Cape Cod Bay Marine Forecast
|This Afternoon...Se Winds 5 To 10 Kt. Seas 1 Foot Or Less.|
|Tonight...Se Winds Around 10 Kt, Increasing To 15 To 20 Kt After Midnight. Seas Around 2 Ft. Rain. Vsby 1 To 3 Nm.|
|Mon...S Winds 10 To 15 Kt With Gusts Up To 20 Kt, Becoming W 15 To 20 Kt With Gusts Up To 30 Kt In The Afternoon. Seas 2 To 3 Ft. Patchy Fog. Rain. Vsby 1 Nm Or Less.|
|Mon Night...W Winds 20 To 25 Kt, Becoming Nw 25 To 30 Kt After Midnight. Gusts Up To 40 Kt. Seas 4 To 7 Ft. Light Freezing Spray.|
|Tue...Nw Winds 25 To 30 Kt With Gusts Up To 40 Kt. Seas 6 To 8 Ft. Light Freezing Spray.|
|Tue Night...Nw Winds 20 To 25 Kt, Becoming W 15 To 20 Kt After Midnight. Gusts Up To 30 Kt. Seas 4 To 6 Ft. Light Freezing Spray.|
|Wed Through Thu Night...Nw Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 2 To 3 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
1253pm EST Sunday Feb 28 2021
High pressure builds offshore by this afternoon and rain spreads in as a warm front lifts toward the region today. Rain continues tonight and into early Monday as a cold front moves through. A strong cold front brings a period of scattered snow showers Monday night, along with gusty winds and well below normal temperatures into Tuesday. Temperatures rebound back to near to above normal for mid to late in the week before a cooldown into the weekend. Mainly dry weather for the rest of the workweek, though turning unsettled by the weekend.
Near Term - Until 6pm This Evening
Leading edge of the light rain has reached NYC area. Plenty of low level dry air in place and much of the daylight hours will be dry. Just a chance of a few showers late in the day from CT to southern RI.
Previous discussion... Widespread high clouds across SNE and cloud cover is pretty thick and not offering much sunshine. Clouds will lower through the day as deeper moisture approaches from the SW so mainly cloudy skies will prevail. Leading edge of overrunning rain is across eastern PA and central NJ. Forecast soundings show plenty of low level dry air that needs to be overcome which will slow onset of showers. Timing wise, expect a few showers to reach portions of CT/RI and possibly south coastal MA after 4 pm, but enough low level dry air should keep it dry through the day in central and eastern MA. Adjusted Probability of Precipitation to reflect this timing, otherwise forecast on track. Not expecting much of a warmup given the amount of cloud cover in place. High temperatures will generally be in the low to mid 40s.
Short Term - 6pm This Evening Through 6pm Monday
* Rain and fog across southern New England tonight.
* Rain tapers off on Monday and skies clearing during the afternoon.
Tonight... Shortwave trough over the central Great Lakes/Ontario lifts into northern Quebec. The primary surface low lifts into Quebec, while a secondary low develops/deepens along the south coast and lifts northeastward.
Rain continues and this should be when the heaviest Quantitative Precipitation Forecast falls. Confidence remains high given the forcing that the highest Quantitative Precipitation Forecast will fall along the south coast - closer to the deepening surface low. Even with this in mind not expecting a lot of Quantitative Precipitation Forecast with up to 0.25 possible. Used a blend of the 50th percentile of guidance and WPC. Low temperatures in the 30s across southern New England.
Think during this window will be when the risk is highest for some dense fog. This is due to the combination of melting snow pack from the rain and southerly warm air advection. Have the lowest visibilities where the snow depth is greater than 5 inches per the latest NOHRSC analysis.
Monday... A ribbon of vorticity extends from the shortwave lifting northward over Quebec early on Monday, while another trough digs in from Ontario. The trough digs into eastern Ontario/Quebec by the evening. At the surface a cold front will slide through.
Have some uncertainty in the forecast for this timeframe as models are spread on how quickly the front and precipitation move through. Once again dealing with an all rain situation until late in the afternoon when scattered snow showers move into northwestern portions of the CWA. Have leaned toward the higher resolution guidance - the ARW/NMM in particular for the precipitation ending earlier in the day. Should see the bulk of the rain end during the morning hours.
Expecting a mild day across southern New England. Will have S/SW warm air advection to start, but with the frontal passage winds shift to the WNW/NW. With the secondary low in the Gulf of Maine am not anticipating the ageostrophic wind to have a northerly component and actually should be southerly. Have gone with the 75th percentile of guidance which brings highs in the 40s and 50s, with the warmest readings along the coastal plain. Do have some concern that colder air could remain locked across the interior as some of the high res models suggest. Think that the southerly ageostrophic wind component and some downsloping later in the day should warm things up.
Should see excellent mixing as colder air advects in. This result in breezy conditions across southern New England during the afternoon. Right now have some 20-35 mph WNW gusts in the forecast with the highest speeds over the higher terrain.
Long Term - Monday Night Through Saturday
Highlights... * Arctic front brings a period of brief snow bursts/snow squalls Monday night, gusty NW winds and well below normal temps Monday night into Tues. Gale-force gusts and freezing spray likely on the waters.
* Temperatures rebound back into the 40s Wednesday into Thurs.
* Turning cooler Fri into the weekend.
What a difference a day makes. 28/00Z guidance has come into considerably better agreement with the overall synoptic pattern through Friday. That said, there are still some detail differences which will need to be worked out over the coming days. Will continue to favor a consensus approach for this portion of the forecast. Still some questions about how a mid level trough over the Pacific will evolve towards next weekend, and the corresponding impacts downstream across the lower 48.
A bit of a rollercoaster temperature-wise into next weekend. Turning sharply colder, with well below normal temperatures Monday night into Tuesday as arctic air briefly moves across our region. Above normal temperatures quickly return Wednesday through Thursday. Expecting near normal temperatures Friday, before trending below normal towards next weekend.
Most of this period is expected to be dry. One notable exception should be Monday evening, with the initial arrival of the arctic air. Still seeing plenty of signals for the risk of snow squalls or snow showers. Timing will be everything, as these snow squalls could impact the latter half of the evening commute. It is also possible these potential squalls do not arrive until after the evening commute. Will need to monitor this closely. Latest guidance suggesting a potential coastal storm will be too far offshore to have much impact on our region. Not yet ready to etch that solution in stone at this time range.
Have adjusted the Gale Watch starting time to earlier Monday evening in case winds ramp up a bit quicker than currently forecast. Otherwise have not made any adjustments to the Small Craft Advisories ending today or the ending time of the Gale Watch.
Today and Tonight...High confidence
Light winds to start as high pressure builds over the waters into the afternoon. As the high moves further offshore will see winds shift to the southeast heading into the evening. Southeast winds strengthen tonight as low pressure deepens along the south coast. Will see speeds of 10-25 kts and gusts of 15-30 kts with the highest speeds across the outer waters. Waves falling to 2-4 feet late this afternoon and increasing to 3-7 feet tonight.
Monday... Southerly and southeasterly winds shifting to the SW/W as a cold front slides through. Will have gusts of 20-30 knots, but could see some borderline gales developing across the outer northeast waters by the evening. Wave heigheights of 3-7 feet with the highest waves across the outer waters.
Outlook /Monday Night through Thursday/... Monday Night through Tuesday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 14 ft. Freezing spray.
Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Freezing spray.
Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.
Wednesday Night through Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Tides / Coastal Flooding
Tides are astronomically high Monday, with Boston at 11.0 FT MLLW (12:36 PM), Nantucket 3.6 FT MLLW (12:02 PM), and Providence at 5.0 FT MLLW (9:23 AM). Current expectation is for a surge of less than one foot along the south coast, and perhaps around 1 foot along eastern MA coast, which would keep the total water level below the minor flood category for both coasts.
In addition, winds are expected to shift to the W/NW in the morning as a cold front moves offshore, lessening the potential along E MA coast. If front ends up slowing down, it is possible we could see minor splashover (sub-Coastal Flood Advisory level) along both coasts, but that seems to be a worst case scenario right now.
Does not appear to be a prolonged period of strong enough S/SE winds to build up seas offshore more than 4-5 FT, so beach erosion is not expected to be an issue right now either.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None. MARINE...Gale Watch from Monday evening through Tuesday evening for ANZ230>237-250-251-254>256. Small Craft Advisory until 7pm EST this evening for ANZ235- 237-256.