Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 130712 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 312 AM EDT Wed Mar 13 2024 .SYNOPSIS... Dry weather persists today and Thursday with unseasonably mild temperatures...but sea breezes on the immediate coast will keep it much cooler in those locations. A more unsettled weather pattern develops Friday into the weekend, with rainy conditions for Fri and again on Sunday. Temperatures trend above normal through this weekend, with a cooling trend toward more seasonable temperatures by early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
310 AM Update... * Plenty of sunshine today with some clouds arriving in the afternoon * Highs mainly upper 50s/lower 60s but cooler immediate coast The closed upper level low east of the Canadian Maritimes will continue to move further east and away from the region today. This will result in rising height fields as a mid level warm front approaches. We still expect plenty of sunshine today...but do expect an increase in mid/high level cloudiness by late in the day. Low risk for a few brief sprinkles by evening...but boundary layer is quite dry so do not expect much more than that. 850T warming to between +4C and +6C coupled with a relatively dry airmass in pre-greenup should allow temps to overachieve a bit. Thinking highs inland from the coast will be mainly in the upper 50s to the lower 60s with perhaps even a few middle 60s in the lower CT River Valley. Winds will be rather light too...so quite a comfortable afternoon for mid March standards. Meanwhile...weak pressure gradient will allow for sea breeze development along the immediate coast. This should keep afternoon temps in the upper 40s to the lower 50s in this region.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
-- Changed Discussion --
Key Points... * Light/Calm Winds tonight with lows mainly in the 30s * Plenty of sun Thu with highs 60s to near 70...cooler coast Details... Tonight... Some mid/high level cloudiness this evening in association with the mid level warm front. We may even see a few brief sprinkles...but given the dry boundary layer do not expected much more than that. Otherwise...expect at least partial clearing overnight with a ridge of high pressure taking control. Light to calm winds will allow for overnight low temps mainly in the 30s...but a few upper 20s are possible in the normally coldest outlying locations. Thursday... Upper level ridge axis approaches from the west. This will set the stage for a beautiful Thursday across most of the region. Plenty of sunshine expected with 925T climbing to between +9C and +12C inland from the coast. Thinking temps likely overachieve a bit in pre- greenup with highs mainly in the 60s inland from the coast. In fact...a few locations in the Lower CT River Valley may hit 70. Weak gradient though will allow for sea breezes along much of the immediate coast...which will hold highs in the 50s in most of those locales.
-- End Changed Discussion --
&& .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Highlights: * Dry weather on Thurs, although increased cloud cover late in the day. Above normal temps. * Soggy, dreary Fri with rain, perhaps with embedded downpours at times, however not expecting rains to rise to level where flooding is expected. Cooler, though still above normal temps for Fri. * Mix of clouds and sun but dry Sat. * Another frontal system around Sun bringing rains to Southern New England to usher in cooler more seasonable temps by early next week. Details: The 500 mb pattern across CONUS turns into a split flow regime as we move into the latter part of the week into the weekend, with a pretty active northern stream and a closed low over the western Four Corners region. Ahead of this split flow pattern is a building ridge over the southeast US, which will help steer initial low pressure over the central Plains into the OH Valley and Northeast by later Thurs night into Fri. Thereafter northern stream troughing then reasserts itself across most of the northern tier of states, with unsettled weather then re- developing around Sunday. Overall, it is an unsettled weather pattern although no one specific storm looks to be particularly impactful. Temps start above normal on Thursday, and while they continue to run generally above normal, a gradual cooldown is expected each day before trending closer to seasonable by late weekend into early next week. Thursday through Friday: First part of Thurs looks dry, albeit with increasing cloud cover through the day. In addition, areas near the coast to see light onshore flow and comparatively cooler temps compared to well inland. Above normal temps however with highs lower-mid 50s for the eastern coastlines, with highs well into the 50s to lower 60s. However our weather pattern then turns more unsettled as we move into Thurs night through Fri. A shortwave disturbance aloft moving around the periphery of (and ultimately topping) the 500 mb ridge over the southeast CONUS will result in low pressure moving in from the Gt Lakes region. This will spread increased cloud cover along with an increase in rain chances late Thurs night but primarily into Fri. With today`s ensembles showing the southeast US midlevel ridge amplifying a bit more than earlier solutions, the track of sfc low pressure and initial warm frontal precip shield shifted northward into northern MA, VT and NH; however flattening ridging should spread widespread rains into Fri. There is a little bit of elevated instability that could be realized with potential for embedded downpours, although did note GEFS/EPS QPF probs reflect a moderate- high chance for 24 hr rain over 0.5" and very low to low probs (5- 15%) of 24 hr rain over an inch. Rain looks to shift offshore Fri evening before trending drier toward early Sat AM, although with lingering/intermittent showers near the coasts. Saturday: Weak shortwave ridging aloft develops over the Northeast as the Friday storm system moves offshore; this occurs well ahead of deepening troughing taking shape over the Northern Plains/Upper Midwest. Expecting more of a mix of sun and clouds on Sat, albeit with cooler though still above normal temps in the mid 40s to the lower 50s. Clouds again redevelop later Sat evening ahead of the next system developing for Sunday. Lows above freezing in the middle to upper 30s. Sunday into Monday: GFS/ECMWF and its ensemble means show split flow becoming increasingly dominated by stronger northern stream troughing, with building midlevel heights over the West Coast. Low pressure then looks to move in from the Gt Lakes region Sunday into Sunday night, with increasing clouds and increasing chances for rains. Still a bit of uncertainty on the timing and strength, and those details will need to be better refined before delving into specifics but this will likely be our next best chance for rain after Fri. After this system exits on Monday, expect temperatures trending cooler and closer to seasonable levels as deep troughing aloft builds into the Northeast states. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06z TAF Update... Today...High Confidence. VFR. Light NNW winds shifting to the SE by afternoon with a sea breeze component developing along portions of the immediate coast. Tonight...High Confidence. VFR. Calm/light winds. Thursday...High Confidence. Light NW winds across the interior with sea breezes developing along the coast. KBOS TAF...High confidence in TAF. ESE sea breeze develops by 15z/16z. KBDL TAF...High confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday Night: VFR. Chance RA. Friday: Mainly VFR, with areas MVFR possible. Breezy. RA likely. Friday Night: MVFR/IFR conditions possible. RA likely. Saturday: Mainly VFR, with local IFR possible. Chance RA. Saturday Night: Mainly VFR, with local MVFR possible. Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Thursday...High Confidence. Any lingering marginal 5 foot small craft seas across our eastern waters will subside by daybreak. Otherwise...a weak pressure gradient will keep winds/seas below small craft advisory thresholds today through Thursday with good vsbys. Outlook /Thursday Night through Sunday/... Thursday: Winds less than 25 kt. Thursday Night: Winds less than 25 kt. Chance of rain. Friday: Winds less than 25 kt. Rain likely. Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain likely. Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/Loconto NEAR TERM...Frank SHORT TERM...Frank LONG TERM...Loconto AVIATION...Frank/Loconto MARINE...Frank/Loconto

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