Marine Weather and Tide Forecast for Grandyle Village, NY

KEY MESSAGES
1) Increasing heat and humidity this week. Heat indices could reach the mid 90s Thursday and Friday.

2) Scattered showers and thunderstorms are expected to return mid- week.

DISCUSSION
KEY MESSAGE 1...Increasing heat and humidity this week. Heat indices could reach the mid 90s Thursday and Friday.

A ridge axis will move across the forecast area today. Warm advection within a developing southerly flow will send temperatures well above normal today with highs in the mid to upper 80s, a few spot could get to 90F across the lake plains and in the Genesee Valley and Finger Lakes. Lower temperatures are expected near the lakeshores.

The warmest days this week appear to be Thursday and Friday as another ridge builds into the region. 850 mb temperatures climb to near +18C and with the combination of an increasingly moist airmass, heat index values could reach in the lower to mid 90s. Heat headlines are possible for some locations during this time period, but confidence is lower with the potential for clouds and scattered convection.

KEY MESSAGE 2...Scattered showers and thunderstorms are expected to return mid-week.

A shortwave trough will approach the region with warm, moist air spreading across the region today and Wednesday, increasing the potential for showers and thunderstorms. Initially, widely scattered showers and thunderstorms are expected to develop as increasing elevated instability moves into western New York today. Dry weather will likely continue east of Lake Ontario.

A surface trough is expected to move through tonight, further increasing chances for showers and a few thunderstorms. A weak mid level disturbance is expected to cross the region Wednesday. Forcing looks limited with this feature, but will encounter and very warm and moist airmass leading to widely scattered thunderstorms during peak heating. Profiles indicated an uptick in shear with a non- zero risk of strong/severe storms, mainly across the Finger Lakes and east of Lake Ontario.

A mid-level ridge within in a warm and moist airmass is expected to build into the region towards the end of the week. Weak impulses embedded in the flow around the ridge could support showers and thunderstorms through Friday. The primary impact from any showers or thunderstorms will be heavy rain, as PWAT values are expected to exceed 1.5", which is above the 90th percentile for this time of year. Drier air is expected to move into the region for the start of the weekend.

AVIATION /06Z TUESDAY THROUGH SATURDAY/
Mainly VFR through the 06Z TAF cycle as surface high pressure settles off the Northeastern coastline.

A weakening shortwave trough will gradually encroach on the Great Lakes from the west today. Mid/high cloud cover will increase this morning with a 5-10kt southerly flow, which will likely preclude any early morning fog development.

The approaching trough may cause widely scattered showers or an isolated thunderstorm to develop west of KROC before 18z. Brief MVFR conditions cannot be ruled out in any showers that manage to develop. Shower/thunderstorm coverage is then expected to increase and spread eastward into this evening.

Outlook...

Tonight...Mainly VFR deteriorating to MVFR/IFR with showers and a few thunderstorms.

Wednesday.. MVFR/IFR gradually improving back towards VFR from west to east. Diminishing chances for showers and thunderstorms across the western terminals.

Wednesday night through Friday...Mainly VFR with a chance of showers and thunderstorms. Localized lower flight CATs within any heavier showers or storms.

Saturday...Mainly VFR. Dry weather.

MARINE
High pressure off the Northeast coast will maintain light winds today with local lake breeze circulations developing.

The passage of a weak low pressure wave will cause southerly component winds to develop tonight and Wednesday with speeds generally less than 15 knots with a light shop developing, but wave heights will remain below 3 feet.

Light to modest west to southwesterly flow will then prevail Wednesday night through this weekend, which may support marginal SCA conditions at times.

The approach of several low pressure waves may generate a few thunderstorms over the lakes at times this week. The most probable timeframe for thunderstorms will be tonight into early Wednesday.

BUF WATCHES/WARNINGS/ADVISORIES
NY...None.
MARINE...None.