Area Forecast Discussion
Issued by NWS Boston, MA

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426 FXUS61 KBOX 161000 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 500 AM EST Tue Jan 16 2018 .SYNOPSIS... Low pressure will push east out of the Great Lakes today, then will redevelop off the mid Atlantic coast this evening. There is the likelihood for several inches of snow across a good portion of the region tonight into Wednesday afternoon. However, there is still some uncertainty for a mix of rain and snow southeast of the Boston to Providence corridor. 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A little leftover light snow was reported at KACK through around 2 AM, while another batch of light snow was clipping NW Mass as seen on latest NE regional 88D radar mosaic. Otherwise, cloudy skies continue across most areas as seen on 08Z observations as well as the latest GOES-E satellite fog imagery. Some breaks in the clouds worked across the CT valley earlier this morning, but filled in as next batch of low clouds worked NE out of the Hudson valley. Expect cloudy skies to linger through the day with the subsidence inversion holding on. As the surface ridge across the region pushes E, light N-NE winds will shift to S-SE this afternoon. As H5 trough digs from the western Great Lakes to the mid Mississippi valley during the afternoon, will see SW wind flow aloft take over. Some question as to how quickly this moisture will push E, as the trough shifts slowly eastward. At this point, seems the short range models in good agreement in backing off the onset of the precip until around 18Z or so into western/N central Mass, then slowly pushing E into the western Merrimack valley toward sunset. Best chance for precip through 00Z will be across NW Mass. Models continue to signal another surface low developing off the mid Atlantic coast this afternoon, with a pretty good slug of moisture at the surface and aloft streaming N but timing keeps this moisture S of the region until tonight. With decent warm air advection especially across SE New England, temps will reach the lower-mid 30s there, but will hold back in the mid 20s to lower 30s further N and W. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Tonight and Wednesday... H5 long wave trough remains positively tilted as it slowly but steadily shifts E. Continue to see a strong jet core, up to 120-130 kt, with right entrance region pushing to the mid Atlantic coast this evening. The coastal low will take shape off of the Delmarva peninsula and shift NE, passing across Cape Cod and the islands around midday or so on Wednesday. Continue to see best and strongest lift moving across the region late tonight through around midday Wednesday. Best snow growth also moves across about that time. 00Z model suite appears to be in pretty good agreement in bring the low across Cape Cod and the islands by around 18Z Wed, then will head to the Gulf of Maine. This will place the best chance for highest snow amounts across NE, central and W Mass into NW RI and N CT. Some question on a mix/changeover to rain across SE Mass and central/S RI, though looking more likely especially across Cape Cod and the islands. Models signal slightly lower QPF amounts, in the 0.4 to 0.6 inch range. Snow to liquid ratios of between 12 and 15 to 1 across in the interior, and 10 to 12 to 1 in much of RI and SE Mass. This continues to support 6 inches or higher pf snow over much of the region of central and northern areas, with diminishing amounts south of a Boston-Hartford line due to temperatures near freezing along with a mix or change to rain. Have converted Winter Storm Watches to Warnings over much of the region from Boston into NW RI and all of N central and NE CT N and W, with Winter Weather Advisories across the remainder of RI and SE Mass to the N of the Cape Cod Canal. Could see a little snow on the Cape and islands overnight, but should change to rain toward daybreak through mid morning Wednesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... 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. && .AVIATION /10Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... Through Today...Moderate confidence. MVFR-IFR CIGS/VFR VSBYS across central and eastern areas through 12Z-14Z, otherwise mainly VFR. Light snow showers will push into western and N Central Mass/N central CT with local MVFR VSBYS during the afternoon. Tonight and Wednesday...Moderate confidence. 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 during Wed. Conditions improve to VFR in CT and Western Mass Wednesday afternoon...and in RI and Eastern/Central Mass Wednesday night. Wind gusts 20-25 knots around Nantucket and parts of Cape Cod. KBOS Terminal...Moderate to high confidence in TAF. MVFR CIGS through 12Z-14Z, then should be mainly VFR through evening push. KBDL Terminal...High confidence in TAF. Mainly VFR through 00Z, then lowering to MVFR-IFR as -SN develops by around 03Z. 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. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/...High confidence. Through Today... N winds may briefly gust to 20 kt E and S of Cape Cod through daybreak, otherwise winds will be below small craft levels. However, seas across the open waters up to 6-10 ft, mainly on E swells. Small craft advisories continue. Tonight... Expect S-SE winds up to around 10 kt, shift to E after midnight. Some gusts up to 20 kt toward daybreak across the southern outer waters. Seas around 5 feet on the outer waters. Mixed snow and rain developing with reduced visibility. Small crafts continue. Wednesday... East winds with gusts 20 to 25 knots. Seas 5 to 7 feet on the outer waters and possibly on the RI waters. Rain through the day, may mix with snow on the eastern nearshore waters toward evening. Visibility 2 to 4 miles. Small crafts continue. 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. && .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 across the river basins through midweek which will limit additional runoff, along with continued ice jams on some of the rivers. There will be an increase of snow pack for much of region today into Wednesday as several inches of snow will fall. 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... 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. && $$ SYNOPSIS...KJC/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...KJC AVIATION...KJC/EVT MARINE...KJC/EVT HYDROLOGY...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.