Area Forecast Discussion
Issued by NWS Boston, MA

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566 FXUS61 KBOX 262138 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 438 PM EST Sun Feb 26 2017 .SYNOPSIS... High pressure centered south of New England brings dry weather through Monday. Milder air moves back into our region Monday, then lingers through much of this week. A couple of weather systems will bring periods of wet weather Tuesday into Wednesday night. Colder air returns late this week into next weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Into this evening /4 pm update/... Winds should taper as cloud cover over W portions of S New England should dissipate. Given the dry conditions across the region with dewpoints bottoming out in the mid- to low-teens during max heating of the day, expect temperature to drop rather quickly with sunset. Much of the region well down into the 30s towards 7p with upper 20s across the N/W high terrain of MA. As to winds, gusts of around 20 to 25 mph continuing, strongest over the high terrain and along the coast. That`ll yield wind chills that are roughly around 10 degrees lower than the ambient. Tonight... No issues anticipated. High pressure emerging off the Mid- Atlantic along the NW-periphery of which warmer H925 air is pushed northward allowing for boundary layer decoupling over the interior. Thinking light winds with mostly clear conditions indicating a radiational cooling setup. A couple of things to consider: 1) Low surface dew points during max heating of the day with blustery W winds that has more than likely led to areas of dry soils, 2) surface winds while light are becoming southerly overnight, and 3) significant snow cover over the high terrain of far N/W MA. All this in mind, leaning towards colder guidance with lows generally around the mid 20s, pockets of low 20s in notorious spots away from urban centers, with upper teens over the N/W high terrain of MA. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday... Continued quiet weather. Roughly 1030+ high pressure prevailing off the Mid-Atlantic, S of New England, slowly moving E. Persistent S/SW flow as forecast models suggest deep boundary layer mixing up to H8 given the milder airmass aloft and expected mostly clear conditions with some increasing mid- to high-cloud late from the SW. Within the modest SW to NE gradient flow, daytime mixing will lead to the mix- down of faster momentum and drier air to the surface. Another dry day on tap with SW wind gusts up around 20 to 25 mph, stronger over the S/SE coast with gusts up to 30 mph possible. Leaned with the warmest of temperature guidance considering: 1) deep boundary layer mixing of warming air aloft, 2) abundant sunshine, and lastly 3) bare ground over much of S New England. Highs around the low to mid 50s. Can not rule out low-lying locations of the Merrimack River Valley to nudge near 60 degrees. Monday night... Perhaps the chance of a spotty shower by morning. The SW-NE gradient tightening out ahead of low pressure emerging along the lee of the Rockies, some initial mid-level vortmax energy emerges from the H5 trough situated across the W CONUS. Invocation of a lifting warm front along which we see initial over-running moisture with higher theta-E values creeping into our region during the morning lending to moistening of the low- to mid- level column, there is some measure of weak lift that may result in a spot shower. Aside, at a minimum, continued increasing and thickening clouds with continued S flow. Given the blanket of clouds, leaning somewhere between the mean to warmer end of temperature guidance with lows fluttering around the mid- to upper-30s. Coolest spot in N/W MA. Thinking slight chance PoPs as a consensus of model forecast guidance has us mostly dry with only higher theta-E creeping in out of the SW by morning, and lift is rather weak, mostly isentropic. Focus of PoPs over SE New England. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Above average temperatures for most of this week * Widespread showers possible Tuesday through late Wednesday night * More seasonable conditions return Friday into Saturday Overview... 26/12z guidance continues to show rather good agreement on the overall pattern through Friday. That said, there are the typical discrepancies in the timing and amplitude of shorter wavelength features toward the end of this week. Since these sorts of details are usually less predictable at this time range, still prefer a consensus approach. Details... Tuesday...High confidence. High pressure to our south will move slowly offshore. This will result in an increasing southwest flow, which means good overruning, with increasing clouds, and eventually rising temperatures. While not close to the record warmth late last week, still expecting temperatures well above normal. The greatest risk for precipitation will be toward the south coast, where moisture should be deeper. Depending upon the timing, it`s possible for some wet snowflakes to fall during the morning along and north of Route 2. Low confidence in that happening. Presence of a strong low level jet Tuesday night should lead to either steady or slowly rising temperatures overnight. Wednesday into Thursday... Moderate confidence. Main weather producer will occur Wednesday into Thursday. Still some uncertainty on the timing and location of the surface low. Our region should remain in the warm sector of a low pressure moving through the Great Lakes. Strong southwest winds aloft are likely to bring an unseasonable amount of moisture our way. This expecting plenty of clouds. Rainfall amounts however are generally expected to be less than one half inch for most of our region. Convective instability will be the wildcard. Most convective indices are rather marginal. However, if we could get some low level instability to go along with the wind shear, then a few thunderstorms may develop. This has been consistent, weak signal the past couple of days. By no means is this a lock, but will keep the mention of isolated thunderstorms in the forecast. Still have high confidence that at least some precipitation will fall, and temperatures will be above average Wednesday into Wednesday night. Cold front will sweep through early Thursday morning, resulting in drying conditions with falling temperatures falling through the day. Strong cold air advection likely to mean gusty west to northwest winds. Friday and beyond... Moderate confidence. 26/12Z GFS remains the model with the strongest hint of a clipper-like low pressure passing by to our south Friday morning. The other models are neither as aggressive, nor as humid. Favored the drier consensus solution for now. This will be something to watch over the course of this week. High pressure remains to our south next weekend. After a period of more seasonable temperatures Friday and Saturday, it appears we get back into more of a warmup next Sunday. Good mixing and cold air over the ocean may result in ocean effect snow showers next weekend, before another clipper system possibly approaches towards late Sunday. && .AVIATION /21Z 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/... Tonight... VFR. SKC. Initially blustery with gusts around 20 to 25 kts, winds become light out the W while gradually turning out of the S. Monday... VFR. Increasing SCT-BKN mid to high level cigs late. S/SW winds around 240 becoming breezy through the day with 20-25 kt gusts, strongest over the high terrain and along the coast, dissipating into the evening hours. Monday night... VFR. Cigs becoming BKN-OVC, lowering to low-end VFR with a risk of MVFR over S-coastal terminals. Light S flow around 5-10 kt. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Tuesday through Friday/... Tuesday into Wednesday...Moderate confidence. Periods of -RA through the period will result in MVFR/IFR conditions. Cannot rule out LIFR in fog during the overnight hours. Thursday...Moderate confidence. VFR conditions from west to east during the morning. Blustery westerly winds are possible. Friday...Moderate confidence. Mainly VFR, with MVFR possible toward the south coast, including the Cape and islands. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...High confidence. Breezy W flow turns out of the S overnight. Overall a prolonged period of continued gusts around 20 to 25 kts with lulls during the overnight hours result in the continuation of small craft advisories as seas are slow to dissipate, remaining at or above 5 feet on the E outer waters and both inner and outer S waters. Small craft advisory conditions persist into Monday evening, concluding thereafter. Outlook /Tuesday through Friday/... Tuesday...Moderate confidence. Improving conditions across the waters as high pressure passes southward. Warm frontal passage late Tuesday could drop vsbys in rain and fog. Wednesday into Thursday...Moderate confidence. Approaching system from the west will push a cold front through on Thursday, increasing both seas and winds during this period. Heavy rain and a few thunderstorms are possible, lowering vsbys. There is the potential for southerly gales across the waters Wed night, and northwesterly gales on Thursday behind a cold front. Friday...Moderate confidence. Gusty west winds continue. Small Craft Advisories likely will be needed for some of the coastal waters. && .FIRE WEATHER... Dry and blustery conditions will persist on Monday pushing minimum relative humidity values at or below 30 percent for a good portion of interior Southern New England as southwesterly flow gusts up around 25 mph. Considering in the last 24 to 36 hours much of Western and Central MA and CT saw around 0.50-0.75" of liquid, with around 0.10-0.25" to the east, there`s some concern of potential fire weather conditions over Northeast CT, RI and Eastern MA as temperatures warm into the mid to upper 50s. && .HYDROLOGY... Rising water levels, partly from rain overnight but also from snowmelt in Northern New England. A couple of rivers in the CT River Valley rose above alert stage during the night, but crested below warning stage. Others crested below alert stage. There is still plenty of water moving downriver from the snowpack. We will need to monitor water levels across southern New England for a while this week. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST Monday for ANZ231>235-237- 251. Small Craft Advisory until 7 PM EST this evening for ANZ230- 236. Small Craft Advisory until 1 AM EST Tuesday for ANZ250-254. Small Craft Advisory until 10 PM EST Monday for ANZ255-256. && $$ SYNOPSIS...Belk/Sipprell NEAR TERM...Sipprell SHORT TERM...Sipprell LONG TERM...Belk AVIATION...Belk/Sipprell MARINE...Belk/Sipprell FIRE WEATHER... HYDROLOGY...

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