Marine Weather and Tide Forecast for Jamesport, NY

KEY MESSAGES
1) A strong cold front will move through the area this evening, preceded by a line of showers and a few strong, to possibly severe thunderstorms. Damaging winds gusts are possible with any severe storms.

2) The coolest air mass of the season so far moves in this weekend along with Gusty NNW winds late tonight into Saturday.

3) Coastal low to form along the Mid Atlantic coast Sunday and to linger through much of the week.

DISCUSSION

KEY MESSAGE 1

SEVERE THUNDERSTORM WATCH IN EFFECT THROUGH 10 PM for the Lower Hudson Valley, NE NJ, NYC, SW CT, and western LI.

An amplifying upper trough across eastern Canada into the Great Lakes and Ohio Valley states will send a strong cold front across the area this evening. Enhanced W/SW winds ahead of the trough with 45 to 55 kt of deep-layered shear and marginal instability will produce a line of showers and a few thunderstorms along or just ahead of the front. Low clouds which have persisted across the region much of the day will dissipate and lift out ahead of the approaching cold front. The greatest uncertainty is whether the airmass can destabilize sufficiently for convection to bring these stronger wind downs to the surface. SPC HRRR MAX SB CAPE values are 500-750 J/KG.
Latest SPC mesoanalysis shows these values over south central PA, which are forecast to expand north and east the next few hours. The one offsetting factor to the lack of instability is the strong vertical wind shear, which may be the reason many of the CAMs are still pointing toward a fine line of convection moving into the NW portions of the Lower Hudson Valley by 6 pm, then racing the line south and east toward the CT coast, NYC metro, and western LI from 7 to 8 pm. The line likely weakens heading east due to decreasing instability. Shear profiles are mainly unidirectional, with some increase in low-level helicity, but main impact will be strong gusty winds, possible bowing line segments. Tornado threat is low (less than 5 percent) from NYC north and west.

What is left of the decaying line likely passes offshore in the 9 to 10 pm time frame. However, models continue to support of period of pose-frontal rain after midnight across coastal locations with the approach of the upper trough and jet dynamics. The best chance at this time looks to be east of the Lower Hudson Valley and NYC. Much of the rain will push east of the area by mid to late morning hours.

Expect a quick quarter to half-inch of rainfall with the heavier showers or thunderstorms this evening, then lighter amounts overnight at the coast with any rain.

Much colder air follows behind the cold front for the weekend with highs only getting into the 50s for Saturday, about 10 degrees below normal.

Gust NW winds develop late tonight with gusts 20 to 30 mph through the day Saturday before gradually subsiding Saturday evening.

KEY MESSAGE 2
Freeze watch in effect Saturday night for portions of the interior as strong high pressure builds in from the west. Lows across the watch area area forecast to get close to freezing with the mid 30s to around 40 elsewhere. The one limiting factor will be north winds which likely stay up enough to keep coastal locations from getting to freezing. Should winds drop off more than currently forecast, freezing temperatures and frost may need to be expanded south.

AVIATION /20Z FRIDAY THROUGH WEDNESDAY/
A cold front moves through late day into early evening.

IFR/MVFR to start, then VFR late afternoon mainly for the city terminals. Line of showers with potential thunderstorms anticipated for most terminals in the 22-00z time frame, except no chance of thunder anticipated for KISP/KGON. Westerly gusts with this line of showers would mostly likely end up 30-40kt.
Winds up to this point mainly SW with gusts around 20kt developing in the afternoon.

VFR for all by midnight tonight with NW-N winds gusting mostly 20-25kt. Showers expected for KISP/KGON through the overnight hours, but could be possible elsewhere except KSWF through the night.

...NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty...
IFR could last until around 19z. Timing of flight category changes could be off by 1-2 hours. Thunderstorm threat timing could be off by about an hour. Isolated gusts 40 to 50 kt are possible with any thunderstorm.

Chance of MVFR in showers through tonight.

OUTLOOK FOR 18Z SATURDAY THROUGH WEDNESDAY

Saturday PM: VFR. N winds G25-30kt, diminishing in the evening.

Sunday-Monday: VFR.

Tuesday-Wednesday: VFR likely, a chance of MVFR in -shra and a chance of NE wind G25-30kt.

Detailed information, including hourly TAF wind component forecasts, can be found at: https:/ www.weather.gov/zny/n90

MARINE
Gale watch converted to SCA for all waters, except the outer ocean zones, where the gale watch has been delayed until Saturday night.

Expect a prolonged period of rough conditions, particularly on the ocean waters through the period. A strong cold frontal passage this evening will result in a strong N flow later tonight through Saturday. Winds diminish some Saturday night on the non-ocean waters and the remaining waters on Sunday.
However, due to low pressure nearly stationary along the Mid Atlantic Sunday into next week, there is the potential for gales on the ocean and SCA conditions elsewhere.

OKX WATCHES/WARNINGS/ADVISORIES
CT...Freeze Watch from late Saturday night through Sunday morning for CTZ005>008.
NY...Freeze Watch from late Saturday night through Sunday morning for NYZ067-068.
NJ...Freeze Watch from late Saturday night through Sunday morning for NJZ002.
MARINE...Small Craft Advisory until 6 PM EDT Saturday for ANZ331-332- 340-345.
Small Craft Advisory until 6 PM EDT Saturday for ANZ335-338.
Small Craft Advisory until 11 AM EDT Sunday for ANZ350-353-355.
Gale Watch from Saturday evening through Sunday morning for ANZ380-383-385.