Area Forecast Discussion
Issued by NWS Boston, MA

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386 FXUS61 KBOX 241750 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 150 PM EDT SUN JUL 24 2016 .SYNOPSIS... Hot and humid weather is expected at times through the middle of next week, at least away from the immediate coast. Another risk for scattered showers and thunderstorms is possible late next week with a cold front dropping south. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 10 AM update... Forecast remains on track. Expect highs topping out around 90 in the CT valley and portions of RI and interior E MA, with 80s elsewhere. Seabreezes develop this afternoon which will cool temps a bit along the coast. Comfortable humidity levels with dewpoints mixing out into the 50s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Tonight... Outside of increasing high clouds late from convective debris upstream, mainly quiet night with temps dropping into the 60s. The initially SKC/weak pres gradient would help here, but expect slight increase in dwpts thanks to return flow. Mon... Potential to be one of the hottest days of the summer thus far as H85 temps will warm to +20C by afternoon. While this could easily support temps in the mid to even upper 90s at several spots, there is some question of the aforementioned cloud debris limiting initial mixing/warming. It looks like enough breaks across the W could support the heat across the CT valley, so will be issuing a heat advisory there as dwpts surge back into the mid-upper 60s. Not as confident elsewhere, but there is still some time to monitor trends. More heat advisories could well be needed in the next 24 hours. The other issue, given the very hot/humid airmass return, will be the risk for convective activity with an acute shortwave passage late in the day on Mon. ML CAPE values are progged to be near 1500j/kg by the late afternoon, and this is on the normally conservative ECMWF. This will come along with a decent cold pool aloft with mid lvl lapse rates nearing 6.5C/km. Shear is minimal to start but does increase through the day as the shortwave approaches. Therefore, will need to monitor for afternoon/evening strong-severe thunderstorm activity. Winds once again the primary issue thanks to good D-CAPE values and increasing LLJ. This correlates to current SPC Day 2 SWO. Given the lapse rates peak late, this could be another instance of very late day convection that lingers well into the overnight hours. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights... * Hot and humid weather at times through mid week, at least away from the immediate coast * Monday night is the highest risk for scattered showers and thunderstorms with the threat for some severe weather, and even very localized urban type flooding * Cold front may bring another risk for scattered showers and thunderstorms sometime late this week but timing uncertain Details... Nearly zonal mid level flow persists through mid week, then transitions to a broad trough. Latest guidance remain consistent on this trend, with only minor variations in amplitude and timing. At the surface, a subtropical high pressure will keep the above normal temperatures and humid weather mainly in place. Will favor a consensus solution to smooth over the minor differences. Monday Night... A weak cold front associated with a low pressure in Quebec is expected to move across southern New England Monday night. While this has been a consistent signal in the guidance the past several days, we will need to watch if this boundary either washes out, or stalls. If this boundary stalls, there may be a very localized urban type flood threat, with precipitable water values around 2.0 inches. Still some uncertainty at this point. Severe weather threat should be diminishing with time, which is typical for our region. Tuesday and Wednesday... Assuming the weak cold front clears our region early Tuesday morning, dry weather should prevail into Wednesday. High temperatures should still be mainly in the 90s during this time away from the immediate coast. Should be less humid during this time, at least compared to Monday. Thursday through Saturday... Above normal temperatures will continue over this time, but probably not quite as hot as early this week. A frontal boundary may approach late this week, and bring the risk for another round or two of showers and thunderstorms. The timing of any showers and thunderstorms appears to be diurnal in nature, at this time. Not looking like a washout. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday night/... 18z update... Through tonight...High confidence. VFR. Monday...Moderate confidence. Mainly VFR, but sct showers/t-storms developing in the afternoon may bring temporary IFR/MVFR conditions and gusty winds. Monday night...Moderate confidence. Sct showers/t-storms in the evening, otherwise areas of IFR stratus and patchy fog may develop along the south coast. KBOS TAF...Expect seabreeze to develop by 19z. KBDL TAF...High confidence. Outlook /Monday Night through Thursday/... Tuesday and Wednesday...High confidence. Mainly VFR. Lower confidence in a few hours of early morning patchy fog in the typically prone locations. Thursday...Moderate confidence. Mainly VFR. Briefly MVFR in scattered showers and thunderstorms. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/...High confidence. Weak high pres builds over the waters today and lingers through most of Monday. Quiet boating weather is expected for most of this time. There is a risk for late day thunderstorms Monday which will need to be watched. Outlook /Monday Night through Thursday/...Moderate to high confidence. Winds and seas should generally remain below small craft advisory thresholds over this time. The main concern is the risk for scattered thunderstorms Monday night, and perhaps again on Thursday. && .EQUIPMENT... The KBOX radar is back in service. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory from 11 AM to 6 PM EDT Monday for CTZ002. MA...Heat Advisory from 11 AM to 6 PM EDT Monday for MAZ010-011. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Doody NEAR TERM...KJC SHORT TERM...Doody LONG TERM...Belk AVIATION...Belk/KJC MARINE...Belk/Doody EQUIPMENT... is the U.S. government's official web portal to all federal, state and local government web resources and services.