Cape Cod Bay Marine Forecast
|Overnight...Nw Winds 15 To 20 Kt, Diminishing To 10 To 15 Kt. Gusts Up To 25 Kt. Seas 4 To 6 Ft. Light Freezing Spray Likely.|
|Sat...Nw Winds 5 To 10 Kt, Becoming S In The Afternoon. Seas 2 To 3 Ft. Snow Likely.|
|Sat Night...S Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. Snow With Rain Likely. Vsby 1 Nm Or Less.|
|Sun...W Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft.|
|Sun Night And Mon...Nw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 5 Ft.|
|Mon Night...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 3 Ft.|
|Tue Through Wed Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 4 Ft. Seas Are Reported As Significant Wave Height, Which Is The Average Of The Highest Third Of The Waves. Individual Wave Heights May Be More Than Twice The Significant Wave Height.|
Area Forecast Discussion|
National Weather Service Boston/Norton MA
1003pm EST Fri Jan 17 2020
Large cold high pressure settles over New England tonight with winds diminishing. Low pressure moves across the Great Lakes and brings accumulating snow late Saturday afternoon into Saturday night. A cold front crosses the region Sunday with perhaps a few brief snow showers late Sunday/Sunday night. Dry, but very cold weather follows Monday through Wednesday as large high pressure builds in from the west. This high pressure system moves east of the region by next Thursday and Friday allowing for temperatures to moderate along with dry weather likely persisting.
Near Term - Until 6am Saturday Morning
Exceedingly dry air in place over interior Southern New England with dewpoints in the -7 to -10F range north and west of I-95. This bone-dry air also is also prevalent at depth with 00z ALB/GYX RAOBs reflecting PWAT (Precipitable Water) values of 0.04-0.05". Enough lingering NW winds for temps running a bit milder/outpacing forecast values a few degrees. Essentially just blended in slightly milder guidance to existing values to bring readings closer in line through about 2 AM. Winds should slacken and radiate even more efficiently by that point. High clouds will fill in towards early overnight in the Berks/CT Valley and pre- dawn hrs into eastern MA and RI, though these clouds probably aren't thick enough to preclude strong radiational cooling. Nonetheless a cold night in store, with easing winds as we move deeper into the overnight. No changes to lows attm.
Previous discussion... Dry high pressure settles over Southern New England, allowing for clear skies for much of the night, and diminishing winds. Gusts of 20- 30 mph linger along the shoreline communities thru early this evening, especially across the Cape and Islands. Then light winds will allow for very good radiational cooling, especially away from the shoreline where light/near calm winds are expected. For overnight lows went with a blend of the colder MOS guidance and bias- corrected guidance. Overnight lows range from -6 below zero to 10 above zero for much of the area, except some lows in the teens for communities along the shoreline.
Expecting some high deck clouds to move into the area late tonight, with partly cloudy skies around daybreak Sat.
Short Term - 6am Saturday Morning Through Saturday Night
Saturday and Saturday Night... During Saturday morning expecting dry conditions with increasing mid and high deck cloud cover. Surface high pressure centered overhead moves quickly offshore.
In its place a quick hitting low pressure system moves through the Great Lakes Region, with an increase in southerly flow as a warm front approaches from the SW. This warm frontal feature will lift across our area into Saturday evening, bringing a period of accumulating snows to our area. Main low pressure center passes thru northern New England Saturday night, with limited deepening of mid level trough in the process. During late Sat/Sat evening there is also some divergence aloft, being in left front quad of upper jet. This is also models also show a southwest low-level jet associated with warm advection aloft, that will likely sweep an axis of 925-700 mb frontogenetic forcing NE thru the area.
Hi-res models and NAM/GFS in general agreement on limited Quantitative Precipitation Forecast over SNE prior to 18Z, and most of the SNE Quantitative Precipitation Forecast falling between 21Z Sat and 06Z Sun. The air mass preceding the warm front is expected to be plenty cold enough at the surface (bolstered by wet-bulb cooling once precipitation starts) to support all-snow as an initial precipitation type.
There is the continued potential for heavy snowfall to fall at rates of an inch per hour, especially across the northern tier of MA and the east slopes of the Berkshires. For this area we have issued a Winter Storm Warning, with snowfall of 4 to 8 inches. Across south central MA, east coastal MA, north central/NE CT and the northern half of RI, have issued a Winter Weather Advisory for 2 to 5 inches of snow. There could be a brief period of 1" per hour snowfall rates in these areas during Saturday evening. For south coastal MA/RI and the Cape/Islands, snowfall should range from 1"-3", so at this time do not have winter weather headlines for that area. A transition to a rain/snow mix or light rain is expected during the overnight, along eastern and southern portions of the region. The far interior should remain cold enough for all snow.
During the overnight a dryslot comes in aloft, which should result in rain or snow becoming more intermittent. There is a slight chance for patchy freezing drizzle, at this time not confident enough to place with headlines.
High temps on Saturday are mainly 20 to 30 degrees, except 30s along the south coastal communities including Cape/Islands.
Overnight lows Saturday night- only fall a few degrees, ranging from the upper teens to 20s across much of the region, to low to mid 30s along the south coastal communities. Temps should actually rise a few degrees before daybreak Sunday.
Long Term - Sunday Through Friday
Highlights... * A cold front crosses the region late Sunday with a reinforcing surge of cold, blustery airmass arriving Sunday night
* Dry but very cold Monday and Tuesday
* Temps moderate approaching 40 Thu and then possibly into the 40s Fri along with mainly dry weather persisting
Details... Sunday... Low pressure along the Maine coast in the morning will exit into the Maritimes during the afternoon, yielding dry WNW flow on the backside into southern New England supporting mainly dry but blustery weather. Should see at least breaks of sunshine especially down in the coastal plain with more clouds in the high terrain given upslope and possibly some lake effect clouds from western NY. Model soundings suggest WNW winds may gust up to 30 mph. Temps will climb into the upper 30s and lower 40s Sunday afternoon, which is 5-10 degs above normal but the blustery WNW winds will make it feel colder than that.
Trailing short wave trough moves across the region Sunday evening with attending cold front that will usher in a reinforcing surge of cold air Sunday night. Robust short wave may be accompanied by some snow showers especially with some low level moisture with dew pts in the 20s, a little above normal (teens). However westerly blyr winds ahead of the front will limit low level convergence and downslope winds may dry out the blyr too much to support much snow shower activity.
Monday through Wednesday... Cold airmass invades the area behind departing northern stream short wave Sunday night. GFS showing its cold bias here so leaned toward the EC/ECENS with 850 temps from -10C to -12C Monday and Tue. Very blustery thru Monday so expecting cold wind chills. Highs likely not getting out of the 20s Monday and Tuesday, so definitely colder than normal and Monday will feel colder given the blustery northwest winds. Not as cold by Wednesday as cold air advection should become neutral by then. Temps may still be below average with highs in the upper 20s to lower 30s but with ensembles having 1030+ mb high cresting over SNE, winds should diminish along with wind chills easing. Dry weather prevails this period with the only exception as previous forecaster mentioned possibly some ocean effect snow showers Tuesday as winds may have some northerly component.
Thursday And Friday
ECENS showing western-central CONUS trough resulting in downstream ridging along the east coast. Thus temps continue to moderate Thu and Fri along with light winds as high pressure remains over or near the region. Not that blyr mixing will extend up to 850 mb but ECENS has 850 mb temps warming to 0C to +2C. However this should be good enough for highs to climb slightly above normal Thu with highs in the upper 30s and lower 40s and possibly into the 40s Fri.
Tonight: As offshore low moves further NE of our area, winds and seas continue to diminish. Based on obs, have cancelled Gale Warnings for eastern coastal waters and replaced them with SCAs. So SCAs (Small Craft Advisories) are now in effect for much of tonight for all coastal waters.
Saturday: By daybreak, most waters near the coast will have dropped below SCA (Small Craft Advisory) criteria. SCA (Small Craft Advisory) headlines may be needed for eastern outer waters, primarily for lingering seas up to 5 feet till the early afternoon hours.
Saturday night: SCA (Small Craft Advisory) headlines for winds/seas likely needed as an area of low pressure approaches our region from the W. SSE winds increasing with gusts 25 to 30 kt, seas building to 5 to 8 feet. Slight chance for gale force gusts on the southern outer waters prior to daybreak Sunday.
Outlook /Sunday through Wednesday/... Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas.
Sunday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 11 ft.
Martin Luther King Jr Day: Winds less than 25 kt. Local rough seas.
Monday Night through Tuesday: Winds less than 25 kt. Seas up to 5 ft.
Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of snow showers. Local visibility 1 to 3 nm.
Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...Winter Weather Advisory from 2pm Saturday to 4am EST Sunday for CTZ002>004. MA...Winter Weather Advisory from 4pm Saturday to 4am EST Sunday for MAZ007-013>019. Winter Weather Advisory from 2pm Saturday to 4am EST Sunday for MAZ011-012. Winter Storm Warning from 2pm Saturday to 7am EST Sunday for MAZ002>004-008>010-026. Winter Storm Warning from 4pm Saturday to 7am EST Sunday for MAZ005-006. RI...Winter Weather Advisory from 4pm Saturday to 4am EST Sunday for RIZ001>004.
Small Craft Advisory until 1am EST Saturday for ANZ233>235. Small Craft Advisory until 5am EST Saturday for ANZ231-232- 251. Small Craft Advisory until 2pm EST Saturday for ANZ250-254- 255. Small Craft Advisory until 3am EST Saturday for ANZ256.