Area Forecast Discussion
Issued by NWS Boston, MA

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013 FXUS61 KBOX 061745 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1245 PM EST Tue Dec 6 2016 .SYNOPSIS... Low pressure off the mid Atlantic coast may bring some mixed light rain and/or snow into Southern New England tonight into early Wednesday with any accumulations generally an inch or less. A cold front crosses the region late Thursday or Thursday evening, followed by another cold front Friday, which will usher in blustery and unseasonably cold conditions Friday night into Saturday. Low pressure may bring some snow or rain Sunday night into Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Damp roadways are gradually drying, allowing any remaining areas of black ice to dissipate. Otherwise, lowered daytime temps by a slight margin given the fact early AM temps were colder than previous forecast. Expect highs mainly in the low-mid 40s at best. Otherwise, forecast remains on track. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... Tonight...Two chunks of short wave energy influence our sensible weather tonight. A short wave trough in the northern stream passes to our NW while another short wave in the southern stream passes s of us. The southern stream short wave trough instigates surface cyclogenesis along the mid Atlantic coast, but this system remains rather flat and will likely slide to the east well south of our area. There could be some warm advection resulting in overrunning clouds/precipitation with the northern system, but associated dynamics stay well NW of the forecast area. Thus, we`re anticipating light precipitation for our area with the aid of a low level trough between the two systems. We may not even measure along portions of the coastal plain. Have gone with chance POPs NE half of area and low likely POPs across the SW half of area. Ptype is also not a sure bet. Thermal profiles look cold enough to support precipitation mainly in the form of snow along and north of the Mass Pike and whatever precipitation falls likely mixed rain/snow across northern CT, northern RI, and along the I-95 corridor between Providence and Boston. If the precipitation intensity should be heavy enough, then we could see the thermal profile cooling close to the wet bulb and perhaps more snow than rain across northern CT. In addition, an easterly low level flow could result in some modest enhancement over the eastern slopes of the Berkshires and perhaps to a lesser degree along the Worcester hills and higher terrain of NE CT and far NW RI. In the end, however, we are expecting only a coating to an inch of snow where the precipitation ends up being mainly snow. By daybreak the deep moisture is gone with possibly just some lingering areas of drizzle under the trapped low level moisture. There is a slight chance of some light freezing drizzle across northern MA around daybreak Wed but confidence is not very high. Expect temperatures to remain fairly steady in the lower 30s across much of the interior and in the mid to upper 30s across the SE coastal plain. Wednesday...Measurable precipitation should be over by around daybreak with possibly just some lingering drizzle for a while in the morning. Areas of light freezing drizzle is a possibility for a time across NW MA. Low clouds may persist through most of the day with no mechanism to dissipate or move them out. Partial clearing is possible late in the afternoon but not a guarantee. Anticipate high temperatures to be in the lower to mid 40s across most of the forecast area on Wednesday. && .LONG TERM /THURSDAY THROUGH MONDAY/... Highlights... * Blustery, and unseasonably cold Friday night into Saturday * Some snow/rain possible Sunday night into Monday Thursday...A mid level longwave trough will pass by Thursday, along with a surface cold front. There appears to be enough moisture to result in abundant clouds, but perhaps not enough to generate widespread rain and snow showers. Still looking like steady west winds, which are generally not favorable for either lake-effect or ocean-effect showers across southern New England. As such, will keep this portion of the forecast mainly dry. Seasonable temperatures expected. Friday and Saturday... This will be the most noticeable change during this portion of the forecast. Unseasonably cold air should arrive Friday afternoon, and really take hold Friday night into Saturday. Expecting temperatures Friday night to be about 10 degrees below normal, with high temperatures Saturday generally below our normal low temperature, some 10-15 degrees below normal. Dry weather should prevail across southern New England. Gusty NW winds both days will result in wind chills in the single digits and teens Friday night into Saturday. Saturday night lows remain tricky, and will ultimately depend on extent of radiational cooling. There remains potential for temperatures to be significantly lower than the current forecast if it ends up clear with winds decoupling. Sunday into Monday... Low confidence in the details of this portion of the forecast. Significant spread in the track and timing of a low pressure moving through the Great Lakes. GFS develops a stronger mid level shortwave, while the ECMWF retains a nearly zonal flow over the USA. Canadian model develops a weaker, more progressive, shortwave than the GFS. Will maintain a chance of some rain and snow across southern New England. However, these details are likely to change over the next several days. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through 03Z this evening...High confidence. Mainly VFR with gradually building clouds from the SW and lowering CIGS. Winds shift mainly E later this afternoon. Some MVFR clouds possible Cape/Islands by about 21Z. Tonight...Moderate confidence. MVFR CIGS overspread the remainder of S New England between 03Z and 06Z. Also, a mix of rain near the coast, and snow inland (both light) spreads SW-NE through 08Z. Some light coating of snow possible on runways mainly 20-30 mph inland of the coast. This snow/rain mix continues through about 14Z along with a mix of IFR/MVFR conditions due to lower vsbys. Winds remain E. Tomorrow and tomorrow night...High confidence. Most of the snow/rain ends between 12Z and 14Z (some may linger a bit later). Conditions remain mostly MVFR due to low cigs through the afternoon, after which some clearing/lifting should lead to more widespread VFR conditions with CIG heights mainly 030-060. Winds shift to the SW. VFR lingers into the overnight. KBOS TAF...High confidence today, and moderate confidence tonight. VFR through this about 02Z (give or take an hour)then lowering to a MVFR ceiling which will linger into tomorrow. Some light rain mainly after 06Z and continuing through about 14Z. KBDL TAF...High confidence today with VFR conditions. Moderate confidence tonight into Wednesday morning. MVFR ceilings and visibilities in light snow likely after 03z tonight. MVFR ceiling and visibilities in fog may linger into a portion of Wednesday morning. Outlook /Thursday through Saturday/... Thursday...Moderate confidence. Mainly VFR cigs. Areas of MVFR possible across the interior with a few snow/rain showers. Friday and Saturday...Moderate confidence. Mainly VFR cigs. Localized MVFR in isolated snow showers far interior MA Fri. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Confidence...High Winds will diminish gradually this morning. Already let some of the Small Craft Advisories expire this morning. Expecting the remaining advisories across the outer coastal waters to expire toward mid morning. Light winds are anticipated this afternoon through Wednesday across this office`s coastal waters. Outlook /Thursday through Saturday/... Wednesday night through Thursday...High confidence. Light winds and seas. Thursday Night...High confidence. Increasing WNW winds, with gusts up to 30 kt possible. Small Craft Advisories may be needed for most waters. Friday into Saturday...High confidence. NW gusts to 30 kt likely. There is a moderate risk for some gale force gusts, too. Winds gradually diminishing Saturday. However, rough seas will take longer to subside across the outer coastal waters. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Thompson NEAR TERM...Doody SHORT TERM...Thompson LONG TERM...Belk AVIATION...Belk/Doody MARINE...Belk/Thompson

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