Severe Weather & Heat Coordination Message #3 – Thursday 8/12/21-Saturday 8/14/21 Severe Weather & Heat Wave Potential

Hello to all…

..Intense Heat and Humidity is expected Thursday and Friday, possibly extending into Saturday. With the intense heat and humidity, it will bring with it the potential for isolated to scattered strong to severe thunderstorms through this period with strong to damaging winds, hail, frequent lightning and heavy downpours leading to urban and poor drainage flooding as the main threats..
..The Storm Prediction Center (SPC) has placed Western Massachusetts and Northwest Connecticut in a slight risk for severe weather with much of the corridor along and northwest of I-95 in a marginal risk for severe weather for Thursday Afternoon and evening. Timeframe is from 4-11 PM today for severe weather potential.
..SPC has also placed the same area in a marginal risk for severe weather for Friday Afternoon and Evening. A general thunderstorm with isolated severe thunderstorm risk extends into Saturday but will depend on convection strength and timing on Friday..
..An Excessive Heat Warning is now in effect from 12-8 PM Thursday and an Excessive Heat Watch is in effect from Thursday Evening through Friday Evening for Northern Connecticut, North-Central Rhode Island, Eastern Franklin, Eastern Hampshire, Eastern Hampden, Worcester, Essex, Middlesex, Suffolk, Norfolk, North-Central Bristol and North Central Plymouth Counties for heat indices of up to 105 or slightly higher for Thursday and heat indices of 102 or slightly higher for Friday.
..A Heat Advisory is now in effect from 12-8 PM Thursday and an Excessive Heat Watch is in effect from Thursday Evening through Friday Evening for Western Hampden, Western Hampshire and Western Hampden Counties of Massachusetts for heat indices up to 97-99 or slightly higher for Thursday into Friday..
..A Heat Advisory is in effect from 12-8 PM Thursday for South Coastal Massachusetts and Rhode Island for heat indices of up to 99 degrees..
..In all Excessive Heat Warning/Watch and Heat Advisory areas, use extreme caution if outside and needing to physically exert yourself. Drink plenty of liquids, take frequent breaks and seek cooler indoor locations wherever possible..
..SKYWARN Self-Activation will monitor the severe weather potential during this heat wave Thursday through Saturday..

Intense heat and humidity will continue Thursday through Friday possibly extending to Saturday across the region. The worst heat is expected this Thursday Afternoon and Evening. The headlines depict the latest Excessive Heat Warnings/Watches and Heat Advisories and basic safety tips.

Severe weather potential increases today with very strong instability expected due to the intense heat and humidity. Wind shear levels are marginal but strong heating and strong to extreme levels of instability will allow for the development of strong to severe thunderstorms for Thursday Afternoon and Evening and offset the marginal/weaker wind shear. Activity is expected to evolve into a line of strong to severe thunderstorms progressing from Central and Eastern New York into Southern New England. Timing will determine how far east the threat extends with a timeframe for severe weather Thursday in the late afternoon through evening.

A marginal risk for severe weather exists on Friday Afternoon and Evening in the same areas affected by Thursday’s potential severe thunderstorms. Part of Friday’s potential will hinge on how severe weather evolves on Thursday. It will also hinge on the overlap of stronger jet dynamics and wind shear with instability levels in the atmosphere as there will be somewhat less instability owing to lower dewpoints and possibly slightly lower temperatures due to possible cloud cover from Thursday’s severe thunderstorms. This will be better understood in future outlooks.

Finally, there is a general thunderstorm risk for Saturday with a mention of isolated severe thunderstorms for the region. This will depend on Friday’s severe weather potential and the position and timing of a cold front which could sweep through late Friday Evening into early Saturday Morning ending the severe weather potential at that time or if that timing is more towards Saturday Afternoon and early evening which could result in another round of isolated to scattered strong to severe thunderstorms. This potential for Saturday will be better understood by Friday Afternoon and evening.

Another coordination message will be posted either by 11 PM Thursday Evening or 11 AM Friday Morning if there is a change in heat headlines and for severe weather potential for Friday and Saturday as needed and time allows for an update as we monitor severe weather potential for late Thursday Afternoon and evening. Below is the NWS Boston/Norton Excessive Heat Warning/Excessive Heat Watch/Heat Advisory Statement, NWS Boston/Norton Area Forecast Discussion, Enhanced Hazardous Weather Outlook and SPC-Day-1, Day-2 and Day-3 Convective Outlooks..

NWS Boston/Norton Excessive Heat Warning/Excessive Heat Watch/Heat Advisory Statement:

NWS Boston/Norton Area Forecast Discussion:

NWS Boston/Norton Enhanced Hazardous Weather Outlook:

SPC Day-1 Convective Outlook:

SPC Day-2 Convective Outlook:

SPC Day-3 Convective Outlook:

Respectfully Submitted,

Robert Macedo (KD1CY)
ARES SKYWARN Coordinator
Eastern Massachusetts ARES Section Emergency Coordinator
Home Phone #: (508) 994-1875 (After 6 PM)
Home/Data #: (508) 997-4503 (After 6 PM)
Work Phone #: 508-346-2929 (8 AM-5 PM)
Email Address:
Like us on Facebook –
Follow us on Twitter –