DAYS 1-5 (JULY 1-5)
July opens with an unsettled, warm, and humid day today. Abundant cloud cover starts the day as a disturbance moves by. There are showers most concentrated closer to the South Coast, with offshore thunderstorms, otherwise most of the activity with the disturbance is passing by to our north. Low clouds and fog exist under the disturbance-related cloud deck especially toward the South Coast. The key to today’s forecast, in terms of shower and thunderstorm chances for this afternoon and evening: How much clearing out occurs, which would result in a more unstable atmosphere and better chance for showers and storms. These will also be triggered by a slow-moving cold front entering our region late today and this evening. This front’s progress looks even slower to me than it did just 24 hours ago. Even without the help of much sun, there will still be a shower and thunderstorm threat, and the slow-moving boundary can allow some areas to see several hours of heavier rainfall, leading to local flooding. Severe weather (hail, wind damage) would become more likely if we have more sun leading up to these, so this will be something to watch during the day. The activity continues into tonight as it slowly presses to the southeast. Wednesday was once a “clean” forecast from me in terms of rain chances, but I can no longer rule out the redevelopment of at least a few showers and thunderstorms with a frontal boundary that will have barely made it southeast of the I-95 corridor by morning, and may take all day to finally move offshore. Areas to the west and north will be dry throughout Wednesday. Thursday’s forecast remains the same – a warm day, with a trough and pool of chilly air aloft swinging through, and while the focus of this is to the north, with the help of a trough we can see showers and thunderstorms develop and move across portions of the WHW forecast area in southern New England during the later afternoon and evening. This feature departs by early Friday, setting up a very nice Independence Day with sun and fair weather clouds, no rain threat, low humidity, and seasonably warm air. High pressure will remain in control with continued fair weather and somewhat warmer conditions for Saturday.
TODAY: Clouds dominant this morning including areas of fog especially south of I-90, along with passing showers also more likely south of I-90. Sunshine at times midday into afternoon, with isolated showers and thunderstorms possible, may become more numerous later in the day. Highs 83-90 except cooler South Coast / Cape Cod. Dew point reaches 70+. Wind SW 5-15 MPH, higher gusts especially this afternoon.
TONIGHT: Mostly cloudy. Showers likely with a chance of thunderstorms. Areas of fog. Lows 66-73. Dew point falls slowly into 60s. Wind SW to variable up to 10 MPH, but can be gusty around any showers and storms.
WEDNESDAY: Sunshine dominant north and west. A sun / cloud mix south and east including the chance of isolated to scattered thunderstorms from mid morning through mid afternoon. Highs 81-88. Dew point falls slowly to below 60 from northwest to southeast. Wind shifting to W 5-15 MPH but can be variable and gusty around any showers and storms.
WEDNESDAY NIGHT: Mostly clear. Lows 61-68. Dew point in 50s. Wind W up to 10 MPH.
THURSDAY: Mostly sunny to partly cloudy. A shower or thunderstorm possible in the afternoon mainly northern MA and southern NH. Highs 82-89. Dew point returns to 60+. Wind W 5-15 MPH.
THURSDAY NIGHT: A shower or thunderstorm possible early, then clearing. Lows 58-65. Dew point falls below 55. Wind shifting to NW 5-15 MPH.
FRIDAY (INDEPENDENCE DAY): Sun and passing clouds. Highs 77-84. Dew point 50s. Wind NW 5-15 MPH.
FRIDAY NIGHT: Mostly clear. Lows 60-67. Dew point sub-60. Wind NW to W up to 10 MPH.
SATURDAY: Mostly sunny. Highs 80–87. Dew point near 60. Wind W 5-15 MPH.
DAYS 6-10 (JULY 6-10)
Heat and humidity July 6 with fair weather. A frontal boundary moves into the region July 7 with high humidity but a chance of showers / t-storms. Weather from July 8 through 10 to be determined by how long that frontal boundary hangs around. Reliable guidance currently indicates little movement of the boundary – more of a gradual dissipation, with a daily chance of showers and thunderstorms into the middle of next week. Temperatures July 7-10 still average a little above normal, skewed more by overnight lows.
DAYS 11-15 (JULY 11-15)
Trend on guidance is to keep that pattern of low pressure and wet weather to the south, high pressure to the north. Today’s indications are a little less high pressure here with additional shower and thunderstorm chances into mid month, and not a lot of influence from Canadian air masses. This is a little inconsistent with previous guidance. Will revisit this next update. Take-away is a somewhat uncertain forecast, leaning toward a few shower and storm chances but no persistent major heat.