411 FXUS61 KBOX 250001 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 701 PM EST Sun Feb 24 2019 .SYNOPSIS... Low pressure tracking along the south coast of New England will provide areas of light rain/drizzle this afternoon. This low intensifies rapidly tonight over Maine and then into the Maritimes Monday as a powerful storm. As a result strong to damaging winds develop tonight, peaking Monday afternoon, then gradually diminishing into Tuesday. Then bitterly cold weather overspreads the region Tue night into Wednesday. Not as cold Thursday and Friday followed by potential winter weather around next Saturday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 7pm update... Low pres is shifting toward the Gulf of Maine this hour, winds are beginning to already take on a slightly stronger W component. However, the cold front is still across E NY and is already outpacing the precip shiled it spawned. Given this, will limit POPs mainly to the E slopes of the Berkshires as drier air will limit the amount of precip that makes it into New England. The fropa will follow 00Z-04Z and with strong pres rises expect winds to rapidly increase in its wake. Gusts 30-40 cannot be ruled out during early AM, but the strongest will still hold off until after sunrise. Previous discussion follows... Secondary low pressure tracking up the I-95 corridor of RI/MA at 3 pm based on latest surface observations. Dry slot aloft combining with moist low levels to yield spotty light rain/drizzle along with areas of dense fog. Potent short wave zipping across OH/PA now and its attending cold front will sweep across MA/CT/RI between 7 pm and 10 pm from west to east. This will shift winds to the west advecting drier air across the region along with gradual clearing. This change in airmass will also be accompanied by our first surge of gusty winds of 40-50 mph! Isolated wind damage is possible with an increased risk across northwest MA where up to 3/8 of an inch of ice accretion occurred this morning. This will increase the risk of branches/limbs snapping. This short wave currently moving across OH/PA will invigorate low pressure tracking along the Maine coast and intensify rapidly to 975 mb over the Maritimes by 12z Monday. This will set the stage for very strong to damaging winds tomorrow. Any spotty light rain/drizzle and fog early this evening will give way to drier weather 7 pm to 10 pm from west to east with wind shift. Later tonight could see a brief snow shower from Lake Effect spill over the Berkshires but overall dry weather prevails. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... *** Damaging Winds & Scattered Power Outages Likely *** Trough amplification continues over the Maritimes with low pressure deepening to about 970 mb. Meanwhile upstream Arctic high pressure of 1040 mb over the High Plains yields a 70 mb pressure gradient into New England. This provides a strong wind field across the region. All models showing 850 mb winds increasing from about 50 kt at 12z to 65 kt by 00z Tue. Meanwhile model soundings reveal dry adiabatic lapse rates up to 850 mb all day tomorrow. Taking the average wind speed in the blyr yields frequent gusts tomorrow of 55- 65 mph with the strongest winds likely in the 1 pm to 4 pm window. Wouldn't be surprised if a few gusts top 70 mph! Thus expecting a fairly widespread high wind event with at least scattered power outages if not more widespread. Therefore High Wind Warnings remain posted for all areas. Mainly dry weather prevails tomorrow however can't rule out a few lake effect streamers spilling over the Berkshires into western- central MA and possibly CT and RI. Interestingly some of the Hi Res guidance such as the HREF (specifically HRW NSSL) shows a long fetch streamer from lake Huron across Lake Ontario into NY state and then western MA. Don't see this trajectory too often, crossing two lakes. Temps slightly cooler than normal tomorrow with highs only in the 30s but the gusty winds will yield wind chills in the teens and 20s. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... */ Highlights ... * Strong, damaging winds with scattered power outages into Mon night. * Very cold air moves in Tuesday-Wednesday, moderating * Modest snowfall Wed night - Thu * Storm system possible next weekend Overview and model preferences... Stacked zonal jet persists across much of the N CONUS through the week. This is a result of a squeeze play between several N Stream gyres and meandering tropical high stretched from Mexico to Cuba. Taking dynamics into consideration, the link to this and the LLJ will help to maintain strong winds into early Tue. Through much of the week, it will also stretch and elongate individual waves and attendant sfc clippers, limiting their impacts. It’s not until yet another round of Pacific energy, something we have dealt with often this seas, is able to link with a central Canadian vort max that the pattern becomes more zonal. Allowing for a deepening longwave trof across the E CONUS by next weekend. Looking at the thermal profiles, the N stream will dominate into mid week, with colder than normal conditions expected to linger, likely until some moderate thermal ridging builds late Fri/Sat. Noting enough agreement between long range guidance that a consensus blend can be used for much of this long term update. Details... Mon night... +1035mb high pres will begin to build E, yielding a gradual slackening of the sfc pres gradient and low-mid lvl height gradients. However, at H85, momentum remains +50kt. Bufkit suggests CAA is able to maintain BL mixing to this level. There will be some diurnal drop off, as sfc sustained winds will drop to between 20-30 mph with gusts more on the order of 40-50 mph. Advisories may need to follow any warnings even into the overnight hours. Bitter cold with these winds and CAA. Ambient lows in the teens are expected, but the winds will lead to wind chill values dropping to around 0F or lower in spots. Tue and Wed... High pres crests across the region late Tue and Tue night. Slackening pres gradient will allow winds to finally drop below advisory level thresholds. H92 temps drop below -20C, coupled with H85 temps near 15C below normal. Cold conditions result, yielding highs in the teens to mid 20s each day. High pres crest Tue night suggests good radiational cooling, so expect mins in the single digits across much of the region. Wed night into Fri... Will be watching two open, very progressive shortwaves linked to sfc clipper systems. The first arrival is Wed night into Thu. Weak parent low pres gives way to modest but progressive cyclogenesis offshore with trowal development. Antecedent airmass cold enough for precip type to remain mostly SN. Moisture content is low and lift is weak, suggesting final liquid QPF values of 0.25 or less. Low risk for low end advisory lvl snowfall of DGZ lift can be maximized. Still time. The second wave is a bit trickier as longwave trof will be gradually deepening upstream early Fri. Poleward exit region of the upper jet orients mainly S of New England per latest guidance so will follow this trend, keeping the bulk of any precipitation to the S, especially if yet another coastal low develops along the stalled baroclinic zone to the S. Better focus for the weekend as Gulf of Mexico convection/moisture is encapsulated by central CONUS low pres. Milder temps both days, but with N stream remaining in play, highs/lows are likely to still fall just short of normal. Next weekend... Deepening wave linked to a blend of Pacific energy and N stream vort-max will begin go occlude with sfc low pres passing across the Great Lakes. Lift to the E across New England, and mass fields suggest some initial cold air damming with mixed precip at onset. Still too early for exact details here, but something to watch. Given this has links to Gulf of Mexico moisture, pockets of heavier precip cannot be ruled out. Timing still a bit uncertain given this feature is still just shy of a week away, but consensus blend suggest Sat sees the most impact in terms of precip. Drying, with another risk for strong winds follows Sun as high pres moves in to replace deepening low pres near 980mb. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/...High confidence. Overnight... IFR conditions will give way to VFR rapidly from W-E between 01-04Z. As winds shift mainly to the W, expect the VFR to follow shortly after. Winds begin picking up during the AM, with gusts 25-35 at times, but the strongest will hold off until during the day Mon. Monday... *** West Winds Gusting 50-60 kt *** VFR cigs but big story will be west winds gusting up to 50-60 kt at times all terminals with strongest winds likely 18z-21z. KBOS Terminal...High confidence in TAF trends. Big improvement 00z-03z tonight then very strong winds after sunrise Monday into the afternoon. KBDL Terminal...High confidence in TAF trends. Big improvement 00z-03z tonight then very strong winds after sunrise Monday into the afternoon. Outlook /Monday Night through Friday/... Monday Night: VFR. Strong winds with gusts up to 50 kt. Tuesday: VFR. Strong winds with local gusts up to 40 kt. Tuesday Night: VFR. Windy with gusts up to 35 kt. Wednesday: Mainly VFR, with areas IFR possible. Breezy. Chance SN. Wednesday Night: Mainly IFR, with areas MVFR possible. Chance SN. Thursday into Friday: Mainly VFR but MVFR/IFR conditions possible. Slight chance SN. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/...High confidence. *** Storm Force Westerly Wind Gusts Tonight & Monday *** Tonight... Wind shift to the west between 7 pm and 10 pm west to east with storm force gusts (greater than 47 kt) after midnight. Patchy dense fog and drizzle early this evening, then improving vsby with the wind shift. Monday... West winds gusting 50-60 kt. Snow showers well offshore but dry weather closer to shore. Good vsby. Outlook /Monday Night through Friday/... Monday Night: Storm conditions continue with gusts up to 50 kt. Rough seas up to 18 ft. Freezing spray likely. Tuesday and Tuesday Night: Moderate risk for gale force winds with gusts up to 45 kt. Areas of rough seas. Freezing spray likely. Wednesday and Wednesday Night: Winds less than 25 kt. Seas locally above 5 ft. Chance of snow. Visibility 1 to 3 nm. Thursday: Winds less than 25 kt. Local rough seas. Slight chance of snow. Local visibility 1 to 3 nm. Thursday Night into Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of snow. Visibility 1 to 3 nm. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...High Wind Warning from 10 PM this evening to 7 PM EST Monday for CTZ002>004. MA...High Wind Warning from 3 AM to 7 PM EST Monday for MAZ005>007- 013>024-026. High Wind Warning from 10 PM this evening to 7 PM EST Monday for MAZ002>004-008>012. RI...High Wind Warning from 3 AM to 7 PM EST Monday for RIZ001>008. MARINE...Storm Warning from 3 AM to 7 PM EST Monday for ANZ231>234-250- 251. Storm Warning from 9 AM to 7 PM EST Monday for ANZ230-236. Storm Warning from 1 AM to 7 PM EST Monday for ANZ235-237. Storm Warning from 11 PM this evening to 7 PM EST Monday for ANZ254>256. && $$ SYNOPSIS...Nocera/Doody NEAR TERM...Nocera/Doody SHORT TERM...Nocera LONG TERM...Doody AVIATION...Nocera/Doody MARINE...Nocera/Doody