Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 281921 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 321 PM EDT Wed Jun 28 2017 .SYNOPSIS...
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High pressure brings dry and cool conditions tonight. A warm front moves through the region Thursday with a few showers and thunderstorms Thursday night as more humid air moves in. Summer heat and humidity arrives Fri and continues into the weekend. A cold front likely breaks the heat and humidity later Sunday and will be accompanied by thunderstorms. Not as warm or humid early next week including the fourth of July holiday.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Sct showers developing across northern New Eng and moving SE. Marginal instability and KI increasing to near 30 along with approaching left exit region of upper jet will bring a risk of a few showers or an isold t-storm this afternoon. Dry weather tonight with high pres south of New Eng. Weak shortwave will spread some mid/high clouds into New Eng with clouds increasing later tonight. Another cool night with dry airmass in place and light winds. Lows in the 50s.
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&& .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
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Thursday... Warm front lifts north across SNE to near the MA/NH border late in the day. No instability across SNE and main focus for showers will be to the north assocd with deeper moisture and mid level omega north of the warm front along with the nose of the 850 mb jet. Can`t rule out a few showers spilling into northern MA in the afternoon but it should be a mostly dry day. Most sunshine will be found toward the south coast with most clouds north of the Pike. Rather gusty S/SW winds developing in the afternoon as the low level jet strengthens across SNE. Gusts to 25-35 mph expected, strongest in the coastal plain. Shallow mixing will limit high temps to the upper 70s and lower 80s. While dewpoints will be increasing, very humid air will remain to the west. Expect dewpoints increasing to 55-60. Thursday night... Warm sector airmass in place. Increasing KI and elevated instability as a piece of the low level jet shifts south into SNE will result in a few showers and isold t-storms moving through. Milder night with lows remaining in the 60s as higher theta-e air moves into the region with increasing dewpoints. This may lead to fog patches developing overnight.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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Highlights... * Hot and humid conditions return Friday into Sunday * Increasing risk for scatter showers/thunder Thursday PM into Sunday * Cooler and less humid Monday and Tuesday Pattern Details... Overall the deterministic models and their ensemble means have a fair handing on the evolution of the synoptic pattern for the period. However, there still remains the timing and strength difference with each shortwave. Beginning on Friday, quasi-zonal flow aloft as a surface warm front pushes through the region. The upper level pattern become more amplified as noted the previous days. This will result in a deeper trough over the northern Plains, and thus a building of the sub-tropical ridge over the East Coast. This ridge stalls an approaching cold front for the weekend before pushing through on Sunday. Pattern change aloft for early next week as the region is more in the broad trough keeping heat and humidity at bay. Overall, trended towards a blend in the guidance unless otherwise noted below. Details... Friday into Sunday... Heat and humidity will filter into the southern New England during this time period. Depending on how Thursday PM goes, it may have impacts to the convection potential on Friday. Surface high pressure well offshore will put southern New England in southwest flow resulting in increasing low level moisture. Plenty of heating with CAPE values over 1000 j/kg with some deep layer moisture per K values. Appear scattered showers and thunderstorms are likely especially across the western half of the region. However the potential is limited as mid-level heights rising through the day. This will limit storms from becoming widespread. Building subtropical ridge will keep the first half of Saturday dry. Southwest flow will continue across the region as PWAT values near 2 STD above normal. LLJ will begin to strengthen as Great Lakes trough begins to approach the region. Surface trough will move through upstate NY towards southern New England later in the day. This trough may be a trigger for a few strong storms. One issue is the 850 mb temps which will be near 17C. This could be a potential cap which could keep most of the area. Something to watch over the next few days. Subtropical ridge will push eastward by Sunday as cold front approaches from the west. Plenty of instability to work with as shear values increase to 30-40 kts. Anticipate scattered showers and thunderstorms, with the potential for a few strong storms. Still timing issues with the frontal passage so confidence is low. Temperatures in this period will be quiet warm compared to the past week. Expect high temps on Friday and Saturday in the upper 80s to low 90s. Cooling temps aloft on Sunday will keep high temps in the mid 80s. Sultry dewpoints reaching near 70F could result in heat headlines on Saturday. Monday into Tuesday... Upper level trough will move over the northeast by early next week. This will limit the heat and humidity. Current guidance shows seasonable temps with highs in the low to mid 80s. Northwest flow takes hold bringing in drier air in the mid-levels. Cannot rule out an isolated shower but appears that the overall period may be dry.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/...High confidence. Through 00z...VFR with sct-bkn cigs 050-070. Low risk for an isold shower or t-storm across northern MA. Tonight...VFR. Light winds. Thursday...VFR. Low risk for a few afternoon showers north of the Mass Pike. Increasing SW winds with gusts to 20-30 kt developing, strongest in the coastal plain. Thursday night...Mainly VFR. But a few showers/t-storms expected to move through with brief lower conditions. Gusty SW winds coastal plain in the evening. KBOS Terminal...High confidence. KBDL Terminal...High confidence. Outlook /Friday through Monday/... Friday into Sunday...Moderate confidence. Patchy early morning fog each day. Otherwise mainly VFR, except local IFR in possible strong thunderstorms, mainly during the afternoon and evening hours through the period. Southwest winds through the period with gusts near 20 kts.
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&& .MARINE...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/...High confidence. Tonight...Quiet boating weather with high pres south of New Eng yielding light winds and seas. Thursday...Increasing S/SW flow as low level jet develops. Enough mixing to support gusts to 25-30 kt in the afternoon over nearshore south coastal waters and particularly Narragansett Bay and Boston Harbor. Less wind over outer waters due to low level inversion. SCA issued for south coastal waters and Boston Harbor. Thursday night...Low level jet remains across the region resulting in SCA SW gusts and building seas. Outlook /Friday through Monday/... Thursday night into Friday...Small craft advisories will likely be needed. Increasing SW winds with gusts to 25+ kt likely, especially over nearshore waters. Building seas may reach 6 to 8 ft. Saturday into Sunday...SW winds continue, mainly 20 kts with lingering seas. Scattered thunderstorms, some with reduced visibilities and strong gusty winds especially on Sunday.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 1 PM Thursday to 8 AM EDT Friday for ANZ231>235-237-255-256. Small Craft Advisory from 3 PM Thursday to 2 AM EDT Friday for ANZ230. Small Craft Advisory from 1 PM Thursday to 4 AM EDT Friday for ANZ236.
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&& $$ SYNOPSIS...KJC NEAR TERM...KJC SHORT TERM...KJC LONG TERM...Dunten AVIATION...KJC/Dunten MARINE...KJC/Dunten

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