Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 142053 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 353 PM EST Tue Feb 14 2017 .SYNOPSIS...
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Quiet and dry weather continues tonight. Another storm center develops Wednesday into Wednesday night across the Gulf of Maine, bringing a period of rain and/or snow to much of the region. The low will be in the Canadian Maritimes Thursday and Friday bringing mainly dry but blustery and cold weather to the region. Dry weather continues this weekend, but with a significant moderation in temperatures especially by Sunday when much of the region may see highs exceeding 50.
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&& .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 1030 AM Update... A band of mid and high clouds will cross the region this afternoon and tonight. Some lower clouds linger across the outer Cape as well as the Berkshires at 15Z. W-NW winds have diminished as high pressure builds across. Dry conditions will continue through the afternoon. Have updated near term forecast to bring conditions current and incorporated into the afternoon trends. Previous discussion... Light winds and a mid-February sun angle while the airmass up at H925 has changed only slightly, leaned towards the warmest of forecast guidance. Expect highs to top off in the lower to mid 30s, cooler across the higher terrain. Overnight, increasing clouds ahead of a clipper-like low pushing S/E out of Canada. Per isallobaric response, winds out of the S/SE and onshore. Temperatures likely to drop during the evening hours but then may hover around midnight. Coastal locations may see a non- diurnal trend going into morning. Mostly dry with a slight risk of a shower over the N/W tier of MA by morning. Lows down into the 20s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Lots of scrutiny. Seemingly better agreement of the 14.00z forecast suite, however subtle variations remain. A challenge in discerning specific outcomes focused in particular upon two timeframes: Initially, broad synoptic-scale lift along a warm frontal boundary in vicinity of strong QG-forcing and broad diffluence of the left front quadrant of a SW-NE H3 jet streak. Trends apparent that we`ll see an accompanying S/SW h925-85 warm nose with a neighboring W H5-7 dry slot as deep layer, rapid cyclogenesis emerges in regions of better baroclinicity over the Gulf of ME. While earlier forecast solutions suggested limitations in both moisture and lift through the column, and more specifically the dendritic growth zone, there are growing indications of N-stream energy tapping into the S-stream impulse. Timing and thermal profiles still a bit tricky but it would appear there is the likelihood of a rain / snow mix across the E- half of S New England as deep layer column moistening develops through which there is pronounced omega well up to the tropopause. It`s possible the entire event could end up as rain with perhaps just some wet snowflakes mixed in across N MA, however with this forecast, kept S/E locations as rain with N/W areas as a wet snow. Thereafter, with rapid cyclogenesis ongoing, mid-level dry air for the most part erodes available column moisture across the region. However, trowaling mechanisms within the anticipated comma-head of the deepening low over the Gulf of ME will wrap back across NE areas of New England, particularly ME. Cold air advection proceeding on the backside of the deepening system, indications of a tropopause fold, lapse rates steepen. Question then becomes whether moisture wraps back across our region behind the low and also as to whether there is available forcing through the dendritic growth zone. Can`t rule it out, especially for NE MA. However the stronger signal of low to mid level forcing continues to be across ME, seemingly along an inverted trough in regions of instability and collocated higher theta-E as cyclogenesis develops further N/E downstream. So likely to categorical PoPs for the E-half of S New England during Wednesday and will keep high chance PoPs across E areas of MA going into Wednesday night. A light snow event with a coating to an inch mainly across the Route 2 corridor, higher amounts up to 2 inches for far N Essex County MA. Becoming blustery with winds out of the W as the storm intensifies over the Gulf of ME. Sustained winds of 20 to 30 mph with gusts 35 to 45 mph. Thinking sub-advisory given the consensus of the forecast guidance has the low intensification fairly N/W of our region up across the Bay of Fundy. Strongest winds along the coast and over the waters. && .LONG TERM /THURSDAY THROUGH TUESDAY/...
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Highlights... * A few snow showers possible Thu otherwise dry into Mon * Blustery and cold Thu into Fri * Moderating temps Sat and unseasonably mild by Sun * Above normal temps continue into early next week Details... Thursday... Rapidly intensifying low pressure will be already lifting into the Canadian Maritimes Thursday morning. While the inverted trough axis extending back from the storm will have weakened, left over low level moisture coupled with shortwave energy/cold pool aloft may result in a few snow showers. Highest risk will be in northern and eastern MA, where better low level moisture will exist. Otherwise, the majority of the day will be dry but strong cold advection behind the system will keep highs in the 30s. Northwest wind gusts of 25 to 35 mph are also expected with good mixing in the cold air advection pattern. Thursday night and Friday... Strong low pressure over the Canadian Maritimes will only slowly lift northeast as a weak ridge of high pressure approaches from this midwest. This should result in mainly dry but cold and blustery weather across the region Thu night/Fri. Low temps Thu night mainly in the teens to lower 20s. Highs on Thu generally in the lower to middle 30s. Saturday and Sunday... Upper trough moves northeast of the region allowing for rising height fields and more zonal flow. So while it will remain dry, the result will be much milder air overspreading the region from the west. High temps should recover into the upper 30s to lower 40s on Saturday, but by Sunday expect highs to break 50 across much of the region. Monday and Tuesday... A backdoor cold front will bring a bit cooler temperatures on Monday, but highs still probably well up into the 40s with above normal temps continuing into early next week. A shortwave may bring a few showers to the region Tuesday afternoon/night, but best forcing/dynamics will probably pass to our north and west.
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&& .AVIATION /21Z TUESDAY THROUGH SUNDAY/...
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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 Tuesday night/... Through this afternoon...VFR. MVFR lingering over the outer Cape for a time into early this afternoon. Light W-NW winds becoming light/variable then backing to SW late. Tonight...VFR initially but expect cigs to develop across the N/W with low-end VFR to MVFR. Overall light S flow with the slight risk of a SHRA/SHSN over the N/W by morning. Wednesday...MVFR-IFR mix as S winds increase ahead of a passing storm system. Widespread RA/SN developing the greater risk of which is across the E-half of S New England. With any SN, reductions in visibility are possible. Winds turning out of the W late. Wednesday night...Cigs lifting VFR over most locations. However MVFR to IFR cigs may linger over E/NE MA including the Outer Cape into morning as winds increase out of the W becoming blustery with gusts up to 40 kts. Strongest winds for shoreline terminals. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Thursday through Sunday/... Thursday...Moderate confidence. Some MVFR ceiling along with a few snow showers remain possible particularly across northern and eastern MA into Thu afternoon. Otherwise, northwest wind gusts of 20 to 30 knots expected. Friday through Sunday...High confidence in mainly VFR conditions.
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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 Tuesday night/...High confidence. Light W-NW winds will back to SW during the afternoon. Seas remain at or above 5 ft on the outer waters, though should subside early this afternoon S of the RI coast. Previous discussion... Winds diminishing, yet seas will continue to run high through a majority of this period. Another storm center deepens across the Gulf of ME Wednesday into Wednesday night with breezy S flow ahead of the system, followed by blustery W flow to the rear. There is the possibility of gales for Wednesday night. Outlook /Thursday through Sunday/... Thursday and Thursday night...Moderate to high confidence. Cold advection will result in northwest wind gusts of 30 to 35 knots Thu into Thu night so Gale Watches will be issued. The airmass will be cold enough to support some light freezing spray late Thu night. Friday...Moderate to high confidence. While pressure gradient weakens a bit, still expect northwest wind gusts of 20 to 30 knots and small craft headlines will be needed for most waters. Saturday and Sunday...Moderate to high confidence. Weak pressure gradient should keep winds and seas generally below small craft advisory thresholds.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 PM EST Wednesday for ANZ231-250- 251-254-255.
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&& $$ SYNOPSIS...Frank NEAR TERM...Belk/EVT - Update coming soon SHORT TERM...Sipprell - Update coming soon LONG TERM...Frank AVIATION...Sipprell/EVT/Frank MARINE...Sipprell/EVT/Frank

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