Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 212241 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 541 PM EST Tue Feb 21 2017 .SYNOPSIS...
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A weak cold front dissipates as it crosses New England late tonight. Unseasonably mild temperatures will remain across southern New England late this week. 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.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... High pres moves offshore tonight with weak warm advection developing along with weakening shortwave moving into New England. Forcing for ascent is limited but models indicating deep moisture plume moving across SNE 06-12z. A few showers possible mainly after midnight as this moisture plume and weak shortwave moves through but some areas may remain dry. Will maintain low chc pops for late tonight. The main issue is the potential for some light freezing rain across interior N MA as the precip moves in as temps will be near freezing here. Elsewhere, expect temps will be mostly above freezing. Since temps will be marginal and some areas may remain dry, no advisory will be issued but will address potential for some spotty icy spots in an SPS. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday... Moisture axis will be oriented south of the Pike by 12z and moving south of the coast during the morning. Clouds and a few showers are possible in the morning across CT/RI and SE MA, otherwise mid level drying moving in from the north should allow ptsunny skies to develop late morning into the afternoon from north to south. SW flow will bring milder temps into SNE with highs likely reaching the low/mid 50s across most locations but cooler Cape/Islands and higher terrain. However, potential for upper 50s to near 60 in the coastal plain if there is sufficient sunshine. Cloud cover may limit full heating. Wednesday night... Mainly dry conditions and above normal temps with modest SW flow persisting. Patchy low clouds and fog may develop overnight. Lows will range through the 30s. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
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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... High pressure off the eastern seaboard will keep steady stream of mild air pushing northward across the region. Could see some isolated showers move across western areas during the day, but models having a tough time handling the low level moisture field. Noting mainly light QPF during Thu night. Leaned toward the drier solution with the weakening system, at least with any shower activity during the day Thu. Noting a strong low level jet pushing across the region Thu afternoon and night ahead of weakening cold front. Low level mixing is marginal, though does improve between H925 and H95 after 00Z Fri across S coastal areas, so could see brief gusts up to 20-25 kt. Area of clouds may linger, especially across central and western areas during the day, which may cut back on the full heating potential. Depending upon how much mixing takes place up to H925, where readings will be around +10C to +11C, and whether the clouds could actually clear for a time, temps may reach the lower-mid 60s. Record highs may be close at KPVD and KORH, but may be tougher to reach at KBOS and KBDL. 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-Sunday... Potent shortwave will move through the flow and approach southern New England on Saturday. This wave will drag a cold front across the region ending the chances for above average temperatures. Ahead of the front, anomalous southerly flow with LLJ increasing to 35-45 kts as 925 mb temps warm to 12C. This will result in above average temperatures for the region as well as gusty winds. PWAT values also increase near 3 STD above normal as southern stream moisture is fed into the system. Will have to watch for secondary surface low that may develop along the front, which could indicate heavy rain for the region. Low confidence on thunder potential as EC ensemble mean indicates some instability. FROPA will be quick as temperatures plummet behind the front. Could see some wet flakes on the backside depending on how much moisture is left as front moves through. Sunday into Tuesday... Chilly and blustery NW flow will take over the region by Sunday into Monday. Temperatures difference between Saturday and Sunday could be close to 20F. Wind gusts could also increase close to 30 MPH as the region mixes well above 850mb. A weak wave appears to move through the flow on Monday into Tuesday, which could result in some rain/snow showers for the region. Low confidence on timing, but it is moving quickly and bringing in another round of cold air.
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&& .AVIATION /22Z TUESDAY THROUGH SUNDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Through 00z... VFR with increasing high clouds. Coastal seabreezes developing. Tonight...Moderate confidence. VFR cigs, but areas of MVFR developing late tonight in western MA and portions of northern CT. A few showers possible mainly after midnight with low risk of patchy freezing rain in interior northern MA. Wednesday...Moderate confidence. Patchy MVFR cigs/vsbys in the morning, mainly from CT valley to the south coast, improving to VFR in the afternoon. Low risk of a morning shower near the south coast. Wednesday night...Moderate confidence. Areas of MVFR/IFR cigs may develop along with patchy fog. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Thursday through Sunday/... Thursday...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 Thu afternoon/night. 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.
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&& .MARINE...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/...High confidence. Persistent SW flow through the period with windspeeds and seas remaining below SCA. However, may see a few gusts 20-25 kt late tonight into Wed morning across eastern MA waters. Outlook /Thursday through Sunday/... 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. 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.
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&& .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...KJC/EVT NEAR TERM...KJC SHORT TERM...KJC LONG TERM...EVT AVIATION...KJC/EVT MARINE...KJC/EVT CLIMATE...Staff

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