most of the summer. Frankly, personally, I think this has been one of the worst months of July in memory.

The Details:

High pressure centered to our northwest will crest over the area tonight before shifting offshore tomorrow. A seasonably dry airmass will be over the region tonight as dewpoints will be in the upper 30s to mid 50s. Cresting high pressure will lead to mostly clear skies and light winds allowing for radiational cooling tonight with lows dropping to near 40F in northern valleys to the mid 50s across southern urban centers. Despite the dry airmass, efficient cooling tonight will allow for areas of fog to develop, especially along the CT River Valley and northern valleys.

High pressure shifts offshore Thursday with return flow advecting higher dewpoint air back into the forecast area. All the while multiple short waves will be translating through the persistent mid- level trough that has dominated our weather pattern the past several weeks. Mesoscale guidance shows that with multiple short waves there will be a triple barrel low/multiple mesolows approaching from the west Thursday afternoon.

The general consensus is that at least one low center will pass to our north and another low center passes to our south with middle low passing near overhead Thursday night. This setup, with at leas one mesolow passing to our south, will keep a warm front from advancing farther north than southern New England as well as keeping the best instability to our south.

For the most part, am expecting the first half of Thursday to be dry with increasing clouds from southwest to northeast. Showers with embedded convection are expected to develop over New Hampshire by mid-afternoon spreading into western Maine by early evening. Precipitable Water estimates will run around 1.5 to 1.75 inches and with elevated instability moderate to potentially heavy rainfall can be expected late Thursday into early Friday morning. Weather Prediction Center has the entire forecast area outlined in a marginal risk for excessive rainfall, which seems reasonable given the antecedent wet weather pattern and the potential for heavy cells to track over the same area. However, current Quantitative Precipitation forecasts are between 0.75 to 1 inch, which should not bring much in the way of hydrologic impacts, although will need to watch for training convection.

There are signs that as we head into the middle part of next week that there will be a change in the weather pattern. For much of July we have been dealing with an east coast trough of low pressure with a west coast ridge of high pressure. The new pattern that appears to be setting up has a trough of low pressure over the middle of the continent and an upper level ridge developing off the east coast. This could promote a Bermuda High surface weather pattern just beyond this long term period. Before we get there on Tuesday and Wednesday we will be in a more zonal flow with moderating temperatures and no significant rain makers.

If you`re looking for a typical summer day, today will defintely dissapoint. With occlusion just our south, and fairly strong surface high centered over Nova Scotia, onshore flow at the surface, and moist southerly flow aloft will bring a lot of clouds, and keep temps mostly in the 60s. The warmest spots will be in the CT River Valley and in the mountains on the NW sides of the slopes, where the downslope will allow for added warming and some breaks of sun. There`s some scattered light showers moving through NH this morning, which will weaken in the face of ridging aloft before they make it into ME, and will eventually wind down by this afternoon as the warm air advection aloft weakens as well.

Cloudy tonight with a chance of drizzle along the coast and here in Southern NH. Otherwise it will remain cloudy with temps falling off a little but lows will mostly fall into the 60-65 range, except for the mid-coast and the ME mountains where lows make it to the upper 50s. There`s till a slight chance of a stray shower popping up, given the weak warm air advection aloft, with the best chance along the international border as a weak wave passes across Quebec toward daybreak.

On Wednesday the surface front begins to make some headway into southern and western NH. This may allow some breaks of sun in NH by midday, and temps to rise into the mid 70s to around 80, while the marine layer will remain tough to break in ME, with mostly cloudy skies and highs in the low 70s, except mid to upper 60s mid-coast. Also on the rise will be dew point temps, as they work into the mid-upper 60s. More humid. After some spotty drizzle in the first part of the morning, I think the day will be mostly dry, but approaching weak wave from the west, will allow for a very weak cold front to approach from the west. This will produce a line of showers and thunderstorms, probably not moving into the W zones until late afternoon, and spreading E toward sunset. Given the increasing instability as well as the strengthening flow aloft, could see some significant wind gusts with this line as well.

A trough of low pressure will begin the long term portion of the forecast Wednesday night triggering showers and with sufficient instability, perhaps a thunderstorm across the region. In agreement with the Storm Prediction Center with the marginal chance for a strong to severe storm to potentially be over the Connecticut River Valley. Chances remain high over southernmost New Hampshire as well. Meanwhile, a southerly flow will allow for patchy drizzle and fog to move in off the Gulf of Maine which will last into Thursday morning.

There will not be much in the way of push to this front over the weekend. This system will likely get hung up across southern New Hampshire and southern Maine, allowing for more scattered showers and storms on Saturday and Sunday. This unsettled pattern may last into Monday.

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