Very Heavy Rain Tomorrow

Good evening! Update post regarding the multi-hazard system tomorrow. I may do an update on the Friday and weekend rain threats later this evening; HOWEVER, I felt it was necessary to get the more immediately important info out first.

Rain/Flooding

This will be a big rainmaker, and the big story among this mess as well, with an area of low pressure in the Mid-Atlantic and a cold front nearthe west edge of precipitation. Rain will continue to move into the region through the evening – current doppler:

Capture

The rain will continue throughout the day tomorrow, heaviest in the northern two thirds of New England, and continue overnight Wednesday night before tapering off early Thursday morning to scattered showers throughout Thursday. When all is said and done, expect a widespread 2-5″, with locally higher totals, especially in Maine. There may be less than 2″ in the southern half of Southern New England.

In the areas of high vertical velocity (pink), expect very heavy rain at times – map valid for 2 PM tomorrow:nam_rapid-vvelprs-700-nepoolnerc-24-C-000

This will likely lead to some urban flooding problems, as well as problems in poor drainage and low-lying areas. The smaller and faster-responding rivers and streams could also see some issues. I am not expecting any issues in the main stem rivers, such as the Merrimack River and the Connecticut River. Do not drive your vehicle into areas where water covers the road. Move to higher ground if necessary. An areal flood watch is in effect for much of New England:

Capture2

Additionally, with very heavy rainfall in some spots, there is a concern for some flash flooding, with the very heavy rain around midday (also in the morning). Combined with the morning commute, this could become a serious situation.

Thunderstorms/Severe Weather

This is not a huge concern. Even though there are still some good shear and helicity values, which would often indicate a strong risk for damaging winds and perhaps an isolated, brief tornado, instability is going to be quite low tomorrow, which should limit severe weather chances tomorrow, even with decent lapse rates modeled. However, there may be enough instability to fire off a few embedded thunderstorms, with very heavy rain which could lead to additional flash flooding. As noted, favorable shear and helicity values are there, meaning the potential for strong to damaging winds and maybe a very isolated, very short-lived and weak tornado somewhere. It’s not likely, though, considering things against it.

Wind

This storm, by itself, will not be much of a wind maker for much of the duration. Just a little on the windy side. Onshore winds 10-20 mph, gusts to 25 mph. Winds could become an issue in the evening, mainly near the coast, with gusts of 30-40 mph possible Wednesday evening through Friday as the bulk of the rain begins leaving. An exception to this would be within any thunderstorms or stronger showers, with strong winds possible, and MAYBE a localized damaging gust as noted in the severe section above.

Coastal Flooding

There could be minor coastal flooding issues at the time of astronomical high tide Wednesday morning, mainly along the coast of southeast Massachusetts and coastal Rhode Island as well as the NH/Maine coast, with increasing seas and wind. More coastal flooding issues are possible at the high tides Wednesday evening and Thursday. A coastal flood advisory is in effect for south coastal MA/coastal RI, and a coastal flood watch for the NH/Maine coast to near Portland.

Current NWS Alerts

Areal Flood Watch for NW CT/Far Western MA/Southern VT; Areal Flood Watch for Central VermontAreal Flood Watch for Western/Central/NE MA, and Northern CTAreal Flood Watch for NH and Western MaineAreal Flood Watch for Eastern Maine; Coastal Flood Watch for NH/Maine Coast to Just East of PortlandCoastal Flood Advisory for South Coastal Southeast MA and Coastal RI. Colors are clickable links.

Have a good evening!

-Nathan

Significant Rain Likely – Warm Day First

Good morning! Let’s just cut to the basics of today’s forecast, because we have a significant rain event on the horizon.

Today will be partly sunny to start with increasing clouds throughout the day, and pretty much the exact same high temps as yesterday, maybe a nudge cooler. 70-80, region-wide, locally cooler in the highest elevations, a hair warmer in some spots in CT and perhaps isolated spots in eastern MA, with south winds to 10 mph again. Some isolated showers with a widely isolated rumble of thunder may occur late this morning into this afternoon, with eventually full-on widespread rain entering this evening into overnight tonight.

Let’s get into a discussion of hazards with this storm.

Timing

Let’s start with the timing for this storm. The widespread shield of rain will enter the region sometime this evening into the early overnight. A true washout is expected throughout New England tomorrow, no way around it. Precipitation will finally leave the region Thursday, probably around midday.

Rain/Thunderstorms/Flooding

A widespread 2-4″ of rain is likely across New England, with locally higher amounts possible within embedded thunderstorms, which will be possible due to elevated instability, particularly across Southern New England and adjacent Southern NH, starting Wednesday morning and continuing throughout the day. That instability will be on the elevated side, but it will not be high CAPE by any means; however, rather good shear is in place, meaning a strong to maybe even embedded severe thunderstorm is not out of the cards: (both images below are for the same time, at 1 km and 3 km. Not pictured, but 6 km shear is also rather strong).

nam---usne-36-C-shear0-3km_whitenam---usne-36-C-shear0-1km_white

Something interesting to note is there will be high helicity values for many. A spin-up tornado cannot be 100% ruled out; however, this is not an immediate concern, rather an interesting observation.

nam-hel--usne-36-C-hel3000_white nam-hel--usne-36-C-hel1000_white

Lifted index and lapse rates are looking better at the lower levels in the morning, however. More severe updates this evening.

The main story, however, is the 2-4″ of rain. Some of the smaller rivers may see rapid rises, but urban flooding is the main threat (especially in any embedded thunderstorms), as well as poor drainage and low lying areas. Main stem rivers, such as the Merrimack, Connecticut and Charles, should stay in their banks. An areal flood watch is out for a substantial portion of New England for this storm, in dark green on the map below.

watches

Coastal Flooding

Yes, this storm also has a coastal flood threat, even if rather minor. There could be some localized minor splashover during astronomical high tide Wednesday, as a result of increasing seas and said high tide. Wednesday evening, there may be a more significant coastal flood threat, and more coastal flooding is possible through the rest of the week.

Wind

This storm will not be a big wind producer, at least not near the surface. Expect northeast winds 10-15 mph, with highest gusts to 25-30 mph, locally higher in the evening for both sustained and gusts. HOWEVER, the exception will be within thunderstorms, where gusts near or even over 45 mph are possible. Can’t completely rule out an isolated severe wind within those, as mentioned.

Current Alerts: Flood Watch for Southern Vermont/Far Western MA/Northwest CTFlood Watch for Northern CT/Western, Central and Northeast MAFlood Watch for Central VermontFlood Watch for NH and Southwest Maine; Coastal Flood Watch for NH and Southwest Maine Coast.

Have a great Tuesday!

-Nathan

Warmer Day Today

Good morning!

With a south-southwesterly wind up to 10 mph and partly sunny skies, temperatures will be between 74-80 for much of New England; cooler in the highest elevations of northern New England, and scattered warmer spots in Connecticut and the CT River area in MA.

I’ll be back this evening with an update on the rain threat Tuesday PM into Thursday. Have a great day!

-Nathan

Chilly Start, Strong Bounceback

Good morning!

After much of New England got into the 30s last night, with even scattered locations in eastern MA getting below freezing, a nice bounceback will be on tap today. With south-southeast winds up to 10 mph and sunny skies (clouds moving in to southwest New England this evening), temperatures will be in the range of 65-73 for most of New England. There will also surely be some cooler spots, 60-65 in most of these, in some widely scattered areas of Northern New England (mainly northern Maine).

Have a great day!

-Nathan

Fall Weather Continues

Good morning!

Today will be mostly sunny with highs in the 60s throughout New England. The same onshore flow will prevail, with wind up to 10 mph for most, slightly higher at the coast.

Have a great Saturday!

-Nathan

High Pressure Still Dominates

Good morning!

Today will be a little cooler than yesterday – highs in the 60s for most, with some scattered upper 50s in northern Maine, scattered 70s in eastern MA and more widespread low 70s in Connecticut. This will be under mainly sunny skies and a light onshore flow.

Have a great Friday!

-Nathan

(Mostly) A Repeat of Yesterday

Good morning!

As high pressure stays in control, under sunny skies and a generally light onshore wind, temperatures will be in the upper 60s to mid 70s for most with upper 50s-low 60s in northern Maine and upper 70s in most of CT.

Have a great day!

-Nathan