Area Forecast Discussion
Issued by NWS Boston, MA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KBOX 261359 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 959 AM EDT Wed Oct 26 2016 .SYNOPSIS... The coldest air of the season so far will bring patchy clouds and chilly temperatures today. High pressure will push across the region this afternoon and tonight. Strong low pressure will push across the region late Thursday into Friday, which will bring a period of wintry weather well inland at the start, rain heavy at times elsewhere along with gusty winds at the coast. A drying trend develops later Fri along with temperatures becoming more seasonable this weekend and probably into early next. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
10 AM Update...Temperatures have climbed above freezing for most locations at this time so the freeze warning was allowed to expire as scheduled at 9 AM. Ocean effect clouds continue to stream over the outer Cape. Expect this to continue through the day. Made minor changes to temperature and sky cover forecast to account for the latest trends. Overall, the forecast was on track. Large high pressure ridge will build E during the late morning and afternoon, with N-NW winds at around 10-15 mph. Some gusts up to 25-30 mph will linger through midday along east coastal areas. Short range models continue to signal ocean effect clouds across the outer Cape, possibly reaching into Nantucket and portions of the mid Cape this afternoon. With sea surface temps in the upper 50s, noted strong signals on the lake effect parameter on the NAM 4 KM and GFS BUFKIT soundings for later this afternoon at KCHH for at least ocean effect clouds and possibly a few showers. Only question at this point will be whether the wind direction will be more northerly to bring in the showers. At this point, should remain mainly NW through today there. With cold airmass in place across the region, with H85 temps in the -6C to -8C range, will be tough for temps to climb out of the 40s today. Might see a few readings up to around 50 along the immediate S coast though.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... Tonight... High pressure will slowly build east tonight. This should allow lighter winds, veering mainly from the N across the eastern waters. As mentioned above, short range models continue to signal best shot for any ocean effect clouds and showers to push into the mid and outer Cape and well as Nantucket during the overnight hours. Winds may start to veer to more N-NE toward daybreak, which could push the clouds closer to the coast from Plymouth to the Cape Cod Canal. If any showers do occur, best chance will be from Provincetown to Chatham. In the meantime, the high will build E overnight. Overrunning well ahead of low pressure across the eastern Great Lakes will bring clouds into central and western areas mainly after midnight. The ridge will hold off the precip until during the day Thursday. Expect temps to fall back to the 20s across most inland areas, ranging to the mid 30s to around 40 along the immediate coast. The lows may occur around midnight or so, then may level off or slowly rise as winds shift to light northeast. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Updated 427 AM... Highlights... - A period of snow possible high terrain Thu - Rain heavy at times late Thu into Thu night - A period of gusty winds possible Thu ngt south coast Thursday... Snow Potential...very cold airmass in place early Thu with 850 temps down to about -4C at 12z. Airmass is very dry as well and this yields large potential for evaporative cooling. This will support a deep layer of cold air that will be conducive for ptype of snow. However models have trended deeper/stronger with parent low moving from OH to western NY. This results in a longer duration of ESE low level winds across the region triple point low development is delayed until Thu evening somewhere vicinity of PHL-NYC-CT coast corridor. As a result this yields more boundary layer warming with freezing levels only dropping to about 1500 ft per model soundings. Heavy qpf would be able to offset this blyr warmth and lower freezing levels but only the NAM is showing robust qpf Thu. Even the Hi Res ARW and NMM cores are much lighter than the NAM. Appears the NAM mid level winds /700 mb/ are much stronger than the remainder of the guid and this is resulting in the higher NAM qpf. Thus have followed a non-NAM solution here. This scenario supports precip beginning as snow across northern CT (esp higher terrain) into western-central MA including the Worcester Hills. Given the marginal blyr and surface temps any minor accumulations would likely be confined to the highest elevations /esp above 1500 ft/. Also given precip intensity may be lacking accumulations more likely on non paved surfaces. As of now not expecting much impact...however still need to watch this unfold closely because if models trend weaker with parent low and give way to triple point low quicker...blyr will be colder across our region and yield a higher snow potential. Heavy Rain Potential... good trough amplification Thu night along with mid level trough taking on a negative tilt in concert with dry slot approaching from the west. This will yield rain heavy at times Thu afternoon and night with heaviest rain possibly 06z-09z as nose of dry slot approaches. Any poor drainage flooding should be minor as non-NAM model consensus on QPF is 0.75 to 1.25 inches with isolated higher amounts given convective potential on nose of dry slot. System is dynamic but remains progressive which will limit qpf to some extent. Strong Winds Potential... low level southeast jet strengthening up to 50 kt as it moves across RI and southeast MA Thu night. With triple point low expected to track along or near the I-95 corridor warm sector likely to overspread coastal RI into southeast MA. This will lessen the low level convergence and increase the probability of gusty winds aloft reaching the surface. Model soundings indicate potential up to 40-50 kt gusts at BID/HYA/CHH and ACK. In addition some elevated and surface based instability in warm sector. So more robust showers or isolated Thunder may increase the risk for strong winds. So eventually may need a wind advisory for this region Thu night. Friday... The day begins with triple pt low over eastern MA at 12z and continuing to deepen/strengthen as it tracks northeast to off Cape Ann midday. However its slow to exit as mid level low captures surface reflection just offshore late Fri. This results in a blustery day with NW winds gusting 30 to 40 mph. Although post frontal airmass fairly seasonable so expecting highs in the 50s. Will feel cooler given the gusty northwest winds. Warmest readings will be over southeast MA where warm sector airmass overspreads the area Thu night with temps rising into the 50s to near 60 late Thu night into early Fri. The Weekend... Deterministic and ensemble guid continues to struggle with the amplitude of northern stream short wave energy moving across the northeast this weekend. Not expecting a washout but there will be the risk for a period of showers sometime over the weekend. So followed a model blend given the uncertainty. More certain on temps not being as cold as previous days with highs close to normal both days...55 to 60 with Sunday possibly the milder of the two days. Next week... Ridge over the MS valley Mon builds northeast into New England Tue. This will support dry weather along with near seasonable temps Mon trending to slightly warmer than normal Tue-Wed. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 7 am update... No change from previous TAFs. Marginal MVFR/VFR will be confined to the higher terrain and Cape Cod/Nantucket. NNW winds will gusts up to 25 kt thru today. Earlier discussion below. ==================================================================== Short Term /through Tonight/...High confidence. Through Today...VFR. Ocean effect clouds may cause brief periods of MVFR CIGS across outer Cape Cod through mid morning. NW winds gusting to around 20 kt through midday across the outer Cape and Nantucket. Tonight...Mainly VFR. N winds 10-15 kt will bring ocean effect clouds into coastal Plymouth county, Cape Cod and the islands with MVFR CIGS. Sct -SHRA move onshore on the outer Cape overnight, though VSBYS should remain mainly VFR. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Thursday through Sunday/... Updated 427 AM... Thursday into Friday...Moderate confidence. Cigs lowering to IFR-LIFR into Thursday. Initial brief period of snow is possible across northern CT-western/central MA, transitioning to -RA/RA with embedded +RA, TSRA over S/SE coastal terminals along with gusty winds up to 35 kts through around midnight Friday. Winds back out of the W towards Friday morning, becoming VFR. Saturday and Sunday...Low confidence. Mostly VFR. Perhaps a mix of MVFR/VFR to places N of the Mass Pike in widely scattered showers. W/SW winds throughout. Gusts up to 20 kts. && .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. Through Today...NW winds gusting up to around 25 kt across the open waters, but will diminish as high pressure builds east. Seas up to 5 to 7 ft, but will subside through midday across the near shore bays and sounds. Small crafts will expire there, but will continue through the day mainly on the eastern outer waters as seas remain high. Tonight...North winds diminish. Small crafts on the eastern outer waters should end as seas finally subside by midnight. Scattered ocean effect rain showers mainly east of Cape Cod, but may extend into eastern Cape Cod Bay and Nantucket Sound overnight. Outlook /Thursday through Sunday/...Moderate confidence. Updated 427 AM... Thursday into Friday... Low pres over western NY state Thu gives way to a new low along the Southern New England coast Thu ngt...intensifying into a Gale Center as it tracks into the Gulf of ME Fri. Could see a period of SE gales Thu night followed by NW gales Fri. Vsby may drop below 1 mile Thu afternoon and night in periods of heavy rain and fog...improving around daybreak Fri. Saturday into Sunday... Modest westerly winds Sat ahead of a weak cold front...followed by modest northwest winds Sun behind the front becoming NNE Sunday night. && .BOX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
CT...None. MA...None. RI...None. MARINE...Gale Watch from Thursday evening through Friday morning for ANZ231>234-254-255. Gale Watch from late Thursday night through Friday morning for ANZ230-250-251. Small Craft Advisory until 11 PM EDT this evening for ANZ250- 254. Small Craft Advisory until 11 AM EDT this morning for ANZ251. Small Craft Advisory until 2 PM EDT this afternoon for ANZ255- 256.
-- End Changed Discussion --
&& $$ SYNOPSIS...Nocera/EVT NEAR TERM...RLG/EVT SHORT TERM...EVT LONG TERM...Nocera AVIATION...Nocera/EVT MARINE...Nocera/EVT is the U.S. government's official web portal to all federal, state and local government web resources and services.