Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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111 FXUS61 KBOX 032313 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 713 PM EDT Wed Jul 3 2024 .SYNOPSIS... A warm front lifts north across the region late tonight bringing increasing humidity levels and a few showers or thunderstorms in the interior on Thursday. Very warm and humid weather this weekend and into early next week. Saturday will have the highest humidity levels. While there is a risk of rain and thunderstorms throughout the weekend and early next week, it won`t rain continuously. There will be significant dry periods, with Saturday into Saturday night having the greatest chance for heavier rains. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... High pres near the SNE coast drifts offshore tonight with broad SW flow in place. A mid level warm front will move across the region late tonight and will be accompanied by a modest instability burst as higher PWAT air and decreasing static stability advect into the region from the west. This may result in a few showers developing late tonight in the interior. Otherwise mainly dry conditions with increasing clouds. The evening will start out with just some high clouds so will likely see a period of radiational cooling with lows dropping to 60-65 before temps stabilize overnight. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Thursday... A few morning showers possible with the mid level frontal passage, otherwise partial sunshine although expect more clouds than sun as the column will be quite moist with PWATs exceeding 2 inches. A weak shortwave approaches from the west in the afternoon which may lead to a few showers or a t-storm developing across interior MA into CT where marginal instability exists with CAPES around 500 J/kg. But areal coverage will be limited. No instability in the coastal plain which should remain dry. Temps aloft are pretty warm with 17C at 850 mb but cloud cover will prevent temps from achieving full potential. Highs generally low-mid 80s, except upper 70s near the south coast. But humidity levels will be increasing as dewpoints rise to the mid- upper 60s. Thursday night... Any lingering evening convection in the interior should dissipate, then will have to watch for a renewed area of showers and isolated t- storms possibly developing and moving across the region late Thu night as a weak front sags south into the region. Areal coverage of any convection is uncertain as hi-res CAMs are not in agreement on the most preferred location. 2+ inch PWAT axis will shift southward but the south coast will remain on the northern edge of these higher PWATs and this may be where best chance of showers and a few t- storms will be. Given the high PWATs and a weak boundary, localized heavy rainfall will be a risk with any convection that develops. It will be a mild and humid night with lows 65-70. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Friday: There could be some lingering showers in the late morning along the south coast from the exiting frontal boundary, otherwise subtle height rises will lead to mainly dry conditions. There is a low chance for a low topped shower in Western MA and CT with a few hundred J/kg of SBCAPE. Temperatures and dewpoints will be on the rise as strong southerly flow kicks in with highs nearing 90F and dewpoints nearing 70F. Heat indicies Friday stay in the low 90s due to partial sunshine with diurnal cumulus clouds and high cirrus clouds filtering in ahead of the shortwave. Saturday: Shortwave trough exits out of the Great Lakes, but latest guidance has trended it further north keeping the forcing out of SNE. MUCAPE values do jump into the 1000-1500 J/kg range with sfc-6km bulk shear values nearing 30-40 knots. PWATS will be above 2.0 inches, possibly approaching 2.5 inches with warm cloud depths between 11kft to 13kft. This environment is supportive for severe thunderstorms with very heavy rain and isolated flash flooding. The main questions that remains ahead of Saturday is how much capping will be present and if there will be enough forcing to overcome the cap. Not quite as warm saturday due to the chance for precip and extensive cloud cover. Highs should be in the low to mid 80s with dewpoints in the low mid 70s. Even with could cover, the high dewpoints will push heat indices into the low 90s. Sunday: Upper level shortwave retreats to the NE with subtle mid level height rises in the afternoon. The column begins to dry out which will keep the region dry, but dewpoints remain near 70F. Mostly sunny skies will allow temperatures to reach the low 90s. Next week: The week starts out dry with rising heights. More unsettled weather looks possible going into middle to end of next week as the upper level ridge breaks down a bit. Temps stay warm early in the week in the upper 80s to low 90s, trending slightly cooler towards the middle to end of next week. && .AVIATION /23Z WEDNESDAY THROUGH MONDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight: High confidence. VFR cigs. Low risk of a shower 09-12z in the interior. SW wind 5-15 kt. Thursday: High confidence. Mainly VFR cigs, but patchy MVFR possible over higher elevations. Isolated morning shower possible, then a few showers or a t-storm possible in the afternoon in the interior. SW wind 10-20 kt. Thursday night: Moderate confidence. Cigs gradually lowering to MVFR with IFR possible near the south coast. A few evening showers possible, then scattered showers and possibly a t-storm near the south coast after midnight. KBOS TAF...High confidence in TAF. VFR. SSW winds around 10 knots continue overnight and through tomorrow. Not expecting a sea breeze to develop with 2000ft winds over 20 knots. KBDL TAF...High confidence in TAF. VFR with SSW winds around 10 knots tonight and tomorrow. Low chance for a weak shower tomorrow afternoon Outlook /Friday through Monday/... Friday: Mainly VFR, with local MVFR possible. Slight chance SHRA. Friday Night: Mainly VFR, with local IFR possible. Chance SHRA, isolated TSRA. Saturday: MVFR/IFR conditions possible. Breezy. Chance SHRA, isolated TSRA. Saturday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA, isolated TSRA. Sunday through Monday: VFR. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight through Thursday night...High confidence. Winds and seas below SCA thresholds. Light SW winds tonight, then SW 10-20 kt Thu and Thu night. Areas of fog and reduced vsbys should develop Thu night with scattered showers and possibly a t-storm late Thu night. Seas through the period generally 3 ft or less on all waters. Outlook /Friday through Monday/... Friday: Winds less than 25 kt. Slight chance of rain showers. Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers, isolated thunderstorms. Saturday through Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, isolated thunderstorms. Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, isolated thunderstorms. Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Monday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...KJC/KP NEAR TERM...KJC SHORT TERM...KJC LONG TERM...KP AVIATION...KJC/KP MARINE...KJC/KP