Area Forecast Discussion
Issued by NWS Boston, MA

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041 FXUS61 KBOX 251759 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1259 PM EST Sat Feb 25 2017 .SYNOPSIS... Mild air remains over the region today. A strong cold front will cross the region tonight, bringing showers and a low chance for thunderstorms as this front passes. Blustery conditions with temperatures close to seasonal normals expected for Sunday and above average on Monday. A couple of weather systems will bring periods of wet weather Tuesday into Thursday. Colder air looks to return late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 10 AM update... Fog is lifting and sunshine developing across portions of E MA and RI. Further west, stratus lingering across the interior. Cross sections indicate abundant low level moisture across western New Eng where clouds should prevail through the afternoon although some breaks of sun are possible. More sunshine expected in eastern New Eng. Much of the region will remain dry as leading edge of showers assocd with the cold front and lead shortwave not expected to move into western MA until early evening. Lowered PoPs and have just low chc pops in western MA for late today. Also slight chc pops Cape/Islands late today as models indicate some elevated instability moving up from the ocean so can`t rule out an isold shower here. Temps already mid 50s to lower 60s and should see maxes top out 65-70 degrees this afternoon, cooler south coast with southerly flow. Best chance for records today are at BOS and ORH. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... The cold front arrives in the Hudson Valley around 6-7 pm and crosses into western New England around 8-9 pm...Central sections 9-10 pm...and eastern New England 10 pm to midnight. This front will be supported by the sharp upper shortwave. Airmass stability will decrease through the evening...for example, Totals will climb into the lower 50s. This supports the concept of sufficiently unstable conditions for a few thunderstorms as the cold front approaches and moves through. The greatest risk for tstms would be in Western MA and Western CT where the low level inflow is least maritime. Low level southerly winds will increase during the afternoon, so that by evening we expect a 50-knot jet at or below 5000 feet. Confidence is not high as to how much of that wind may be brought to the surface in gusts during showers/tstms, but its presence suggest a chance of strong wind gusts this evening...possibly isolated damaging wind. Greatest risk would again be in western areas early tonight. Precipitable water fields continue to advertise values a little over an inch, which is 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 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 late at night. Wind gusts at that time will have a potential of reaching 30-35 knots. Sunday...High confidence. The shortwave trough moves offshore Sunday morning. The last of any pcpn should end by that time. So Sunday shapes up to be a dry day as high pressure builds in from the west. Cold advection continues during the day. Mixing due to this advection will tap winds aloft of 25-35 knots and possibly a few areas of 40 knots. These winds will diminish during the afternoon as the high pressure area approaches. Temps aloft chill behind the front, but hover on Sunday at levels that support sfc max temps around 40 or the lower 40s. Given the morning temps starting in the 30s, we have forecast max temps in the upper 30s to mid 40s. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Above average temperatures for next week * Widespread showers possible Wednesday/Thursday * More seasonable conditions return on Friday Pattern Overview... The 00z models and their ensembles have been in generally good agreement through the period with the GFS just a bit displaced. Therefor used a blend of the ensembles for the bulk of the forecast. Overall, zonal flow over the region as Bermuda high begins to build in the mid-levels. By mid-week the western trough is forecast to transition into the east as a surface front will move from the Great Lakes towards the Northeast around Wed/Thurs. Still some issues with the timing of the front as a surface wave may develop along it, which could slow it down a bit. This appears to be more inline with the EC/GEFS and ECENS. Otherwise, northwest flow behind the front could result in several clippers for next weekend. Details... Monday... High confidence. Westerly flow across the region as high pressure builds south of the region. Developing LLJ of near 40 kts will develop with high pressure to the south and quick moving wave to the north. This will make conditions a bit gusty at times. As surface high pressure moves farther to the east, winds will begin to back resulting in WAA. Surface temps could reach into the mid 50s on Monday with full mixing. Otherwise dry weather will prevail. Tuesday...High confidence. More of a transition day for Tuesday as high pressure moves eastward as upper level trough approaches. Southwest flow aloft will help saturate the profile. Guidance does show a weak wave developing a coastal low but appears to be just to far east to bring significant rainfall to the region. Depending on when this occurs, we could see a few flakes north of the Pike but confidence is low on this occurring. For now expect a few showers and clouds on Tuesday. Wednesday into Thursday... Moderate confidence. Main weather produce for the long term will occur Wed into Thursday as upper level trough approaches the region. Warm front ahead of the system will bring some showers to the area as temperatures rise well above average. Upper level low will move from the Plains towards northern Maine. This will drag a potent cold front through the region. Good agreement amongst the guidance with this system, just some issue`s with the exact timing of the front. Trended towards the slower side as there is the potential for a secondary low to develop along the front. This is more inline with the ensembles. This is an anomolous system with PWATs 3 STD above normal as Gulf moisture is tapped out ahead of the frontal passage. Heavy precip is a possibility if secondary low does develop bringing the better dynamics over southern New England. Also have noticed that there is a potent southerly LLJ out ahead of this system with 925 mb LLJ increasing to near 50-60 kts. If heavy rain does develop then we could tap into these stronger winds as the system moves through. Lastly appears that there is some elevated instability so have kept with iso thunder in the forecast. Still a lot of details to work out, but a system to watch in the coming days. High confidence in above average temperatures with a non-diurnal trend Wednesday night. Went several degrees above guidance and could still be a bit low. Friday and beyond... Moderate confidence. As the cold front passes through, northeast winds take a hold of the region. Models appear to be inline with a few shortwaves/clipper systems moving through the flow. So some snow showers are certainly possible as temps drop back to seasonable. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... Through 00z...Mix of VFR/MVFR cigs this afternoon, but IFR stratus and patchy fog expected to develop along the south coast and Cape/Islands toward 00z. Tonight...Moderate confidence. Widespread showers and isold t-storms will move through western New Eng 00-02z then diminish as it moves into eastern New Eng 03-06z. Brief heavy rain and gusty winds possible with any t-storms in western New Eng. Precip may end as brief snow showers in the Berkshires 03-06z. IFR/MVFR cigs with patchy fog will improve to VFR after cold fropa and wind shift to W/NW 02-06z. W/NW gusts to 30 kt developing after the wind shift, with G35 kt possible over higher terrain. Sunday...High confidence. VFR with sct-bkn cigs 4-5k ft. W/NW gusts to 30 kt, higher gusts possible over higher terrain in the morning. Sunday night...High confidence. VFR. Diminishing W wind becoming SW overnight. KBOS TAF...Moderate confidence through this evening, then high confidence in improving conditions overnight. KBDL TAF...Moderate confidence through this evening, then high confidence in improving conditions late this evening. Outlook /Monday through Wednesday/... Monday...High confidence. VFR with westerly wind gusts near 20-30 kts. Tuesday...Moderate confidence. Generally VFR with MVFR conditions possible south of the Pike. Wednesday...Moderate confidence. MVFR to possible IFR in -SHRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. Today...High confidence. Increasing southerly winds through the day, with gusts to 25 knots mid to late afternoon. Seas will increase through the day with 5 to 6 foot heights on the southern waters by mid to late afternoon. Tonight...Moderate confidence. A cold front sweeps across the waters the first part of the night. This will bring showers and a widely scattered thunderstorm. The showers may tap strong winds at 2000 to 4000 feet above the surface and bring them to the surface in strong southerly wind gusts. Seas build to 5-8 feet on the exposed waters of the south and the outer waters of the east. Behind the front, winds shift from the West or West-Northwest and bring cooler air. Winds late tonight should gust 30 to 35 knots. Seas will continue at 5 to 8 feet. Sunday...High confidence. West-Northwest winds continue to gust 30 to 35 knots during the morning and early afternoon. Winds may slowly diminish during the later afternoon. Seas will linger at 5 to 8 feet on the exposed waters. Outlook /Sunday Night through Wednesday/... Monday...High confidence. Improving conditions on Monday with gusts near 20 kts and seas beginning to relax as high pressure builds over the southern waters. Tuesday into Wednesday...Low confidence. Wind and seas will be below SCA for Tuesday. Approaching system to the west could see lower vsbys in rain and fog. Seas build late Tuesday night into Wednesday as low pressure system approaches. There is the potential for southerly gales across the waters. && .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. && .CLIMATE... RECORD HIGH TEMPS FOR YESTERDAY BOS 73/2017 - previous record 70/1985 PVD 72/1985 - topped off at 71 degrees (no record) BDL 73/1985 - topped off at 72 degrees (no record) ORH 69/2017 - previous record 67/1985 RECORD HIGH MIN TEMPS FOR YESTERDAY BOS 49/1930 - bottomed out at 46 (no record) PVD 45/2017 - ties previous record of 45/1984 BDL 43/1981 - bottomed out at 42 (no record) ORH 48/2017 - previous record 46/1985 RECORD HIGH TEMPS FOR TODAY BOS 65/1930 * broken 67/2017 PVD 69/1976 BDL 70/1976 ORH 64/1976 RECORD HIGH MIN TEMPS FOR TODAY BOS 46/1891 PVD 45/1930 BDL 45/1930 ORH 37/1996, 1984, 1976 DEW POINTS OF NOTE FOR YESTERDAY BOS Max Dew Point 54 ties highest for date set in 1985 PVD Max Dew Point 53 is highest for date. Previous high 50/1990 BDL Max Dew Point 54 is highest for date. Previous high 49/1990 ORH Max Dew Point 53 is highest for date. Previous high 48/1985 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Gale Warning from midnight tonight to 7 PM EST Sunday for ANZ231>235-237-250-251-254>256. Small Craft Advisory from midnight tonight to 7 PM EST Sunday for ANZ230-236. && $$ SYNOPSIS...WTB/Dunten NEAR TERM...KJC SHORT TERM...WTB LONG TERM...Dunten AVIATION...KJC/Dunten MARINE...WTB/Dunten HYDROLOGY... CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.