Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 290619 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 119 AM EST Tue Nov 29 2016 .SYNOPSIS...
-- Changed Discussion --
An approaching warm front will allow rain to overspread the region this morning, which may become heavy at times across Connecticut... Rhode Island and south of the Massachusetts turnpike this afternoon and early evening. A brief period of drying will occur late tonight into part of Wednesday morning, before the next period of rain heavy arrives Wednesday afternoon and night as low pressure moves into New England. Improving conditions Thursday as the low moves into the Maritimes with mainly dry and cooler weather for Friday through Sunday.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 5 AM THIS MORNING/...
-- Changed Discussion --
1:15 AM Update... Not much change from previous forecast as new 00z guidance continues to support the risk of freezing rain across northwest MA from about 5 am to 10 am. Dilemma remains timing of qpf and erosion of low level cold air. Greatest risk for a brief period of freezing rain appears across western sections of Franklin and Hampshire counties as dry layer between 900-800 mb may preclude precip from reaching the ground farther east into Worcester county. However given only trace amounts of qpf in the form of freezing rain can glaze roadways will leave configuration of freezing rain advisory as is for now. Earlier discussion below. Previous discussion follows... Light winds and mostly clear skies into a good chunk of this evening will allow temps to quickly fall after sunset. Clouds will then increase from west to east, particularly after midnight ahead of an approaching low pressure system. Most locations should see low temps drop into the upper 20s to the lower 30s, with even some middle 20s across the normally coolest outlying locations. These low temps will likely occur near or shortly after midnight. Temps should then level off or rise a few degrees as clouds increase as well as thicken. Dry weather should prevail through 4 am.
-- End Changed Discussion --
&& .SHORT TERM /5 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... * Brief period of freezing rain possible across interior northern MA between 5 and 9 am Tue morning * Rain overspreads the region Tue am and may be heavy for a time during the afternoon/early evening south of the MA Pike * Areas of fog may be locally dense late Tue night/early Wed am Wave of low pressure approaches from the southwest Tuesday morning increasing the forcing for ascent. Guidance appears to hint an initial band of precipitation that may sweep through our western and northern zones between 5 and 9 am in the warm air advection pattern. It is uncertain how much of this precipitation will reach the ground, but concerned for the risk for a brief period of light freezing rain with this activity. Most of the raw 2 meter temperature guidance shows readings above freezing during this time frame. However, noticed that MOS guidance had virtually no wind with temps near or just below freezing around 12z which has us concerned. The raw guidance may end up a few degrees too mild in this scenario, given little wind to scour out boundary layer cold. So despite the uncertainty, opted to issue a short-fused Freezing Rain Advisory for northwest/north central MA given the potential impacts just a small amount of light freezing rain often has on roads/walkways. Confidence is not as high as we would like for a short term forecast, but the timing near rush hour certainly increases the concern. It is possible that we luck out and temps are already above freezing by the time precipitation arrives. On the flip side of the coin, if activity arrives earlier than expected, we may even need to extend the advisory a bit further south and east. Certainly no issues on the coastal plain, as rain overspread the region Tuesday morning. An impressive 50 to 60 knot southerly low level jet develops by Tue afternoon, coupled with PWATS 2+ standard deviations above normal for this time of year. With that said, expect a soaking rainfall Tuesday afternoon/early evening. The rain may be heavy at times, south of the Pike where low level jet intersects wave of low pressure tracking across the region. In fact, a rumble or two of thunder certainly can not be ruled out across RI/southeast MA along with brief nuisance poor drainage street flooding. Rainfall from this first event should average between 0.50 to 1.25 inches, but localized 2 inch amounts are certainly possible in any convection with the highest risk for this across CT/RI/SE MA. The bulk of the rain should be over by late Tuesday evening, with dry weather prevailing overnight. Biggest concern will then be for areas of fog developing, which may become locally dense in the typically prone locations where winds decouple. Temps are tricky Tuesday afternoon and night. Much of the region should eventually warm sector, but may take until Tue evening, when highs reach between 55 and 60 south of route 2 in MA. North of route 2, it is possible that temps remain below 50 as that area may never warm sector. Lows by daybreak Wed should mainly be in the upper 30s to the middle 40s in most locations. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights... * More rain, heavy at times Wed afternoon and night * Improving conditions Thu with cool and blustery weather Fri through the weekend * Uncertainty for Sunday night/Monday regarding potential for another low pressure system Overview... High amplitude longwave trof with closed low initially centered over the Great Lakes Region will contribute to another round of soaking rainfall for southern New England during Wed/Wed night. Continue to expect more of a split flow pattern by the end of this week and this weekend, with low amplitude northern stream across the Gt Lakes and NE. This will bring mainly dry and cooler weather for late this week and into this weekend, but series of fast moving shortwaves move through the flow so can`t rule out brief rain/snow showers at times but timing uncertain. Greater uncertainty exists for Sunday night/Monday regarding potential for an upper trof advancing from the west. Details... Wednesday into Wednesday night... Wednesday looking dry to start, may even have some breaks of sunshine initially, but then through the morning and the course of the day we see steadily increasing moisture as another wave of low pressure heads our way from the southwest. This results in a quick increase in cloud cover and rain developing for the afternoon. Precipitable water increases to 1 to 1.5 inches, accompanied by a SW low level jet and divergence aloft. Continue to think that the majority of the rainfall from this event will occur during Wed afternoon and evening, close to timing of when low level jet works its way into our region. Another soaker anticipated with the potential for 0.75 to 1.5" of rainfall, possibly localized totals of around 2". Area rivers and streams should be able to handle this second round of rainfall, though some street flooding could occur with any leaf-clogged drains. Highs Wed will be dependent on how far north warm front gets. Best chance of temps reaching the upper 50s continues to be along south coastal MA and RI, since front may get hung up south of the Mass Pike for this event. Cooler upper 40s to possibly low 50s likely further to the north across northern MA and possibly over part of northern CT. South of the front models indicate some modest instability which is accompanied by decent lift, so can`t rule out rumbles of thunder. Surface low deepens some as it traverses our area, but should start pushing NE of our region towards 12Z. Rainfall dwindles after midnight. Thursday... Low pres in the Gulf of Maine will lift NE into the Maritimes with drier westerly flow into SNE. With mid level trof axis still to the west and shortwaves rotating through, can`t rule out a brief rain shower, especially in the vicinity of the east slopes of the Berkshires. But by midday moisture becomes quite limited. Anticipating some diurnal stratocumulus clouds with partly to mostly sunny skies. While it is cooling aloft, low level temps are fairly mild so temps should reach well into 50s in the coastal plain with upper 40s interior high terrain. Friday through Sunday... Mainly dry, cooler and blustery conditions with westerly flow as broad trof settles in over the NE. Still a few shortwaves rotating through the flow and weak surface low passes thru northern New England on Fri, so a low risk for a brief rain/snow shower, mainly interior high terrain. Seasonable temps Fri cooling a bit below normal next weekend. Sunday night/Monday...Operational/ensemble model spread is large regarding forecast conditions for this timeframe. One area of uncertainty is with placement of mid level ridging/trof for this timeframe. ECMWF has a blocking surface high to our N/NE, which could allow for wintry precipitation in our area. Other solutions are warmer/rain. Going with a model compromise for chance pops for this timeframe. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... 1:15 AM Update... Thru 12z... VFR conditions at 06z will lower to MVFR around 12z across western MA along with the risk of freezing rain in this region. Elsewhere dry weather and VFR continues. Forecast confidence is moderate to high. After 12z... VFR to start except MVFR western MA along with risk of freezing rain across this region. Risk of freezing rain ends by 15z across western MA. Then by 18z much of the region is MVFR with moderate to heavy rain overspreading the area from SW to NE. Heaviest rain 21z-00z with widespread MVFR and IFR across the higher terrain. Low risk of isolated Thunder too 21z-00z. LLWS likely toward 00z as 50-60 kt SSW low level jet moves across the area. Forecast confidence moderate to high. Tonight... Heavy rain with isolated thunder at 00z begins to exit offshore. LLWS at 00z weakens 03z-06z. Period of IFR begins to improve toward 06z. However as modest south winds shift to the west in the evening and then become light and variable areas of dense fog are possible after midnight. Moderate to high confidence on trends but lower especially on details of dense fog potential. Wednesday... Low risk of patchy IFR in dense fog. Otherwise VFR and dry weather in the morning gives way to IFR and rain for the afternoon. KBOS TAF...MVFR arrives around 15z and IFR about 21z along with moderate to heavy rain. Heaviest rain and risk of isolated thunder may slide south of Logan 21z-02z. KBDL TAF...MVFR arrives around 13z followed by IFR near 18z along with moderate to heavy rain. Outlook /Wednesday Night through Saturday/... Wednesday Night...Moderate confidence. Patchy IFR/fog to start, otherwise initially VFR. Then deteriorating to IFR cigs/vsbys Wed afternoon and especially Wed evening as another round of moderate to heavy rain moves in. Rain exits overnight with conditions possibly improving to VFR late Wed night. Thursday thru Saturday...Moderate confidence. Mainly VFR cigs with isold MVFR possible. Blustery W winds expected.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... Tonight...High confidence. A ridge of high pressure will keep winds and seas well below small craft advisory thresholds. Tuesday and Tuesday night...Moderate confidence. Impressive 50 to 60 knot low level jet develops by Tue afternoon and continues into the early evening ahead of a wave of low pressure. The result will be southerly wind gusts into the lower 30 knots. Small craft headlines posted all waters except Boston Harbor. There is the risk for a brief period of Gale force wind gusts, but given inversion over the waters opted to go with strongly worded small craft headlines. In addition, periods of heavy rain Tue afternoon/early evening along with fog will reduce VSBYS and there may even be a rumble or two of thunder. Outlook /Wednesday Night through Saturday/... Wednesday...Moderate confidence. Seas remain at SCA threshold across southern outer coastal waters, with building seas expected across the waters Wed night. Winds becoming E/SE and gusty during Wed afternoon/evening, and along the south coast winds become S during Wed evening. Vsbys lowering again in developing rain and fog later in the afternoon and Wed night. Thursday thru Saturday...Mainly W/NW winds with gusts to 25 kt at times. SCA seas persist over the south coastal waters. Good vsbys.
-- End Changed Discussion --
&& .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None. MA...Freezing Rain Advisory until 10 AM EST this morning for MAZ002>004-008-010-026. RI...None. MARINE...Small Craft Advisory from noon today to 1 AM EST Wednesday for ANZ231-232-251. Small Craft Advisory from 10 AM this morning to 7 AM EST Wednesday for ANZ233>235-237-254>256. Small Craft Advisory from noon today to 11 PM EST this evening for ANZ236. Small Craft Advisory from noon today to 7 AM EST Wednesday for ANZ250.
-- End Changed Discussion --
&& $$ SYNOPSIS...Frank/NMB NEAR TERM...Frank/Nocera SHORT TERM...Frank LONG TERM...NMB AVIATION...Nocera/NMB MARINE...Frank/NMB

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.