Marine Weather and Tide Forecast for Great Barrington, MA

KEY MESSAGES
1) Confidence is high for above normal temperatures and increasing humidity through Friday. While there remains some uncertainty regarding exact heat indices, the best chance to reach heat advisory criteria (95-104F) will be Thursday and Friday for portions of the Hudson and/or Mohawk Valleys.

2) There is a Marginal Risk (level 1 of 5) for severe thunderstorms mainly west of the Hudson Valley on Wednesday and Thursday. Severe storms are also possible on Friday, mainly in eastern New York. Locally heavy rainfall also expected with thunderstorms this week.

3) A cold front will bring slightly cooler temperatures over the weekend, with noticeably lower humidity levels.

DISCUSSION
KEY MESSAGE 1...

An anomalously warm airmass with 850 mb temperatures running +1 to +2 STDEV, will persist through the rest of the work week.
While humidity levels will rise, they will still be relatively comfortable today with dewpoints mainly in the 50s. There should be plenty of sunshine today under the 500 mb ridge axis, with just high level cirrus clouds passing through filtering the sun.
Highs should reach the mid/upper 80s in most valley locations.
Temperatures will be slightly cooler Wed, with more clouds and showers/T-storms developing although dewpoints look to rise well into the 60s making it feel more humid.

More substantial heat and humidity builds on Thu, as a warm front lifts well north of the area. Highs expected to reach the upper 80s/lower 90s in valleys with heat indices of 95-100F in parts of the mid Hudson Valley/S. Taconics. Fri looks to be the peak of the heat and humidity, with highs in the lower 90s in most lower elevations and heat indices in the mid 90s to lower 100s in much of the Hudson Valley, Mohawk Valley, S. Taconics and even parts of S. Berkshire and Litchfield counties. There is some uncertainty in the magnitude of high temperatures with possible convection in the afternoon.

KEY MESSAGE 2...

After another dry day today, chances for showers and some T-storms will increase on Wed associated with an upper level disturbance and surface warm front. SBCAPE from HRRR mainly in the 500-1000 J/Kg range, with the greatest values west of the Hudson Valley. This is where a Marginal Risk (level 1 of 5) of severe storms has been introduced by the Storm Prediction Center. 0-6 km shear does look fairly weak ~20 kt, so the probability of severe storms is low from the Hudson Valley east.
Some downpours will occur within any convection with PWAT anomalies increasing to +1 to +3 STDEV.

On Thu, there is a conditional threat for severe storms. With building heat and humidity in wake of the warm front, more significant instability is expected to build with most guidance showing SBCAPE of 1500-2000 J/Kg. NAM is a max outlier due to Td likely too high. Deep layer shear and synoptic scale forcing are lacking though due to broad upper level ridging. There is a subtle disturbance seen in the guidance, so if storms can break through the cap, there could be isolated damaging wind gusts/large hail with steepening mid level lapse rates due to an EML moving overhead. SPC has issued a Marginal Risk (level 1 of 5) for roughly the same areas as Wednesday.

Better synoptic scale forcing is anticipated ahead of a cold front approaching from the west, but the timing looks more delayed compared to prior forecasts. With heat/humidity peaking, there will likely be moderate SCAPE of at least 1500-2000 J/Kg again. With the slower approach of the cold front, deep layer shear looks to remain weak, but storms could produce wet microbursts given the high-PWAT environment. SPC has issued a Day 4 equivalent Slight Risk (level 2 of 5) for eastern NY with a 15-29% chance of severe storms.

KEY MESSAGE 3...

While temperatures still look above normal over the weekend, there will be some relief to the heat and humidity starting Sat.
Highs should reach well into the 80s, but dewpoints will be noticeably lower so heat indices should be below 90F.
Temperatures and humidity levels look similar on Sun, so it will be warm again but not oppressively hot/humid. Cooling trends expected to continue into early next week associated with an upper level trough gradually moving in from the west.

AVIATION /09Z TUESDAY THROUGH SATURDAY/
Through 12z Wednesday...Flying conditions remain VFR at ALB/POU/PSF as of 5:55 AM EDT, but GFL continues to see some intermittent IFR vsby reductions due to patchy fog/mist. This fog/mist should dissipate within the next hour or so. Then, all terminals will see VFR conditions through the rest of the TAF period. Just a few mid and high clouds expected today, with BKN mid-level cloud deck around 5000 ft developing by late tonight. A few isolated showers are also possible towards the tail end of the TAF period, so have mentioned VCSH at all terminals after 09-10z tonight. Winds will be light and variable to start the day, increasing to 5-10 kt from the S/SW by mid-morning and lasting through around sunset tonight. Winds tonight become light and variable again at GFL/POU/PSF. but remain at 5-10 kt from the S/SE at ALB.

Outlook...

Wednesday Night: High Operational Impact
Definite SHRA
TSRA.
Thursday: Moderate Operational Impact
Chance of SHRA
TSRA.
Thursday Night: Moderate Operational Impact. Chance of SHRA.
Friday: Moderate Operational Impact
Chance of SHRA
TSRA.
Friday Night: High Operational Impact
Likely SHRA
TSRA.
Saturday: Low Operational Impact. Slight Chance of SHRA.
Saturday Night: No Operational Impact. NO SIG WX.
Sunday: Moderate Operational Impact
Chance of SHRA
TSRA.

ALY WATCHES/WARNINGS/ADVISORIES
CT...None.
NY...None.
MA...None.
VT...None.