Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 221952 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 352 PM EDT Wed Mar 22 2017 .SYNOPSIS... Blustery and very cold conditions will tonight will gradually moderate Thursday with less wind. Becoming windy and milder Friday. A cold front will move through Saturday then stall south of New England into early next week which will the potential for periods of rain and mixed precipitation. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Cold and very dry airmass across SNE with dewpoints in the single numbers below zero for much of the region. Gusty NW winds will continue in strong cold advection pattern with near dry adiabatic low level lapse rates promoting excellent momentum transfer with mixing likely to the top of the PBL. Soundings suggest peak of the wind will continue into early evening with gusts to 40-50 mph then gradually diminishing. However, winds will remain somewhat gusty through the night, especially along the coast as strong pressure gradient remains. Mid level trof axis moves east of New Eng this evening, as one last shortwave rotates through the NW flow. Column is very dry so mainly clear skies tonight and very cold. Used a blend of MOS and model temps for lows tonight which yields 5 to 15 degrees across much of SNE. Wind chills single numbers above and below zero. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Thursday... Still some gusty winds in the morning along the coast but trend will be for diminishing wind in the afternoon as high pres builds east into New Eng. Under sunny skies, temps will moderate as low and mid level temps rise, with highs reaching mid/upper 30s which is still well below normal. Thursday night... High pres shifts south of New Eng with developing SW flow warm advection yielding increasing mid/high clouds. There should be a window for good radiational cooling in the evening before clouds thicken which will result in a cold night. Lows ranging from mid/upper teens to mid 20s across the region with temps stabilizing or slowly rising late. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Highlights... * Snow to rain showers on Friday as temps warm near average * Above average temps on Saturday with a few showers * Low confidence next Sun-Tues with unsettled weather possible at times with some rain, ice and/or snow possible Pattern Overview... 00z models and ensembles are in agreement with the general synoptic pattern for the long term. Uncertainty increases in the extended do to mesoscale and thermal issues. Mid-level ridge axis will move through the region on Friday as high pressure slides to the south. Split flow aloft with closed low over the southern Plains and northern stream across southern Canada. The initial closed 500 mb will slowly move into the Midwest over the weekend. The low comes into confluent flow and weakens into an open wave as it comes towards the Northeast early next week. Due to the confluent flow aloft, high pressure persists over northern New England keeping surface temperatures cool, resulting in mixed precip at times for the weekend into early next week. The models have slowed compared to 21.00z guidance. However, the EC is a bit faster compared to the GFS/GEFS mean in the forward progression of the upper trough for early next week. Still a lot of uncertainty with this timeframe. Details... Thursday night...High confidence. Mid-level ridge will build overhead Thursday night allowing for WAA to develop. Temps will radiate out during the first half of the night thanks to light winds and clear skies. Clouds will build into the area during the later half limiting radiational cooling. While overnight lows will fall, appears that they may hold steady during the later half of the night within the strong WAA pattern. Friday...Moderate confidence. Surface high pressure shifts eastward resulting in warm/moist advection in the mid-levels. Tighten pressure gradient will result in gusty winds near 30 MPH. Ascent due to isentropic lift will eventually saturate the column, resulting in periods of precipitation during the day and into the night. A weak shortwave in the mid-levels will help increase precipitation chances. P-type will be dependent on timing of precip as well as mid-level warmth as surface temps will start out below freezing especially across the higher terrain. Model guidance and BUFKIT data shows warm nose inching in at 800 and 850 mb with cooling at 925mb. This will help support a transition from snow to sleet to eventually rain during the day on Friday. Low confidence on if freezing rain will occur, something to watching in the coming days. Saturday...Moderate confidence. A bit tricky forecast is in store for this timeframe. Used a non- diurnal trend in the Friday night into Sat morning forecast thanks to increasing WAA. 850 mb temps Saturday morning will be close to 8C but drop through the day. Surface temperatures will reach into the mid 50s, cannot rule out a few 60s if the mid-level ridge continues to build. Surface cold front will push through the region during the day. Could see a few rain showers but not expecting widespread rainfall as heights continue to build overhead. Sunday into Tuesday...Low confidence. While guidance is in agreement synoptically, still a lot of details to work out for this portion of the forecast. Biggest uncertainties will be the placement of the upper level low and how quickly it will diffuse over the weekend into early next week. Already have seen a slower track and could see northern High pressure strengthen moreso leaning towards a slower precip time on Sunday. Right now, 00z guidance shows stalled boundary draped across southern New England on Sunday with a few shortwaves moving through the flow. High pressure building in from the north has the potential to push the front farther southward on Sunday which could leave the first half of it dry. Diffusing closed low will become an open wave and track through southern New England early next week with another wave right behind it. Believe timeframe where we will see the heaviest precip is when the open wave approaches Sunday night into Monday. As mentioned before, still a lot of uncertainty as to the thermal profiles. Looking at the latest EC, it has trended a warmer in the mid-levels versus the GFS with both models indicating surface temps near freezing. Believe that there could be a period where the region could see a mixed bag of precip. Still a lot of uncertainty with this timeframe as thermal profiles will change. Will continue the mentioning of snow, sleet, ice and/or rain for the forecast until thermals come better in alignment. && .AVIATION /19Z WEDNESDAY 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/... High confidence. VFR. NW gusts to 30-40 kt into early evening will gradually diminish but still gusts to 25 kt overnight along the coast. NW wind gusts to 20 kt Thu becoming light Thu night. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Friday through Monday/... Friday...Moderate confidence. VFR to MVFR conditions in snow to rain showers during the day. Cannot rule out the potential for sleet across western terminals in the morning. Gusty southwest winds near 30 kts are possible. Saturday into Sunday...Low to moderate confidence. A period or two of showers along with some MVFR cigs are possible at times. Saturday night into Sunday has the better chance for wintry precip. && .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. Tonight...NW gales continue into the evening before gradually diminishing from west to east. Freezing spray will also continue. Seas building to 12-15 ft over outer waters east of Cape Cod this evening before slowly subsiding. Thursday...Still gusty NW winds in the morning with gusts 25-30 kt diminishing a bit in the afternoon. Freezing spray will subside in the afternoon. Hazardous seas over outer waters but gradually subsiding. Thursday night...Diminishing NW winds becoming light SW overnight. Seas subsiding below 5 ft over outer waters. Outlook /Friday through Monday/... Friday...Moderate confidence. Southwest wind gusts of 20 to 30 knots may develop ahead of frontal passage. Small craft headlines may be required. Low chance for gales across the outer eastern waters. Saturday...Moderate confidence. Cold frontal passage Saturday will help increase seas and winds. SCA may be needed. Sunday...Low confidence. Cold front will be south of the waters as surface high pressure moves northeast of the region. && .CLIMATE... Record lows for Wednesday, March 22: Boston (BOS) 8/1885 Hartford (BDL) 12/1934 Providence (PVD) 15/1988 Worcester (ORH) 8/1988 Record cold highs for Wednesday, March 22: Boston (BOS) 24/1885 Hartford (BDL) 29/1960 Providence (PVD) 28/1914 Worcester (ORH) 25/2002 Record lows for Thursday, March 23: Boston (BOS) 6/1934 Hartford (BDL) 9/1934 Providence (PVD) 8/1934 Worcester (ORH) 4/1934 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Wind Advisory until 6 PM EDT this evening for CTZ002>004. MA...Wind Advisory until 8 PM EDT this evening for MAZ004>007- 012>024-026. Wind Advisory until 6 PM EDT this evening for MAZ002-003- 008>011. RI...Wind Advisory until 8 PM EDT this evening for RIZ001>008. MARINE...Freezing Spray Advisory from 7 PM this evening to 11 AM EDT Thursday for ANZ231>235-250-251-254>256. Gale Warning until 2 AM EDT Thursday for ANZ231-232-251-255- 256. Gale Warning until midnight EDT tonight for ANZ230-233>235-237. Gale Warning until 10 PM EDT this evening for ANZ236. Gale Warning until 5 AM EDT Thursday for ANZ250-254. && $$ SYNOPSIS...KJC NEAR TERM...KJC SHORT TERM...KJC LONG TERM...Dunten AVIATION...KJC/Dunten MARINE...KJC/Dunten CLIMATE... is the U.S. government's official web portal to all federal, state and local government web resources and services.