As of Wednesday morning, a warm front continues to push through New England. Showers associated with the front will continue to weaken and break apart as they move out of Massachusetts and New Hampshire and into Maine. The rest of the day will feature gradual clearing and warming will occur as warm air advection continues on a southwest flow.
Temperatures today should reach the 60s across northern New England and the low to mid 70s for southern New England. A temperature inversion and some clouds may prevent temperatures from reaching their full potential today as opposed to the setup for Halloween. Temperatures will be much cooler for Maine today as the warm front stalls out in the western part of the state. Highs in Maine will likely remain in the upper 40s to mid 50s.
Below: Euro showing potential temperatures early this afternoon:
The southwest flow will increase dew points to the upper 40s and 50s within the warm sector of the warm front, which will finally cross Maine tonight. This will keep overnight lows fairly mild, with air temperatures only falling to the 40s and 50s.
With all of New England firmly within the warm sector on Thursday along with high pressure set up to the southwest, more sunshine and good mixing, it is a perfect recipe for one of the warmest Halloweens on record for New England. Highs will be in the 70s for most, if not all, of New England with the typical warm spots of southern New England pushing toward the 80° mark.
Aiding these record high temperatures will be the strong ridge of high pressure to New England's southwest. Very warm air (for the time of year) will be over New England aloft. On Thursday afternoon, temperatures at the 925 millibar level (about 2,500 feet above sea level) will push to the upper 50s to mid 60s. With good mixing and sunshine, this is what will allow temperatures to get so mild for Halloween with 70s to low 80s at the surface.
Below: Expected temperatures at the 925mb level on Thursday afternoon:
These warm temperatures aloft (and at the surface, of course) are being provided by a strong ridge of high pressure over the southeast. The ridge will reach a height of around 588 decameters with New England seeing a height of 575-585 decameters. Basically, the higher the height of the ridge is, the stronger it is. The ridge will begin to flatten on Halloween, but the better conditions for temperatures (more sunshine, better mixing) will allow Halloween to be the warmest day.
Below: Euro showing geopotential heights Wednesday evening, showing the expansive 588 dam ridge over the east:
For comparison, the major June heat wave had a height of nearly 600 decameters. In mid-June, this brought temperatures well into the 90s. So, to get a ridge height in the 580 dam range at the very end of October is notable and will produce plenty of 70s to low 80s this time of year. This is, of course, if smaller scale factors cooperate for warm weather as well, which they will in this case.
A cold front will slip through New England on Friday, but the cooler air will likely lag behind the cold front, so, as a result, Friday's temperatures will be mild as well. Widespread highs in the 60s and 70s will likely continue for a third day. The real cooler air will be felt over the weekend with a return to the 50s as a secondary cold front moves through New England.
This morning's showers have provided temporary relief from very high fire weather concerns, but very warm temperatures and increasingly windy conditions will raise the threat level for Halloween through the end of the week. The 0.1-0.3 inches for southern New England is better than nothing, but it will take a widespread, soaking rainfall to end this fall fire season for New England. According to Massachusetts officials, over 100 fires have burned 548 acres over the past week. The largest being the Salem and Middleton fires.
Below: National Interagency Fire Center significant fire potential for October 31:
Right now, a soaking rain isn't really in the cards, unfortunately. The cold front on Friday will provide very limited shower activity, if anything. The next chance for rainfall for New England will come early next week as an area of low pressure passes well to the north of New England. Like previous events, this will likely bring the most rainfall to the northern tier of New England with more minimal shower chances south.
Below: Weather Prediction Center 7-day rainfall outlook:
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