Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 190237 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1037 PM EDT Wed Oct 18 2017 .SYNOPSIS... High pressure will maintain dry weather and warmer than normal temperatures through the weekend. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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1035 PM Update... corrected SREF to HRRR. At 10 PM, skies were crystal clear across southern New England. Temperatures had dropped to the mid 40s to lower 50s except mid 50s at the coast. Have lowered temperatures a tad to fit with current trends. Lows should range from the lower 40s to lower 50s in the larger cities. Some patchy frost possible in northwest MA. As noted by previous forecaster, the 23Z North America Rapid Refresh Ensemble System (NARRE) has continued to emphatically show development of low cloudiness beginning in eastern CT around 06Z and then expanding everywhere south of the Mass Pike by 11Z. The HRRR has the same trend, only later and farther east, only across RI and southeast MA, mainly after daybreak. Have decided to increase sky cover grids to 60-70 percent across eastern CT and RI late tonight and around daybreak, since the NARRE is often quite good at picking up on these trends.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Tomorrow... Upper lvl shortwave continues opening trend as it moves across S New England during the late afternoon/evening hours. The attendant cold front loses its baroclinicity and is associated with little to no moisture increase so aside from a few more SCT clouds are possible, but this fropa passes with little fanfare. SFC pres gradient response yields an increase, so S-SW flow will be breezy with a few wind gusts around 25 mph during the afternoon. Temps a bit milder in spite of the SCT clouds thanks to weak warm advection aloft ahead of the wave. Looking at widespread low 70s. Tomorrow night... Weak front shifts E. Gradient winds shift to the W but weaken inland as pres gradient weakens rapidly with the core of a stronger high pres shifting E. Winds may remain elevated near shore. The slight increase in moisture thanks to S gradient flow during the day will limit overnight mins further still, suggesting more widespread upper 40s to low 50s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... * Above average temps and dry conditions lasting into Monday * Precipitation chances are increasing for mid-next week. Pattern Overview/Confidence... 12z guidance is in good agreement for the long term. Passing frontal system an associated trough will push offshore by Friday morning. Anomalous ridging will develop across the East Coast pushing heights and temperatures 2 STD above normal. This strong ridge will last into early next week before a pattern change appears to take hold of the area. Digging trough will dip into the Gulf states with the potential for a closed low peeling off. Another wave will begin to dive into the Ohio Valley which could result in phasing to a negatively tilted trough putting much of the East Coast near 3-4 STD below normal in heights fields. This pattern change will result in cooler conditions and unsettled weather. Details... Temperature Forecast... Overall trend in the forecast is for above average temperatures through the period. Cool front will sweep through the region Thursday night leading to a cooler day on Friday, but still above average. Anomalous ridge will begin to build for the weekend into Monday resulting in high temps into the mid 70s. Tuesday`s and even Wednesday`s temperature forecast is a bit trickier as it is dependent on the timing of the front. Thus will trend towards a model consensus until guidance gets a better handling on the FROPA. Precipitation Forecast... High pressure will take over the area on Friday through Monday leading to dry weather. Next chance or precipitation will be around the Tuesday timeframe when a potent trough will dig into the Ohio Valley and towards the East Coast. Ensemble guidance is trending towards a very wet pattern with high PWAT values and strong southerly LLJ. This is in conjunction with the several waves of low pressure that will ride along the trough both Tuesday and Wednesday. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/...Generally high confidence. VFR through 06Z. Confidence is increasing in the development of some IFR ceilings developing especially 08-13Z across northern CT, RI, and southeast MA. Patchy MVFR-IFR in fog in a portion of those areas. VFR then returns tomorrow and most of tomorrow night. SW flow expected today through the daylight tomorrow, then gradual shift to the W is expected tomorrow evening/overnight. KBOS Terminal...High confidence in TAF. KBDL Terminal...Moderate confidence in TAF. Although VFR dominates there is a moderate risk for some IFR ceilings developing late tonight into early tomorrow morning. Outlook /Friday through Monday/... 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 Thursday Night/...High confidence. Overnight... Quiet boating weather into tomorrow morning. Tomorrow and tomorrow night... S-SW winds increase tomorrow afternoon with gusts to around 25 kt likely over all waters by late afternoon and a slight increase in outer seas to near 5 ft. These winds persist into the overnight but slowly diminish as they shift to the W late tomorrow night. Small Craft Advisories will be issued for all waters. Outlook /Friday through Monday/...High confidence. Great boating weather as high pressure prevails through the upcoming weekend with sub SCA conditions. && .FIRE WEATHER... Ahead of a very weak cold front tomorrow (with which no precipitation is expected) S-SW winds will gust 20-25 mph across much of the region. Relatively mild conditions (highs in the low-mid 70s) and continued dry dewpoints in the mid 40s to low 50s will yield min RH values near 30 percent. With an overall lack of precipitation of late this suggests elevated fire weather for the day tomorrow. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 2 PM Thursday to 6 AM EDT Friday for ANZ231>234. Small Craft Advisory from 2 PM Thursday to midnight EDT Thursday night for ANZ230-236. Small Craft Advisory from 4 PM Thursday to 6 AM EDT Friday for ANZ235-237-255-256. Small Craft Advisory from 2 PM Thursday to 8 AM EDT Friday for ANZ250-251-254. && $$ SYNOPSIS...Doody/Dunten NEAR TERM...Field SHORT TERM...Doody LONG TERM...Dunten AVIATION...Field/Doody/Dunten MARINE...Field/Doody/Dunten FIRE WEATHER...Doody is the U.S. government's official web portal to all federal, state and local government web resources and services.