Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 221524 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1024 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. Near seasonable temperatures will return early next week, with blustery conditions on Sunday and Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1015 am update... Main update for late this morning regards sky cover, with clearning noted across much of MA as of 10 am. May see some diurnal stratocumulus development today, along with some passing cirrus. So there will still be some clouds around, mostly sunny to partly sunny skies. Kept potential for onshore flow during the afternoon hours across eastern MA. This could keep temps slightly cooler than the interior. Will continue to monitor temps, if there isn`t much by way of clouds redeveloping may need to up max temps some. Early morning Discussion follows... 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.
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&& .SHORT TERM /6 PM THIS EVENING 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... * Temperature spread possible due to backdoor cold front on Friday * Mild with widespread showers likely Sat into Sat night * Blustery and cooler Sun/Mon * More active pattern for next week Pattern Overview... 00z guidance is in general agreement synoptically, still have some mesoscale features to resolve. Ensemble guidance continues to indicate mean ridging over the region on Friday as upper level trough pushes across the Plains. This shortwave will become more diffuse and stretched as it approaches the Northeast due to building ridge. A cold front will sweep through the region late Saturday as upper level trough moves through. Ensembles this indicate a more zonal pattern beginning next week as a few shortwaves move through the flow. Next system to watch is Wednesday/Thursday timeframe but model sensitivity to this system is high. Overall high confidence in above average temperatures Friday and Saturday with more seasonable by Sunday. Also increasing confidence in precipitation falling on Saturday/Saturday night. Lower confidence on precipitation chances Friday into Sat morning and again for middle of next week. Details... Friday... Again a good check of Friday appears to be dry, but low level moisture trapped within an inversion could result in a drizzle potential for the area. Highest confidence is across the south coast. Guidance continues to show a back door cold front moving through early Friday morning which could limit high temperatures. Still some uncertainty on how far southward this front will sag. Highest confidence in across Northeast MA. Believe the region could see a large temperatures spread with 60s in southern CT and mid 40s in NE MA. Bust potential is possible with this forecast and anticipate a better handle with hi-res guidance. A warm front will push through the region late Friday keeping temperatures overnight well above average. Could see a few showers associated with this warm front. Saturday... 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 2 STD above normal as southern stream moisture is fed into the system. Along the front, a secondary low will develop but the 22.00z guidance develops it just far enough offshore to keep southern New England out of the heavy qpf. This appears to be inconjunction with the GEFS as well as the EC Ensembles which has just a 20 percent prob of qpf over 0.5 inch. This is quite different then 24 hours ago. Will need to continue to watch this secondary low and see where it will eventually develop during this system. Otherwise appears that the bulk of the precip will be across upstate NY and VT including the east slope of the Berks. This area is where the better dynamics will be as well as enhancement due to upslope. May need to watch river levels after this system because of the heavy rainfall potential and snow melt up north. Right now ensembles are pointing towards a few sites near action stage. 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 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. Wednesday and beyond... Large spread in the guidance for this period as the GFS is more progressive versus the more amplifies EC. Right now a quick warm up is possible on Wednesday as mean level ridge begins to take hold. Another low pressure system will develop dragging a cold front through the region. Low confidence on when this will occur, either Wed or Thursday. This timing will impact temperatures, dewpoints etc. && .AVIATION /15Z WEDNESDAY 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 Thursday/... Today...High confidence. Generally VFR. Patchy MVFR cigs possible this morning. There is the potential for sea breeze development for eastern terminals. 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. Moderate probability in weak sea breeze after 19z. KBDL TAF...High confidence in TAF. Outlook /Thursday Night through Sunday/... Friday...Low confidence. A mix of MVFR/VFR is possible across the region depending on low cloud development as well as position of back door cold front. This front will also dictate surface wind direction. Saturday...Moderate confidence. Potential for widespread MVFR/IFR conditions with rain overspreading the region. Sunday...Moderate confidence. Improving conditions with blustery NW wind gusts near 30 kts.
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&& .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. Southerly flow will switch to a more northeast to east flow during the day. Vsbys restriction possible in fog and drizzle especially across the southern waters. Saturday...Moderate confidence. Increasing southerly flow with the potential for SCA gusts. Waves will also increase in response. Vsbys reduced in developing rain and fog. Sunday...High confidence. Northwest winds will keep seas up and increase wind gusts near 30 kts. Low probability for gales across the outer 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/Dunten NEAR TERM...WTB/Dunten/NMB SHORT TERM...WTB LONG TERM...Dunten AVIATION...WTB/Dunten MARINE...WTB/Dunten CLIMATE...

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