Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
107 FXUS61 KBOX 231853 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 253 PM EDT Mon Apr 23 2018 .SYNOPSIS...
-- Changed Discussion --
High pressure remains in control through Tuesday bringing dry weather with mild daytime temperatures. Low pressure approaches and then passes through New England Tuesday night into Wednesday night, bringing rain to the area. Another weak low pressure center may bring another round of showers to the area Friday night.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
250 PM Update... The high pressure that was centered overhead today begins to shift to the southeast of our area tonight. Clear skies continue. With winds expected to be light, expect good radiational cooling. Forecasting lows in the 30s for much of the area, except for low 40s in some urban centers and portions of the Cape and Islands. Patchy/areas of frost are expected to develop.
-- End Changed Discussion --
&& .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
Tuesday... As the surface high moves further offshore, Tuesday will bring developing S to SW wind. A sea breeze is possible along east coastal MA for part of the day, however as the SW flow increases some during the afternoon, the east coastal sea breeze should come to an end. Mostly sunny skies expected for much of the day, with increasing clouds during the afternoon. A slightly warmer day with highs in the 60s across much of the area, some locales may reach 70 degrees. The cooler area will be the immediate south coast of MA/RI, where the persistent S wind will keep highs in the upper 50s to near 60. Tuesday night... Models show mid level ridging moving east of our area while deep trough currently over the lower Ohio/Mississippi Valleys works its way eastward. This pattern shift prompts a moisture-rich low pressure system to track eastward towards the Delmarva coastline. Moisture well ahead of this system will result in skies becoming cloudy during the evening, but it will take some time to moisten the column with respect to any precipitation. Expecting rain to become likely after midnight. PWATs during the overnight increase to 1 to 1.3 inches, so some moderate rainfall possible but generally thinking rainfall of a tenth to half inch prior to 12Z Wed. Cloud cover and increasing dew points will keep overnight lows somewhat milder, lows in the low to mid 40s for much of the area.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Highlights... * Showers Wednesday into Wednesday night * Another round of showers possible Friday night and late Saturday Discussion... Multiple short wave energy systems will be affecting our area during this forecast period. A southern stream short wave trough and surface low will affect southern New England late Tuesday night into Wednesday night. This system begins to phase with a northern stream short wave as it passes through our region. Still another southern stream short wave and an associated weak surface low pressure center may affect the area around Friday night, but consistency in handling this feature among the medium range models is low. This system currently looks as though it will will run a little ahead of an approaching northern stream trough which then becomes a dominant feature with possibly cooler temperatures for the rest of the weekend. There is a signal for a long wave pattern change leading to higher heights and warmer temperatures across our region after this forecast period. Tuesday night to Wednesday night... The 00Z operational model runs have converged some on timing for the southern stream short wave energy during this time period. As the mid tropospheric southern stream short wave begins to phase with the northern stream short wave, the surface weather pattern may take on the look of a surface low that moves north up the mid Atlantic coastal plain and ends up with the look of a triple point low passing over or near central New England. Suspect that cooler air will be somewhat resistant to an approaching warm front due to onshore maritime polar air being fed on E to SE winds. Anticipate rainfall will be showery but confident that all areas will measure. PWATs look to crest about 1.2 to 1.4 inches, and a 50 to 60+ knot low level SE jet at 925 mb will help focus that moisture over southern New England. There also looks to be some elevated instability Wednesday evening with embedded convection a possibility. This is reflected on the latest GFS run with mid level lapse rates of 6.5 to 7 degrees C/km as well as other typical instability indices such as Showalters a little below 0, total totals of 50+ and K indices above 30. As far as QPF, may see some upslope enhancement given the nose of the SE low level jet across the Worcester hills and/or east slopes of the Berkshires depending upon the exact track of the low level features. Suspect that rainfall amounts could end up higher than model output due to subtropical moisture source, strength of the low level jet, and some convective enhancement but variable due to the showery nature. A preliminary estimate would be a fairly widespread .5 to 1 inch amounts with locally higher spot amounts of 1.5 to possibly 2 inches. Thursday through Friday... Except for possibly widely scattered late Thursday afternoon or early evening instability showers over the NW higher terrain, it looks dry Thursday afternoon through at least most of Friday. Confidence has increased of at least most of daytime Friday remaining dry. Friday night system... The second southern stream short wave upper trough with a weak surface low passing along or off the coast may produce showers across at least some of southern New England, but confidence is low due to poor model consensus on this feature. The new 00Z ECMWF keeps this system far offshore, although some of its ensemble members have it passing very near SE New England. Thus, given the uncertainty, we will just indicate low chance POPs for now. There is also some uncertainty as to how much interaction, if any, with an approaching northern short wave trough. Rest of Weekend... A cold front associated with the northern stream trough may result in scattered showers late Saturday, but there`s no real model consensus on that now so confidence is low. That northern stream short wave trough brings cooler temperatures to southern New England for the latter half of the weekend into Monday of next week. && .AVIATION /19Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. Remainder of this afternoon...VFR with clear skies and excellent visibility. Local sea breezes persist. Tonight...VFR with clear skies and excellent visibility. Tuesday...VFR. Prevailing wind out of the SSW, initially light enough where a sea breeze may develop along east coastal MA for a time. Then as winds aloft strengthen somewhat during the afternoon, the winds along east coastal MA should shift back to the SSW. Tuesday night...VFR to start. Becoming mainly MVFR after midnight, with local IFR possible towards daybreak. SHRA spreading into the area mainly after midnight. KBOS Terminal...High confidence in TAF. Sea breeze this afternoon, with a sea breeze probable for late morning into early afternoon Tue. KBDL Terminal...High confidence in TAF. Outlook /Wednesday through Friday/...High confidence. Wednesday: Mainly IFR with SHRA and areas BR. Areas of MVFR conditions possible during the afternoon. Potential for LLWS. Becoming windy along the coast with local gusts to 30 kt during the afternoon. SHRA and areas BR. Wednesday Night: Mainly MVFR, with local IFR possible. Windy with gusts to 30 kt in the evening. SHRA diminishing overnight. Isolated tstms during the evening. Thursday: Mainly VFR, with local MVFR possible over higher terrain. Breezy. Slight chance SHRA over NW higher terrain. Thursday Night and Friday: Mainly VFR.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. Tonight... High pressure over the waters tonight with South winds 10 kt or less, seas 1 to 2 feet on the outer coastal waters. Good visibility. Only concern for recreational boaters continues into early this evening is for sea breezes along the coastline today with 15-20kt gusts and choppy seas near shore, especially when opposing outgoing tide. Tuesday... South wind increasing over the course of the day to 10 to 20 kts. Sea breeze along east coastal MA possible late morning/midday, then S winds should prevail as they strengthen. Seas 1 to 3 feet. Tuesday Night...SE winds less than 25 kt. Seas locally approaching 5 ft, especially on the southern outer coastal waters. SCA headlines may be needed. Rain showers becoming likely towards daybreak. Outlook /Wednesday through Friday/...High confidence. Wednesday: Small Craft Advisory winds possible with gusts up to 30 kt possible. Low risk of gale force gusts, especially south and east of Nantucket. Areas of rough seas above 5 feet, especially over the exposed south coastal waters. Rain showers, areas fog. Visibility 1 to 3 nm. Wednesday Night: Small Craft Advisory winds possible with gusts up to 30 kt. Low risk of gale force gusts east of Cape Cod. Rough seas up to 13 ft over the outer coastal waters. Rain showers. Thursday: Winds less than 25 kt, but areas of seas at or above 5 feet. Thursday Night: Winds less than 25 kt. Local rough seas around 5 feet. Friday: Winds less than 25 kt. Areas of seas approaching 5 feet over the outer south coastal waters. Slight chance of rain showers late.
-- End Changed Discussion --
&& .EQUIPMENT... The NOAA Weather Radio transmitter serving Providence is out of service due to phone line problems. The phone company has prioritized the issues and is working to get the weather broadcast back on the air as soon as possible. The transmitter serving Hyannis is back in service. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Thompson NEAR TERM...NMB SHORT TERM...NMB LONG TERM...Thompson AVIATION...NMB/Thompson MARINE...NMB/Thompson EQUIPMENT...Staff

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.