Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170842 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 442 AM EDT Sun Sep 17 2017 .SYNOPSIS...
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Expect warm and humid conditions today. A few showers and an isolated thunderstorm are possible late tonight into early Monday across southern areas, then a few more showers may push in during Monday afternoon. Hurricane Jose will bring high surf and dangerous rip currents through the middle of this week. Wind and rain effects are possible, especially across Cape Cod and the islands Tuesday into Wednesday. However, the full extent of these impacts and their timing remains dependent on the still uncertain storm track. High pressure then builds over the region with drier and seasonable weather Thursday through Saturday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Areas of low clouds and fog, with very low visibility along coastal areas and a few spots inland, continue early this morning across most of the region. Mainly clear conditions in place across N central to SW Mass into portions of N central CT at 07Z as noted on latest observations. The clear slots across the interior are showing up nicely on the GOES-16 non-op prelim fog product. Have continued the Dense Fog Advisory for coastal areas and a few sections of interior E Mass. The fog continues to be intermittent along the western edge of the fog bank. With no clouds above the low stratus and fog, they will start to burn off after sunrise. Fog will also improve close to the shoreline, but will further offshore with light E-SE winds. Otherwise, expect skies to become partly to mostly sunny for most areas. 00Z models runs continue to show some lingering weak mid level troughing and vorticity caught in the parallel flow aloft wavering across the region. However, not as much organized low and mid level moisture to work with, so will will probably only see an isolated shower or two develop inland. Looks like best shot for any organized convection could occur across the E slopes of the Berkshires where there will be some weak upslope wind could trigger a few showers this afternoon. Might even see a shower or two across the northern Worcester hills around midday or so. Will be another mild day away from the coast with highs to the upper 70s to lower 80s, but expect light E-SE winds to keep temps cooler at the coast, only from about 70 to 75. High surf...Will continue to see increasing long period southerly swells from Hurricane Jose push into the southern waters. Expect the surf to increase to 6 to 7 feet, leading to high surf developing along south facing beaches. There will also be a high risk of dangerous rip currents. High surf advisories remain in effect for the southern beaches of Mass and RI.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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Tonight... Light easterly winds continue to bring moist low level air off the ocean, so will see another repeat performance of the low stratus clouds and areas of fog moving inland. Patchy dense fog will also move in, but should be confined to along coastal areas. May need another Dense Fog Advisory for some areas during the night. Models are hinting that a band of showers may push N during the night, crossing the southern islands after midnight. So, have mentioned slight chance to low CHC POPs. Also some marginal instability with this, so can not rule out an isolated thunderstorm approaching parts of the S coast toward daybreak. Expect temps to fall back to the upper 50s to lower 60s. Monday... Areas of fog should lift again Monday morning, but may linger along the coast during the day. Noting increasing PWATs working up the coast during the day up to 1.5 to 1.6 inches where a band of showers increases during the morning and early afternoon across N CT/RI into SE Mass. By late in the day, PWATs up to 1.8 inches along the S coast. Noting decent lift and a pretty good H3 SW jet up to 40-50 kt also crossing S coastal areas during the afternoon. Models all suggesting another area of precip lifting N ahead of the approaching tropical system. Should be light precip for the most part but can`t rule out a few brief downpours. Noting some cooler air working S across E Mass/RI during Monday, with H925 temps at +15C to +16C, ranging to +18C to +19C over western areas with the onshore winds in place. So, expect highs to only be in the lower 70s across eastern areas, rising to to the upper 70s over the CT valley.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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The main issue with this portion of the forecast remains Jose. Two distinct camps now in the 17/00Z deterministic guidance. The first is the GFS/CMC camp, which passes Jose just SE of the 40N/70W benchmark Tuesday night. The other camp has the ECMWF and UKMET, which heads Jose right for southern New England, but halts its northward progress right around 40N Wednesday, before moving Jose east out to sea along 40N Wednesday night. Two very different outcomes for our region. Looking at the 17/00Z ensembles from the CMC and GFS for more info, one finds most of their members well clustered for a pass near the benchmark. However, there are also about 6 members out of 41 between the two which bring Jose closer to the southern New England coast. Have not yet been able to examine the 17/00Z ECMWF ensembles. The 12Z version had pretty much the entire south coast of New England as a possible path, but also had about 15 members out of 51 with a more direct impact to southern New England. The majority stalled Jose about 40N, then slowly moved it east. What does this all mean? While the most likely outcome is for the center of Jose to stay a little farther offshore and brush by the Cape and Islands, we cannot completely close the door on a track closer to southern New England. Those with interests in southern New England should remain wary of a closer approach, particularly those along the south coast. The 5 year average error of a hurricane track forecast 48 to 72 hours in advance is about 75-100 nautical miles either side of the forecast track. Nantucket is only about 85 miles north of the 40N/70W benchmark, well within the margin of error. Once Jose finally departs our region, we should receive a prolonged period of more tranquil weather late this week into next weekend.
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&& .AVIATION /09Z SUNDAY THROUGH THURSDAY/...
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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 Monday/... High confidence in trends. Lower confidence in timing. Today...Expect IFR-LIFR conditions early this morning, then should improve to mainly VFR by around 14Z. However, some patchy MVFR-IFR CIGS/VSBYS may linger through midday along coastal areas. May see scattered showers and even an isolated thunderstorm this afternoon across E slopes of the Berkshires but should not last long. Weak E- SE winds in place. Tonight and Monday...Will see return of low clouds and areas of fog with IFR-LIFR conditions, mainly along coastal areas and just inland. Well inland, will see areas of MVFR-IFR conditions. Should improve again Monday morning, but may linger along the S coast where and band of scattered showers moves onshore. KBOS Terminal...High confidence in trends. Lower confidence in timing. IFR-LIFR CIGS/VSBYS into the morning push, then should see conditions improve from 13Z-14Z. Periods of IFR conditions redevelop around 03Z-04Z through 11Z-12Z Monday. KBDL Terminal...High confidence in trends. Lower confidence in timing. Periods of IFR conditions redevelop after midnight through 10Z. Outlook /Monday Night through Thursday/... Monday Night...Moderate confidence. MVFR cigs/vsbys should reach the south coast during this time, depending on the track and speed of Jose. Tuesday-Wednesday... Moderate confidence. MVFR with areas of IFR in low clouds/rain/fog. Northeast winds with potential for 35-40 kt speeds. Poor visibility on Cape and Islands in rain and fog. Conditions are dependent on the track and speed of Hurricane Jose. Some improvement possible from west to east Wednesday afternoon. Thursday...Moderate confidence. Early morning MVFR/IFR cigs/vsbys in fog in the Connecticut River Valley, then mainly VFR.
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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 Monday/... Mainly light E-NE winds 15 kt or less through the period. Increasing south swells continue from Hurricane Jose, up to 6 to 7 feet by tonight across the southern open waters, approaching 8 feet on the outer waters during Monday. SCA for hazardous seas and high surf advisories continue. Poor vsbys in areas of dense fog at times offshore through Monday, pushing toward the coast tonight. Outlook /Monday Night through Thursday/...Moderate confidence. Seas will continue to build Monday and Tuesday in advance of Hurricane Jose with values of 10 feet or higher in the exposed waters. Highest values will be in the southern outer waters with values 7 feet or higher on the exposed inner waters. High seas will spread to the eastern coast of Massachusetts, especially Outer Cape Cod Tuesday and Wednesday. Seas will subside Wednesday night. Seas of 5 feet will linger on the outer water east of Massachusetts Thursday. East winds 10-15 knots Monday increase Monday night. Tuesday winds 15-25 knots with higher gusts on the southern waters. Strong winds turn from the north and shift into the eastern waters Wednesday. Winds diminish west to east Wednesday afternoon and night. North winds 10-20 knots Thursday. Expect marine headlines for much of this period, especially across the southern coastal waters. Much of this depends on the track of Jose, which has plenty of time to change over the next few days. Mariners are strongly urged to monitor the latest forecasts regarding Jose this weekend into early next week.
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&& .TIDES/COASTAL FLOODING... Jose`s large wind envelope will likely produce significant seas with a large swell component moving onshore early to mid next week. Significant wave action should occur on top of relatively high astronomical high tides and a building surge. As a result, we believe there is a high risk of moderate to severe beach erosion over a prolonged period early next week. Multiple high tide cycles of large swells breaking onshore have us concerned that we could experience a very serious beach erosion event along portions of both our south and east facing ocean- exposed shorelines next week. In addition and dependent upon how close Jose gets to our coast, there is also a risk for minor to moderate coastal flooding along portions of the coast with probably southeast and east facing shorelines most at risk. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...Dense Fog Advisory until 8 AM EDT this morning for MAZ006-007- 015>024. High Surf Advisory until 8 PM EDT this evening for MAZ020-023- 024. RI...Dense Fog Advisory until 8 AM EDT this morning for RIZ006>008. High Surf Advisory until 8 PM EDT this evening for RIZ006>008. MARINE...Small Craft Advisory for hazardous seas until 6 AM EDT Monday for ANZ235-237-254>256.
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&& $$ SYNOPSIS...Belk/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...Belk AVIATION...Belk/EVT MARINE...Belk/EVT TIDES/COASTAL FLOODING...Belk

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