Area Forecast Discussion
Issued by NWS Boston, MA

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702 FXUS61 KBOX 171810 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 110 PM EST Fri Feb 17 2017 .SYNOPSIS... Milder and dry weather persists through this weekend. A couple of moisture-starved cold fronts move through late this weekend, and again the middle of next week. This will mean dry weather through much of next week, too. Temperatures near to above normal next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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1 pm update... Ridge of high pressure continues to build into our region this afternoon, with sunny skies prevailing. W/NW winds 10 to 15 mph with gusts up to 25 mph this afternoon. Could still have a few wind gusts 25-30 mph during early afternoon across higher terrain of Worcester Hills/east slopes Berkshires. Continue to expect highs ranging around the mid to upper 30s. Could see locations in and around Providence RI reach 40 degrees.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/... Tonight... High pressure overhead and very light winds. Two things to consider: 1.) Surface dewpoints, and 2.) Mid-level cloud decks. There will be snowmelt through the day but not enough to considerably offset the dry airmass still in place. Thinking dewpoints will range in the upper teens to low 20s overnight. With regards to mid-level clouds, indications of upsloping higher theta-E around H5-7 yielding a mix of scattered to broken cloud decks developing towards evening and sweeping the region overnight. So the two considerations ultimately impact forecast low temperatures. If it remains clear with light winds, would expect lows to drop into the single digits within the interior sheltered valleys given deep snowpack. However, with a good signal per a consensus of forecast guidance of very moist 1000-500 mb RH upsloping across the region, leaning that a blanket of clouds will limit the radiational cooling. Lows down into the low 20s to upper teens. Saturday and Saturday night... Perhaps during the morning hours with continued upslope flow of warm moist air across the region ahead of a lifting warm front we`re able to squeeze out a shower over the high terrain. Otherwise, looking at a day defined by a mix of sun and clouds with an increasing presence of dry air and subsidence. Mixing somewhat limited, however the S flow should drive warmer air across the region pushing highs well into the 40s, despite the snowpack across the region, with possible 50s in the S CT River Valley. Yet a potential issue. The combination of increasing dewpoints from the S along with snowmelt yields a fairly moist, shallow boundary layer environment that pools beneath the building dry, subsidence inversion, consequential of N and S stream disturbances flanking the region. Leaned mild on forecast dewpoints. With temperatures dropping overnight, would expect a mix of low clouds and fog. Considering the acceleration of W flow between the two disturbances, may see more low clouds than fog. However not confident that winds will remain breezy, but rather could remain light. Signals not all abundantly clear from neither the SREF, MOS, nor any other ensemble probabilistic guidance even CIPS analogs. Yet, some signal is there and we`ll have to evaluate with later forecasts for now. Went partly to mostly cloudy overnight with no mention of fog. Lows mild around the low to mid 30s. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Big Picture... Mid level flow continues to advertise split streams across the USA through much of this period. As previously mentioned, with the southern stream remaining to our south, moisture will be hard to come by with any weather feature which could give us a chance for precipitation. This has been a consistent theme the past few days, raising confidence a bit in keeping this forecast dry. Model mass fields are similar through Tuesday, adding to confidence in the forecast through that time. Large scale features are similar after that, while shortwave features show differences Wednesday and Thursday. Forecast height contours are above normal for much of the period, and arguably well above normal mid week next week. This suggests above normal temperatures. Favored a consensus approach to smooth over the less predictable detail differences. Details... Sunday through Monday... Surface low swings a cold front through our region Sunday afternoon and evening. Too dry to see much more than a few clouds with this front. Above normal temperatures continue Sunday, with near normal temperatures Monday. Tuesday through Thursday... High pressure builds over the region Tuesday, then lifts northeast Wednesday. 17/00Z guidance coming into better agreement for a pair of shortwave to pass through, or nearby, southern New England both Wednesday and Thursday. Moisture is a bit higher with the Wednesday wave. Not confident enough in this timing to introduce a period of precipitation at this time. Definitely something to watch evolve over the next several days. Near to above normal temperatures continue. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Range /through Friday night/...High confidence. This afternoon...High Confidence. VFR. Gusty N/W winds continue. Gusts up to 25 kts, except a few gusts over 25 kts possible thru 20Z KORH/Worcester Hills and east slopes Berkshires. Winds diminishing towards evening. Tonight...High Confidence. VFR. Winds becoming light out the W/SW. SCT-BKN mid-level cigs. Saturday into Saturday Night...Moderate Confidence. W/SW flow becoming breezy. Potential for 25 kt gusts over the Cape and Islands. Low confidence concerning the potential presence of IFR low clouds and/or fog overnight. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Sunday through Tuesday/...Moderate confidence. Sunday...Mostly VFR. Warmer air moves in Sunday, and may support areas of IFR in fog in the CT River Valley and South Coast early in the morning as it moves over the remaining snowpack. Monday-Tuesday...VFR through this period.
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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 Range /through Friday night/...High confidence. Small Craft Advisory extended until 22Z Boston Harbor, and until 00Z Nantucket/Vineyard Sound/Buzzards Bay, for lingering NW/W wind gusts around 25 kt. W/NW winds remain gusty through the evening period, diminishing below 25 kts over all waters during the overnight hours. This allows for good boating weather by Saturday morning across all waters with wave heights less than 5 feet. A light W/SW flow initially Saturday increasing through the day and overnight with gusts up around 25 kts resulting in waves building back up to 5 to 6 feet on the outer waters requiring a period of Small Craft Advisories. Outlook /Sunday through Tuesday/... Sunday...Westerly winds gust near 25 knots. A Small Craft Advisory may be needed. There is a low chance for winds reaching 35 knots, which would mean a WNW gale. Most seas should remain below 5 feet, although parts of the outer waters may approach 5 feet. Monday...North winds may gust 25-30 knots. Seas will be less than 5 feet, except east of Cape Cod where seas may approach 5 feet. A Small Craft Advisory may be needed. Tuesday...Winds less than 25 knots and seas less than 5 feet.
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&& .EQUIPMENT...
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110 pm update...Technicians continue to work on KBOX radar, which will be out of service at times today for repair.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ232>234. Small Craft Advisory until 5 PM EST this afternoon for ANZ230. Small Craft Advisory until 1 AM EST Saturday for ANZ231-251- 256. Small Craft Advisory until 1 PM EST this afternoon for ANZ235- 237. Small Craft Advisory until 4 AM EST Saturday for ANZ250-254- 255.
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&& $$ SYNOPSIS...Belk/Sipprell NEAR TERM...Belk/Sipprell/NMB SHORT TERM...Sipprell LONG TERM...Belk AVIATION...Belk/Sipprell/NMB MARINE...Belk/Sipprell/NMB EQUIPMENT...NMB

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