Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 220757 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 257 AM EST Wed Feb 22 2017 .SYNOPSIS... A weak cold front over New England dissipates early this morning. Unseasonably mild temperatures will remain across southern New England through the end of the week as weak low pressure systems pass west of the region. A strong cold front will cross the region Saturday afternoon and evening, bringing showers and possibly a few thunderstorms. Near seasonable temperatures will return early next week, with blustery conditions on Sunday. && .NEAR TERM /THROUGH TODAY/... Moisture axis moves across Southern New England this morning, supported by a dissipating upper shortwave. Cloud bases with the showers remained at or above 6000 feet as of 3 am, while surface dew point depressions had lowered to around 5F. This would suggest continued virga but with widely scattered sprinkles reaching the surface. We will continue to show slight chance pops through mid morning. Moisture lingers below 850 mb through the day. But deeper dry air layer works in above that level. This should be enough to generate partial clearing by the afternoon. Southwest flow surface and aloft will bring a warming trend. Mixing to 950 mb supports max sfc temps in the 50s. Mixing to 925 mb would support max temps around 60. Limited sun and warm advection just off the deck would favor the shallower mixed layer. The forecast for today will aim for the 50s. && .SHORT TERM /TONIGHT THROUGH 6 PM THURSDAY/... Tonight... Dry weather with continued southwest flow. Guidance shows no rising trend on dew points, but it does show developing fog and low clouds. This seems a little contradictory, but may allow for patches of fog especially on the South Coast and the interior. Min temps will be near dew point, roughly 34 to 40. Thursday... High pressure remains offshore with southwest flow across Southern New England. Shortwave moving through the Great Lakes drives low pressure into Ontario and Quebec. Forcing with this feature is primarily in Canada as well as adjacent parts of NY and VT/NH. Will favor a dry forecast for Southern New England during Thursday. Southwest jet associated with this system brings 20-25 knot low level winds to our area Thursday afternoon. Could be a few gusts in this range during the afternoon especially across RI and Eastern MA. Thursday...High confidence. S-SW winds in place, gusting up to around 20 kt during the afternoon. Gusts up to 25 kt and seas building to around 5 ft on the outer waters Thu night. May see patchy drizzle and fog develop Thu night along the S coast with reduced visibilities. Mixing depth will continue limited due to the differential warm advection. But temps within the layer will have climbed a few degrees, with values equiv to 850 temps of 1-3C which would support max sfc temps of 59-63F. Noting the record high temps listed in the Climate section, this would suggest values at or near record high at PVD and ORH, while BOS and BDL records are well above this. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Highlights... * Record warmth remains possible Thursday * Scattered showers possible with mainly mild temps on Friday * Widespread showers expected Saturday-Saturday night, with a few thunderstorms possible * Blustery and seasonably cool Sunday-Monday Overview... Overall upper level pattern continues across the lower 48 late this week, with building H5 ridge across the eastern U.S. as a trough digs out of the Rockies into the Plains states. This trough will slow surface systems down on Thu and Fri, with high pressure pushing offshore. A weak cold front may briefly work into northern areas Fri, but will retreat quickly north as S-SW winds pick up so could see another mild day for most areas. The big question is the timing of the surface system/developing cutoff H5 low that will work slowly east either Fri or Sat. Models seem to have a decent handle on the movement and shearing of the mid level system into Quebec, but some question as to the timing of the associated cold front. At this point, looks like it should push across Saturday into Saturday night. This will likely bring a decent amount of rainfall, and may even see a few thunderstorms ahead of the front. Beyond this, cutoff low pres over central Canada should keep progressive pattern in place through the remainder of the weekend into early next week with seasonable temperatures returning. Details... Thursday night... Low level capping seen on 12Z BUFKIT soundings Thu night, which could trap low level moisture along the S coast with the SW winds in place. Have mentioned patchy drizzle during the nighttime hours for those areas. May also see some isolated showers during the overnight as well, mainly across central and western areas, but precip will be light. Friday... Cold front stalls just S of the region Fri morning, but temps will not get too cool as H925 and H85 temps remain on the mild side. Light E-SE winds in place early in the day will shift to S-SW again as system returns as a warm front during the afternoon. This will be ahead of low pressure moving across the Great Lakes. May see scattered showers mainly from the Mass Pike northward during the day ahead and with the front. With a light onshore flow on both coasts, temps will be a bit cooler there. However, another mild day on tap for inland areas though not quite as warm as expected on Thursday. Readings away from the coast and into the inland valley could approach or exceed 60 in some spots. Otherwise temps mainly reaching the 50s. Saturday... Will be an active day. Low pressure will push into Quebec during the day with the weakening upper level cutoff low. However, its associated short wave will wrap across the region. Strong vorticity ribbon with this short wave, along with band of instability. Noted LI/s near zero, total totals in the lower 50s and TQ values up to 18-19 for elevated convection. So, have also mentioned a slight chance for thunderstorms Sat afternoon and evening for now. Have also noting good low level southerly jet up to 35-45 kt ahead of the front, so could see some of this mix down with any convection. Cold air will wrap in quickly overnight Sat night as the precip tends to cut off. Could still see a quick mix or changeover to snow showers across central and western areas. System pushes offshore quickly though, so may not see much of a wintry mix toward the coastal plain as the moisture ends quickly. Highs on Saturday may reach the lower 60s across interior E Mass and the CT valley, otherwise readings mainly in the 50s. Temps fall quickly overnight, bottoming out in the 30s at most locations, except around 40 on the outer Cape and the mid-upper 20s over the higher inland terrain. Sunday through Tuesday... Cold front pushes offshore by 12Z Sun, so should see mainly dry conditions for Sunday. Blustery NW winds in place, with gusts up to 25-30 kts, highest along the immediate coast and higher terrain. The gusty winds will make it feel more like temperatures in the mid 20s to mid 30s during the day, though actual highs will be close to seasonal normals /mid 30s to mid 40s/. May see another weak short wave quickly move across Sunday night-Monday. Have only carried slight chance POPs with this system as it appears to be moisture starved in the W-NW flow aloft. ThiThursday...High confidence. S-SW winds in place, gusting up to around 20 kt during the afternoon. Gusts up to 25 kt and seas building to around 5 ft on the outer waters Thu night. May see patchy drizzle and fog develop Thu night along the S coast with reduced visibilities.s is ahead of another reinforcing cold front. Timing of this system is in question though with fast flow aloft. For now, Tuesday should be a dry and seasonable day as high pressure builds across. Winds should diminish. Systems continue to move quickly in progressive flow aloft, so timing this far out is in question. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/... Today...High confidence. Generally VFR. Patchy MVFR cigs possible this morning, mainly in Northern MA. Widely scattered showers this morning. Tonight...Moderate confidence. VFR through midnight. Areas of MVFR/IFR cigs and vsbys develop with patchy fog. Thursday...Moderate confidence. Lingering MVFR/IFR cigs and vsbys in the morning, but trending to VFR by late morning and through the afternoon. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday night...Moderate confidence. Mainly VFR across most of E Mass. MVFR-IFR CIGS lingering along the S coast, Cape Cod and the islands, possibly into the CT valley. Patchy fog may develop overnight as well with local MVFR-IFR VSBYS. Friday...Low confidence. Leftover MVFR-IFR VSBYS through mid morning in patchy drizzle/fog. CIGS improve to VFR, though may see patchy MVFR-IFR CIGS as warm front pushes N during the day, especially across central and N Mass. Scattered showers linger across the interior. Light E-SE winds shift to S from S-N Fri afternoon and evening. May see gusts up to 20 kt along the S coast. Saturday...Moderate confidence. Areas of MVFR-IFR CIGS/VSBYS in showers and patchy fog. Low risk for isolated thunderstorms Sat afternoon/evening. A few snow showers possible across western areas before precip ends. Conditions may improve to VFR after midnight across western areas. Sunday...Moderate confidence. A few rain and/or snow showers may linger across central and eastern areas through mid morning Saturday with local MVFR conditions. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/...High confidence. Persistent SW flow through the period. Wind speeds today and tonight remain light. Speeds Thursday increase as winds strengthen aloft. This may be enough to bring gusts 20-25 kt Thursday. Seas remain light today and tonight, but may approach 5 feet on the outer waters Thursday afternoon/evening. Outlook /Thursday Night through Sunday/... Friday...Low confidence. Winds should become light N-NE across the eastern waters Fri morning, with light/variable winds on the southern waters. Expect winds to shift back to S-SW during the day as warm front pushes N. May see gusts up to 20 kt on the outer water Fri night. Local visibility restriction in patchy fog. Saturday...Moderate confidence. S winds increase, gusting to around 25 kt. Small crafts likely. Seas build up to 5-8 ft on the southern outer waters. Reduced visibilities in showers and patchy fog. Low chance for thunderstorms Sat afternoon/evening. Sunday...Moderate confidence. Winds shift to W and gust up to 25-30 kt. Seas up to 6-9 ft on the open waters. && .CLIMATE... Record Highs for Thu Feb 23 BOS...65/1990 BDL...68/1990 PVD...60/1990 ORH...61/1990 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT CLIMATE...

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