Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 041431 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 931 AM EST Mon Mar 4 2024 .SYNOPSIS... Quiet and mild weather continues into Monday. Clouds linger through a large part of the upcoming week, with better chances for steady rains Tuesday, Thursday, and late Saturday. Temperatures for the workweek are above normal, but start to trend cooler by the latter half of the week. && .NEAR TERM /THROUGH TONIGHT/...
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Update: 930am Forecast challenge this morning revolves around cloud cover and cloud bases, mainly an aviation issue. We are watching the marine layer shift west towards eastern Massachusetts with CIGS around 400-800 ft. With the low clouds/stratus areas of patchy fog and drizzle is possible, did adjust our vsby grids to reflect the latest trends. Not out of the question vsby drops to a mile or less for an hour or two. Prior discussion below... Clouds were coming and going across the western half of southern New England early this morning, but were more prevalent towards the east coast of MA. The lowest clouds bases, and a herald of what is expected to come, were over the Cape and islands. High pressure centered over eastern Canada will continue to provide subsidence today, leading to a dry day for most. However, it will also mean NE to E wind for much of the day. Water temperatures around southern New England were right around 40F, so that will take a bit off temperatures. Still about 5-15 degrees above normal, with the lowest high temperatures towards the east coast. Cannot completely dismiss the idea of a few light showers Shallow moisture trapped beneath a subsidence inversion again today, although with the general E flow, it should be a little deeper. Combined, with the lower temperatures to reduce boundary layer mixing, and thinking clouds will be more persistent across the eastern half of southern New England, once the offshore cloud bank pushes inland. Should there be more mixing than currently anticipated, there will likely be more breaks in the clouds, and temperatures will likely be higher.
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&& .SHORT TERM /TUESDAY/... High pressure moves across the Maritimes tonight, then over the North Atlantic Tuesday. This will clear a path for a weak low pressure moving north along the East Coast to arrive in southern New England sometime Tuesday. Increasing risk for showers late tonight into Tuesday. Looking more likely for rainfall during the day Tuesday. Rainfall totals currently expected to remain less than one half inch, which would be good for area waterways to have more time to recede from the rainfall this past weekend. Still expecting low temperatures tonight to be rather close to normal high temperatures for early March, meaning above normal high temperatures for Tuesday as well. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Key Points * Mainly cloudy weather this week with above normal temps Wednesday, then trending cooler Thursday into the weekend * Impactful heavy rain event Wednesday night through Thursday. River and poor drainage flooding likely. * Another storm system moves through late in the weekend which could bring either heavy rain or winter precipitation to the region, but details remain uncertain. Wednesday: High Confidence The weak low departs to the north, while a stronger low begins to move north from the southern Appalachian Mountains. Surface winds turn SW in the morning and should allow the boundary layer to dry out for a short while before moisture ahead of the next system arrives. This could mean some sun breaking out Wednesday allowing for high temps to top out in the upper 50s to low 60s. Wednesday evening - Thursday: Moderate Confidence A southern stream shortwave trough will intensify as it exits to the NE from the Gulf of Mexico. At the same time, a northern stream trough dips south into northern New England. This brings a stronger coastal low to the area Wednesday night into Thursday. Confidence in this portion of the forecast is beginning to increase with much less spread in guidance along with run to run consistency. This system will likely bring impactful heavy rain to SNE with moderate ensemble probs of 40-60% for 2in of rain, and low probs of 10-20% for 4in of rain. PWATS ahead of the system could approach 1.5 to 1.7 inches which is 3-4 standard deviations above climatological mean according to the NAEFS and ECMWF ensemble situational awareness tables. MMEFS is already showing high probability for minor river flooding region wide and low probs for moderate river flooding. WPC has also highlighted the region under a marginal risk for excessive rain. The axis of heaviest precipitation has shifted around in the last few model runs, however, the 00z suite of guidance is starting to narrow in on the heaviest band being over SE MA and RI. This will need to be closely monitored considering the 1-3 inches of rain that fell Saturday in the same areas. Poor drainage flooding is likely during this event with a low chance of flash flooding. This system also has the possibility to bring strong NE winds as the pressure gradient tightens behind the low. NBM shows moderate probs (40-60%) for 46mph gusts. High temps trend cooler Thursday only in the low to mid 40s. Friday: Moderate Confidence Low pressure and 500mb shortwave move out to sea with a quick moving 500mb ridge and surface high pressure moving in. This should allow for a brief period of dry weather before the next system arrives for the weekend. There may be some sunshine around Friday with dry air and subsidence aloft. High temperatures top out in the low to mid 50s away from the coasts, where temps likely stay in the low to mid 40s. Saturday and Sunday: Low Confidence Another potent shortwave trough and associated low pressure center exit out of the Ohio River Valley. Timing and track of this system remains quite uncertain with large spread in the models and ensembles. With colder air in place to the north, this system could bring some wintry precipitation to the region, but also could be another impactful heavy rain event. Stay tuned for details. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...Moderate confidence. Mid level status has developed across much of the region this morning, while low marine status is working its way into the Cape and Islands right now and will spread east today. What that means is that the interior will start at VFR/MVFR this morning, but IFR/LIFR conditions will slowly push west today. Marine status should reach the BOS/PVD/BED between 14-17z, and and ORH/BDL between 18-00z. The Cape and Islands will remain IFR/LIFR today. Tonight...Moderate confidence. IFR with localized LIFR. Periods of fog and drizzle possible. Tuesday...Moderate confidence. Mainly IFR, with local MVFR possible. Periods of rain after 12z. KBOS TAF...Moderate confidence in TAF. MVFR/VFR to start today before marine status brings in IFR/LIFR conditions for this afternoon and tonight. Marine status should reach the terminal between 14-17z. KBDL TAF...Moderate confidence in TAF. VFR through this afternoon. IFR tonight as marine status slowly moves west. light rain moves in after 12z tomorrow. Outlook /Tuesday Night through Friday/... Tuesday Night: MVFR/IFR conditions possible. Breezy. Chance RA. Wednesday: Mainly VFR, with local IFR possible. RA likely. Wednesday Night: Mainly IFR, with areas MVFR possible. Windy with gusts up to 30 kt. RA. Thursday: Mainly MVFR, with areas IFR possible. Windy with gusts up to 35 kt. RA likely. Thursday Night: Mainly VFR, with local IFR possible. Strong winds with areas of gusts up to 40 kt. Chance RA. Friday: VFR. Windy with gusts up to 35 kt. Slight chance RA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Relatively light E to NE winds expected across the waters through tonight, then winds shift to E to SE for Tuesday. Rough seas however, should take the longest to subside across the eastern outer coastal waters of MA. Timed Small Craft Advisories to end as seas diminish. Tuesday will be tricky, as increasing SE winds should start building seas once again as a low pressure approaches the waters from the SW. Not confidence in the timing just yet, so will hold off on extending any advisories for now across the southern outer coastal waters. Outlook /Tuesday Night through Friday/... Tuesday Night through Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Rain, isolated thunderstorms. Thursday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 11 ft. Rain likely, isolated thunderstorms. Thursday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 13 ft. Chance of rain. Friday: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 12 ft. Slight chance of rain. && .HYDROLOGY... River Flood Warnings continue for Wood River at Hope Valley and the Pawcatuck River at Westerly. Wood River at Hope Valley is forecast to fall below flood stage late Monday morning. As for the Pawcatuck River at Westerly, it will remain in flood through at least Monday afternoon. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EST Tuesday for ANZ250-254. Small Craft Advisory until 4 PM EST this afternoon for ANZ255- 256.
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&& $$ SYNOPSIS...Belk/KP NEAR TERM...Belk/Dooley/KP SHORT TERM...Belk LONG TERM...KP AVIATION...Belk/Dooley/KP MARINE...Belk/KP HYDROLOGY...Belk is the U.S. government's official web portal to all federal, state and local government web resources and services.