Area Forecast Discussion
Issued by NWS Boston, MA

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037 FXUS61 KBOX 241953 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 253 PM EST Fri Feb 24 2017 .SYNOPSIS... High pressure over the Atlantic Ocean will maintain dry and unseasonably warm conditions through Saturday. A strong cold front will cross the region Saturday night, bringing showers and areas of fog. There will be a low chance for isolated thunderstorms as this front passes. Near seasonable temperatures will return Sunday and Monday, with blustery conditions. Wet weather returns to the area for the Mid- week. Another shot of cold air moves back into New England on Thursday. && .NEAR TERM /THROUGH TONIGHT/... *** Record Warmth Across Much of Southern New England *** This afternoon...adjusted temperatures for this afternoon one last time based on observed trends. Wind direction will be key to see if Providence can tie their highest February max temperature. At last check, they were still one degree shy. Tonight...Expecting the unseasonably mild weather to continue. Min temperatures tonight should range about 25 to 30 degrees above normal. Not seeing a lot of snowpack left in visible satellite imagery this afternoon. However, whatever is left will certainly continue to melt. This, combined with a persistent south wind, will keep the lowest levels of the boundary layer fairly humid. This is turn should at least lead to areas of fog. Also expecting some stratus to develop, with a fairly strong inversion developing. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... Not much change to expectations during this period. Low clouds and areas of fog likely to start Saturday. This will limit sunshine for a while, resulting in lower max temperatures, which will still be well above normal. Guidance has not been handling the warmth the past couple of days very well, so kept the trend of going a couple degrees higher than the warmest guidance. Still thinking a strong cold front will move across southern New England Saturday evening, about the same time as a potent mid level shortwave. Mid level lapse rates should be more unstable than moist adiabatic. So despite a climatologically unfavorable time, cannot completely rule out the possibility for a few thunderstorms during the evening and overnight hours. The greatest risk for thunderstorms would be across western MA and northern CT. Higher temperatures will lead to greater mixing depth of the boundary layer. This should lead to more gusty southwest winds of 25 to 30 kt, particularly toward the coast and over the coastal waters. Any convection could bring stronger gusts to the surface across the interior, too. Precipitable water values continue to show just over an inch, well above normal. But this is a narrow and fast-moving zone, so while showers may be briefly strong, total amounts should be 0.50 inches or less. Colder air rushes in late Saturday night behind a cold front. It will be a race between the cold air and the departing showers, but a brief changeover to snow is possible at the end. Any accumulations should be limited, generally less than an inch and mainly over the higher terrain of the Berkshires and Worcester Hills. Finally, the colder air advection behind the front will bring mixing of strong WNW winds aloft to the surface. Wind gusts will have a potential late Saturday night of reaching 30-40 knots. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Highlights... * Blustery and more seasonable temperatures Sun and Mon * System on Tuesday will bring some snow/rain showers to the area * Widespread showers possible Wednesday/Thursday Pattern Overview... 00z guidance is in general agreement with some mesoscale differences especially in regards to timing. Synoptically, the ensembles show rather good agreement in the medium range for next week. This includes the Western trough lifting northeastward as upper ridging over the southeast US continues to build by Mid-week. Towards the end of the week, troughing will move into the eastern half of the CONUS bringing temps back to average. Confidence level was increasing until the new 24.00z EC. The EC is more amplified and develops a couple of surface lows along the warm and cold front as it passes over New England. This deviation has resulted in issues with precip timing, type and temperature profiles. While normally the deterministic appears an outlier, the GEFS and previous GFS runs were also indicating this potential. Because of this increasing spread, will continue with moderate confidence in the overall forecast. Details... Sunday into Monday...High confidence. Upper level trough axis begins to push towards the Maritimes as surface high pressure builds across the southeast. This will put the region in CAA and northwest flow. Temperatures on Sunday will feel quite chilly compared to the previous few days as high remain in the 40s. True mixing up to 850 mb where a 40-45kt LLJ will develop. Expect blustery conditions with gusts near 30-35 mph. Weak shortwave will move through the flow on Monday but with building high pressure to the south, the region should remain dry. However this will tighten the pressure gradient resulting in a LLJ of 35-45 kts. Again another blustery day for southern New England. Temperatures will be a bit warmer however with highs into the 50s. Tuesday and Wednesday...Moderate confidence. Guidance begins to diverge on this portion of the forecast resulting in low confidence. High pressure south of the region will help increase low level moisture into the area due to southerly winds. Approaching low pressure system across the Great Lakes will extend its warm front near the region as well. This may result in overrunning of precipitation and with thermal profiles near freezing, could see some snow showers on Tuesday morning. As temperatures rise precipitation will turn more to rain. However the more amplified EC is developing a low along the front where as the GFS/CMC and UKMET are more progressive and this low develops over the Atlantic. Latest ECENS develops this low further east than deterministic guidance. Therefore will trend towards the ensembles resulting in a cloudy and wet day on Tuesday. Surface low pressure over the Great Lakes will move towards southern Canada, dragging a cold front through the region. Timing appears to be the bigger issue with the more amplified EC several hours slower then the GFS. Right now appears that the CMC is in the middle of guidance. There is also the potential for a secondary low to develop along this front which could increase rainfall amounts. Spread is still to great to nail down amounts etc. However confidence is increasing the precip will move through the region later Wed into Thursday morning. In fact both the ECENS and GEFS continue to show high probability or qpf after 12z Thursday, so the timing may slow down a bit. Lastly, large temperature spread amongst the guidance during this time period with the GFS indicating upper 50s and the EC in the mid 40s. All dependent on the placement of the low and how quickly will the warm front move northward. Trended towards the warmer side of the guidance with support from the GEFS/GFS and ECENS. Thursday...Low confidence. Still a chance for showers across the region but overall should be a dry day on Thursday. Reinforcing arctic air will drop temperatures back to seasonable with blustery conditions. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/... Through 00Z...High confidence. VFR. Tonight...Moderate confidence. VFR with areas of IFR/LIFR developing in areas of fog. patchy LLWS possible as a southwest low level jet develops over southern New England. Greatest risk for LLWS north and west of KLWM-KORH-KBDL. Saturday...Moderate confidence. Lingering IFR in morning fog, otherwise VFR. Showers approach from the west and are most likely between 21Z and 03Z in the west, and between 00Z and 06Z in the east. Conditions may briefly lower to IFR in any rain showers. Isolated thunderstorms are possible as this band of showers moves through. Rain may change to snow across the higher terrain as it tapers off Saturday night. More LLWS is possible in the evening with S-SW winds at 40-50 knots at 2000-3000 feet AGL. Winds shift from the west during the early night as a cold front sweeps through from west to east. WNW winds will become gusty overnight with gusts to 30 to 35 knots possible. KBOS TAF...High confidence in TAF through 25/04Z. Moderate confidence in TAF after 25/04Z. KBDL TAF...High confidence in TAF through 25/04Z. Moderate confidence in TAF after 25/04Z. Outlook /Sunday through Tuesday/... Sunday and Monday...High confidence. VFR with blustery NW wind gusts near 30-40 kts. Tuesday...Moderate confidence. MVFR conditions possible in -SHRA or -SHSN. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday Night/...High confidence. Tonight...Winds and seas remain relatively light. South to southwest winds continue. Saturday...Moderate confidence. A cold front sweeps across the waters Saturday evening and early night with showers, and perhaps isolated thunderstorms. Strong winds aloft may produce a couple of strong wind gusts in any showers and storms. Winds shift behind this cold front. Winds from the west after midnight will have potential gusts of 30 to 35 knots. This would be borderline conditions for gales toward Sunday morning. Outlook /Sunday through Tuesday/... Sunday and Monday...High confidence. Northwest winds will keep seas up and increase wind gusts near 30-35 kts. Low probability for gales across the waters. Improving conditions on Monday with gusts near 20 kts and seas beginning to relax as high pressure builds over the southern waters. Tuesday...Low confidence. Wind and seas will be below SCA for the day. With approaching system to the west could see lower vsbys in rain and fog. && .CLIMATE... RECORD HIGH TEMPS FOR TODAY BOS 73/2017 - previous record 70/1985 PVD 72/1985 BDL 73/1985 ORH 69/2017 - previous record 67/1985 RECORD HIGH MIN TEMPS FOR TODAY BOS 49/1930 PVD 45/1984 BDL 43/1981 ORH 46/1985 RECORD HIGH TEMPS FOR SATURDAY BOS 65/1930 PVD 69/1976 BDL 70/1976 ORH 64/1976 RECORD HIGH MIN TEMPS FOR SATURDAY BOS 46/1891 PVD 45/1930 BDL 45/1930 ORH 37/1996, 1984, 1976 && .HYDROLOGY... We will need to monitor rising water levels across southern New England into early next week. Much, if not all, of our snowpack has, or will have, melted. There is still much more snowpack upstream, over northern new England, that will push into the headwaters and head downstream. Some river levels could approach action stage. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Dunten NEAR TERM...Belk SHORT TERM...Belk LONG TERM...Dunten AVIATION...Belk/Dunten MARINE...Belk/Dunten CLIMATE...Staff HYDROLOGY...Belk is the U.S. government's official web portal to all federal, state and local government web resources and services.