Area Forecast Discussion
Issued by NWS Boston, MA

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929 FXUS61 KBOX 210859 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 359 AM EST Tue Feb 21 2017 .SYNOPSIS... High pressure centered over New England today moves offshore tonight and Wednesday. This brings us dry weather and a trend toward milder temperatures through the week. A weak cold front dissipates as it crosses New England late tonight. A series of low pressure systems move through the Great Lakes Wednesday through Saturday maintaining unseasonably mild temperatures in New England, with near record warmth possible Thursday. A strong cold front will cross the region Saturday, likely bringing some rain, followed by blustery and more seasonable conditions Sunday and Monday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Chilly start to the day with clear skies and light winds allowing radiational cooling. With inland dewpoints between 10 and 17, expect min temps in that same range. Dewpoints along the coast, especially over Cape Cod and Islands, are mostly in the 20s. Expect min temps 20-25 in those are High pressure over the region today will bring dry weather and light wind. Cirrus moves in from the Great Lakes today may thicken during the afternoon, but still expect sufficient heating to tap temps at 925 mb and bring sfc temps into the 40s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Tonight... High pressure shifts offshore. Airflow is light during the evening, which should allow temps to cool initially. South- southwest flow then increases a little overnight. Sky cover mostly thin in the evening with high clouds, but this thickens through the night. Because of both factors, we expect temperatures to cool in the evening, but then rise slowly after midnight. Dying cold front is being pushed along by a 105 knot upper jet which is also diminishing. Sufficient moisture for clouds overnight. Possible brief period of lift between midnight and dawn. This doesn`t inspire great confidence of pcpn, but enough to maintain low-end chance pops. If there is pcpn, what type will it be. Surface temps will be either side of freezing in the interior, and in the mid 30s closer to the coast. So there is a chance that showers may produce scattered icy spots in the interior. With the scattered distribution of the showers and their possibly drying up as they move east, expect any icy spots to be limited in coverage. But drivers will need to exercise caution. Wednesday... High pressure lingers offshore with a south-southwest flow of air into Srn New England. Lingering clouds during the morning should thin and provide at least partly sunny skies. Temps at 1000 mb and 950 mb support max sfc temps near 50. Temps at 925 mb support max sfc temps in the upper 50s. Expect max sfc temps in the 50s, possibly close to 60 if we get sufficient solar heating. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights... * Record warmth possible Thursday * Linger cold front on Friday make keeps temps cooler * Mild with widespread showers likely sometime Sat/Sat night * Blustery and cooler Sun/Mon Pattern Overview... 00z guidance is in general agreement synoptically, still have some mesoscale features to resolve. Overall, mean ridge to start the forecast period for southern New England as digging trough develops of the western CONUS. This trough will eject across the Plain and eventually move towards the Northeast by Saturday/Sunday. Before then, a weak northern stream wave will move through late Thursday into Friday which could sag a weak cold front through the region. After potent trough moves through the area pattern appears to turn more zonal resulting in several shortwaves moving through the flow for next week. High confidence in above average temperatures for Thursday and Saturday as well as precipitation on Saturday into Saturday night. Details... Wednesday night into Thursday... High pressure will move offshore on Wednesday night resulting in the return of southerly flow. Guidance keeps most of the day dry on Thursday, however have noticed and increase in low level moisture. BUFKIT soundings do show a saturated profile in the low levels with dry air aloft, so cannot rule out low level clouds and/or drizzle for the area. Best location will be across the south coast. These low clouds may limit the amount of heating during the day. But with the potential mixing up to 950mb could still see low to mid 60s. Right now trended towards the low 60s because of low level moisture. This will be close to records for a few sites in southern New England. Cannot rule out the potential for some wind gusts on Thursday as 925 mb LLJ increases to 30-40 kts. If we mix higher than 950 mb then we could see gusts close to 25-30 MPH. Friday... Again a good check of Friday appears to be dry, but low level moisture continues to increase which could keep the drizzle potential for the area. Guidance continues to show a back door cold front late Thursday into Friday which could limit high temperatures. Highest confidence in across Northeast MA but the front could sag a bit farther southward. Large temperatures spread is possible and high confidence in bust potential, will have 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 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. && .AVIATION /09Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... Today...High confidence. VFR with some high clouds. Light wind. Tonight...Moderate confidence. VFR much of the night. Possible MVFR cigs/vsbys in showers especially over Northern CT and Western MA. Depending on surface temperatures, there may be the potential for patchy freezing rain in interior MA. Wednesday... High confidence. VFR with south-southwest wind. Leftover MVFR cigs/vsbys possible in the morning, but this will quickly improve to VFR. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Wednesday Night through Saturday/... Thursday...Moderate confidence. Mainly VFR but low clouds could keep conditions MVFR. Friday...Low confidence. Potential for easterly flow and MVFR cigs if backdoor front slips to the south. However, VFR with SW winds if front remains to the north. Saturday...Moderate confidence. Potential for widespread MVFR/IFR conditions with rain overspreading the region. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... High confidence. Today... High pressure builds over the waters. This will bring diminishing winds and seas. All lingering Small Craft Advisories will be dropped. Tonight... High pressure moves off to the east, bringing increasing wind from the south-southwest. Winds and seas remain below Small Craft thresholds. A diminishing cold front may bring scattered showers to the waters late at night. Wednesday... Any showers will dissipate. Winds will increase from the southwest, but should remain at 20 knots or less. Seas will be 3 feet or less. Outlook /Wednesday Night through Saturday/... Wednesday night into Thursday...High confidence. Mainly SW flow with gusts to 20 kt. A few gusts to 25 kt possible Thu afternoon. Friday...Low confidence. Winds will depend on location of a backdoor front. Easterly flow if the front moves to the south, but continued SW flow with gusts to 20 kts possible if front remains to the north. Saturday...Moderate confidence. Increasing southerly flow with SCA gusts likely. Waves will also increase in response. Vsbys reduced in developing rain and fog. && .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 SHORT TERM...WTB LONG TERM...Dunten AVIATION...WTB/Dunten MARINE...WTB/Dunten CLIMATE...staff

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