Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 171947 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 347 PM EDT Sat Mar 17 2018 .SYNOPSIS... Dry but unseasonably cold weather will continue into early next week. A multi-part storm system moves to the Mid Atlantic states midweek. This system may affect parts of Southern New England Wed and Thu, but it is also possible the storm stays to our south with little impact. However uncertainty remains high on the evolution of this storm especially its eventual track. High pressure builds with drier weather Friday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 4 PM Update... A cold front entering northern MA at 3 pm with a noticeable wind shift from west to northwest behind the front. Some returns on radar across northeast MA but given high cloud bases around 6 kft along with dew pt depressions 20-25 degs, unlikely any flurries or snow showers will reach the surface. Perhaps some virga. Otherwise a dry frontal passage this evening. Gusty west winds ahead of the front with gusts up to 40 kt/45 mph, about 30-35 kt behind the front. Not as windy after sunset as blyr becomes more shallow. Very cold airmass behind the front tonight with -22C air at 850 mb currently along the Canadian/northern New England border! Given this leaned toward the colder MOS guid for lows tonight as winds decouple especially outside the urban areas and high terrain. Not record cold but about 10-15 degs colder than normal with mins in the teens regionwide and single digits northern MA. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... Sunday... Cold and dry NW flow continues with more sunshine than clouds. However a chilly day with highs only 30-35 with upper 20s across the high terrain. These temps are about 10-15 colder than normal. The only good news is fairly light winds will not contribute to much of wind chill. Sunday night... Another cold night with 1034 mb high pres over Ontario building southeast into New England, decoupling winds away from the urban areas and high terrain. Another round of mins in the teens. Monday... Dry but cold NW flow continues. Not as cold with highs in the mid to upper 30s, low 30s high terrain. Fairly light winds and more sunshine than clouds will make the cold conditions a bit more tolerable. Monday night... Potentially good radiational cooling with ridge of high pres cresting over the area combined with mostly clear skies, light winds and a very dry airmass. Mins in the teens once again outside of the urban areas. && .LONG TERM /TUESDAY THROUGH SATURDAY/... */ Highlights... - Tuesday into Wednesday, keep it cold and dry, N winds - Wednesday night into Thursday, monitoring potential storm - Friday into Weekend, keep cool, dry pattern for now */ Overview and discussion... Evaluating potential storm development. At set, SE Canadian gyre as Pacific energy train continues. La Nina tendencies still at play, N- Pacific H5 ridge re-emerges poleward. N-stream energy dislodged, the trof-ridge-trof pattern amplifies downstream thru the week ... but where exactly? NE CONUS perspective, progged upstream energy, even NW CONUS, bowls within a preferred H5 trof. Yet downstream pattern becomes lax, opens, suppressive wave presently slips E, NAO forecast positive. This as a mild Pacific C CONUS punch emerges. A wave-train nudge E allowing cyclonic trof digging further offshore? Or can N- stream energy, colder air cut S faster, sharper-amplified baroclinic setup closer coastal, less flat, more pronounced, per enhanced H5 C CONUS ridging? Lot of moving parts, chaotic, expect adjustments in later forecasts. Focus late Wednesday into Thursday when suppressive, confluent flow can eject E as N-stream cyclonically digs through preferred H5 trof pattern, creating a favorable environment towards storm development near NE CONUS. Believe any activity prior will be suppressed S, off- shore, beneath confluent flow aloft, only maintaining cold air. Only certainty, looks chilly through the end of the month. Threats, impacts, precipitation amounts? Way too early to say with any specificity. Proximity of any storm, thermal fields, intensity, time of day, etc., etc., all fairly unknown for now. Best advice, stay informed, keep tuned to later forecasts. && .AVIATION /20Z SATURDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...High confidence. 18z update... VFR and dry weather thru Mon night. Gusty WSW winds up to 40 kt late Sat will shift to the NW up to 40 kt Sat evening behind a cold front, then diminishing later Sat evening. Not as windy remainder of the period including Sun thru Mon night. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Tuesday through Thursday/... Tuesday: VFR. Breezy. Tuesday Night: Windy with areas gusts to 30 kt. Slight chance SN. Wednesday through Wednesday Night: Windy with gusts to 35 kt. Slight chance SN. Thursday: Windy with gusts to 35 kt. && .MARINE... Short Term /through Monday Night/...High confidence. Tonight... Gale warnings continue all waters until 7 pm and then a downward trend. Cold front across the northern waters late Sat afternoon slides south this evening with a wind shift from west to north. Low risk of areas of light freezing spray across the eastern MA waters. Sunday thru Monday night... Modest NNW winds with possible areas of light freezing spray eastern MA waters at night, then diminishing Mon night as ridge of high pres builds across the waters. Outlook /Tuesday through Thursday/... Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Slight chance of snow. Tuesday Night: Low risk for gale force winds with gusts up to 35 kt. Local rough seas. Slight chance of rain, slight chance of snow. Wednesday: Moderate risk for gale force winds with gusts up to 35 kt. Rough seas up to 10 ft. Chance of snow, chance of rain. Wednesday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 11 ft. Chance of snow. Thursday: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 11 ft. Slight chance of snow. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Warning until 7 PM EDT this evening for ANZ232>237. Gale Warning until 6 PM EDT this evening for ANZ230. Gale Warning until 8 PM EDT this evening for ANZ231-250-251- 254>256. && $$ SYNOPSIS...Nocera/Sipprell NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...Sipprell AVIATION...Nocera/Sipprell MARINE...Nocera/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.