Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261945 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 345 PM EDT SUN JUN 26 2016 .SYNOPSIS... High pressure remains in control through Monday. A cold front will slowly approach the region, bringing showers and possibly some thunder Tuesday and Wednesday. High pressure then brings dry seasonable weather for the late week. Another cold front may bring more showers sometime Saturday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 4 PM UPDATE... Surface high pressure continues to move offshore today. 850 mb temps warmed near 15C today resulting in temps reaching the upper 80s with a few locations near 90F. Diurnal CU that has developed will dissipate by early evening as heating is lost. Anticipate sea breeze to washout as well around 23/00Z. Aside from a few minor updates the overall trend in the forecast remains on track for this afternoon. TONIGHT... Upper level ridge remains over the region tonight as surface high pressure continues to move offshore. Light southerly flow will continue overnight and with mostly clear skies, anticipate another round of radiational cooling. Temps won`t drop as far as they did early this morning as dewpoints are higher then previous days. Overnight lows will range into the mid to upper 50s, with low 60s for the metro regions of PVD/BOS. May see patchy ground fog in low- lying regions prior to dawn as temp/dewpoint spread will be load. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Tomorrow... 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. Tomorrow 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 THROUGH SUNDAY/... */ HIGHLIGHTS... - Showers and thunderstorms Tuesday into Tuesday Night - Interior wet weather for Wednesday as cooler air settles in - Dry, seasonable, comfortable Thursday and Friday - Another shot of wet weather for Saturday - Looking to return dry and seasonable beginning next Sunday */ DISCUSSION... Forecast solutions seemingly coming into consensus. An analysis of atmospheric teleconnections, leaning with low pressure maintaining over the Gulf of Alaska with ridging over the W and Central CONUS. Further downstream troughing prevails from the Hudson Bay region of Canada down into the Great Lakes. New England for the most part resides along the E periphery of the trough up against the Atlantic ridge. It is through the troughing pattern we`ll see several waves of activity bringing chances of wet weather throughout the long-term forecast period. Still believe these N impulses will interact with the sub-tropical flow round the Atlantic ridge. Setups can vary as to whether deeper moisture is drawn N, or rather a squeeze play setup evolves between the two areas of disturbed weather drawing a region of higher heights and drier weather, a trend that has been seen extending SW to NE from Newfoundland, Nova Scotia, across the Gulf of Maine and into SE New England. Focusing on a broader view evaluating synoptics parent with moisture, lift and instability should it be present. Closely following ensemble means as well as probabilistics with this forecast. Overall the forecast does not put an end to the rainfall deficits, hardly, but it is welcoming. Expect the first wave Tuesday into Wednesday. Increasing moisture from the S beneath mid level vortex energy sweeping N/E across New England and diffluence aloft, a fair amount of forcing ahead of an initial pre-frontal boundary Tuesday met up with a cool front for Tuesday night before exiting E early Wednesday will yield a prolonged period of showers and thunderstorms. Column moistens with pwats up to 1.5 inches as the profile becomes conditionally unstable yielding a measure of instability especially if there`s any diurnal heating. Still a challenge to nail down cloud cover as we could be dealing with marine stratus / fog in addition. Perhaps some initial activity early Tuesday, remnants from Monday along the pre-frontal boundary. Otherwise as ingredients come together ahead of the cool front out of Upstate NY / PA should see chance to likely PoPs N/W, lesser S/E under the influence of continuing subsidence and drier air. This changes into Tuesday night as the environment shifts N/E. Big question is whether offshore sub-tropical moisture becomes involved or whether SE New England remains in a squeeze play as outlined earlier. Following closely with ensemble probabilistics and consensus of the forecast guidance. Heavier rainfall amounts forecast N/W around half an inch with lesser S/E. Not a soaker and not one that`ll put an end to the drought-like conditions. Will keep shower and thunderstorm wording similar throughout the sweep of the cool front behind which for Wednesday cooler air follows and lapse rates steepen. An environment beneath continued cyclonic flow and additional mid level energy, diurnally-forced convection is expected though a greater probability further N beneath the crux of the cold pool and closer to stronger dynamics, this in addition to orographic influences. Chance PoPs mainly N/E of the MA-CT border. UPDATE: 26.12z EC has slowed the cool frontal progression as was the case with yesterday`s model runs. 26.12z UKMET is not that far off from the EC. Some handling challenges with mid level vortex energy lifting N/E through the timeframe. A time difference of 6-12 hours between model solutions. Will linger activity into Wednesday but looks to clear out into Thursday. For Thursday and Friday, expect a quiet forecast period. Seasonably dry weather, comfortable with low humidity. Initial N/W flow Thursday reverts S into Friday ahead of disturbed weather for the weekend. Will see increasing humidity and dewpoints Friday night into Saturday morning. Could see some emerging issues with marine stratus and fog. Over the weekend, placing most of the emphasis on Saturday. Strong low over the S Hudson Bay region of Canada. Cyclonic flow through which jet dynamics and mid level energy promote an environment of decent forcing, pulling cooler air S the leading edge of which becomes a focus for showers and thunderstorms across the NE CONUS. Increasing moisture along and ahead with the atmospheric profile becoming conditionally unstable. Instability grows with any diurnal heating. Overall synoptics seem stretched within the flow and not sharp, thus leaning more of a daytime event supported by diurnal heating. Will keep similar shower and thunderstorm wording within PoPs. Thereafter for Sunday into early next week, going with a dry and seasonable forecast beneath continued cyclonic flow and a cooler airmass across the region. Appearing dry as high pressure sweeps the NE CONUS. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/... Through tonight...High Confidence. VFR. East Coast sea breeze dissipating around 23z. May see brief pockets of MVFR- IFR CIGS/VSBYS in patchy fog in low lying terminals. Monday...High Confidence. VFR. Expect S-SW winds gradually increasing, gusts up to 20-25 kt Mon afternoon. Monday night...Moderate Confidence. Mainly VFR. Conditions could deteriorate as showers and iso thunder moves across western terminals. Low-lying stratus and fog could develop ahead of approaching showers. KBOS TAF...High confidence. Sea breeze dissipates around 23z. Southerly winds increase Mon, gusting up to around 25 kts Mon afternoon. KBDL TAF...High confidence. VFR. Very low chance for MVFR-IFR conditions in patchy fog 07Z-11Z tonight and again Monday night. Outlook /Tuesday through Friday/... Tuesday into Wednesday...Moderate confidence. SHRA and TSRA. Low end VFR / MVFR during the day. MVFR / IFR during the evening periods. May be contending with LIFR marine stratus along the S coast as well. TEMPO lower conditions with any RA / TSRA. S winds ahead with potential gusts up to 20 kts at times. Clearing out Wednesday as winds back W though there is a chance of additional SHRA / TSRA activity across the N/W interior with TEMPO MVFR / IFR. Thursday into Friday...Moderate confidence. VFR. N/W winds Thursday turning out of the S into Friday. SCT to BKN low-end VFR cigs possible during the day. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/... Tonight...High Confidence. Quiet boating weather tonight. 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 through Friday/... Tuesday into Wednesday...Moderate confidence. Showers and thunderstorms moving into the waters late Tuesday on through Wednesday morning associated with a sweeping cool front. Ahead of this likely to see S winds with gusts up to 20 kts. Some marine stratus / fog possible with visibility restrictions, focusing on the S/SE waters. Potentially soupy. With cool frontal passage during the early half of Wednesday, winds back W and conditions should improve. Waves up to 5 feet. Thursday into Friday...Moderate confidence. Good boating weather. N/W winds but not expected to be gusty behind the front. Wave action diminishing rather quick. Winds veering out of the S into Friday. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas from 1 PM Monday to 2 AM EDT Tuesday for ANZ250. && $$ SYNOPSIS...Dunten/Sipprell NEAR TERM...Dunten SHORT TERM...Dunten LONG TERM...Sipprell AVIATION...Dunten/Sipprell MARINE...Dunten/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.