Area Forecast Discussion
Issued by NWS Boston, MA

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837 FXUS61 KBOX 230827 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 427 AM EDT SAT JUL 23 2016 .SYNOPSIS... Hot conditions continue today, along with another risk for thunderstorms this afternoon, some of which may become severe. An approaching cold front will bring another round of scattered showers and thunderstorms from Monday into early Tuesday. More warm weather follows midweek. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Pre-frontal trof is currently shifting through central S New England as initial upper lvl shortwave/associated cold pool are moving offshore. While some moderate convection continues in advance, the bulk of this should remain offshore for the rest of the morning hours. Very weak post convective ridging is clearing things out to the NW. This clearing will allow for atmospheric reloading, so-to-speak, through the morning. In fact, guidance is likely underdoing today`s diurnal destabilization as progged dwpts/temps are initializing lower than current obs suggest. H85 temps only drop to about +18C, so another day (given plenty of sunshine to start) with temps in the upper 80s to low-mid 90s is likely. Dewpoints only drop into the upper 50s to mid 60s behind the stalling boundary. Other than heat, will need to monitor for another round of potential severe weather today, thanks to another round of instability with ML CAPE values near 1200 J/kg. Very acute shortwave combined with H5 temps dropping to near -13C suggest one last taste of the remnant EML which helped convection overnight. Noting mid level lapse rates will approach 7.0 C/km with this upper level cold pool. Therefore primed for another round of TS today, peak timing of the shortwave suggests a slightly earlier start/end, mainly 18Z (2 PM) to 01Z (9 PM). Primary issue will once again be wind, as mean shear exceed 40 kt with H92 winds nearly 40 kt, and high D-CAPE values thanks to a well mixed BL. Would not be surprised to see localized downburst and straightline wind damage similar to Friday evening. Although this shear could allow for storm organization, tornado risk should once again be low thanks to very high LCLs and a well mixed BL. Hail also a risk, as high lapse rates once again support hail CAPE values mainly +300 J/kg. Therefore, stay tuned to forecast updates through the morning as this thinking correlates to latest SPC SWODY1 Marginal Risk. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... Thunderstorms/showers should end earlier than Friday night thanks to faster movement of the forcing shortwave. Drier air will lead to some drying during the overnight but leftover convective debris cloudiness will likely keep temps from dropping too far. Expect mins mainly in the 60s. A few spots of fog possible, especially where late day rainfall is observed. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Overview... Not much change from the previous model cycle. High pressure covers much of the southern USA for most of next week. This will mean any fronts will struggle to get very far south of our region next week. Mid level flow transitions to a near zonal flow by early next week, then to a broad trough by mid week. Temperatures should generally be above seasonable levels most of this portion of the forecast. Details... Sunday... High pressure in place through the day. Winds appear to be light enough where seabreezes may develop along both coasts. Moderate confidence in seabreezes. Above normal temperatures continue for most of southern New England. Monday... A mid level shortwave moves across our region late Monday into Monday night. Most of the day should be rain-free. Some signs of marginal instability crossing during the morning, which may be a warm front with a couple of light showers. Greater instability moves in from the west during the afternoon and evening, in the warm sector ahead of a cold front. Precipitable water values remain high, so locally heavy rainfall is still possible in stronger thunderstorms. Scattered showers and thunderstorms should continue into Monday night as a cold front passes by. Tuesday and Wednesday... High pressure takes control and brings fair weather. Above normal temperatures continue. Thursday and Friday... Latest operational guidance continues to indicate some potential for showers, largely due to a stalled front to our south, and another cold front approaching from the north. Still have low confidence in the details. Will continue to mention a chance of showers and thunderstorms due to the presence of these boundaries. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Through 12Z...moderate confidence. Mainly VFR except localized ground fog. Areas of TSRA will dissipate across SE MA through 08Z, giving way to clearing there as well. Winds mainly 10-20 kt outside of TSRA where gusts to 40 kt are possible. Today...moderate confidence. VFR through at least 18Z. Then another risk for sct TSRA possible mainly E of a line from EEN-ORH-WST. Some strong winds possible once again in some of these storms. Otherwise, winds mainly W-SW 10-15 kt. Tonight...High confidence. Mainly VFR after any storms/showers end through the overnight hours. KBOS TAF...Moderate confidence. Another round of thunderstorms is likely this afternoon to early evening. Some of those storms could produce strong wind gusts. KBDL TAF...High confidence of VFR prevailing. There could be some patchy fog with MVFR visibility through 12Z. Outlook /Sunday through Wednesday/... Sunday...High confidence mostly VFR. Possible areas of IFR in early morning fog. Monday...Moderate confidence. Mostly VFR. Possible IFR in early morning fog. Brief MVFR/IFR cigs/vsbys in afternoon and early night showers/thunderstorms. Tuesday and Wednesday...High confidence VFR. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...High confidence. Seas will continue to dissipate through the morning as winds outside of thunderstorms have already dropped to or below 20 kt. Seas will also gradually dissipate this morning allowing the remaining small craft advisories to be dropped. Otherwise, another round of showers and thunderstorms are possible over the waters this afternoon and evening which could contain localized strong wind gusts. Outlook /Sunday through Wednesday/...Moderate confidence. Winds less than 20 knots and seas less than 5 feet through this period. A cold front will bring scattered showers/thunderstorms Monday afternoon and night, with potential for strong wind gusts and brief poor vsbys in heavy downpours. && .EQUIPMENT... The KBOX radar continues to experience calibration issues, causing reflectivity values to be overestimated. Technicians are expected to work on the radar this morning, which will also lead to a period of downtime through the morning hours especially. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ235- 237-255-256. && $$ SYNOPSIS...Belk/Doody NEAR TERM...Doody SHORT TERM...Doody LONG TERM...Belk AVIATION...Belk/Doody MARINE...Belk/Doody EQUIPMENT...Doody is the U.S. government's official web portal to all federal, state and local government web resources and services.