405 FXUS61 KBOX 252101 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 401 PM EST Mon Feb 25 2019 .SYNOPSIS... Low pressure will continue to intensify rapidly over the Maritimes today. As a result, strong to damaging winds will peak this afternoon, then gradually diminishing into Tuesday. Bitterly cold weather overspreads the region Tuesday night into Wednesday. Light snow is likely late Wednesday into early Thursday, followed by somewhat milder conditions late week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... **Damaging Winds & Scattered Power Outages Likely** 1250 PM Update... Most of the bands of snow showers have tended to weaken as they shifted to the S coast around midday, while the stronger lake effect snow bands across most of NY state have tended to weaken as they reach the Hudson Valley into the Berkshires. Good subsidence moving across into the region as strong pressure rises approach as seen on latest MSAS isallobaric tendencies map. However, can't rule out a few more snow showers working eastward, but looks like they should be confined to the CT Valley westward through around 20Z-21Z. Very tight pressure gradient continues to result in very strong wind gusts, up to 67 mph at KMQE, 66 mph at KAQW and 62 mph at KBAF at 18Z. Been received reports of damage as well as power outages. Expect the strong gusts to continue into this evening at least. Updated near term to bring conditions current, along with keeping the strong wind gusts in through around 00Z or so, though beginning to slowly diminish across the CT valley. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Pressure gradient gradually weakens tonight into Tuesday as a high pressure becomes centered over Ontario, Canada. Will most likely be able to downgrade the High Wind Warnings to Wind Advisories for a time this evening as this process begins. Winds remain gusty after midnight, but should be considerably weaker compared to today. Besides the decreasing wind, it will also become noticeably colder. Low temperatures tonight in the single digits above zero and teens, with highs struggling to get out of the teens and 20s Tuesday. Dry weather continues for just about all of southern New England through Tuesday, except for the risk of some snow showers this evening towards NW MA. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Highlights... * Modest snowfall Wed night-Thursday * Storm system possible next weekend Overview and model preferences... Zonal jet remains the most prominent feature across the NE CONUS mid week thanks to a synoptic squeeze play between tropical high pres and N stream vort maxes rotating through Ontario into the Maritimes. However, within this setup, N stream remains the dominant player throughout, maintaining the generally colder than normal conditions into the late week timeframe. The first wave pushing through this jet remains well open, and is linked to sfc clipper system which will impact the region Wed into early Thu. The second loses much of its available thermal/moisture profile as Pacific energy and a vort- max currently near Nunavut phase, leading to deepening longwave trof upstream, favoring a stronger system for the weekend. Regarding this particular storm, given both the phasing aspect and uncertainty regarding the Pacific vort, there is some uncertainty whether parent, inland low pres will remain dominant, or coastal development will take over. Previous runs favored the former, however with today’s updates there is stronger emphasis on a coastal low. Will lean most heavily on ensembles for the weekend given this uncertainty, as it will better represent both current trends. Otherwise, will use a consensus blend of long range guidance. Details... Wed and Wed night... Antecedent airmass remains cold, with H85 temp anomalies as much as 15C below normal. H92 temps still below -20C. This should limit highs, especially given building cloud deck to the 20s across much of the region. Focus then shifts on approaching clipper, which climatologically is linked to an open mid lvl wave and generally moisture starved. Still modest lower lvl convergent lift is noted, however it is generally below the DGZ, so SLRs will unlikely be maximized unless things change. Light snowfall expected, beginning late afternoon-overnight, potentially leading to some impact to the Wed evening commute. Final QPF values on the order of 0.25 inches suggest risk for low end advisory lvl snowfall possible by the time it ends early Thu AM. Thu and Fri... Gradual moderation to the airmass in response to mid lvl ridging. However, noting that both H92 and H85 temps remain below seasonal normals thanks to continued impact from N stream. Therefore, anticipate that lows/highs will remain below normal as well, with the former in the teens and 20s, and highs in the mid-upper 30s. As mentioned above, a secondary open wave will approach on Fri, but the deepening wave upstream is usurping most of the moisture and thermodynamic lift. Therefore, will feature some lower end POPs, but favor the weekend storm for more impacts. Guidance favors initial suppression of the low pres to the S. Sat... Longwave trof linked to yet another round of Pacific energy and an arctic vort-max approaches. There is some suggestion that as the phasing occurs, the trof takes on a negative tilt which does favor coastal redevelopment if fully realized. However, given each of the waves are not well sampled just yet, am not surprised to see guidance struggling to decide which sfc low remains the dominant player. This will be something to watch, because with ensemble trend toward coastal development would suggest a risk for more SN/wintry precip rather than widespread RA. Details forthcoming, but this update will favor the colder solution that ensembles also favor. This is especially true, given the ensembles also favor less progressive pattern, erring on the side of more amplified solution. Sun and early next week... Given the uncertainty regarding the timing/impacts from storm system, timing of nearly 1030mb high pres and drier also carries uncertainty. However, do anticipate another arctic influence, as the longwave trof allows for conduit of arctic airmass. Following the low pres, anticipate a return of colder and blustery conditions for early week. && .AVIATION /21Z MONDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. This Afternoon... **West Winds Gusting 50-60 kt** VFR cigs with brief reductions to MVFR-IFR in scattered SNSH through around 19Z or so across the CT valley and E slopes of the Berkshires. West winds will gust up to 50-60 kt at times at all terminals. Strongest winds are likely through at least 00Z. Tonight... Mainly VFR, but may see brief MVFR CIGS E slopes of the Berkshires through 02Z-03Z. W winds gust up to 40-50 kt through this evening will diminish to 35-40 kt by around 03Z, then to 25-35 kt toward daybreak. Tuesday... VFR. W wind gusts up to 25-35 kt through the day, except approaching 40 kt on the outer Cape Tue morning. Winds slowly diminish Tue afternoon across W Mass/N central CT terminals. Tuesday night... VFR. Leftover W-NW wind gusts up to 25-30 kt across central and eastern areas Tue evening, then slowly diminish. KBOS Terminal...High confidence in TAF trends. Timing strong winds may be off by an hour or so. KBDL Terminal...High confidence in TAF trends. Timing strong winds may be off by an hour or so. Outlook /Wednesday through Saturday/... Wednesday: Mainly VFR early, with areas IFR possible late day. Breezy. Chance SN. Wednesday Night: Mainly IFR, with areas MVFR possible. SN likely. Thursday: Mainly VFR, with local IFR possible. Slight chance SN. Thursday Night: Mainly VFR, with local IFR possible. Slight chance SHSN. Friday into Saturday: MVFR/IFR conditions possible. Chance RA, chance SN. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. **Storm Force Westerly Wind Gusts Today** Through This Afternoon...W winds gusting 50-60 kt. Snow showers well offshore, but dry weather closer to shore. Good visibility. Tonight and Tuesday...West wind gusts continue at 50-55 kt this evening, then gradually diminish to gale force especially after midnight. Freezing spray develops overnight, especially across the coastal waters east of MA. A Freezing Spray Advisory posted for some of the eastern coastal waters where confidence is highest. This Advisory may need to be expanded with later forecasts. Outlook /Wednesday through Saturday/... Wednesday into Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of snow. Local visibility 1 to 3 nm. Thursday Night into Friday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain, chance of snow. Visibility 1 to 3 nm. Saturday: Winds less than 25 kt. Areas of rough seas. Chance of rain, chance of snow. Local visibility 1 to 3 nm. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...High Wind Warning until 7 PM EST this evening for CTZ002>004. MA...High Wind Warning until 7 PM EST this evening for MAZ002>024- 026. RI...High Wind Warning until 7 PM EST this evening for RIZ001>008. MARINE...Storm Warning until 10 PM EST this evening for ANZ231-232. Freezing Spray Advisory from 11 PM Tuesday to 5 AM EST Wednesday for ANZ232-255. Storm Warning until 7 PM EST this evening for ANZ233-234. Storm Warning until 8 PM EST this evening for ANZ230. Freezing Spray Advisory from 5 AM Tuesday to 9 AM EST Wednesday for ANZ231-250-251-254. Storm Warning until 5 PM EST this afternoon for ANZ236. Storm Warning until 9 PM EST this evening for ANZ235-237-256. Storm Warning until 2 AM EST Tuesday for ANZ250. Storm Warning until 1 AM EST Tuesday for ANZ251. Storm Warning until midnight EST tonight for ANZ254. Storm Warning until 11 PM EST this evening for ANZ255. && $$ SYNOPSIS...Doody/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...Doody AVIATION...Doody/EVT MARINE...Doody/EVT