Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 280853 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 353 AM EST Mon Nov 28 2016 .SYNOPSIS...
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High pressure cross the area today. A warm front will bring widespread rain to the region Tuesday into Tuesday evening. A brief period of drying is likely into Wednesday morning then more rain, heavy at times is likely Wednesday afternoon and night as low pressure moves into New England. Improving conditions Thursday as the low moves into the Maritimes with mainly dry and cooler weather for Friday through the weekend.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Early AM temps have dropped well into the low-mid 20s thanks to mainly SKC skies and light/calm winds. What little near sfc winds there are have shifted mainly to the W this morning and turned the bulk of the ocean effects offshore. Plenty of sunshine today and subsidence inversion evident under high pres slowly building across the region. This subsidenceinversion, although allowing for the dry/mainly clear conditions to continue will suppress BL mixing this afternoon. Combine this with the cool start this morning, and it`s likely highs will be similar to yesterday even though H92 temps warm to nearly +3C by late afternoon. Therefore, expect mainly 40s for highs.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
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Through midnight... Evening hours will be similar to this past night. Enough clearing/calm winds to allow for early radiational cooling. Afternoon dwpts dip into the low 20s so there should be plenty of room for temps to once again dip into the upper 20s and low 30s early. High mid clouds will build and likely mitigate further radiational cooling holding temps or even slightly raising them as S LLJ continues to develop over the region from the SW. Dry wx continues through the evening hours. After midnight and into Tuesday... Early issues with approaching warm front and strong overruning will be p-type at onset. LLJ increases through the AM hours increasing low-lvl convergence within an airmass where PWATS approach 1.2 inches by daylight (nearly 2 std deviations above normal). Soundings are very dry through 12Z, so timing of the precip onset will also be a factor in determining P-type. Noting there is decent Nly ageostrophic flow and this is typically a pattern where warm front is slow to push N. Also, expecting wetbulb process with the dry column. Therefore, particularly in the higher terrain of interior MA/CT, may see a brief period of freezing rain as the precip shield approaches, before warm air is able reach the BL. Initial QPF is light enough to suggest that any cold/untreated sfc could see a trace to a few hundredths of ice before the change to all rain. Note timing is somewhat uncertain, especially if a secondary wave develops across the S tier and locks in the cold air. Stay tuned to forecast updates over the next 24 hours for where/if some icing impacts may occur through mid morning Tue. The remainder Tue should be wet. As mentioned above the building LLJ (GFS is likely too robust with nearly 75 kt, prefer the slightly weaker Ecmwf between 50-50 kt) with pwats exceeding an inch. Widespread QPF could reach 0.5-1.25 inches. This is the first in a series of waves through mid week. No flooding issues expected given the recent dry conditions.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
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Highlights... * Rain ending Tue evening near the coast * More rain, heavy at times Wed afternoon and night * Improving conditions Thu with cool and blustery weather Fri through the weekend Overview... High amplitude longwave trof across the central CONUS with closed low across the Gt lakes will result in another period of widespread rain Wed afternoon/night as shortwave energy and low pres moves into the region. Split flow pattern evolves by the end of the week into the weekend with low amplitude northern stream across the Gt Lakes and NE. This will bring mainly dry and cooler weather but series of fast moving shortwaves move through the flow so can`t rule out brief rain/snow showers at times but timing uncertain. Details... Tuesday night... Expect a band of moderate to heavy rain across SE New England to start the evening assocd with the low level jet and strong low level convergence. Otherwise dry slot from the west will quickly move into SNE bringing an end to the rain during the evening from west to east. Weak wave develops on the boundary and moves into the Gulf of Maine overnight with weak ridging nosing down from the north and may see some partial clearing. The ridging will push the front back to the south with low level cooler air moving back south across the region. Wednesday into Wednesday night... Dry weather should prevail to start the day and may even see some morning sun before clouds quickly return. Next shot of rain overspreads the region Wed afternoon into Wed night as similar set up to Tue event with approaching warm front and low level jet with sfc wave moving into SNE. It appears heaviest rainfall will occur late Wed into Wed evening assocd with the low level jet with precip tapering off overnight. Potential rainfall for this second event expected to be 0.75-1.50". Highs Wed will be dependent on how far north warm front gets. Best chance of temps reaching the upper 50s will be along the south coast but front may get hung up south of the Mass pike so cooler 40s are likely further to the north across northern MA and possibly into the CT Valley in northern CT. Thursday... Low pres in the Gulf of Maine will lift NE into the Maritimes with drier westerly flow into SNE. With mid level trof axis still to the west and shortwaves rotating through, can`t rule out a brief rain shower, but otherwise mainly dry weather expected with partial sunshine. While it is cooling aloft, low level temps are fairly mild so temps should reach well into 50s in the coastal plain with upper 40s interior high terrain. Friday through Sunday... Mainly dry, cooler and blustery conditions with westerly flow as broad trof settles in over the NE. Still a few shortwaves rotating through the flow so a low risk for a brief rain/snow shower, mainly interior high terrain. Seasonable temps Fri cooling a bit below normal next weekend.
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&& .AVIATION /08Z MONDAY THROUGH FRIDAY/...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/... Today and tonight...High confidence. VFR. Generally light W-NW winds with some building high clouds starting late tonight. Tuesday...Moderate confidence. Early VFR conditions will gradually give way to MVFR, then finally IFR by late afternoon/evening due to a mix of low CIGS and vsbys in fog and mod rain. Will also have to watch for some light icing during the morning when the precip starts, this will be most likely in the CT Vally as well as the higher terrain of N MA. More details on this to follow. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Tuesday Night through Friday/... Tuesday night...High confidence in trends. MVFR/IFR in rain and fog, especially SE New Eng in the evening then improving conditions from west to east, possibly to VFR overnight. However, it is possible stratus and patchy fog may linger. Wednesday...Moderate confidence. VFR to start, then deteriorating to IFR late Wed and especially Wed evening as another round of heavy rain moves in. Rain exits overnight with conditions possibly improving to VFR late Wed night. Thursday and Friday...Moderate confidence. Mainly VFR cigs with isold MVFR possible. Blustery W winds expected.
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&& .MARINE...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/... Through tonight... Seas will gradually dissipate across the E and SE waters through the day today, allowing the current round of small craft advisories to drop. Winds will remain at or below 20 kt through much of the day as well, mainly out of the W. This quiet weather continues into the overnight. Tomorrow... An approaching frontal system will yield increasing winds and swell across the waters. S-SE winds will increase to 25-30 kt and seas reach nearly 7 ft once again by the evening. Another round of small craft advisories is likely. Rain/fog leads to low vsbys by mid day. Outlook /Tuesday Night through Friday/... Tuesday night...Moderate confidence. SCA SW winds Tue evening with low risk for marginal gales around Cape Cod, then diminishing and shifting to NW overnight. Rough seas. Low vsbys in rain and fog in the evening, improving overnight. Wednesday...Moderate confidence. Winds becoming E/SE during the afternoon with a period of gusty southerly winds and rough seas across south coastal waters Wed evening. Vsbys lowering again in developing rain and fog later in the afternoon and Wed night. Thursday and Friday...Mainly west winds with gusts to 25 kt at times. SCA seas persist over the south coastal waters. Good vsbys.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 PM EST this afternoon for ANZ250- 254-255. Small Craft Advisory until 9 AM EST this morning for ANZ251.
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&& $$ SYNOPSIS...KJC/Doody NEAR TERM...Doody SHORT TERM...Doody LONG TERM...KJC AVIATION...KJC/Doody MARINE...KJC/Doody

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