Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 222114 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 414 PM EST Wed Feb 22 2017 .SYNOPSIS...
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High pressure centered southeast of New England will bring dry and unseasonably warm conditions into Thursday night. A cold front moves into southern New England Thursday night. However this front pushes northward, away from the area on Friday as a warm front. A strong cold front may cross the region Saturday afternoon and evening bringing showers. Near seasonable temperatures will return early next week, with blustery conditions on Sunday and Monday.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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4 PM update... Dry weather anticipated overnight with surface high pressure centered offshore and southeast of our area. A weak shortwave passing thru overnight could produce a period of mid deck clouds. Otherwise, light winds out of the SW/S becoming calm or light and variable for much of the area. This will allow for good radiational cooling. Continue to expect min temps near dew point, mid 30s to near 40. Expecting some patchy fog/areas of fog to develop.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
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Thursday... High pressure remains offshore with southwest flow across Southern New England, while low pressure passes well north of our area, from the northern Great lakes Region into southern Ontario and Quebec. Continue to favor a dry forecast for Southern New England during Thursday. Our area remains in a SW flow, dry and unseasonably warm. Any fog should lift/dissipate early, but may see stratocumulus developing during the day. Hence partly to mostly sunny skies expected. 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. Continuing with previous forecast high temps for Thu, favoring the high end of model guidance. 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. Thursday Night... May see patchy drizzle and fog develop Thu night with reduced visibilities. A light SW wind holds up for part of the night. However a cold front is expected to sag southward into our area. Although exact placement of this front not for certain, models on average showing it extending roughly E-W across MA for 12Z Fri. There is a slight chance to low chance pop for showers with the front. High surface dew points south of the front should be 40-45 for much of the area. With a light SW wind south of the front, areas of fog greater for locales with a leftover snow pack at that point, as well as south coastal MA/RI with SW flow off the water.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/... 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 /21Z WEDNESDAY THROUGH MONDAY/...
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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 Night/... This evening...High confidence. VFR. Sea breeze where established subsides to a light SW or light and variable wind for eastern terminals after 00Z. Overnight...Moderate confidence. VFR through midnight. Areas of MVFR/IFR cigs and vsbys develop 06Z and later with patchy fog. Thursday...Moderate confidence. Lingering areas of MVFR/IFR cigs and vsbys early morning with fog dissipating/lifting. Cigs trending to a mix of MVFR/VFR by late morning and through the afternoon. Thursday Night...Moderate Confidence. Potential for areas of MVFR and especially IFR cigs and vsbys in low clouds and areas of fog. A cold front pushing southward into Massachusetts late Thu night could bring scattered showers to southern New England as well, possible decrease in clouds north of the front. KBOS TAF...High confidence in TAF thru this evening. Sea breeze returning to a light SW wind after 00Z. Moderate confidence in TAF for tonight into Thursday. There is a low chance for IFR conditions in low clouds and fog between 06Z and 12Z. VFR anticipated for Thu, SW winds should be strong enough to prevent sea breeze development. KBDL TAF...High confidence in TAF for this afternoon, with VFR. Moderate confidence in TAF tonight into Thursday. Anticipating MVFR vsbys generally 07Z-12Z in patchy fog, but there is a low chance of IFR cigs/vsbys in fog for that timeframe. Outlook /Friday through Monday/... 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...
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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 Night/...High confidence. Tonight... High pressure to the SW. Coastal sea breeze ends early with winds returning to SW mainly 5-10 knots for the overnight. Seas 1-3 feet. Thursday and Thursday night... Wind speeds Thursday increase some as winds strengthen aloft. This might be enough to bring gusts 20-25 kt to the coastal waters Thursday afternoon. Seas may approach 5 feet on the outer waters Thursday afternoon/evening. Outlook /Friday through Monday/... 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.
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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...Dunten/NMB NEAR TERM...Dunten/NMB SHORT TERM...NMB LONG TERM...Dunten AVIATION...Dunten/NMB MARINE...Dunten/NMB CLIMATE...Staff

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