Marine Weather and Tide Forecast for Westerly, RI

NEAR TERM /THROUGH TODAY/

Key Messages...

* Rain ending Tuesday morning from west to east, becoming sunny shortly after the rain moves out, though the Cape and Islands may not escape the low clouds much of the day.

* Quite a bit warmer, with highs in the mid to upper 70s away from the cooler south coast.

Rain showers resulting from a frontal system crossing New England this morning will continue off and on through the early morning hours before a mid level cold front and accompanying dry air in the upper/mid levels bring rain to an end from west to east. For locations west of Worcester rain likely ends before sunrise with low clouds clearing by late morning. Further east the bulk of the precipitation should be out by 8am but the Cape and islands may hang onto some scattered showers through the morning. Rapid clearing is likely for southern New England, with sunny skies for everyone but the Cape and islands by 1-2pm, though it will be filtered by high clouds moving in in the afternoon. Guidance indicates a stubborn low level inversion that's hard to break over Cape Cod and the islands which would not only keep clouds around all day, but while temperatures inland reach well into the 70s, upper 50s to near 60 are more likely. A dry surface cold front drops through today, likely stalling out for a time over southeast MA where that low level moisture holds on longer. Eventually the cold front does fully push through, dropping dewpoints from the upper 50s Tuesday to upper 30s after midnight. This will mean clearing skies by sunrise Wednesday.

SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/

Key Messages...

* Dry and sunny.

Quiet, zonal flow continues on Wednesday with surface high pressure building overhead. This brings quiet, if cooler weather in the post frontal airmass. Even so, 925 mb temps around 10-11C should result in highs warmer than average for late April, in the upper 60s and low 70s; not a drastic temperature gradient to the coast today given offshore flow.

LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/

Key Messages:

* Warm and mostly dry Thursday and Friday, outside of a stray shower in northern Massachusetts Thursday evening/night.

* The next chance for widespread rain comes in Saturday, but there are uncertainties with the exact timing.

* Drier conditions Sunday into early next week.

The Big Picture: Nearly zonal flow at 500mb across the CONUS Thursday and Friday, a subtle 850mb shortwave may produce a couple of spotty showers late Thursday evening into predawn Friday.
Otherwise, do think much of this time remains dry as surface high pressure builds across New England. This feature moves northeast towards Nova Scotia ahead of the only soaking chance of rain for this part of the forecast, arriving Saturday, but confidence with exact timing is low given the uncertainty amongst the guidance.
Behind the system, mid-level ridging, surface high pressure builds in from the northwest with drier conditions Sunday into Monday of next week.

Wednesday Night through Friday Night: Surface high pressure builds across New England with a weak 850mb high centered off the Mid- Atlantic coast. Will have drier air for part of Thursday and think it will be the sunnier of the two days. Guidance has a shortwave riding around the northern edge of the 850mb high, the better forcing is to the north in Vermont and New Hampshire, cannot rule out spot rain in northern Massachusetts. While the NBM did not show POPs during this timeframe, did opt to use CONSALL, which gave 10-20 percent POPs for locations along and north of Route 2. As for temperatures, will have mild conditions both days as 850mb temperatures trend above normal, around +10C across western/central Massachusetts and Connecticut and +7/8C over eastern Massachusetts and Rhode Island. A quick look at BUFKIT and GFS does show mixing Thursday afternoon to 850mb. Highs Thursday afternoon reach the low to middle 70s, though at the coast will likely have a seabreeze given the time of year, and there the highs cooler in the 60s, perhaps upper 50s for the Islands and outer Cape Cod. As for Friday, little change in the airmass, perhaps +1C or +2C degrees warmer, would expect resulting highs for Friday to be a few degrees warmer than the prior day. Overnight temperatures for Thursday and Friday night are in the upper 40s and lower 50s.
Temperatures were inline with NBM and did not deviate.

Saturday: Low amplitude mid-level trough moves across the northeast and development of a low-pressure system with a southerly LLJ. Will have anomolous PWATs advect into southern New England, 1.2" to 1.5", which is ~3 standard deviation above normal. There remains a good amount of uncertainty with respect to the exact timing of the onset and endtime the rain, but are increasing chances for a widespread soaking rain during the daylight hours. Given the inherent uncertainties due to the timeframe of day 5/6, did not deviate from the NBM. Are modest probabilities for rainfall amounts greater than 0.5" across the region at 50 to 60 percent. Increase the potential rainfall to 1.0" or greater will have probabilites between 20 and 30 percent. Will want to check back with us if you have outdoor plans for Saturday.

Sunday and Monday: Mid-level ridging and surface high pressure will result in drying conditions Sunday and Monday. North-northeast flow Sunday lends a cooler day with highs in the upper-50s and low-60s.
The flow may become southwest by Monday and bring in slightly warmer temperatures in the upper-60s.



AVIATION /07Z TUESDAY THROUGH SATURDAY/
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

06z TAF Update:

Through 12Z: Moderate confidence.

VFR east to start. Categories then continue to deteriorate to MVFR, potentially IFR through 08z from W to E, in 4-6 SM -SHRA and ceilings 010-020. Confidence in IFR is low. -SHRA should be ongoing from ORH east by end of this period, while trending dry for BAF/BDL. S winds around 10 kt, with areas of low level shear as SW jet of 40 kt moves overhead.

Today: High confidence in trends but moderate on timing.

MVFR/IFR cigs early, quickly scattering out to VFR 13-16z. It may take longer for south-coastal/Cape airports to scatter out to VFR and showed MVFR-IFR ceilings thru at least 18z before trending to VFR. SW winds around 5-10 kt then shift to WSW/W around 10 kt, with occasional gusts to 20 kt for the interior.

Tonight: High confidence.

VFR. WNW winds around 5-10 kt.

Wednesday: High confidence.

VFR. Light NW winds 5-10 kts.

KBOS TAF...High confidence in TAF. VFR thru 07z, then categories trend to MVFR with light showers. Improvement to VFR anticipated by 15-16z.

KBDL TAF...High confidence in TAF. Improvement to VFR anticipated by 12-13z.

Outlook /Wednesday Night through Saturday/...

Wednesday Night through Thursday Night: VFR.

Friday: VFR. Slight chance SHRA.

Friday Night: Mainly VFR, with local MVFR possible. Breezy.
Chance SHRA.

Saturday: Mainly MVFR, with local IFR possible. Breezy. SHRA likely.

MARINE
Forecaster Confidence Levels:

Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.

Today through Wednesday: High confidence.

Generally tranquil boating conditions through the period. Winds S/SW around 15-20 kt with passing rain showers early today. SW gusts could reach near 25 kt over the far southeast offshore waters, before becoming west late tonight.

Seas 2-4 ft overnight tonight, perhaps near 5 ft over the southern offshore waters. Seas continue around that range through tonight.

Wednesday winds will be variable 5-10 kts, with seas of 1-3 ft.

Outlook /Wednesday Night through Saturday/...

Wednesday Night through Friday: Winds less than 25 kt.

Friday Night: Winds less than 25 kt. Chance of rain showers.

Saturday: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Seas up to 5 ft. Rain showers likely.

BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...None.