Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 160856 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 356 AM EST Tue Jan 16 2018 .SYNOPSIS...
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Low pressure moves east from the Great Lakes today, then redevelops off the Mid Atlantic coast before tracking across SE New England Wednesday. This will bring the potential for several inches of snow to the region, mainly Tuesday night into Wednesday afternoon, but a changeover to rain is likely Wednesday across portions of Rhode Island and southeast Massachusetts. Mainly dry weather likely Thursday into Sunday, with a warming trend during the weekend. Another low pressure system may affect our region early next week with mostly rain.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1015 PM Update... Continue to see spotty freezing drizzle across portions of Plymouth and western Barnstable counties at 03Z, as well as some mixed precip at KPVC. Band of light precip still skirting along the E coast of Plymouth county as seen on latest KBOX 88D radar imagery, though starting to shrink in coverage as the back edge appears to be from W of KGHG-KPYM. Due to the continuance of the freezing drizzle, have extended the Winter Weather Advisory for eastern Plymouth county for a few more hours. Also included Barnstable county, felt it was enough to include them for a few hours mainly across the lower Cape. Should see precip taper off by around 1 AM. Winds are slowly backing to 350-360 degrees, so should see drier air work eastward. However, solid low level cloud deck continues across the region, though gradually increasing across the CT valley at 03Z. Temps look to remain steady or maybe fall a few degrees through the remainder of the night. Previous discussion... Tuesday... Should see cloudy skies early Tuesday morning with light north winds. Approaching system from the west will help flip wind to a more southerly direction by the afternoon hours. Guidance continues to suggest more or a southwest flow aloft as WAA moves in the region. This will help keep the region socked in with clouds, however temperatures do warm into the low to mid 30s. Within this warm advection pattern, snow showers will break out across the area with some moderate lift in the snow growth region. The Tuesday evening commute may be impacted especially across western MA but the bulk of this system will occur Tuesday night into Wednesday. See the short term section for more details. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
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Tuesday night through Wednesday... Upper trough over the eastern USA with jet core 130-145 knots. The trough axis maintains a progressive orientation through midweek. The right entrance region of the jet moves near the Carolina coast Tuesday evening, which will generate cyclogenesis along the coast. The resulting coastal low will then move up the coast overnight and pass Cape Cod and Islands Wednesday afternoon/evening. Cross sections show some initial elevated lift early Tuesday night, but the best and deepest lift over Southern New England runs from after midnight until midday Wednesday. This will be the best time for accumulating snow. There are differences among the models regarding the track of the storm center. The NAM and GFS are slower and pass about 70 miles inside 40N/70W, while the GGEM and ECMWF are about 6 hours faster and pass directly over Cape Cod. We favored the offshore track. QPF continues to be expected in the 0.40 to 0.75 inch range, with snow to liquid ratios of between 12 and 15 to 1 in the interior and 10 to 12 to 1 in much of RI and Southeast MA. This supports 6 inches or higher over much of the region, with diminishing amounts south of a Boston-Hartford line due to temperatures near freezing along with a mix or change to rain. This brings the heaviest snow over interior Southern New England, affecting an area broader than the current watch. We have expanded the existing Winter Storm Watch to include Northern CT, NW RI, and Norfolk/Suffolk Counties in MA.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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Highlights... * Cold and dry Thursday * Continued dry with a warming trend through the weekend * Another storm may bring mostly rain Monday Wednesday night and Thursday... Coastal low over the Gulf of Maine Wed evening will lift into the Maritimes. Some lingering light snow eastern New Eng is possible early as sharp mid level trough swings through, otherwise drying with gradual clearing overnight. Thursday looks dry and cold with a mix of sun and clouds. Somewhat breezy as well with gusty NW winds at times. Temps in the mid 20s to lower 30s. Friday through Sunday... Looks mainly dry though the weekend. Moderating trend begins Fri with temps recovering to near seasonable normals then a mild day Sat with temps in the 40s. Some uncertainty with temps Sun which will depend on a possible frontal passage. ECMWF further south with northern stream shortwave across SE Canada which drives cold front through with high pres building to the north, while GFS/GGEM/UKMET keep boundary to the north and mild temps. We leaned toward milder consensus of the guidance, but will have to monitor this trend as ECMWF would suggest some ice potential on front end of next shot of precip late Sun night/early Mon. Monday... Amplified mid level trough and cold front approaches from the west with decent pre-frontal low level jet moving into the region. Timing this far out is uncertain but a period of rain appears likely sometime Mon into Mon night. One caveat is ECMWF would suggest some mixed precip/ice would be possible at the onset with cold high pres to the NE.
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&& .AVIATION /08Z TUESDAY 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 Wednesday/... Overnight...Moderate to high confidence in TAF. Patchy -SN/-FZDZ across eastern Plymouth county to Cape Cod should wind down by around 06Z. Mixture of MVFR to low end VFR CIGS with lowest conditions across eastern MA including the Cape and the Islands. Tuesday...Moderate confidence in TAF. Any VFR will fall to MVFR cigs through the day. Light snow showers will over spread the region by the afternoon esp across western MA. Tuesday night-Wednesday... Mainly IFR/LIFR cigs/vsbys in snow, with areas of heavy snow north of a BOS-HFD line. Snow may mix with or change to rain south of a Marshfield-Providence-Westerly line. Conditions improve to VFR in CT and Western Mass Wednesday afternoon...and in RI and Eastern/Central Mass Wednesday night. Wind gusts 25 to 30 knots around Nantucket and parts of Cape Cod. Thursday...VFR. Northwest winds gust to 25 knots Cape Cod and Islands, with gusts to 20 knots elsewhere. KBOS Terminal...Moderate confidence in TAF. Should remain snow free, but cannot rule out a few flurries during the evening push. KBDL Terminal...High confidence in TAF. Outlook /Wednesday Night through Saturday/... Wednesday Night: Mainly VFR, with local IFR possible in the evening. Breezy. Slight chance SN. Thursday through Saturday: VFR. Breezy.
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&& .MARINE...
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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 Wednesday/... High confidence. Overnight into Tuesday...N-NE winds overnight with gusts near 20 kts will diminish by the morning as they shift to SE. SCA has been expanded as seas will remain about 5 feet or higher. Tuesday night...S-SE winds with gusts to 25 knots. Seas 5 feet on the outer waters. Mixed snow and rain developing. Visibility 4 to 6 nm. Small Craft Advisory may be needed. Wednesday...Easterly winds with gusts 20 to 30 knots. A few gusts to 35 knots possible southeast of Nantucket. Seas 5 to 7 feet on the outer waters and possibly on the RI waters. Rain and snow will diminish in the afternoon. Visibility 2 to 4 miles. Small Craft Advisory may be needed. Low chance of a gale warning southeast of Nantucket. Wednesday night...Winds turning from northwest at 20 to 25 knots. Seas remain at 5 to 7 feet on the outer waters. Snow tapers off at this time. Small Craft Advisory may be needed. Thursday...Northwest winds gusting to 25 knots. Seas remain 5 to 7 feet on the outer waters. Small Craft Advisory may be needed. Outlook /Wednesday Night through Saturday/... Wednesday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of snow. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Friday: Winds less than 25 kt. Local rough seas. Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.
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&& .HYDROLOGY... Minor flooding continues along Taunton and Pawcatuck Rivers where Flood Warnings remain in effect. A Flood Warning is also in effect for the Connecticut River at Hartford and Middle Haddam, where ice is causing some river fluctuations. Colder weather will persist through midweek which will limit additional runoff, although we should see some building of snow pack for much of region Tuesday into Wednesday. For details on specific area rivers, including observed and forecast river stages, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...Winter Storm Warning from 1 AM to 6 PM EST Wednesday for CTZ004. Winter Storm Warning from 7 PM this evening to 3 PM EST Wednesday for CTZ002-003. MA...Winter Weather Advisory from 1 AM to 1 PM EST Wednesday for MAZ017>019. Winter Storm Warning from 1 AM to 6 PM EST Wednesday for MAZ004>007-012>016-026. Winter Storm Warning from 7 PM this evening to 3 PM EST Wednesday for MAZ002-003-008>011. Winter Weather Advisory from 1 AM to 9 AM EST Wednesday for MAZ020-021. RI...Winter Weather Advisory from 1 AM to 1 PM EST Wednesday for RIZ002>004. Winter Storm Warning from 1 AM to 6 PM EST Wednesday for RIZ001. Winter Weather Advisory from 1 AM to 9 AM EST Wednesday for RIZ005>007. MARINE...Small Craft Advisory until 5 PM EST this afternoon for ANZ231. Small Craft Advisory until 6 PM EST Wednesday for ANZ250- 254>256. Small Craft Advisory until 1 AM EST Wednesday for ANZ251.
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&& $$ SYNOPSIS...KJC NEAR TERM...EVT SHORT TERM...WTB LONG TERM...KJC AVIATION...KJC/EVT MARINE...KJC/EVT HYDROLOGY...

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