Friday May 21 2021 Forecast (7:27AM)

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DAYS 1-5 (MAY 21-25)

Upper level high pressure dominates and will continue to do so through the weekend, but this doesn’t automatically mean clear skies, as you can see this morning as the sky is filled with much cloudiness from a disturbance from Canada. This is because the axis of the upper ridge is to the west and the air above us is blowing from northwest to southeast. We often see moisture and energy from the other side of the ridge, or the trough to its west, ride up and over the ridge and down its eastern side. This will continue to be the case through the weekend, which will certainly be no wash-out, but will carry opportunities to see showers (and even thunderstorms by Sunday) as a series of disturbances and finally a stronger cold front comes through. But before that cold front arrives and despite the northwesterly flow aloft, at the surface the dominant air flow is going to be from the southwest, which will work on warming our air up today and bringing the feel of mid summer along with slightly higher humidity for the weekend. Then the cold front will come through, and this sets us up for a dry and cooler Monday as high pressure drops out of Canada. But that high will keep on moving and by Tuesday it’ll be south of the region with warmer air coming back, along with more cloudiness and even another shower threat.

TODAY: Mostly cloudy to partly sunny. Slight chance of a shower mainly north and west of Boston until mid-morning and again late in the day. Highs 68-75 South Coast, 76-83 elsewhere. Wind S 5-15 MPH.

TONIGHT: Variably cloudy. Possible showers. Lows 53-60. Wind SW 5-15 MPH.

SATURDAY: Partly sunny. Isolated to scattered showers and a slight chance of thunderstorms mainly mid afternoon on. More humid, dew point upper 50s to middle 60s. Highs 68-75 South Coast, 75-82 southeastern MA not at immediate coast, and 83-90 elsewhere. Wind SW 5-15 MPH.

SATURDAY NIGHT: Mostly cloudy evening with possible showers. Clearing overnight. Areas of ground fog forming. Lows 58-65. Humid – dew point upper 50s to lower 60s. Wind SW up to 10 MPH.

SUNDAY: Mostly sunny morning-midday. Partly sunny to mostly cloudy with a chance of showers and thunderstorms afternoon. Humid – dew point 60s. Highs 85-92 except 78-85 South Coast and 70-77 Cape Cod. Wind SW 10-20 MPH.

SUNDAY NIGHT: Clearing. Lows 50-57. Much drier – dew point falling to 40s. Wind NW to N 10-20 MPH.

MONDAY: Sunshine and passing clouds. Highs 62-69, coolest coast. Wind N to NE 10-20 MPH, diminishing late.

MONDAY NIGHT: Partly cloudy. Lows 48-55. Wind variable up to 10 MPH.

TUESDAY: Variably cloudy. Chance of showers. Highs 70-77. Wind W 5-15 MPH.

DAYS 6-10 (MAY 26-30)

Early for too many details but a shot of heat possible May 26 with showers/thunderstorms possible, cooler/drier following by May 27 then high pressure may hold over the region with dry weather and a warming trend thereafter.

DAYS 11-15 (MAY 31 – JUNE 4)

Low confidence forecast. High pressure may keep the region dry through May 31 followed by an increase in shower chances sometime in the first several days of June as an air mass boundary may be in the area.

29 thoughts on “Friday May 21 2021 Forecast (7:27AM)”

  3. Thanks TK.

    I was hoping that the 90 degree heat would arrive much later rather than sooner. Oh well.

    1. Thank you. It was great. I got some beautiful pics at the pond, went out with my son for ice cream and then we watched something together we’d been looking forward to seeing. 🙂

  14. Thanks, TK…

    It was 25 years ago today (almost to the hour!) that the Brockton area was hit with a bow-echo storm with 70-100 mph winds.

    Here’s a write-up:

    Bow Echo enters Brockton MA on May 21 1996

    A strong cold front moved across the region during the mid to late afternoon of May 21st, producing strong thunderstorms and numerous reports of damaging winds. A downburst occurred in the Brockton MA area, producing winds estimated at 70 to 100 mph and causing extensive damage. A Severe Thunderstorm Watch was issued for all of southern New England; subsequently, Severe Thunderstorm Warnings were issued for Hartford, Tolland, and Windham Counties in northern Connecticut, and for Hampden, southern Worcester, Plymouth, and Barnstable Counties in Massachusetts.

    In the image, note the “horseshoe” pattern of the line of thunderstorms south of Boston. Dry air is being drawn into the rear of this storm. The evaporation and cooling caused as this dry air entered the storm resulted in the downburst that moved through the Brockton area. Also note the thin line from Middleboro MA to East Greenwich RI; this is the leading edge of the cool air outflow from these thunderstorms.

    Here’s the image of the bow echo from BOX radar:

    https://imgur.com/jL9aNiG

    1. I left my weather job in Bedford MA at mid afternoon that day with SAK and we picked up my girlfriend who lived in Medford and also a weather enthusiast and headed south to chase. We got right behind that cell on Route 3 and it may be fortunate that we were held up by traffic because our target location would have put us right in the worst of that. While it would have been amazing to witness, the amount of damage that we saw coming in behind just as the storm departed was enough to make me feel lucky to have not been in it. We’d very possibly have been hit or at least trapped on a street somewhere. That was the most damage I have ever witnessed from any storm in person.

    2. Thanks, Captain and TK

      I don’t recall this. It wasn’t the same system that hit the western MA area was it?

      1. It was all part of the same event. Strong cold front sweeping across the region into a warm muggy air mass. I remember getting to work that day and making a plan to chase very early.

        1. Ahhh then I remember it well. My oldest and a friend were camping in the north Hampton area. They were grooming for their trainer at a show. I suspect I was too focused on finding out if they were ok.

          Thanks TK

        2. As I say this, I have a feeling the tornado in western MA was earlier than 96. Would there have been one around the Northampton area earlier in 1996?

          1. The only weather event from 1996 that I recall vividly is the massive flooding that October.

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