Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 050554 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 154 AM EDT Fri Jun 5 2020 .SYNOPSIS... Summer-like warmth with increasing humidity is expected through Friday, with scattered showers and isolated thunderstorms possible. Showers and thunderstorms arrive Saturday afternoon ahead of a cold front. A few of those storms could be locally strong or severe. High pressure builds in from Canada for Sunday afternoon, which will allow for cooler temperatures into Monday. High pressure remains parked over the northeast into mid week, this will return us to a period of dry and seasonably warm temperatures. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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150 AM Update... A complex of showers and embedded thunderstorms were tracking across New Jersey and into southeast New York. This activity will continue to lift east northeast aided by a modest low level jet and some elevated instability. Guidance still struggling with how well the complex holds together and its exact track. Based on current radar trends and latest CAMs feel that much of the region will see some showers overspread the region through daybreak. Thinking activity will be somewhat more numerous south of the MA Turnpike with a bit better elevated instability/forcing. A few embedded thunderstorms with brief heavy rain are possible too with the highest risk near the south coast. Increasing low level moisture should keep overnight low temps generally in the 60s.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Friday... A warm front lifts north of our area. Surface dewpoints increase a bit further in the 60s, which will make for muggy conditions. Airmass is quite saturated, with precipitable water of 1.5 to 2 inches. Exiting short wave could bring some lingering showers in the morning. Then we may have considerable cloudiness through the day. Model soundings show a tall skinny CAPE profile, with a few hundred J/kg if we stay cloudy, but 1000-1500 J/kg CAPE if the sun breaks out. We will likely have partly to mostly cloudy skies. While dry weather should dominate, the instability will bring scattered showers and potentially a few thunderstorms, mainly during the afternoon/early evening, with the greatest risk across interior southern New England. Weak shortwave energy/jet dynamics and poor mid level lapse rates should limit areal coverage. Friday Night... Southern New England remains in the warm sector overnight as a surface trough and mid level shortwave approach from the Great Lakes Region. Model soundings continue to indicate marginal elevated instability (up to a few hundred J/kg CAPE) so scattered showers and isolated thunderstorms are possible, though forcing will lacking. With surface dewpoints in the mid to upper 60s it will be quite a muggy night, with lows 65 to 70. Areas of fog possible along the south coast, Cape and Islands. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights... * Sct`d showers/t`storms Saturday afternoon * Dry and seasonably warm early next week Saturday... Showers and t`storms are expected heading into Saturday. One of the first curve balls will be how much rain and cloud cover we see from a first batch of morning rain. If we can clear out the clouds and heat up the lower atmosphere we could support a few strong to severe thunderstorms by the mid-afternoon. Model guidance continues to suggest the passage of the cold front between 18z to 00z. Now... depending on when the front moves across Southern New England it will determine whether or not we see any strong t`storms. The guidance supports a threat for strong thunderstorms because of the dynamic forcing in place from Worcester and Hartford and points east. Across the area described the CAPE values are between 1,000 to 1,500 J/kg. Additional perimeters such as the lift index are between -4 to -6, mid-level lapse rate of 6.0 to 6.5 degrees/km, and 60 to 70 kts of bulk shear. Those ingredients mixed with a well timed cold front could lead to some strong or severe storms. The primary threats include cloud to ground lightning, gusty wind, small hail, and brief heavy downpours. Sunday into Monday night... Clouds linger with a few post frontal showers. Cooler air will be advected south out of Canada. Sunday afternoon highs will struggle to reach the low 70s; with the exception of the Connecticut River Valley. There we could see mid-70s from Springfield to Hartford. Clouds decrease as high pressure sets up shop Sunday night into Monday. Monday afternoon we are back to sunny skies and highs in the middle to upper 70s. Tuesday into Wednesday... More of the same thanks to a ridge of high pressure across the northeast. Plenty of dry weather and temperatures seasonably warm with afternoon highs in the upper 70s to low 80s and overnight lows near 60-degrees. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06Z Update: Today...Moderate confidence. Conditions should lower through 12z with mainly lower end VFR to some marginal MVFR ceilings today. IFR conditions possible for a time this morning near the south coast in a period of lower clouds and fog. Otherwise, scattered showers will be possible at times today especially this morning into mid afternoon south of the MA Turnpike. A few embedded thunderstorms are possible too. Areal coverage of precipitation and thunder risk is uncertain though and later shifts will likely need adjustments. SW of 10 to 15 knots develop by afternoon with some gusts around 20 knots. Tonight...Moderate confidence. Conditions should deteriorate to low end MVFR-IFR in lower clouds from south to north as boundary layer cools tonight. Lowest conditions likely near the south coast where some LIFR cigs/vsbys are possible. Scattered showers and a few embedded t-storms are expected at times tonight, but the focus for the activity will mainly be near the south coast, Cape and Islands. SW winds of 5-15 knots. LLWS a concern across the far southeast New England coast. Saturday...Moderate to high confidence. Areas of low clouds/fog patches should lift to VFR by afternoon except for areas near the south coast. Otherwise, the main concern is the potential for a few strong thunderstorms Sat afternoon although areal coverage remains uncertain at this time. SW winds of 10 to 15 knots by afternoon with a few gusts around 20 knots possible. KBOS Terminal...Moderate confidence in TAF. KBDL Terminal...Moderate confidence in TAF. Outlook /Saturday Night through Tuesday/... Saturday Night: VFR. Sunday: VFR. Breezy. Slight chance SHRA. Sunday Night through Tuesday: VFR.
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&& .MARINE...
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1015PM Update... * Small Craft Advisories continue for the southern waters for 5 ft seas * Tonight through Friday Night...High confidence. Persistent S-SW winds of 10 to 20 knots through Friday Night. Lingering 3-6 foot seas across our southern waters, where SCAs are in effect. Areas of fog are expected at times across our southern waters, especially during the overnight and early morning hours, when visibility may be reduced to under 1 mile. Outlook /Saturday Night through Tuesday/... Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, chance of thunderstorms. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Sunday: Winds less than 25 kt. Seas up to 5 ft. Sunday Night through Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday Night through Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 AM EDT Saturday for ANZ254>256. Small Craft Advisory until 5 AM EDT Saturday for ANZ235-237. && $$ SYNOPSIS...Gaucher/NMB NEAR TERM...Frank SHORT TERM...NMB LONG TERM...Gaucher AVIATION...Frank/Gaucher MARINE...Gaucher/NMB

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