Cape Cod Bay Marine Forecast
|Tonight...E Winds 15 To 20 Kt With Gusts Up To 35 Kt, Increasing To 25 To 30 Kt With Gusts Up To 55 Kt After Midnight. Seas Around 4 Ft, Building To 8 Ft After Midnight. Rain. Vsby 1 To 3 Nm.|
|Fri...E Winds 25 To 30 Kt With Gusts Up To 50 Kt, Becoming Nw With Gusts Up To 35 Kt In The Afternoon. Seas Around 8 Ft, Subsiding To 5 Ft In The Afternoon. Rain Likely In The Morning With Vsby 1 To 3 Nm.|
|Fri Night...W Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 4 To 5 Ft.|
|Sat...W Winds 15 To 20 Kt With Gusts Up To 30 Kt, Diminishing To 10 To 15 Kt With Gusts Up To 20 Kt In The Afternoon. Seas 3 To 4 Ft.|
|Sat Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 3 Ft.|
|Sun...Nw Winds 5 To 10 Kt. Seas Around 2 Ft.|
|Sun Night...S Winds 5 To 10 Kt. Seas 1 Foot Or Less. A Chance Of Showers After Midnight.|
|Mon...Sw Winds 5 To 10 Kt, Becoming W 10 To 15 Kt In The Afternoon. Gusts Up To 20 Kt. Seas 1 Foot Or Less, Then Around 2 Ft In The Afternoon. A Chance Of Showers In The Morning.|
|Mon Night...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 3 Ft.|
|Tue...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 2 Ft.|
|Tue Night...Nw Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 3 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
339pm EST Thu Nov 15 2018
Synopsis: A high impact but short duration snowstorm is on tap for areas away from the very immediate coast this evening. Precipitation transitions to mainly ice and then rain overnight, except perhaps portions of the high terrain in Massachusetts. Dry weather with chilly temperatures move in Friday afternoon through most of the weekend as high pressure builds across. A weak low may bring patchy light rain and/or snow late Sunday into Monday. Another shot of colder air moves in by the middle of next week, though it should be mainly dry.
Near Term - Until 6am Friday Morning
235 pm update... * High impact/short duration snowstorm this evening for many * Winter Storm Warnings posted for northwest of I-95
A high impact/short duration winter storm is on tap across much of the region this evening. Potent closed mid level energy across the Ohio Valley was inducing an 80+ knot winds at 700 mb. The result has been for heavy snow to break out across portions of the mid Atlantic States this afternoon.
1) Heavy Snow Away From The Very Immediate Coast This Evening:
This potent speed max/convergence zone at 700 mb will continue to lift northward resulting in very strong frontogenetic forcing this evening across southern New England. Heavy snow should develop after 4 or 5 pm across our northern CT zones and spread northeastward into northeast MA after 7 or 8 pm. Highest impact expected in our CT zones...given the heavy snow with 1 to 2 inch per hour rates will impact a large portion of the evening rush hour. The latter half of the evening rush hour will likely be impacted in the Springfield...to Worcester to Providence areas.
The biggest question with this forecast is how well this band of strong frontogenesis will maintain itself as it lifts northeast. Confidence is highest across our CT/RI and interior southeast MA zones. Further north...the guidance is somewhat split on that potent speed max at 700 mb. The RGEM/NAM maintain it across northern MA...while the ECMWF/GFS tend to weaken it and shunt it further east. Regardless...it will snow heavy across much of the region for a time but this will impact accumulations. We still feel that 4 to 7 inches of snow looks good for much of the region. Given the short duration/high impact event and considering some light icing will persist after the main event...feel warnings are warranted for much of the region. Snow amounts will likely be much lighter on the very immediate coast. SST around 50 with an easterly wind will result in making it difficult to get more than an inch in these locations before a quick change to rain.
2) Warming Aloft/Mid Level Dry Air Late This Evening:
Much of the region appears cold enough for mainly snow through 02z or 03z. However...the very potent 700 mb southerly jet will transport mid level warmth northward across the region. Ptype should transition from snow to ice/rain from 02z through 06z across southern New England. At the same time...mid level dry air will be cutting off our snowgrowth. Regardless...it appears that the damage will be done across the region but some lighter rain/ice will linger. Ptype will mainly be rain across eastern MA/RI...but some light sleet/freezing rain may persist for a time across the interior.
It does appear that temperatures by daybreak Friday will be above freezing for most of the region for the morning rush hour. The exception will be some of the high terrain...especially interior northern MA where some light sleet/freezing rain may still result in slippery travel
3) Strong to Damaging Winds:
A strong easterly low level jet of 55 to 65 knots is expected to develop at 925 mb during the overnight hours along with impressive pressure falls. Low level lapse rates are fairly steep along the coast. This will result in a period of easterly wind gusts of 40 to 50 mph along the eastern MA coast and up to 60 mph across the Cape/Islands. High wind warnings have been issued for the Cape/Islands with wind advisories along the eastern MA coast. Will have to watch for some downed trees and isolated to scattered power outages
Short Term - 6am Friday Morning Through 6pm Friday
Friday... The surface low pressure system looks to track near the southeast New England coast Friday morning. Its associated closed 700 mb level will also track across the southeast portion of our region. The result will be periods of rain through Friday morning...before coming to an end by afternoon. However...colder air wrapping in behind the system may allow for portions of interior MA /especially the high terrain/ to transition back to a period of snow. It is possible that some of these areas see an additional 1 to 3 inches of snow in this region. However...for the rest of the region temps should remain above freezing with perhaps just some wet snow flakes mixing in at the end.
Precipitation petty much ends by Friday afternoon and we may see some peeks of sun late in the day. Afternoon temps should be in the 30s to the lower 40s with gusty northwest winds
Long Term - Friday Night Through Thursday
Highlights... * Below average temperatures persist * Weak low pressure brings periods of rain and snow late Sunday into Monday * Dry and cold mid week
Overview... The extended forecast features a few high pressure systems sandwiched around a relatively weak low pressure disturbance or two in the Sunday night/Monday time frame which will bring the return of both rain and snow chances. Model consensus is good that the flow pattern becomes much less amplified and more zonal behind Friday's system, persisting through late weekend. By then a mid level shortwave digs south, crossing the region Sunday/Monday which will generate a weak surface low in the vicinity of SNE with another round of light snow/rain. Beyond this, models diverge a bit, with the GFS keeping things unsettled into Tuesday before the high returns, while the Euro returns a dry high pressure more quickly. Either way, by mid to late week heigheights begin to rise ever so slightly and a cold and dry pattern returns.
Details... Friday night and Saturday... Friday night the low continues to exit to the northeast, relaxing the surface pressure gradient as it leaves. Winds will take a good while to come down, however, and the 30-35 H925 jet doesn't leave SNE until late Saturday. Thus, expecting gusty west winds to persist through the period, especially over the Cape, islands, and waters, decreasing through the day Saturday. Clearing skies early Saturday will give way to more clouds as mid level moisture invades from the west. With good Cold Air Advection behind the system lows Friday night dip into the low 30s with wind chills in the 20s. Highs on Saturday won't get out of the 40s.
Sunday and Monday... Sunday high pressure sits over the northeast with light winds and highs in the upper 30s-40s under a cold airmass; should be a mostly dry day before snow/rain chances increase from the west by the evening/overnight hours. The upper trough over Canada digs south helping to generate a surface low in the vicinity of SNE which brings weak fronts through in quick succession Sunday night/Monday. Still expecting mainly snow outside the coastal plain, with rain along the coasts. Quantitative Precipitation Forecast amounts are lackluster; a few hundredths to a few tenths of liquid equivalent.
Tuesday through Thursday... After the system exits zonal flow returns at the base of a large 500 mb trough over the eastern US Tuesday/early Wednesday. Some disagreement on slight precipitation chances Tuesday, but overall looks dry; maybe some showers over the high terrain. By mid week a surface high returns bringing dry weather. Given the overall weak longwave trough pattern, cold temperatures will persist with highs in the 30s and low 40s.
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.
Short Term /through Friday/...High confidence.
Tonight...Strong Easterly LLJ will result in 50 knot wind gusts across much of our waters late tonight with strong Small Craft Advisory across Boston Harbor/Narr Bay. Seas will build to between 15 and 20 feet across our eastern waters by daybreak Friday. VSBYS reduced at times in mainly a windswept rain.
Friday...Storm force wind gusts should diminish to gales during the morning and persist into part of the afternoon with still a decent pressure gradient in place. Seas will remain very high.
Outlook /Friday Night through Tuesday/... Friday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 12 ft.
Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.
Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.
Sunday Night: Winds less than 25 kt. Slight chance of rain. Local visibility 1 to 3 nm.
Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
Renewed river flooding is possible across RI and eastern MA with 0.50 to 1.0 inches of rainfall possible tonight into Friday after a few inches of snow first. Will have to watch this closely
Tides / Coastal Flooding
Astronomical tides are very low (below 9 ft) in Boston. Thus with this upcoming storm worse case scenario would be isolated minor flooding possible
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...Winter Storm Warning until 7am EST Friday for CTZ002>004. MA...High Wind Warning from midnight tonight to 9am EST Friday for MAZ022>024. Winter Weather Advisory until 1am EST Friday for MAZ017>021.
Wind Advisory from midnight tonight to 9am EST Friday for MAZ007-014>016-019. Winter Weather Advisory until 2am EST Friday for MAZ007- 013>016. Winter Storm Warning until 7am EST Friday for MAZ002>006- 008>012-026. RI...High Wind Warning from midnight tonight to 9am EST Friday for RIZ008. Winter Weather Advisory until 1am EST Friday for RIZ002>007. Winter Storm Warning until 7am EST Friday for RIZ001. MARINE...Storm Warning from midnight tonight to 9am EST Friday for ANZ231>235-237-250-254>256.
Gale Warning from 10pm this evening to 4pm EST Friday for ANZ230-251.
Gale Warning from midnight tonight to 9am EST Friday for ANZ236.