Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 240553 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1253 AM EST Sat Feb 24 2018 .SYNOPSIS... A weak wave of low pressure moves offshore tonight followed by drier air later tonight into Saturday. Another frontal system will bring more rain and interior mixed precipitation Saturday night and Sunday. A near-seasonable, quiet pattern for early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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1250 AM update... Low clouds persist across the region with areas of fog, especially along the coast. Expect partial clearing to develop early this morning, but stratus and patchy fog may linger along the south coast.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... Saturday... Dry weather returns Saturday as a high pressure builds into the region from the NW. Lingering fog is possible after 12z along the southern coast, but should quickly burn off due to surface heating. Clouds will continue clearing, with most of the interior seeing periods of sun by midday. With NW flow, temps will reach well into the 50s across the interior and coasts. Cooler upper 40s over higher elevations NW MA. Saturday night...Rain showers expected after midnight, with a chance of higher elevation seeing freezing rain and sleet just before sunrise. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Widespread precip on Sunday with wintry mix in the interior * Dry and above average for early next week * Stormy pattern emerging for the beginning of March Overview... 12z guidance is in general agreement with the extended forecast. Just some minor differences related to thermals which provide different outcomes in p-type for late Saturday night into Sunday. Deamplifying trough across the CONUS as potent shortwave moves up into the Great Lakes bringing occluded system and triple point low into southern New England on Sunday. Afterwards high pressure and strong ridge takes hold over the eastern CONUS by early next week. The GEFS and EPS continue to show anomolous high pressure building over Greenland which will influence a cut-off low to either retrograde towards the Maritimes or remain across the North Atlantic. This all due to the NAO turning negative by early March. While the pattern begins to jam up, digging shortwave out of the southern Plains on Thursday needs to be watch as it could be the first of several waves impacting southern New England. Details... Late Saturday night into Sunday...Moderate confidence. Potent wave will eject out of the desert Southwest producing a surface low pressure system up into the northern Great Lakes. Stalled front to the south will begin to lift northward as a warm front. This will result into another overrunning precip set-up as moisture from the south increases as warm front begins to lift northward. Surface high pressure will be set-up north to northeast of the region allowing for surface temps to fall. Triple point low developing along the stalled front, will reinforce the cold air especially in the 950-925mb layer leading to cooler temps at the surface, esp across the high terrain.Models are always to quick at warming temps above freezing, so trended towards cooler 2m temps and wet-bulb effects. P-type will once again be the issue as models are still struggling with the warm layer. EC continues to remain on the cold side with the 12z NAM as the warmest. GFS/CMC and now 18z NAM are in the middle of the ground and thus trended towards the ensembles guidance. As with the prev forecaster, kept a bit of snow/sleet at the onset, as cold air looks to be deep enough north of the Pike and esp Route 2. In fact with good omega in the snow growth region, could see a few inches of snowfall. Once the mid-level warm front pushes into the region, a transition to more freezing rain event will occur leading to slick travel across the interior. Highest confidence will be across the east slope of the Berkshires and the Worcester Hills as the higher terrain locations will see the coolest surface temps. This is due to warm layer remaining around 800mb. Cannot rule out northern CT and the higher terrain of RI for some wintry weather impacts, but confidence is higher across northern MA. South of the Pike and especially across RI and SE MA conditions look to warm for any wintry weather, but still will have to watch as a change in just a few degrees will impact p-type. This system continues to be quite robust resulting in more widespread precip, esp as we continue to tap into that Gulf moisture. PWAT values are around 2-3 STD above normal for this time of year. When this system is all said and done, could see about an inch across the south coast with a half of an inch near the MA/NH border. Guidance from NERFC suggest that the rivers should remain within their banks, but may need to watch some of the flashier streams. Lastly, with the surface warm front trying to push northward, may have a large gradient in surface temperatures somewhere across southern New England. While warm fronts tend to struggle to lift northward this time of year something to watch as we could see low 50s across the south coast and mid 30s across the interior. Sunday night into Wednesday...High confidence. Surface cold front will push through the region resulting in a drying trend for Sunday night. Strong high pressure over the Ohio Valley will begin to strengthen Monday into Tuesday as anomolous ridge sets-up over the Mississippi Valley. This high appears to stay in place into middle of next week before a quick moving wave from the southwest gets kick into the flow. Thanks to ridging and surface high, dry weather will prevail as temperatures turn slightly above average. Thursday and beyond...Low confidence. To many pieces to the puzzle to have confidence in the forecast for the end of the week. Approaching shortwave from the southern Plains will spawn a surface low, just uncertain on its direction and location as it will depend on large scale features downstream. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...Moderate confidence. Through 12z...MVFR/IFR conditions will gradually improve to VFR from north to south through 12z, but IFR persisting over the islands. Today...Stratus and patchy fog may linger for a few hours past 12z along immediate south coast and especially the Islands. Otherwise VFR. A brief period of showers may move across portions of N CT and RI and SE MA late in the day and early evening. Tonight...VFR in the evening, lowering to MVFR from west to east late. Rain, sleet and freezing rain developing from SW to NE well after midnight with snow/sleet across northern MA. Mainly rain mixed with sleet coastal plain. Sunday...Widespread IFR/LIFR developing. Rain, mixed with sleet at times in the morning in the coastal plain. Snow, sleet and freezing rain changing to rain interior. KBOS Terminal...High confidence in trends. Conditions improving to VFR early this morning, but exact timing may be off a few hours. KBDL Terminal...High confidence in trends. Conditions improving to VFR early this morning, but exact timing may be off a few hours. Outlook /Sunday Night through Wednesday/...Moderate confidence. Sunday Night: Mainly VFR, with local IFR possible. Slight chance RA. Monday through Wednesday: VFR.
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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 Term /through Sunday/...High confidence. Tonight...Winds shifting to west with gusts up to 20 kt. Areas of fog will limit vsbys over south coastal waters. Saturday...Diminishing westerly winds becoming northerly in the evening. SCA might be needed for the southern waters early Saturday where seas reach 5 feet. Outlook /Sunday Night through Wednesday/... Sunday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Rain. Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain. Monday: Winds less than 25 kt. Seas up to 5 ft. Monday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday Night through Wednesday: Winds less than 25 kt.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Nocera/Dunten/Correia NEAR TERM...KJC SHORT TERM...Nocera/Correia LONG TERM...Dunten AVIATION...KJC/Dunten MARINE...Dunten

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