Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 030834 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 334 AM EST Sat Dec 3 2016 .SYNOPSIS... Low pressure over the maritimes will circulate a dry but chilly airmass into New England today on blustery northwest winds. Chilly and dry weather persist into Sunday however winds slacken as high pressure builds into the area from the west. A weak trough of low pressure may yield a brief period of light snow or flurries Monday morning. High pressure builds back into the region Tue yielding dry and seasonably cool weather. Another weak trough of low pressure may impact southern New England with a period of rain and/or snow showers mid week. Then a polar front crosses the region late next week resulting in a trend toward colder than normal temperatures. && .NEAR TERM /THROUGH TODAY/... 330 am Update... Potent northern stream short wave moving across Maine during the predawn hours. Some cloudiness associated with this feature along with a brief rain/snow shower. As this short wave exits eastward into the Gulf of Maine the main impacts for southern New England will be a reinforcing surge of colder air on gusty northwest winds. This will result in high temperatures about 5 degs cooler than Friday...with highs today about 40-45...except upper 30s for the high terrain. These temps are near normal however it will feel colder given gusty NW winds of 20 to 30 mph. Dry weather prevails today with cyclonic flow aloft and some lake effect influence yielding some cloudiness from time to time. && .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/... 330 am update... Tonight... Cold air advection continues along with gusty northwest winds of 15 to 25 mph. However inland winds will drop off to less than 10 mph. Thus leaned toward the colder MOS guidance for low temperatures...20s for most locations...low 30s for the immediate coastline where winds will not decouple. Some cold advection strato-cu from time to time but dry weather will prevail. The only exception may be across the outer Cape as cold air advection on NNW winds will result in ocean effect clouds and snow showers. However hi res guid including the ARW and NMM keep the bulk of the ocean effect snow showers offshore as boundary layer winds may have enough westerly component...about 320 degs. Given this uncertainty will carry chance and slight chance pops for snow showers across the outer Cape. Sunday... Heights begin to rise a bit so probably more sunshine than today. However sunshine will be fairly ineffective given a cold airmass over the area and less blyr mixing as subsidence inversion lowers with approaching high pressure. Temps will be about 5 degs cooler than today with highs only in the upper 30s to lower 40s...mid 30s high terrain. These numbers are about 5 degs colder than normal. The good news these height rises will be accompanied by high pres building over the region. Thus pgradient will weaken resulting in winds not as gusty as today. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Temperatures running a bit below seasonal normals through at least Tuesday * Low pressure moving out of the Ohio Valley/mid-Atlantic states may push some mixed precipitation into the region Tuesday night and Wednesday, but confidence remains low * Low confidence regarding timing of unsettled weather next Thu/Fri. Sunday...High confidence. Lower clouds and spotty ocean effect rain showers may initially continue into Sunday morning across outer Cape Cod as colder air moves across the milder waters on strong N-NW winds. Otherwise high pressure builds into the area with dry conditions and mostly clear skies. Could see wind gusts to 25 kt initially along the shoreline, but as high builds in and pressure gradient relaxes, winds will lower. Temperatures will be a few degrees cooler than normal, with highs in the 30s to low 40s. Sunday night through Monday...Moderate confidence. Continue to expect a band of clouds moving thru the area from a weak mid level short wave that pushes into/thru the region Sun night into Monday. Not much moisture to work with this feature as it pertains to our area, though 12Z ECMWF does shows some light QPF amounts during Sunday night/Monday morning, accompanied by a very weak surface low. GFS solution is drier...and with W/NW flow still looking to be in place for Monday...thinking that a mainly dry, low QPF solution looks reasonable. Will go with mainly a slight chance pop for a few showers or snow showers. Monday night...Moderate confidence. Dry conditions and mostly clear skies prevail Monday night with surface high pressure centered over southern Quebec...and upper level ridging...being the main influence on our weather. Tuesday and Wednesday...Low confidence. Models continue to differ regarding how much precipitation makes its way into southern New England during this timeframe. Low pressure system to our SW tries to bring moisture into our area. Elongated precip shield lies to the S and W of the region as high pressure shifts E of the region Tuesday and Tuesday night. Big question will be the timing as the high exits, if it does. Models still show the potential for 2 surface low pressure centers developing, one moving thru the southern Great Lakes Region and another moving off the Carolina or Mid-Atlantic coastline. Uncertainty exists on whether we end up with minimal QPF between these 2 systems. Model and ensemble solution spread lending to lower than average confidence. Will continue to lean toward a model blend at this point due to the remaining uncertainty and timing, with chance pops late Tuesday as well as Wednesday. Precip could be a wintry mix of light snow/rain. Thursday and Friday...Low confidence. While models show a deep mid level trof digging into the central and eastern US, there are significant differences in timing/placement. This in turn makes a difference in surface features, along with issues with how the sensible weather evolves. ECMWF shows a surface low approaching from the SW, while 12Z GFS shows a weaker solution for our area. Overall, low confidence continues. Will continue chance POPs at this time. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 115 am update...high confidence thru Sunday Thru 12z... Mainly VFR with marginal MVFR across the higher terrain. Other than a brief sprinkle/flurry early this morning expecting mainly dry weather to prevail. WSW winds will become WNW with gusts up to 35 kt toward daybreak...highest gusts over high terrain and Cape Cod and islands. After 12z... More of the same...VFR and dry but gusty WNW winds up to 30-35 kt. Tonight... VFR and dry with gusty WNW winds up to 25 kt or so...strongest winds across the high terrain and Cape Cod and islands. Sunday... VFR and dry along with diminishing NNW winds. KBOS TAF...High confidence in TAF. Main impacts will be gusty WNW winds today and tonight with gusts up to 30 kt at times. KBDL TAF...High confidence in TAF. Main impacts will be gusty WNW winds today and tonight with gusts up to 30 kt at times. Outlook /Sunday Night through Wednesday/... Sunday night and Monday...Moderate confidence. May see patchy MVFR conditions in spotty -SHRA/-SHSN Sunday night into Monday morning, then should be mainly VFR by Monday afternoon. Monday night...Moderate confidence. VFR. Tuesday and Wednesday...Moderate confidence for overall trends, lower on exact timing. Mainly VFR Tuesday morning. May see MVFR CIGS/VSBYS move into central and western areas Tuesday afternoon in mainly -RA, but may see mixed precipitation interior. MVFR CIGS/VSBYS possible Tue night into Wed with chance of light rain/snow. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... 330 am update... Today... WNW winds 20 to 30 kt. A few gusts to 35 kt possible but the majority of the time subgale winds will be observed. Any ocean effect snow showers should remain well offshore. Tonight... NNW winds 20-25 kt. Given more northerly wind direction ocean effect snow showers will track closer to the coast especially just east of Cape Cod. Sunday... NNW winds 20-25 kt early but then diminishing as high pressure builds over the area. Any ocean effect snow showers across eastern MA waters early will diminish by afternoon. Outlook /Sunday Night through Wednesday/...Moderate confidence. Sunday night and Monday...Expect winds and seas to diminish below small craft criteria during Sunday, then should remain below small craft Sunday night and Monday. Monday night and Tuesday...Winds and seas remain below small craft criteria for most of the waters. N-NE winds gusting up to 25 kt and seas may build to 4-5 feet during Tuesday night along the southern coastal waters. Wednesday...Winds/seas may reach small craft criteria, especially along the southern coastal waters. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 6 AM EST Sunday for ANZ231>235-237- 250-251-254>256. Small Craft Advisory until midnight EST tonight for ANZ230. Small Craft Advisory until 1 PM EST this afternoon for ANZ236. && $$ SYNOPSIS...Nocera NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...NMB AVIATION...Nocera/NMB MARINE...Nocera/NMB

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