Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230012 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 712 PM EST Wed Feb 22 2017 .SYNOPSIS... High pressure centered southeast of New England will bring dry and unseasonably warm conditions into Thursday night. A cold front moves into southern New England Thursday night. However this front pushes northward, away from the area on Friday as a warm front. A strong cold front will cross the region late Saturday afternoon and night, bringing areas of rain and patchy fog. There will be a low chance for isolated thunderstorms as the front passes. Near seasonable temperatures will return early next week, with blustery conditions on Sunday and Monday. There may be another chance for precipitation around the middle of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 4 PM update... Dry weather anticipated overnight with surface high pressure centered offshore and southeast of our area. A weak shortwave passing thru overnight could produce a period of mid deck clouds. Otherwise, light winds out of the SW/S becoming calm or light and variable for much of the area. This will allow for good radiational cooling. Continue to expect min temps near dew point, mid 30s to near 40. Expecting some patchy fog/areas of fog to develop. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Thursday... High pressure remains offshore with southwest flow across Southern New England, while low pressure passes well north of our area, from the northern Great lakes Region into southern Ontario and Quebec. Continue to favor a dry forecast for Southern New England during Thursday. Our area remains in a SW flow, dry and unseasonably warm. Any fog should lift/dissipate early, but may see stratocumulus developing during the day. Hence partly to mostly sunny skies expected. Southwest jet associated with this system brings 20-25 knot low level winds to our area Thursday afternoon. Could be a few gusts in this range during the afternoon especially across RI and Eastern MA. Continuing with previous forecast high temps for Thu, favoring the high end of model guidance. Noting the record high temps listed in the Climate section, this would suggest values at or near record high at PVD and ORH, while BOS and BDL records are well above this. Thursday Night... May see patchy drizzle and fog develop Thu night with reduced visibilities. A light SW wind holds up for part of the night. However a cold front is expected to sag southward into our area. Although exact placement of this front not for certain, models on average showing it extending roughly E-W across MA for 12Z Fri. There is a slight chance to low chance pop for showers with the front. High surface dew points south of the front should be 40-45 for much of the area. With a light SW wind south of the front, areas of fog greater for locales with a leftover snow pack at that point, as well as south coastal MA/RI with SW flow off the water. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Highlights... * Front shifts north of the region late Fri/Fri night with scattered showers * Areas of drizzle and patchy fog Fri night/early Sat * Mild with widespread areas of rain Sat into Sat night * Dry, blustery and cooler Sun/Mon Overview... 12Z models suite continues showing a good overall handle on the surface and upper level features even in the progressive flow aloft through the weekend. Timing and track differences with individual features work in from about Monday onward, especially with a possible system that may pass near or S of the region around the late Monday/Monday night timeframe. Another front may try to approach around Wednesday, but again with fast flow across the northern stream, low confidence with the timing and track of this system. Details... Friday... Cold front looks to stall across the N CT/RI into SE Mass Fri morning. This will keep a chance for showers across most of the region. As H5 ridge axis crosses the region, will see winds aloft shift to SW, which will help push the front back to the N of the region taking most of the showers with it. Big question will be whether there may be enough breaks in the clouds mainly across southern areas Fri afternoon to bring temps up to around 60. Onshore winds will keep temps cooler along the coast. Clouds and leftover showers will also limit the temp rise generally N of the Mass Pike. Most model guidance was stubborn in keeping temps close to 60 across N CT/RI and SE interior MA Fri afternoon, then mainly in the lower-mid 50s for highs across most of the remainder of the region. With an onshore flow, readings will hold in the upper 40s across the outer Cape and Nantucket. SW flow at the surface and aloft ahead of approaching strong cold front and H5 cutoff low pres will slowly shift E Fri night. Will see areas of drizzle and patchy fog along with lingering showers in the moist low level flow. Saturday... Cutoff H5 low shears N-NE into western Quebec late Saturday, but remaining strong short wave will shift E Sat night. Surface front will quickly push E across the region. Short range models, specifically the 12Z NAM, signaling quite a bit of instability with and ahead of this front, including LIs near zero, total totals from 50-54, Showalter index of -2 to -3 and TQ values around 20. Also lapse rates on order of 7C/km or higher at about H7 at both KALB and KBDL Sat evening, and up to 8C/km at KORE overnight. However, noting some mixed signals. BUFKIT soundings showing several saturated soundings until just before the instability moves in, with the best shot across the E slopes of the Berkshires as well as the CT valley region. Strong low level jet will move across as well, with forecasted speeds on order of 50 kt at 3kft at both KBDL and KBAF and 52 kt at 2kft at KALB. Again, though, there is capping in place so will have to see if the cap can be broken. Will be most difficult along the S coast where the marine layer could keep conditions more stable. A lot to consider, but have put slight chance of thunder back in the forecast for all areas, as large area of TT in the lower 50s crosses the region. Looks like best chance of thunder will occur between 22Z and 05Z. But, if the convection does indeed get going in the vicinity of the strong low level jet, could see some gusts with any thunderstorms. They will be few and far between, though. Feel the best shot for thunder will occur across central and western Mass into N Central CT. Also noting a band of moderate to heavy rainfall crossing ahead and with the front. QPF amounts from 0.25 to 0.5 inches, with highest amounts across the E slopes of the Berkshires. If this does materialize, could help mix some of the strong winds down as well even without any convection. Generally east of a KFIT- KORH-KIJD line, precip will be lower as the front will tend to speed up as it crosses the region. As the front pushes across, temps will drop quickly behind it. The back edge of the precip will quickly follow, but could see some mix of change over to snow across the higher inland terrain before ending. At this point, may see the light snow around or after midnight for a few hours before ending. A few snow showers may linger across the higher terrain of NW Mass. Sunday and Monday... Expect dry and seasonable conditions for Sunday, but blustery NW winds will make it feel much cooler. Expect gusts up to around 25-30 mph with excellent low level mixing in place, especially across the higher terrain and along the coast. Will see temps reach the mid and upper 40s across the coastal plain, but holding in the mid 30s to around 40 across the higher terrain. With the cooler temps and gusty winds, wind chill values may be below 20 degrees across the E slopes of the Berkshires, and in the mid 20s to lower 30s elsewhere. On Monday, high pressure ridge pushes offshore as fast progression of weather systems continue. SW winds increase, with gusts up to around 25-30 mph possible, highest across the higher terrain and along the S coast. Questions on timing and track of passing low pressure system late Mon or Mon night. 12Z GFS/ECMWF has fairly good agreement in keeping most of moisture S of the region, but could see some widely sct showers as it moves across. Not a lot of confidence with the evolution of this system, however. Tuesday-Wednesday... Leaned toward a blend of the 12Z GFS/ECMWF along with their ensembles during this timeframe, showing a bit better agreement with timing and track of fast moving systems. Low pres should push offshore S of New England Tuesday morning, taking any leftover showers with it. Big questions surface with yet another system moving across the northern stream during the Tuesday night/Wednesday timeframe. 12Z Canadian Global GEM was most aggressive with this low, likely due to its associated cutoff H5 low, while the GFS and ECMWF kept a more open H5 wave with it. Does look like this system should pass across the Great Lakes, but wide variance on timing and track of this feature keep rather low forecaster confidence. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/... This evening...High confidence. VFR. Light/variable or light SW winds. Overnight...Moderate confidence. VFR through midnight. Areas of MVFR-IFR CIGS/VSBYS develop around or after 05Z in patchy fog. Thursday...Moderate confidence. Lingering areas of MVFR-IFR CIGS and VSBYS early morning with fog dissipating/lifting. CIGS trending to a mix of MVFR-VFR by late morning and through the afternoon. Thursday Night...Moderate Confidence. Potential for areas of MVFR and especially IFR cigs and vsbys in low clouds and areas of fog. A cold front pushing southward into Massachusetts late Thu night could bring scattered showers to southern New England as well, possible decrease in clouds north of the front. KBOS TAF...High confidence in TAF thru this evening. Sea breeze returning to a light SW wind after 00Z. Moderate confidence in TAF for tonight into Thursday. There is a low chance for IFR conditions in low clouds and fog between 06Z and 12Z. VFR anticipated for Thu, SW winds should be strong enough to prevent sea breeze development. KBDL TAF...High confidence in TAF for this afternoon, with VFR. Moderate confidence in TAF tonight into Thursday. Anticipating MVFR vsbys generally 07Z-12Z in patchy fog, but there is a low chance of IFR cigs/vsbys in fog for that timeframe. Outlook /Friday through Monday/... Friday...Low confidence. A band of IFR CIGS/MVFR-IFR VSBYS early Fri along the S coast will shift N during the day. Conditions lower to widespread MVFR-IFR in CIGS, areas of drizzle and patchy fog Fri night. Areas of drizzle along S coast. Saturday...Moderate confidence. Should see widespread MVFR-IFR conditions as rain moves in across the region. May see areas of LIFR CIGS develop Sat afternoon/night along the coast and interior higher terrain. Low chance for isolated thunderstorms from 21Z Sat to 04Z- 05Z Sun as cold front passes. May see period of light snow after midnight Sat night across higher inland terrain as precip tapers off. Sunday...Moderate confidence. Conditions rapidly improve to VFR by mid morning Sun. W winds gusting to 25-30 kt, highest across the higher terrain and along the coast. Monday...High confidence. Mainly VFR conditions. A low chance for showers south of the Mass Pike as weak low pressure passes S of New England. Low chance for brief MVFR conditions in any showers. W winds gusting to around 25 kt during the late morning and afternoon across the higher terrain and along the coast. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/...High confidence. Tonight... High pressure off the mid Atlantic coast. Near shore SE winds noted at buoys at 23Z will shift to S-SW 5-10 knots for the overnight. Seas 1-3 feet. Thursday and Thursday night... Wind speeds Thursday increase some as winds strengthen aloft. This might be enough to bring gusts 20-25 kt to the coastal waters Thursday afternoon. Seas may approach 5 feet on the outer waters Thursday afternoon/evening. Outlook /Friday through Monday/... Friday...Low confidence. Southerly flow will switch to a more northeast to east flow during the day. Vsbys restriction possible in fog and drizzle especially across the southern waters. Saturday...Moderate confidence. Increasing southerly flow with the potential for SCA gusts. Waves will also increase in response. Vsbys reduced in developing rain and fog. Sunday...High confidence. Northwest winds will keep seas up and increase wind gusts near 30 kts. Low probability for gales across the outer waters. && .CLIMATE... Record Highs for Thu Feb 23 BOS...65/1990 BDL...68/1990 PVD...60/1990 ORH...61/1990 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...EVT/NMB NEAR TERM...EVT/NMB SHORT TERM...NMB LONG TERM...EVT AVIATION...EVT/NMB MARINE...EVT/NMB CLIMATE...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.