Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 161805 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 205 PM EDT Mon Apr 16 2018 .SYNOPSIS... A wind swept rain along with isolated thunderstorms will move through the region today. Precipitation will wind down by this evening. The mid level system will keep unsettled conditions across the region through mid week. As this system exits, another fast moving low will cross the region Thursday into Friday, bringing another round of showers. Dry conditions look to finally return across the region next weekend. Temperatures will remain below normal through most of this week, with some moderation possible next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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2 PM update... Axis of heavy rain and embedded convection across western New Eng will move east across rest of SNE through late afternoon. Heavy rain and a few tstms will accompany this area as it moves through. This system is progressive and the dry slot is already moving into SW CT. Steady rain will end in CT and western MA 4-6 pm and across eastern New Eng 6-8 pm. No changes regarding potential for strong wind. Have seen gusts up to 50 mph across LI where temps upper 50s to near 60. Temps in the lower 50s in southern RI and SE MA and temps should reach upper 50s here by late afternoon which will help to erode the inversion. Given 3 hr pressure falls around 5 mb moving across SNE and weakening inversion, risk of brief gusts to 50 mph near the south coast as the low level jet swings through. Timing of strongest winds 3-5 pm RI and 4-7 pm SE MA and Cape/Islands. Temps still mid/upper 30s northern MA and high temps in the mid/upper 40s will occur early evening. Previous discussion... * Heavy rainfall, isolated thunder, strong winds and areas of urban and poor drainage flooding. Heavy rainfall... Numerous showers, locally heavy moving across SNE but bigger concern is area of heavy rain and convective line lifting NE from SE NY through NJ along the nose of the low level jet. This jet is rather anomalous at 4+SD above normal and combined with 2SD PWATs will lead to heavy rainfall. Hi-res guidance shows this line moving through SNE 16-22z. Up to a 3 hour period of heavy rain with localized rainfall rates 0.5 to 1 inch/hr expected as this area moves through. MUCAPES 200-300 J/kg so isold t-storms are expected and lightning strikes noted across LI and SE NY. Areas of urban and poor drainage flooding likely although system is progressive which will reduce risk of very heavy rainfall amounts. Still expect widespread 1 to 2 inch amounts with localized 3 inch amounts possible. Heaviest rainfall should be tied to upslope areas of the Worcester hills and east slopes of the Berkshires. Strong wind... Already seeing east gusts 40+ mph along the coast. These gusts are a result of decent mixing from still cool low level temps. This afternoon, the risk for strong winds will come from low level jet which moves along the south coast 18-23z. Soundings do show a low level inversion and it appears temps will need to reach near 60 to erode the inversion enough to bring stronger winds down to surface. We expect temps to reach well into the 50s across from NE CT through RI and SE MA with a chance a few locations could hit 60. In addition, convective line moving through will increase risk of bringing these stronger winds down so we issued a wind advisory for southern RI and south coastal MA including the Cape/Islands for a brief period of gusts 45-50 mph.
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&& .LONG TERM /TUESDAY THROUGH SUNDAY/... Overview... 165/00Z guidance remains in rather good agreement through Friday, with only typical minor differences further out in time. Will continue to favor a consensus approach for this portion of the forecast. Expecting an active pattern to persist through Thursday, with more quiet weather towards next weekend. Temperatures near to below normal for this part of the upcoming week. Details... Tuesday through Wednesday...Strong mid level cutoff low will slowly approach the Maritimes sometime Wednesday. With the continued cyclonic mid level synoptic flow, along S-SE winds, will keep decent low level moisture across the region, especially along the coast. Lift gets weaker as the core moves away from our region. Can`t rule out isolated to scattered showers both days. Wednesday night through Friday night... Another fast moving mid level shortwave heads towards the Great Lakes Wednesday night into Thursday. This wave looks potent enough to generate a clipper low pressure, and move it through our region Thursday into Thursday night. While this low pressure should be off to our east by Friday, still expecting to be stuck in cyclonic flow across southern New England. Looking at another round of wet weather during this time, mostly late Wednesday night into Thursday. Looks to be all rain this time, expect across the highest terrain of northern MA, where some wintry precipitation may mix in for a time during the night. Saturday and Sunday... Large high pressure will move SE from near Hudson Bay and central Canada, and will expand SE across New England to the mid Atlantic states through this weekend. && .AVIATION /18Z MONDAY THROUGH SATURDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Through 00z...Widespread IFR/LIFR with patchy dense fog near the south coast. Heavy rainfall axis along with embedded t-storms in western New Eng will move through eastern half New Eng 19-22z. Rain ends from west to east 20z-00z. Brief SE gusts to 40-45 kts possible along the south coast. Tonight...Moderate confidence. MVFR/IFR stratus and patchy fog will gradually improve to MVFR/VFR overnight. Diminishing wind. Mainly dry with just a few rain/snow showers possible, mainly over the Berkshires. Tuesday...Moderate confidence. Mix of MVFR/VFR cigs, lowest conditions in the west. A few rain showers possible, mixed with snow over higher elevations. SW gusts 20-25 kt Cape/Islands. KBOS Terminal...Moderate confidence in TAF. Heavy rain/isold thunder through 23z. LLWS this afternoon. KBDL Terminal...Moderate confidence in TAF. Heavy rain/isold thunder ending by 20z. Outlook /Tuesday night through Friday/...Moderate confidence. Tuesday Night through Wednesday: Mainly VFR, with local MVFR possible. Breezy. Wednesday Night: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance FZRA. Thursday: Mainly MVFR, with local IFR possible. Chance SHRA, slight chance FZRA. Thursday Night through Friday: Mainly VFR, with areas MVFR possible. Chance SHRA.
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&& .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...High confidence. Gale warnings will continue today and should drop to SCA by tonight. E/NE gusts increasing to 35-40 kt across south coastal waters this morning will transition to E gusts to 40-45 kt over eastern MA waters today. Strong waves over the near shore eastern waters, with near 6-12 foot seas right up to the shoreline. Vsbys will lower today as fog becomes more widespread with a period of heavy rainfall and isold thunder. Passing cold front this evening will switch the winds to the west towards dawn on Tuesday. Gusts should begin to subside allowing for seas to be relax. Outlook /Tuesday through Friday/...Moderate Confidence. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Slight chance of rain showers. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Wednesday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers. Thursday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers. Friday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. && .TIDES/COASTAL FLOODING... 1050 AM update... We expanded the coastal flood advisory south to include Boston and Suffolk county and Plymouth county. Tidal departure running around 1.5 ft at Boston. With seas already 13-14 ft this should be enough for areas of minor flooding of the typical vulnerable shore roads. Previous discussion... Looking at the coastline, feel that the Coastal Flood Advisory for coastal Essex county appears to be on track for the midday high tide. Thanks to strong easterly gales, seas will build to 15-20 ft just offshore from NE MA coast. Guidance continues to suggest a storm surge up to 1.5 ft. This combined with these waves may be enough for minor flooding of vulnerable shore roads along the Essex county coast where highest wave action expected. Tides are a bit higher for the Monday night tide just after midnight but wave action and surge a bit less. Especially as the wind will switch to a more southerly direction. At least splashover is possible, but feel that weak winds and offshore direction will lessen the risk. Along the south coast, it appears the strongest winds and surge will occur late afternoon between the high tides so this may limit minor flood potential. && .CLIMATE... New record lowest max temperatures set for April 15 BOS 39 in 2018. Previous 40 in 1881. PVD 41 in 2018. Previous 42 in 1972. BDL 40 in 2018. Previous 41 in 1943. ORH 34 in 2018. Previous 39 in 1943. New record daily snowfall set for April 15 PVD trace in 2018. Previous trace in 2007. BDL 0.5 in 2018. Previous trace in 2014. ORH 0.4 in 2018. Previous 0.2 in 1988. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...Wind Advisory until 8 PM EDT this evening for MAZ017>024. Coastal Flood Advisory until 2 PM EDT this afternoon for MAZ007-015-016-019. RI...Wind Advisory until 6 PM EDT this evening for RIZ002>008. MARINE...Gale Warning until 7 PM EDT this evening for ANZ231>237-255- 256. Gale Warning until 2 PM EDT this afternoon for ANZ230. Gale Warning until 10 PM EDT this evening for ANZ250-251-254.
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&& $$ SYNOPSIS...Belk/Dunten NEAR TERM...KJC SHORT TERM...Dunten LONG TERM...Belk AVIATION...Belk/KJC MARINE...Belk/Dunten TIDES/COASTAL FLOODING... CLIMATE...

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