Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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342 FXUS61 KBOX 231809 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 209 PM EDT Mon Sep 23 2024 .SYNOPSIS... Weak high pressure will build over our region into Tuesday, but continued onshore winds should keep cloudiness in place, especially near the coast. Rain chances return late Wednesday into Thursday as a front moves through the area. Dry and warmer weather looks to follow through the weekend. && .NEAR TERM /THROUGH TONIGHT/... Area of light showers assocd with a weak shortwave are moving into SE NY and SW CT and will remain mostly south and west of Hartford county this afternoon where deeper moisture present. Further E across CT drier air in low-mid levels should prevail. Meanwhile a few very light showers continue to back in from the ocean across eastern MA into RI so can`t rule out a spot light shower or sprinkle into this evening. Weak upper trough moves east of New Eng tonight followed by mid level ridging moving in from the west. Meanwhile, surface ridging will build south into SNE. Surface and deeper layer ridging will promote large scale subsidence with wedge of drier air from the north resulting in dry conditions. Varying amouts of cloud cover expected and patchy late night fog possible in the CT valley. Lows will range from the upper 40s interior to low-mid 50s coastal plain. Still a bit breezy over the Cape/Islands with gusts to 20 mph at times. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... Tuesday... Very little change in the pattern with surface and upper level ridging in place. Wedge of somewhat drier air in the column persists with deeper moisture remaining to the west. Expect another mainly dry day, although considerable cloudiness again with a low risk for a few light showers or sprinkles from persistent easterly flow and low level moisture. Very similar low level temps to today will lead to highs mid-upper 60s to around 70 in parts of the CT valley, with E-NE winds 10-15 mph. Tuesday night... Upper level ridge axis shifts to the east as a weak shortwave moves to the north and west. Deep moisture plume assocd with the shortwave approaches but bulk of showers will remain to the west where best moisture and forcing is located. Just a low risk for a shower spilling into western MA late at night. Lows will range from the upper 40s to mid 50s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Key Points: * Showers possible late Wed-Thu with passing front * Dry and warmer pattern follows through early next week Main focus is on Wed-Thu time frame as deepening upper trough and its associated fronts cross region bringing our next chance at any appreciable rainfall which is certainly needed despite parts of SNE receiving a good dose of rain over weekend. Not seeing a lot of parameters that suggest much in way of rainfall, more like 0.25 to 0.50 inch this time, and even convective indices are not overly impressive or favorable for thunderstorms, though a few cannot be ruled out due to decent lapse rates and limited surface-based CAPE. Once this system departs Thu, it appears we`re in for another stretch of dry and seasonably warm weather into at least early next week. Broad upper ridge builds from Great Lakes into New England which takes appearance of an omega block, meaning ridge doesn`t go anywhere for several days and maintains troughing over middle of country and over north Atlantic. && .AVIATION /18Z MONDAY THROUGH FRIDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18z TAF update... Through Tuesday...High confidence. Persistent conditions with mainly VFR cigs which may at times lower to MVFR, especially east of CT valley. Patchy late night fog possible in the CT valley. E-NE wind 5-15 kt, with gusts to 20-25 kt at ACK. Tuesday night...Moderate confidence. Cigs expected to lower to MVFR with areas of late night IFR possible. But uncertainty with areal coverage of lower cigs. E-NE wind less than 10 kt. BOS TAF...High Confidence in TAF. Mainly VFR cigs but occasional SCT MVFR layer may go BKN at times. BDL TAF... High Confidence in TAF. Outlook /Wednesday through Friday/... Wednesday: Mainly VFR, with areas MVFR possible. Wednesday Night: Mainly VFR, with local IFR possible. Chance SHRA. Thursday: Mainly VFR, with areas IFR possible. Slight chance SHRA. Thursday Night through Friday: VFR. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight through Tuesday night...High Confidence. NE flow will gradually weaken through tonight. Gusts to 25 kt over SE waters will diminish below SCA tonight with E-NE wind 10-20 kt Tue abd Tue night. Rough seas, up to 9 ft, over outer waters will slowly subside Tue into Tue night but remain above 5 ft through the period. SCA for outer waters extended through Tue night. We extended the High Surf Advisory through tonight, then transitioned it to a high rip current risk for Tuesday. Seas are slowly subsiding but leftover easterly swell will support dangerous rip currents. Outlook /Wednesday through Friday/... Wednesday: Winds less than 25 kt. Areas of rough seas. Wednesday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of rain showers. Thursday: Winds less than 25 kt. Local rough seas. Slight chance of rain showers. Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...High Surf Advisory until 8 AM EDT Tuesday for MAZ007-019-020- 022>024. High Risk for Rip Currents from Tuesday morning through Tuesday evening for MAZ007-019-020-022>024. RI...High Surf Advisory until 8 AM EDT Tuesday for RIZ006>008. High Risk for Rip Currents from Tuesday morning through Tuesday evening for RIZ006>008. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ231>235-237. Small Craft Advisory until 8 AM EDT Wednesday for ANZ250-251- 254>256. && $$ SYNOPSIS...KJC/JWD NEAR TERM...KJC SHORT TERM...KJC LONG TERM...JWD AVIATION...KJC/JWD MARINE...KJC/JWD