DAYS 1-5 (MAY 9-13)
Forecasts always present challenges in the longer term as it’s naturally more difficult to predict the air flow through the atmosphere and its impact on a given region the further out from “now” you get. Sometimes those challenges are realized in a much shorter term. Such was the case yesterday. Yes, the forecast was “right” in terms of a warm front causing one swath of showers and embedded thunder earlier in the day and then an approaching cold front setting off showers and thunderstorms later. The hail potential was definitely realized in the storms with many reports of it across portions of southern New England. What was a bit of a surprise was the coverage of the second round of activity, and the persistence of it. I was definitely lead a bit astray by buying too much into shorter range guidance that had the activity, but less widespread and of a shorter duration. But now that show is over, and we have some other forecast adjustments to make. You might recall several days ago I indicated some hope for Thursday in a longer stretch of unsettled weather starting Wednesday, then abandoned the idea based on more pessimistic looking guidance. Well, once again, should have stuck with the other idea. High pressure indeed noses its way in enough to give us a fairly decent day today. While we won’t have wall to wall sun, there is a good mix of sun and clouds across the region to start the day, with some high clouds streaming in from the west above patchy lower level stratocumulus clouds drifting north to south. This north-to-south motion is indicative of that drier air flow at the surface, and the difficulty of the higher clouds from the west to overspread and thicken during the day today indicate somewhat drier air above us too. It is tonight, finally, when a wave of low pressure approaches New England from the southwest, and the surface wind turns more northeasterly, that we’ll see clouds collect in a more concentrated fashion. A few of the lower clouds around during the day can build up just enough to produce a few rain showers mainly over southern NH and the northern half of MA, but these will be rather isolated. From late evening tonight to the very early hours of Friday morning, we can see an area of rain from the low pressure area to our southwest moving into the region, only to be obliterated by a renewed push of drier air. While I expect cloud cover to be more dominant on Friday than it will be today, the rain chance will likely be held at bay again after that initial push, for most of the day and into the evening. Finally, the low pressure area makes its closest pass Friday night and first thing Saturday morning as it slides east northeast, to our south. This is when a little more wet weather can occur, but most of it looks like it will be toward the South Coast, especially Cape Cod, while much of the rest of the region may be spared or just see brief light rainfall. Behind that, a shift of wind to the north will dry the region out again, and breaks in the clouds allow partial sun for Saturday, which is definitely a more optimistic outlook than I was carrying before. Does this means the entire weekend is saved? Probably not, because it still looks like another upper low and associated surface trough will drift eastward into the region on Sunday when I cannot rule out some showers, but some guidance does keep the region mainly dry for much of the day, so the potential definitely exists to salvage much of the weekend rain-free. Monday’s weather looks ok as upper level low pressure starts out nearby then shifts to the east, with a sun/cloud mix and maybe a pop up shower.
TODAY: Sun/cloud mix. A possible shower favoring southern NH and northern MA late afternoon. Highs 57-64. Wind NW 5-15 MPH, higher gusts.
TONIGHT: Mostly cloudy. Chance of light rain favoring central MA, eastern CT, and RI late evening / overnight. Lows 46-53. Wind NE 5-15 MPH.
FRIDAY: Mostly cloudy. Potential for early-day rain favoring the South Coast. Highs 55-62, coolest coast. Wind E 5-15 MPH.
FRIDAY NIGHT: Cloudy. Rain returns to areas mainly near and south of I-90. Patchy drizzle possible elsewhere, especially eastern coastal locations. Lows 46-53. Wind NE 5-15 MPH.
SATURDAY: Early-day rain potential for South Coast / Cape Cod, and patchy drizzle possible eastern coastal locations, otherwise clouds break for partial sun with a chance of an afternoon pop-up shower. Highs 57-64. Wind NE to N 5-15 MPH.
SATURDAY NIGHT: Mostly cloudy. Lows 45-52. Wind N to NE up to 10 MPH.
SUNDAY: Mostly cloudy. Chance of showers, mainly late in the afternoon. Highs 57-64. Wind NE to variable up to 10 MPH.
SUNDAY NIGHT: Mostly cloudy. Chance of showers. Lows 48-55. Wind variable up to 10 MPH.
MONDAY: Variably cloudy. Chance of a shower. Highs 58-65. Wind variable 5-15 MPH.
DAYS 6-10 (MAY 14-18)
Early period milder and fair weather expected with a short-lived southwesterly flow as high pressure shifts offshore and a frontal boundary sits to the north and west. After this, a cooling trend and occasionally unsettled with some wet weather episodes middle to latter part of next week. More precise timing and details TBD of course.
DAYS 11-15 (MAY 19-23)
Medium range trends point to fair, cool then milder weather to start this period then a return to somewhat unsettled weather later in the period.