Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 270756 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 356 AM EDT MON JUN 27 2016 .SYNOPSIS...
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High pressure remains in control through Monday. A cool front will slowly approach the region, bringing showers and thunderstorms Tuesday and Wednesday. High pressure then brings dry seasonable weather for the late week. Another cold front may bring more showers and thunderstorms Friday night and Saturday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1035 PM Update... Other than patchy high thin clouds across portions of southern New England this evening, skies were mainly clear. Noting some more mid and high clouds working SE out of N NY and VT in the NW flow aloft, which will tend to thin out as they move into the region overnight. Dewpts have been slowly rising across most of the region, mainly in the mid 50s to around 60, expect a bit lower across interior SE Mass though they are rising there as well. Do not see fog developing yet, but will be monitoring as temp/dewpt spreads tending to lower mainly along the S coast. Temps at 02Z were in the lower-mid 60s across most of E Mass into RI, ranging to the lower 70s in the CT valley into N central Mass. Overnight forecast pretty much on track. Have updated near term information to bring current. Will continue to monitor as dewpts continue to slowly rise. Previous discussion... Stout dry inversion just above the surface beneath which S winds continue to advect moisture N. Surface dewpoints have risen slightly and are expected to continue to do so overnight. Coupled with mostly clear conditions, expect another round of radiational cooling. Temperatures overnight won`t drop as low as they did during the early morning hours Sunday, but still low enough such that there is the threat of patchy ground fog or stratus. Focus across E CT into W RI. Perhaps even Southeast MA where radiational cooling is most favorable. Lows falling down into the mid 50s. Elsewhere upper 50s with urban centers in the low 60s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/... Monday... Pre-frontal trough will push through the Great Lakes region resulting in southwest flow across southern New England. Offshore mid-level low will stall the trough keeping Monday mostly dry. Clouds will begin to increase from west to east during the afternoon hours. Due to increasing pressure gradient, southwest flow will increase aloft. Appears mixing will reach up to 900 mb which would allow for gusts near 20-25 mph. Otherwise temperatures will warm into low to mid 80s across the area, cooler conditions along the South Coast due to onshore flow. Can`t rule out upper 80s to near 90s across the Merrimack Valley due to good mixing in southwest flow. Monday Night... The pre-frontal trough will slowly approach from the west but weaken on Monday night. Very weak forcing and limited upper level dynamics as this system moves through. Still plenty of moisture to work with so expect isolated to scattered showers overnight. Appears that there will be some elevated instability, so cannot rule out a rumble of thunder. Aside from the convection potential, higher dewpoints will spill into the region overnight. This will result in muggier conditions, and the potential for fog development. Overnight temps will only drop into the low to mid 60s. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Big Picture... Longwave scale continues to show a ridge-west/trough-east pattern over North America. This may shift east a little during the holday weekend. One shortwave rippling through this flow moves across New England later Wednesday. A second moves down from Canada and sweeps across New England next weekend. Model mass fields are similar with the broad pattern through Friday. There are differences in positioning of the cold front associated with the first shortwave. The ECMWF is farthest west and the GGEM farthest east. This means a consensus as to the broader forecast, showers/tstms, but uncertainty regarding the details such as timing. With the second shortwave, the GFS and ECMWF are similar while the GGEM is slower and farther south. The mass field agreement and the variations in details Tuesday night/Wednesday favor a blend of model data. Details... Tuesday night through Wednesday... Shortwave over the Eastern Great Lakes digs over New England while the associated surface cold front moves through Eastern New York Tuesday night and New England Wednesday. The upper flow through the shortwave will be SSW to NNE across our area, almost parallel to the cold front. Until the shortwave axis swings across our area and turns the upper flow across the front, the cold front will move very slowly. Upper jet flowing through the shortwave will provide dynamic support for lift. Model data shows precipitable water values pooling along and just ahead of the front with max values 1.6 to 1.8 inches. Three of four models show total-totals in the upper 40s Tuesday night through Wednesday afternoon in the area leading the cold front. Cross sections show the moisture will be through a deep column. All of this points to showers and possible thunderstorms. We will stay with likely pops Tuesday night and chance pops Wednesday. Thursday through Saturday... Weak high pressure builds over the region Thursday and lingers into Friday. The second shortwave approaches with difluent flow aloft Friday afternoon/evening and increasing precip water values toward evening. Favorable instability remains to our west and northwest during Friday but then moves across Southern New England Friday night. Timing on this shortwave and surface cold front will continue to vary, but for now we will show chance pops for showers/tstms in extreme western MA Friday afternoon and chance pops for most of the area Friday night. Showers/thunder end from west to east Saturday morning. Temps aloft 13-15C should support max sfc temps in the low to mid 80s. Sunday... The Saturday cold front moves south of New England, but with long range data suggesting it may stall to our south. In this scenario, a low pressure wave would move along the front from the Ohio Valley and pass south of us. There is some potential for clouds and a chance of showers for July 3rd, mostly along our South Coast with diminishing liklihood to the north. This will need to be monitored.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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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 Tuesday/... 0230Z Update... Overnight...High Confidence. Mainly VFR. Low chance for IFR-LIFR conditions in patchy ground fog and/or low clouds across portions of W CT/W RI into SE MA. Light S winds. Monday...High Confidence. VFR. Any IFR-LIFR fog / cigs erode by 13Z. Expect S-SW winds gradually increasing, gusts up to 20-25 kt during the afternoon. Monday night...Moderate Confidence. Mainly VFR. Conditions could deteriorate as SHRA and isolated TSRA move into W New England. IFR-LIFR stratus and fog could develop ahead of approaching showers over S/E portions of New England. KBOS TAF...High confidence. S winds increase Monday, gusting up to around 25 kts during the afternoon hours KBDL TAF...High confidence. VFR. Very low chance for MVFR-IFR conditions in patchy fog 07Z-11Z tonight and again Monday night. May reside just to the S/E. Outlook /Tuesday night through Friday/... Tuesday night-Wednesday... Moderate confidence VFR with areas of MVFR in showers and thunderstorms Tuesday night and Wednesday morning. Areas of IFR possible in fog and low clouds. South winds gusting to 20 knots will shift from the West after the cold front moves through Wednesday. Thursday-Friday...Moderate confidence VFR. North winds become variable Thursday, then from the south Friday. Showers/tstms will develop over New York State, and may move into Southern New England Friday evening and night. These showers and storms would have areas of MVFR cigs/vsbys.
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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 Tuesday/... 1030 pm update...No changes to overnight forecast. Overnight...High Confidence. Winds and seas below small craft criteria. Monday into Monday night...Moderate Confidence. High pressure moving offshore as system approaches from the west. Near shore winds will gust close to 25 kts during the afternoon tomorrow. SCA may be needed but confidence is low. Increase LLJ across northern waters will result in seas building to 5 feet. SCA will continue. Outlook /Tuesday night through Friday/... Moderate confidence. Tuesday night-Wednesday...Moderate confidence. Showers and thunderstorms cross the waters with south wind gusts near 20 knots at times. Winds shift from the west Wednesday as a cold front crosses the waters. Low vsbys possible ahead of the cold front in showers and storms as well as in fog. No headlines planned at this time. Thursday-Friday...Moderate confidence. High pressure builds over the waters Thursday and moves off to the east Friday. A cold front approaches from the west Friday night. Winds and seas should remain below Small Craft Advisory criteria. Scattered showers/thunderstorms possible Friday night as the cold front approaches.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 1 PM this afternoon to 2 AM EDT Tuesday for ANZ250.
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&& $$ SYNOPSIS...WTB/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...WTB AVIATION...WTB/EVT MARINE...WTB/EVT

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