Marine Weather and Tide Forecast for Glastonbury Center, CT

NEAR TERM /UNTIL 6 PM THIS EVENING/

Key Points:

* Slow-moving Thunderstorms will bring heavy rain, scattered flash flooding, and isolated severe wind gusts to the western interior

* Seasonably warm and humid conditions again today

Today starts off very similar to the last few days with low stratus and light fog this morning, burning off within a few hours after sunrise. High temperatures stay seasonal in the mid-80s today with partly sunny skies. Dewpoints rise into the low to mid 70s today, making it feel very muggy.

Flash Flood Threat:

A flood watch is in effect from noon to midnight today for the CT river valley and west into the Berkshires. A weak shortwave trough and frontal system will be the focus for slow-moving thunderstorms today across the western interior. The environment is primed for very heavy rain and scattered flash flooding as PWATS jump to 2 inches with dewpoints in the 70s. There will be very efficient rain processes with warm cloud depths around 13-14kft with long skinny cape profiles. Steering winds aloft are very weak, on the order of 20-30 knots from the WSW. What that means is that storms will be very slow-moving and may train over the same spots for extended periods of time. Although the highest probabilities lie southwest of SNE, the HRRR highlights far western MA and CT for 3 inches of rain in 3 hours. The href also highlights the far western interior with moderate probs (15-30%) for rainfall totals to exceed 5-year ARIs. The flash flood threat drops quickly to the southeast of the flood watch as storms will run out of instability and diurnal heating by the time they exit the CT river valley.

Severe Threat:

The best axis of instability lines along a SW to NE line in the far western interior with roughly 1000-1500 J/kg. Even with little to no shear, there is a chance for wet microbursts, mainly in western MA. Thunderstorm updrafts will become very hydro-loaded and will likely drop their cores on top of the updrafts. Steep low-level lapse rates near 10 °C km mean the momentum of the precip cores will easily continue to the surface. With freezing levels around 14-15 kft, hail is unlikely as any frozen precip will melt before reaching the surface. While the environment is not supportive of rotating updrafts, the one wild card would be if any thunderstorms can hook onto outflow boundaries. 0-3km CAPE values are around 130 J/kg, which just might be enough to spawn a brief landspout should an outflow boundary be able to create enough low-level spin. The severe threat will remain confined to the northwestern interior as Cape values drop off quickly to the southeast.

Timing of thunderstorms:

Guidance is still somewhat mixed regarding convective initiation placement and timing, but the general consensus seems to be that a line of thunderstorms will form near the high terrain in eastern NY or western MA around 2-4 pm. Storms then slowly move east through about 8-10 pm, weakening as they move southeast past the CT River Valley.

SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/

Key Points:

* Warm and muggy conditions continue tonight

* Hot and humid conditions begin Tuesday

Tonight:

The frontal system will not bring any relief to the humid conditions, with lows bound by dewpoints remaining in the low 70s.
Low stratus and fog will form once again, especially in areas that receive rainfall during the afternoon.

Tuesday:

Hot and humid conditions are expected to return starting Tuesday, with high temperatures rising into the upper 80s to low 90s and dewpoints in the low 70s. The heat index values currently look like they will fall just short of 95, but with heat indices likely above 95 for Wednesday, heat advisories may be needed starting Tuesday.
Most model guidance sources keep the region dry as a weak mid-level ridge builds in. However, the NSSL WRF does have some convection breaking the mid-level CAP.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/
Key Messages:

* Hot and humid during the middle of next week, with elevated heat indices around 95-100F. Heat Advisories likely for at least Wed & Thur

* Becoming more unsettled late Thursday-Friday with increasing chances for showers/storms.

Wednesday-Thursday:

Heat and Humidity...

Weak mid-level ridging persists over the region Wednesday with more zonal flow arriving Thursday. Temperatures aloft increase with 850mb temperatures peaking at around 20C in the Weds- Thurs timeframe. Ensemble guidance shows a plume of above normal moisture in the flow which will add increased humidity to the mix. Temperatures Wednesday through at least Thursday will range in the upper 80s to mid 90s with the exception of the immediate coast. With the the added element of higher humidity, it will feel more like mid 90s to near 100 Wednesday and Thursday. This combo provides a good signal for potential heat impacts. NWS Heat Risk reflects this potential well with Heat Risk in the Major Category Wednesday and Thursday. There is a high probability that we will need Heat Advisories for Wednesday and Thursday. We'll need to keep an eye on cloud cover for Thursday as this may limit highs a bit. Friday may also end up being a hot day as well with ensembles showing little change in the temperatures aloft with again a similar risk of clouds limiting high temperatures.

Precipitation...

Wednesday stay mainly quiet when it comes to the passage of any substantial system. Despite a weakly forced atmosphere, above normal moisture, hot temps, and marginal daytime instability will support isolated shower activity. Ensemble members are still spread across the board with timing and given the low coverage nature of the showers and lack of definitive forcing.
This has made it it bit more difficult to message in the forecast. Overall, expect a tropical-like atmosphere with periods of higher cloud cover and perhaps a spot shower.

There will be a better signal for more organized forcing later Thursday and a weak trough shifts in from the west. This will bring higher chances for more widespread showers/storms. Weak winds aloft will support slower storm motions and given the high amounts of moisture signal a threat for flash flooding. We'll have to keep eyes on that as we go through the week.

Friday-Weekend:

Ensemble guidance shows the main axis of the trough pushing across the region by early Saturday. Similar story to Thursday with increased chances for showers/storms later Friday ahead of an approaching cold front. Winds aloft are slightly higher than Thursday, but slower moving storms still look to bring a potential threat for flash flooding. Friday may be another potentially hot day. Ensemble members show more of a wider envelope of solutions for temperatures Friday. However, there are still plenty of very warm members that would support another Heat Advisory criteria given the humidity. We'll have to watch cloud cover as this could keep it cool enough to not meet Advisory criteria.

Behind the trough, conditions dry out through the day on Saturday.
Ensembles hint at potential for another system later Sunday, although confidence is low this far out.

AVIATION /07Z MONDAY THROUGH FRIDAY/
Forecaster Confidence Levels...

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

Rest of Tonight: High Confidence

IFR/LIFR CIGS build north again tonight with continued ESE flow.
The stratus should have similar timing to last night (02-06z).

Monday: Moderate Confidence

Low stratus and fog burn of gradually after sunrise, similar to the last couple of days. VFR by mid to late morning. A line of slow moving showers and thunderstorms forms or moves into western MA and CT in the mid to late afternoon, continue to move east through about 10pm to midnight. How far east convection gets is still uncertain, with terminals inside the I-95 corridor possibly being spared.

Monday Night: Moderate Confidence

After remaining showers and thunderstorms dissipate, winds turn SSW brining in yet another round of low stratus and fog. Highest confidence near the south coast and CT river valley. Less certain in and around Boston.

Tuesday: Moderate Confidence

VFR outside the Cape and Islands where IFR stratus may hang on much of the day. Low chance for a weak shower or thunderstorm.

KBOS Terminal...Moderate confidence in TAF.

Stratus deck is not quite as low or expansive as the last couple nights, and may burn of quicker this morning, perhaps lifting by 12z, then VFR around 14-15z. Thunderstorms will struggle to reach the terminal this evening, likely just left over showers, thus have downgraded the prob30 -tsra to -shra for now.

KBDL Terminal...Moderate confidence in TAF.

MVFR stratus deck becoming IFR before sunrise. The stratus deck took longer then anticipated to burn off yesterday, however, winds turn more SSW today which should allow it to lift mid morning. VFR this afternoon with slow moving heavy showers and thunderstorms.

Outlook /Tuesday Night through Friday/...

Tuesday Night: VFR.

Wednesday: VFR. Slight chance SHRA.

Wednesday Night: VFR. Slight chance SHRA, slight chance TSRA.

Thursday: VFR. Breezy. Chance TSRA, slight chance SHRA.

Thursday Night: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

Friday: VFR. Chance SHRA, chance TSRA.

MARINE
Forecaster Confidence Levels...

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

Today through Tuesday...High confidence.

Weak pressure gradient will keep winds/seas below Small Craft Advisory thresholds through Sunday: seas 2-3 ft with E winds over the southern waters and SE winds over the eastern waters up to 15 kts during the afternoon hours, remaining light in the overnight hours. Main concern for mariners will be areas of fog tonight that may redevelop again tonight. Inland Thunderstorms are unlikely to affect the waters this evening. Winds turn more SW on Tuesday between 10-15 knots.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Wednesday Night: Winds less than 25 kt.

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers, slight chance of thunderstorms.

Thursday Night through Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, slight chance of thunderstorms.

BOX WATCHES/WARNINGS/ADVISORIES
CT...Flood Watch from noon EDT today through this evening for CTZ002.
MA...Flood Watch from noon EDT today through this evening for MAZ002-003-008>011.
RI...None.
MARINE...None.