Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 170535 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 135 AM EDT Sat Mar 17 2018 .SYNOPSIS... Mainly dry but unseasonably cold weather will continue this weekend into at least Monday. The potential continues for a Noreaster sometime between next Tuesday into Thursday, but confidence on if/how we are impacted remains highly uncertain. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 10 pm update... The combination of strong cold advection already in place in the low levels and a secondary arctic shortwave approaching from the north has already led to temps dropping into the upper 20s and low 30s. This is likely to lead to the coldest night in recent past with mins in the upper teens mainly across NW MA, to the low-mid 20s elsewhere. Windy conditions persist thanks to an increase in magnitude of the height rise/fall couplet with the approaching wave. This will lead to wind chills in the teens across much of the area by morning. Forecast is on track for the most part, so will bring temps/dwpts up to current trends with this update. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SUNDAY/... Saturday... As the H5 vortex continues to spin across Labrador, most of the model suite shows another cutoff mid level low that dived S out of Hudson Bay and moved into May Sat morning. This is a rather potent short wave, but most of the energy looks to push into the Gulf of Maine. Will see a piece of the energy move S across the region Sat in the form of a cold front. Will see some isolated to scattered snow showers push from N-S through mid afternoon, then should weaken as the mid level energy shifts offshore. A few spots might receive a dusting of snow during the day, not much more than 0.5 inches if that. The low level jet remains across the region, so will continue to see gusty W-NW winds, with gusts up to 25-30 kt along the coast, and 20-25 kt inland. May see a few gusts close to 35 kt along the coast through early afternoon. Conditions should improve after 18Z or so. Temps will be rather cold for St. Patrick`s Day, ranging from the mid and upper 20s across the higher terrain to between 35 and 40 across N CT/RI/SE Mass. Saturday night... Winds should finally diminish Sat evening, but temps more typically of mid winter will be in place as skies clear out. High pressure will begin to build SE out of central Canada overnight. Temps bottom out in the single digits to lower teens well inland ranging to around 20 along the S coast. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Dry but unseasonably cold Sun/Mon * Potential Noreaster sometime next Tue into Thu but low confidence on if/how we are impacted Details... Sunday and Monday... Northwest flow aloft and at the surface will result in dry but unseasonably cold weather for this time of year. Low temperatures will mainly be in the teens to lower 20s. Highs mainly in the 30s...but some lower elevations may reach 40 on Monday. Tuesday through Thursday... We continue to watch the potential for a Noreaster to impact the region sometime in the Tuesday through Thursday time frame. Confidence though remains low as this is a very complex situation. Numerous pieces of shortwave energy are involved and their specific timing/strength and location will determine if/how our region is impacted. The models are also struggling with timing of the event as they appear unsure which piece of energy they want to amplify. Overall...there is not much more we can do at this point than indicate the potential for a Noreaster and run with chance pops over this time frame. We also need to keep all options on the table from a miss, to a wintry mix, or a significant snowstorm. Given this will likely be a few more days until we get a better handle on this situation. Needless to say though it does bear watching. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. Through 00Z this evening... Mainly VFR. Although occasional light SHSN/SHRA possible mid morning through mid afternoon with very brief MVFR/IFR conditions. Winds W-NW shift to mainly NW late afternoon. Gusts 25-35 kt at times. Tonight and Sun... Mainly VFR with clearing. Winds also diminish this evening but remain out of the NW. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Sunday Night through Wednesday/... Sunday through Monday Night: High confidence in VFR conditions. Tuesday: Low confidence. VFR conditions may deteriorate to MVFR-IFR thresholds late depending on the timing/track of a coastal storm which is highly uncertain. Chance SN, chance RA. Tuesday Night and Wednesday: Low confidence. MVFR/IFR conditions possible depending on the timing/track of a coastal storm. Windy with gusts to 30 to 40 kt possible along the coastal plain. Chance SN, chance RA. These conditions are highly uncertain and dependent on strength/timing of coastal low pressure. && .MARINE... Through Saturday... W-NW winds will increase this evening, with gusts up to 30-35 kt over the open waters. The gusts may diminish briefly around sunrise, but will pick up again as a cold front approaches. Seas will run from 5 to 9 ft. Gale warnings remain on the open waters and Boston Harbor, with Small Crafts on the near shores. May see a few snow showers on Saturday with brief visibility restrictions. Saturday night... Expect NW winds begin to diminish as the cold front moves offshore and high pressure ridge starts to build in from the NW. Gales will continue on the open waters through most of the night, but may lower to Small Crafts after midnight. Have continued that headline through most of the night. Small Crafts forecast to end around or after midnight on the near shore waters. Good visibility. Outlook /Sunday Night through Wednesday/... Sunday: Moderate to high confidence. Small Craft Advisory winds possible with gusts up to 30 kt. Areas of seas approaching 5 ft. Sunday Night: Moderate to high confidence. Small Craft Advisory winds possible with gusts up to 30 kt. Local rough seas. Monday through Monday Night: Moderate to high confidence.Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday: Low to moderate confidence depending on track/timing of a coastal storm. Winds less than 25 kt. Chance of snow, chance of rain. Visibility 1 to 3 nm. Tuesday Night and Wednesday: Low confidence. Potential for gale force winds with gusts between 35 and 45 kt. Rough seas up to 15 ft. Chance of rain, chance of snow. Visibility 1 to 3 nm. These potential conditions are highly uncertain and hinge on the track and strength of a potential coastal storm. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until midnight EDT tonight for ANZ232>235- 237. Gale Warning from 9 AM this morning to 6 PM EDT this evening for ANZ230. Gale Warning until 5 AM EDT Sunday for ANZ231. Small Craft Advisory until 6 PM EDT this evening for ANZ236. Gale Warning until 7 AM EDT Sunday for ANZ250-254>256. Gale Warning until 6 AM EDT Sunday for ANZ251. && $$ SYNOPSIS...Frank/EVT NEAR TERM...Doody SHORT TERM...EVT LONG TERM...Frank AVIATION...Frank/Doody MARINE...Frank/EVT is the U.S. government's official web portal to all federal, state and local government web resources and services.