658 FXUS61 KBOX 222021 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 321 PM EST Fri Feb 22 2019 .SYNOPSIS... High pressure over the Great Lakes builds into New England tonight and Saturday, then moves offshore Saturday evening. This will bring a period of dry and seasonably cool weather to the region. Low pressure then tracks along the coast Sunday with a wind swept rain, except freezing rain/ice for the interior Sunday morning. Strong to damaging winds develop Sunday night, peaking around Monday then gradually diminishing into Tuesday. A mostly quiet week thereafter, watching a potential following weekend storm. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 330 PM update... 1033 mb high pressure over the Great Lakes advects into New England tonight resulting in winds diminishing with sunset. Fairly dry atmosphere with dew pts in the upper teens and 20s combined with just some thin cirrus clouds spilling over the ridge to our west, will promote radiational cooling tonight. Thus temps will fall fairly quickly after sunset. Therefore have based mins tonight on the colder MOS guidance. Lows will range from the upper teens to lower 20s, mid 20s in the urban areas of Boston, Providence and Hartford. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... 330 PM update... Saturday... Very nice day by late Feb standards with plenty of sunshine as deep layer ridge axis remains just west of New England supporting anticyclonic flow and associated subsidence into MA/RI/CT. Perhaps some mid/high clouds dimming the sun late in the day but otherwise abundant sunshine. 1032 mb high pres over the region tomorrow will promote light winds. Thus this combined with full sunshine and highs climbing into the lower 40s will make for very pleasant late winter conditions. Little cooler along the coast as light onshore winds develop in the afternoon. && .LONG TERM /SUNDAY THROUGH FRIDAY/... 330 pm update... */ Highlights ... - Lingering interior freezing rain early Sunday, otherwise rain - Drying out late Sunday - Strong, damaging winds around Monday, wind headlines likely - Could be quiet and dry through the week, weekend storm possible */ Overview ... Poleward latent heat release transfers across both the N Atlantic and N Pacific contributing to stout ridging over W Europe and AK, respectively. Arctic squeeze-play, N-stream energy bowled S over N America, cross-polar flow into the CONUS courtesy AK ridging as the NW Atlantic remains wide open. With a mild Pacific stream persisting from favorable Hawaiian troughing into the W CONUS it remains to be seen as to whether S-stream energy will buckle or rather phase with diving N-stream, whether a flat trof-base flow with parent thermal gradient or rather more pronounced troughing emerges with conveyor belt motions, respectively. Wildcards with Typhoon Wutip, as well as transitioning enhanced tropical convection across the Atlantic into the Indian Ocean signaled via the phase 8 to phase 3 forecast MJO via EC, anomalous mild westerlies shifting downstream accordingly. A lot playing out into the end of February, accompanying nuisances. After the weekend / early week wintry mess followed by strong to damaging winds there's not a lot of forecast confidence. Certain that Arctic air will make its presence well- known, but uncertainty concerning any storm morphology and accompanying airmass. If the forecast EPO remains largely negative as the EC suggests, prefer to lean colder beneath a continental-polar airmass, the more favorable baroclinic zone shunted well S of our region. Lighter yet wintry outcomes with the better storm-track well outside our area, out to sea. Preference to the EC / ECens guidance. Break down the details below. */ Discussion ... Sunday ... Continuing interior freezing rain. Prefer maintaining a shallow cold airmass given secondary coastal low forecast. N-wedge drainage flow with ageostrophic / isallobaric winds, slowly scouring out with rain releasing latent heat at the surface as over time it falls through a deeper H9-7 warm layer. Maintain freezing rain as late as midday by which point the attendant storm system / frontal boundaries should be lifting N resulting in any N winds to shift W/SW. Additional ice accretion of a coating up to 0.1 inches mainly focused over N/W MA. Icing on untreated surfaces, slick and hazardous. Sunday night into Monday diminishing into Tuesday ... Strong, damaging winds. Expect impacts of downed tree limbs / trees as well as power lines. Anticipate power outages. Robust SE Canada storm development with an accompanying pressure rise / fall couplet of roughly 2 mb / hr across S New England (not as strong as further N but decent enough), cold air advection proceeds rearward yielding steep boundary layer lapse rates (dry-adiabatic) up through H8, with 55 to 70 mph W winds at the boundary layer top. Surface momentum transfer, at a minimum, widespread WIND ADVISORY headlines, gusts exceeding 45 mph. Not out of the question we could see HIGH WIND WARNING criteria across the high terrain and along the coastline with gusts around 60 mph. Height of winds around Monday morning that'll gradually diminish into Tuesday while the boundary remains well-mixed, yet subsiding with increasing presence of high pressure. Wednesday onward ... Watching additional energy and associated continental airmasses that will zip along a rather flat base of a h5 trof persisting across S Canada, bowled over the N/NE CONUS. Favoring the EC, some light snow outcomes possible at times, otherwise high pressure and colder than average conditions. Focus on a following weekend storm system that has been consistently signaled. Low confidence forecast, simply watch and wait for now. && .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/...High confidence. 1 PM update ... Today ... VFR, dry weather and light NNW winds. Tonight ... VFR, dry weather and winds becoming calm. Saturday ... VFR and dry weather continues. Light and variable winds becoming light onshore during the afternoon along the coast. Saturday night ... VFR and dry weather thru the evening, then MVFR and precip after midnight from west to east. Ptype, rain except freezing rain across the interior. LLWS likely toward 12z Sunday morning along the south coast including Cape Cod and Islands. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Sunday through Wednesday/... Sunday: MVFR/IFR conditions possible. Windy with areas of gusts up to 30 kt. Chance RA, FZRA. Sunday Night: Mainly VFR, with local MVFR possible. Strong winds with gusts up to 45 kt. Monday: VFR. Strong winds with gusts up to 50 kt. Monday Night: VFR. Strong winds with gusts up to 45 kt. Tuesday: VFR. Windy with gusts up to 35 kt. Tuesday Night: VFR. Windy with gusts up to 30 kt. Wednesday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 330 PM update... Short Term /through Saturday Night/...High confidence. High pressure tonight and Saturday yields tranquil weather on the waters with light NNW winds tonight becoming locally onshore and light Saturday. Saturday night east winds increase to 20-30 kt toward Sunday morning as low pressure lifts northeast from NJ coast. Vsby lowering in rain toward morning. Outlook /Sunday through Wednesday/... Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain. Local visibility 1 to 3 nm. Sunday Night: Low risk for gale force winds with gusts up to 45 kt. Rough seas up to 15 ft. Monday: Moderate risk for storm force winds with gusts up to 50 kt. Rough seas up to 16 ft. Monday Night: Moderate risk for gale force winds with gusts up to 45 kt. Rough seas up to 14 ft. Chance of freezing spray. Tuesday: Moderate risk for gale force winds with gusts up to 35 kt. Rough seas up to 11 ft. Chance of freezing spray. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Chance of freezing spray, slight chance of snow. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas locally approaching 5 ft. Chance of freezing spray. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Watch from Sunday evening through Tuesday morning for ANZ230>237-251-255-256. Gale Watch from Sunday afternoon through Tuesday morning for ANZ250-254. && $$ SYNOPSIS...Nocera/Sipprell NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...Sipprell AVIATION...Nocera/Sipprell MARINE...Nocera/Sipprell