7:00 AM | After another nice weekend, the weather gets more unsettled with the approach of another cold front

6-Day Forecast

Today

Mostly sunny, breezy, hot and more humid, highs in the lower 90’s

Tonight

Partly cloudy, mild and muggy, lows in the low-to-mid 70’s

Tuesday

Partly sunny, hot, humid, chance for showers and thunderstorms, low-to-mid 90’s

Tuesday Night

Mostly cloudy, mild, muggy, chance for showers and thunderstorms, low 70’s

Wednesday

Mostly cloudy, a little less hot, humid, still the chance for showers and thunderstorms, near 90

Thursday

Mostly sunny, warm, mid 80’s

Friday

Partly sunny, warm, mid 80’s

Saturday

Partly sunny, warm, maybe a late shower or thunderstorm, mid-to-upper 80’s

Discussion

After another pleasant weekend in the Mid-Atlantic region, the weather will become hotter and more humid today and the threat for showers and thunderstorms will return later tomorrow and some of those storms can be on the nasty side. High pressure will works its way to the east today and this will open the door for hotter and more humid air to push in from the southwest. Another cold front will approach the region later tomorrow night and Wednesday enhancing the chances for showers and thunderstorms. It should move far enough to the south of the area to allow for the return of high pressure on Thursday and Friday with moderately warm temperatures returning to the region.

Video

httpv://youtu.be/h29wgIrDeQY

7:00 AM | Drier air pushes in today as Hurricane Arthur accelerates away from the east coast leading to another nice weekend

6-Day Forecast

Today

Becoming partly-to-mostly sunny, breezy, cooler and less humid during the afternoon hours, highs in the low 80’s

Tonight

Mostly clear, quite comfortable, lows near 60 degrees

Saturday

Mostly sunny, pleasant, low-to-mid 80’s

Saturday Night

Mostly clear, cool, near 60

Sunday

Mostly sunny, nice, mid 80’s

Monday

Mostly sunny, quite warm, near 90

Tuesday

Partly sunny, hot, more humid, chance for showers and thunderstorms, low 90’s

Wednesday

Partly sunny, hot, humid, chance for showers and thunderstorms, near 90

Discussion

Hurricane Arthur is still pounding the Outer Banks of North Carolina early this morning, but it will accelerate to the northeast today sparing the Mid-Atlantic coastline from the brunt of its effects as it slides a couple hundred miles to the east. In fact, the tropical system will move so quickly as the day progresses that drier air will push into the I-95 corridor region and the weekend will turn out to be quite nice with a refreshing air mass pushing in from the Midwest.

3:00 PM | ***Powerful storms headed towards the I-95 corridor***

Discussion

The mid-afternoon radar map is much more active than just a couple of hours ago as indeed upper-level energy is fueling the development of strong-to-severe thunderstorms to the west of I-95. These storms are expanding in coverage and increasing in intensity and are now crossing over the higher elevation locations of central PA, eastern West Virginia and western Virginia. The most likely timetable for these severe thunderstorms to reach the big city regions along I-95 is as follows:

3-8PM in DC, 4-9PM in Philly, and 5-10PM in New York City.

These storms can cause damaging wind gusts, hail, and torrential downpours with flash flooding due to excessive amounts of rainfall in a short period of time. Also, clearly visible on this recent NEXRAD radar image are the spiraling bands spinning around Hurricane Arthur near the Carolina coast which is closing in on the Outer Banks (NEXRAD radar map courtesy University of Wisconsin).

12:00 PM | ***More torrential downpours and severe storms around here later this afternoon and tonight...an update on Hurricane Arthur***

[Simulated radar loop; courtesy Weather Bell Analytics at weatherbell.com]

Discussion

Hurricane Arthur intensifies Arthur continues to slowly intensify as it heads to the North Carolina coast having reached hurricane status in the overnight hours. The 11am readings on the storm are as follows: 90 mph max sustained winds, movement to the NNE at 10 mph, central pressure is now down to 28.97 inches. The category 1 hurricane could very well reach category 2 status before it reaches the Outer Banks of North Carolina later tonight as some additional strengthening is likely. Wind gusts of 100 mph are possible late tonight and early tomorrow on the Outer Banks as Arthur passes overhead. Arthur will begin to accelerate tonight as it turns to more of a northeasterly direction and its forward speed will continue to increase on Friday as it moves to higher latitudes. The simulated radar reflectivity for the next several hours (above) shows the heavier rain bands reaching the southern sections of the Outer Banks by early tonight (evacuations are underway). This simulated radar data is produced by an experimental high-resolution (3-km) computer forecast model at NOAA called the “High Resolution Rapid Refresh (HRRR)” [radar maps courtesy Weather Bell Analytics at weatherbell.com]. If Arthur makes landfall in the U.S. on Friday, it would be the first hurricane to do so on the Fourth of July, according to National Hurricane Center research that goes back to the 1850s.

Threat continues here for torrential downpours and severe thunderstorms A very slow moving cold front will creep to the east coast by later today and this boundary zone will combine with an entrenched moisture-laden air mass, an upper-level short wave, and additional tropical moisture streaming northward from Arthur to produce off and on torrential downpours in the I-95 corridor from DC-to-Philly-to-NYC later today and tonight. In similar fashion to yesterday, showers and thunderstorms will begin to form during the mid-day hours over the higher terrain sections of central and western Pennsylvania, West Virginia, and western Virginia. Aided by lifting from an intensifying upper level jet streak, this initial area of showers and thunderstorms will then expand in coverage and intensity as the afternoon progresses resulting in widespread coverage by late in the day as the rainfall rolls to the east. Any storm that forms later today can reach severe levels with damaging wind gusts, hail and flash flooding due to an excessive amount of rainfall in a short period of time. The threat for torrential downpours in the I-95 corridor will continue through most of the night and then showers could linger into the morning hours on Friday as Arthur moves by well to the east of the Mid-Atlantic coastline. Drier air will push in later Friday as Arthur accelerates to the northeast to a position off of the New England coastline and then Saturday and Sunday will turn out to be great weather days throughout the Mid-Atlantic region. Rough surf and rip currents, however, could linger through the upcoming weekend in Mid-Atlantic coastal waters.

[Latest NEXRAD radar image showing initial showers/storm development over higher terrain sections of PA, WV and VA; image courtesy University of Wisconsin]

7:00 AM | **Threat for heavy rain continues right through tonight; Arthur now a hurricane**

[Latest visible satellite image of Hurricane Arthur]

6-Day Forecast

Today

Mostly cloudy, not as hot, very humid, showers and thunderstorms likely; primarily, during the afternoon hours, some of the rain can be heavy at times, highs not far from 90 degrees

Tonight

Mostly cloudy, mild, muggy, showers and thunderstorms likely, some of the rain can be heavy at times, lows near 70 degrees

Friday

Early clouds give way to sunshine, windy and cooler, low 80’s

Friday Night

Mostly clear, pleasant, near 60

Saturday

Mostly sunny, pleasant, low 80’s

Sunday

Mostly sunny, nice, mid 80’s

Monday

Mostly sunny, quite warm, upper 80’s

Tuesday

Mostly sunny, hot, more humid, chance for showers and thunderstorms, low 90’s

Discussion

Severe thunderstorms raked much of the Mid-Atlantic region last night with thousands losing power and the atmosphere will remain very unstable through tonight. A frontal system along the east coast will combine with tropical moisture from Arthur to produce heavy downpours in the I-95 corridor right through tonight and some of the thunderstorms that form will be severe with damaging wind gusts and flooding rainfall. Arthur has intensified overnight into a category 1 hurricane and it will slam into the Outer Banks of North Carolina by early Friday - possibly as a category 2 hurricane with nearly 100 mph wind gusts. At this point in time, Arthur will accelerate to the northeast and slide a couple hundred miles east of the Mid-Atlantic coastline later in the day on Friday. Drier air will return to the I-95 corridor by later Friday - most likely in time to allow for fireworks shows to go on as scheduled tomorrow night although there will be a breeze. A refreshing air mass will follow in the Mid-Atlantic region this weekend following the departure of Arthur; Saturday and Sunday should turn out to be great weather days.

Video

httpv://youtu.be/IDiZSS30JKU

12:15 PM | **Impressive severe thunderstorm threat here later today/tonight...latest on Tropical Storm Arthur**

Discussion

Impressive severe thunderstorm threat I am very impressed with the severe thunderstorm threat around here for later today and early tonight. The atmosphere is extremely unstable and while the radar is currently not all that active at this time, it is likely to explode with activity in the next few hours. There are several stability indices that are pointing to the region between DC and NW NJ as prime areas of instability. One such measurement of the stability of the troposphere is called the surface-based “Convective Available Potential Energy (CAPE)” and it has very high values of up to 4000 J/KG showing up right now across DC, eastern PA, and western New Jersey. Lines of thunderstorms are likely to form over the next couple of hours from north-central PA to eastern West Virginia then roll eastward. Any storm that reaches the I-95 corridor later today and tonight can produce damaging wind gusts, torrential downpours and hail. The National Weather Service currently does not have a severe thunderstorm watch up for the I-95 corridor region, but that could (and should) happen later today. The threat continues on Thursday and Thursday night for more heavy rainfall and strong thunderstorms in the I-95 corridor.

Tropical Storm Arthur Arthur is now a strong tropical storm with sustained winds at 60 mph. It is moving slowly to the north at 7 mph and will intensify rapidly tonight and Thursday. The current pressure is down to 29.44 inches and that should drop rather sharply over the next 24 hours. Arthur could very well reach hurricane status – perhaps even category 2 - before directly impacting the Outer Banks of North Carolina late Thursday into early Friday. After Arthur reaches northeastern North Carolina, it will take a turn to the northeast and ride a couple of hundred miles off the Mid-Atlantic coastline later Friday. Showers could linger around here into the morning hours on Friday, but drier air should return by Friday night - Saturday and Sunday look like great weather days in the Mid-Atlantic region.

7:00 AM | **Heavy rain threat from later today into early Friday from combination of front and tropical moisture**

6-Day Forecast

Today

Mostly sunny, hot, humid, showers and thunderstorms possible late, some of the rain can be heavy at times, highs in the mid 90’s

Tonight

Mostly cloudy, mild, muggy, showers and thunderstorms likely, some of the rain can be heavy at times, lows in the mid 70’s

Thursday

Mostly cloudy, not quite as hot, still humid, showers and thunderstorms likely, some of the rain can be heavy at times, near 90

Thursday Night

Mostly cloudy, mild, muggy, showers and thunderstorms likely, some of the rain can be heavy at times, near 70

Friday

Early clouds and possible showers then becoming partly sunny, windy, cooler, low 80's

Saturday

Mostly sunny, pleasant, low 80's

Sunday

Mostly sunny, nice, mid 80’s

Monday

Mostly sunny, warm, upper 80’s

Discussion

The combination of a tropical system along the east coast and a slow-moving strong cold frontal system approaching from the west will lead to occasional heavy downpours in the I-95 corridor from later today into early Friday. A weak tropical disturbance intensified on Tuesday reaching tropical storm status (now named Arthur) and it could very well reach hurricane status upon reaching the Outer Banks of North Carolina later Thursday into early Friday - perhaps even to category 2. Showers and thunderstorms will increase in coverage and intensity around here later today and continue off and on during Thursday and Thursday night as a frontal system closes in on the east coast at the same time tropical moisture pushes northward along the coast. The combination of the front and tropical moisture will help to generate at least a couple inches of rain around here by the time fireworks shows take place on Friday evening - should be dry weather by then. Given the expected timing and track of Arthur, very nice weather conditions should return here for Saturday and Sunday as a refreshing air mass follows the departure of the tropical system.

12:30 PM | ***Hurricane threat for the Outer Banks and heavy rain coming here from later Wednesday into Friday***

[Latest NOAA GOES East visible satellite image of Tropical Storm Arthur]

Discussion

First the good news…Saturday and Sunday look like they’ll be quite nice in the Mid-Atlantic region with plenty of sunshine and pleasant temperatures. Now the bad news…there will be heavy rain to deal with around here before we get to the weekend as a strong slow-moving frontal system interacts with tropical moisture along the east coast from what is likely to become the first hurricane of the season.

Sea surface temperatures (SST) continue to run at warmer-than-normal levels (see latest SST anomaly map below) off the east coast of the US and this may result in more “home-grown” type systems this tropical season that develop close by as compared with the “African-wave” type of tropical system that travels a long distance across the Atlantic Ocean. Indeed, a tropical disturbance meandering off the east coast of Florida has intensified into tropical storm status (named Arthur) over the unusually warm waters off the southeast US coastline. This system will likely reach hurricane status by the time it reaches the Outer Banks of North Carolina later Thursday into early Friday. Arthur is the latest first named tropical storm since 2004 when Alex formed on July 31st and that storm coincidentally took a track quite similar to what this one is likely to do.

[Unusually warm waters off the Southeast coastline]

A strong cold front from the middle of the country will slowly close in on the east coast during the next couple of days and - as tropical moisture interacts with the front - heavy downpours are likely to break out along the I-95 corridor from DC-to-Philly-to-NYC in the time period from later Wednesday into Friday. After Arthur directly impacts the Outer Banks, it will likely push northeastward to the east of the Mid-Atlantic coastline on the 4th of July (Friday) on its way to the New England coastal waters by late Friday night/early Saturday. This timing and current estimated storm track should allow for nice weather to return to the Mid-Atlantic region on Saturday and Sunday although rough surf may linger for awhile in the Atlantic Ocean.

7:00 AM | **Heavy rain threat later this week as front combines with tropical moisture; disturbance off of Florida could become the season's 1st hurricane**

6-Day Forecast

Today

Partly sunny, hot, humid, chance for late day showers and thunderstorms, highs in the low 90’s

Tonight

Mostly cloudy, mild, muggy, chance for showers and thunderstorms, lows in the mid 70’s

Wednesday

Partly sunny, hot, humid, showers and thunderstorms likely late, some of the rain can be heavy, low-to-mid 90’s

Wednesday Night

Mostly cloudy, mild, muggy, showers and thunderstorms likely, some of the rain can be heavy, near 75 for lows

Thursday

Mostly cloudy, not as hot, humid, showers and thunderstorms likely, some of the rain can be heavy, near 90

Friday

Partly sunny, cooler, showers and thunderstorms still possible early in the day, low 80’s

Saturday

Mostly sunny, pleasant, low 80’s

Sunday

Mostly sunny, nice, low-to-mid 80’s

Discussion

The combination of a tropical system along the east coast and a slow-moving strong cold frontal system approaching us from the west will likely lead to heavy downpours in the I-95 corridor from late Wednesday into Friday. While there can be a few showers and thunderstorms late today in the Mid-Atlantic region, a greater chance will occur late Wednesday and then again on Thursday as the front gradually closes in on the east coast. In the meantime, a tropical disturbance now off the east coast of Florida is likely to become the first named storm of the Atlantic Basin tropical season (Arthur) as it slowly rides up along the east coast. This tropical system - which could very well ultimately reach hurricane status - will have a big impact on the Outer Banks of North Carolina by the 4th of July. After that, it is likely to turn to the northeast to a position to the east of the Mid-Atlantic coastline by late in the week and then it should clear out of here in time for a very nice Saturday and Sunday.

Video

httpv://youtu.be/Q5HN-RGKuXo

1:00 PM | ***An update on the late week heavy rain threat and east coast tropical system***

[Low-level "weenie" circulation center seen at end of arrow; image courtesy NASA]

Discussion

Sea surface temperatures continue to run at warmer-than-normal levels off the east coast of the US and below-normal in the region between the west coast of Africa and the Caribbean Sea. As a result, this Atlantic Basin tropical season may very well feature more in the way of “home-grown” tropical systems that develop close by as compared with the “African-wave” type of tropical system that travels a long distance across the Atlantic Ocean. Indeed, a weak disturbance now meandering off the east coast of Florida may become just such a “home-grown” type of system that forms nearby over the unusually warm waters off the southeast US coastline.

This disturbance currently features a rather puny looking low-level circulation center (see satellite image; courtesy NASA) and a somewhat disorganized overall appearance with thunderstorms well displaced to the south of the center. Later this week, however, environmental conditions will improve dramatically for substantial intensification and there is a very good chance that this will become the first named tropical storm of the season (Arthur) and, if so, it would be the latest first named storm since 2004 when Alex formed on July 31st. Furthermore, this system could very well become the first official hurricane of the season by the time the 4th of July rolls around. To make matters even more interesting, a strong cold front from the middle of the country will slowly close in on the east coast during the next few days. This front is likely to stall along the Atlantic seaboard for a brief time late this week and - as tropical moisture interacts with the front - heavy downpours are likely to break out along the I-95 corridor from DC-to-Philly-to-NYC from late Wednesday into Friday. By the way, Saturday is likely to turn out to be a beautiful day around here behind any tropical system that does form with a refreshingly cool air mass for this time of year moving in from the Midwest.

Early looks at potential storm tracks (below; courtesy Weather Bell Analytics) from different computer forecast models suggest that the Outer Banks of North Carolina may get directly affected in the Thursday/early Friday time frame and then the tropical system may slide just to the east of the Mid-Atlantic region. However, no matter what the ultimate tropical storm track is, heavy rain is quite likely in the I-95 corridor with the approach of the strong frontal system and the whole situation still needs to be closely monitored. Also, even without a direct hit in the Mid-Atlantic region, rough surf is possible all the way up the coastline at the end of the week. Stay tuned.

For more on the prospects for this Atlantic Basin tropical season: http://thesiweather.com/2014-tropical-and-mid-atlantic-summer-outlooks/

[Map courtesy Weather Bell Analytics at weatherbell.com]