A Mild October Continues
Earlier this evening on Twitter I mentioned how mild its been, and in came the tweets about how gardens are going on strong well into October!
To date, 13/16 days in October have been at or above average in terms of temperature. For the month, the average temperature is +4.1ºF, which is a pretty significant departure from average. Many have yet to see a frost (certainly not a hard freeze). So not only are gardens and farmer’s markets still alive and well, but mosquitoes and ticks are still lurking out there in spots, too.
That mild trend will continue for the rest of this week, as system after system try to move toward us and weaken/pull up to the northwest of us as they do so. The mean trough position has been in the Midwest, and that’s where the cold air has been living too. Over us, a ridge has generally dominated and kept conditions mild. But there are signs that this party may be over soon, so soak it in while it lasts!
Current 500mb anomalies over U.S., with trough over middle of nation and ridge across Northeast
For the short-term, we’ve just got a lot of clouds to deal with. Mainly cloudy skies and areas of fog will persist tonight as dew points rise into the mid 50s. So a mild night, with temperatures staying in the 50s and a slightly muggy feel. A stray shower or sprinkle can’t be ruled out, but most areas stay dry.
Low clouds will hang on for the first half of the day on Thursday, but will start to erode as we head past lunchtime. Again, there may be a brief stray shower or two early. The only real question is how much sunshine we actually get. If the clouds completely part, we’ll blast up into the 70s. I’m thinking somewhere a bit shy of that though, with some sunshine and highs in the low 70s. Still very enjoyable for October 17th. But the clearing will be short lived, as an wave of low pressure rockets up through the Northeast Thursday night. This will likely trigger a batch of quick-moving heavy rain, which will drop 0.5-1.25″ of rain on areas NW of Boston. Lesser amounts are likely SE of Boston, more on the order of 0-.25″. So not much in the backyard rain gauge for the Cape & Islands, but a heavier dose for NH, VT, and WMass. There quite a bit of water vapor in the atmosphere for this time of year, with PWAT values (precipitable water) about 2x the normal amount. So where it does rain, it will pour!
NAM rainfall forecast through Friday. Shows idea of heavier rain NW of Boston Thursday night/Fri am, much less SE of Boston
That rain will exit as rapidly as it arrives, and will probably be long gone by Friday morning. Skies will clear out Friday, with a gusty west wind developing and topping 25mph at times. Temps will stay mild in upper 60s to near 70. We’ll keep comfortable weather around for Saturday, with highs in the mid 60s and a mix of sun and clouds. The next weather-maker will be a cold front Saturday night into early Sunday, bringing a few showers and a shot of cooler air. Conditions are looking pretty favorable for the Head of the Charles Regatta, and (if necessary) Game 6 of the ALCS at Fenway Park.
Next week is where things will get interesting. A barrage of short-waves will try to push a trough in the jet stream farther east into our neck of the woods. The question is how far east the cold air will get, and how cold will it actually be. Some solutions predict snow in New England and finally a widespread freeze as we head into the October 24th-27th time frame. May be overdone, but this signal in the models has been there for a couple of weeks now and has remained persistent. So in any case, the coldest air of the season may filter in right before Halloween. Frightening indeed!
Surface temperature anomalies for next Thursday (GFS)
Interestingly, this all has to do with Typhoon Wipha. It’s now an extra-tropical storm heading east of Japan. It will blast into the Aleutian Islands of Alaska by Friday morning bringing hurricane force winds and 40′+ waves! But it will also help build heights in the atmosphere out ahead of it. That building ridge in the west will in turn send a trough digging down across the Midwest and Northeast, and produce our cold air outbreak. The beautiful thing about weather is – it’s all connected.