1:00 PM | **The stage is set for a major rain event in the Mid-Atlantic region from tonight into early Thursday that could include strong-to-severe thunderstorms**

Discussion

Summary All of the ingredients are in place for a major rain event to affect the Mid-Atlantic region including the DC, Philly and New York City metro regions from tonight into early Thursday and it might include some nasty thunderstorms along the way. Occasional rain or drizzle will fall this afternoon and evening in the Mid-Atlantic region and some of it will be heavy at times. Additional periods of rain on Wednesday and Wednesday night will fall heavily at times and strong-to-severe thunderstorms can bring torrential downpours and damaging winds to the region. By the time the steadiest of the rain pushes off to our north and east early Thursday, it is likely that many areas in the Mid-Atlantic region will have received 3-5 inches of rain from this unfolding event.

Ingredients Ingredient number 1 is a very chilly air mass that is now well entrenched in the Mid-Atlantic region and is anchored by strong Canadian high pressure. Noontime temperatures are way below normal for this time of year with a 48 degree reading at Philly Airport and 51 degrees at Reagan National Airport in DC (normal highs are 68 and 71 respectively). This chilly air mass will act as an important overrunning surface on Wednesday as warmer air tries to advance northward into the region.

Ingredient number 2 is an impressive transport of tropical moisture in the lower levels of the atmosphere right from the Gulf of Mexico towards the Northeast U.S. The latest map of the 850 millibar moisture transport (above) depicts high transport values in the eastern states and a strong flow of air from the Gulf of Mexico towards our area. High values of 850 millibar moisture transport have been connected to heavy rainfall events with convective systems.

Ingredient number 3 is a large, powerful and slow-moving low pressure system currently centered over Iowa. The slow movement of this surface storm is a result of an “omega-shaped” blocking pattern in the upper atmosphere and it ensures an extended period of precipitation in our region which increases flooding potential.

[Latest nationwide NEXRAD radar image; courtesy University of Wisconsin AOSS]

2:00 PM | ***The potential grows for flooding rainfall between late Tuesday night and early Thursday; 3 to 5 inches of rainfall possible in DC, Philly and NYC***

[12Z NAM computer forecast model total rainfall amounts for the upcoming event where the red region from DC-to-Philly-to-NYC represents 3+ inches of rainfall]

Discussion

A rainy stretch of weather will get underway this evening in the Mid-Atlantic region and the period of biggest concern for flooding rainfall will be from late tomorrow night through early Thursday with more than three inches possible in DC, Philly and New York City by the time the steadiest rain moves away from the area later Thursday morning. The combination of a blocking pattern in the upper atmosphere, persistent low-level moist onshore flow, and copious amounts of moisture streaming this way from the Gulf of Mexico will likely cause “flood watches” to be posted by the National Weather Service in the I-95 corridor for the late Tuesday night/Wednesday/Wednesday night time period. There will be periods of rain or drizzle around here from tonight into early tomorrow night, but the heaviest rainfall is likely to develop late tomorrow night and early Wednesday when warmer air begins to push northward into well-established cool ocean air. Thunderstorms will likely break out on Wednesday and any storm that does form can produce torrential downpours for brief periods of time. While the steadiest rain exits the I-95 corridor to the north and east early Thursday, there still can be shower activity later in the day along with a threat for more thunderstorms.

7:00 AM | **Slow-moving system brings us lots of rain this week with the heaviest rainfall centered on Tuesday night and Wednesday**

6-Day Forecast

Today

Thickening clouds, cool, showers likely by late in the afternoon, highs in the low 60’s

Tonight

Cloudy, chilly, periods of rain or drizzle, lows in the upper 40’s

Tuesday

Cloudy, breezy, chilly, periods of rain or drizzle, upper 50’s

Tuesday Night

Cloudy, breezy, chilly, rain, heavy at times, low 50’s

Wednesday

Cloudy, milder, rain, heavy at times, maybe a thunderstorm or two, upper 60’s

Thursday

Mainly cloudy, quite mild, showers still possible, maybe a thunderstorm or two, mid-to-upper 70’s

Friday

Partly sunny, mild, upper 60’s

Saturday

Partly sunny, mild, showers possible, upper 60’s

Discussion

An “omega-shaped” upper level blocking pattern is unfolding early this week and the result will be an extended period of rainy weather in the Mid-Atlantic region and also in much of the eastern half of the nation. The rainy weather pattern will begin later today around here and continue right into Thursday with the heaviest rainfall likely centered on Tuesday night and Wednesday. After a decent start to the week temperature-wise, it'll become much colder-than-normal on Tuesday with highs in the upper 50's at a time when the normal high is around 70 degrees (at Reagan Airport). While the rain can come down hard at times tonight and on Tuesday, it appears that tomorrow night and Wednesday could feature flooding downpours and the chance for strong thunderstorms. By the time Thursday morning rolls around, many areas in the Mid-Atlantic region may very well have received more than 3 inches of rain.

Elsewhere, the deadliest outbreak of tornadoes this year occurred yesterday with more than thirty reported across Oklahoma and Arkansas. There will likely be another tornado outbreak later today - perhaps another twenty or so - likely centered just to the east of those areas hardest hit on Sunday in places like the Tennessee Valley. The good news is that the severe weather threat will diminish significantly after today and another quiet period should return to that part of the country.

Video

httpv://youtu.be/si900iVUFwM

1:45 PM | An "omega-shaped" blocking pattern in the upper atmosphere to cause an extended period of chilly, wet weather next week in the Mid-Atlantic region

Discussion

Tonight, tomorrow and Sunday Rain will move into the I-95 corridor late today and it will come down hard at times this evening and into the overnight hours with more than half an inch likely by early tomorrow morning. While much of tomorrow will be rain-free, another round of showers is likely to move into the Mid-Atlantic region during the afternoon as a frontal system passes through the area. Each of these two systems can also feature an isolated thunderstorm or two mixed in with the overall rainfall. Sunday then promises to be a breezy and cool day with some sunshine returning to the Mid-Atlantic region.

Next week Next week is looking downright ugly for much of the central and eastern U.S. with an extended period of wet and chilly weather. The main reason for the dismal outlook is an unfolding “omega-shaped” blocking pattern in the upper part of the atmosphere that is likely to set up next week across the eastern half of the nation. An “omega-shaped” blocking pattern – not too unusual for the month of April - is one in which upper level winds at around 500 millibars (~18,000 feet) actually follow the shape of the Greek letter “omega”. In this type of blocking pattern, surface weather systems (fronts, highs and lows) move very slowly which generally result in extended periods of similar weather conditions for a given location. Also, the upper level features are stuck in place and will change very little between Monday and Wednesday (see 500 mb forecast maps above for Monday and below for Wednesday showing very little change).

In this particular case, it looks like the Mid-Atlantic region will suffer through an extended period of chilly and wet weather with the threat for significant rain likely lasting from later Monday night right into Friday of next week and perhaps even into the weekend. Temperatures for much of this time period will be well below normal in the Mid-Atlantic region for this time of year and also for much of the eastern half of the nation. In fact, this pattern could be cold enough that some late season snow falls in parts of the Upper Midwest and northern Plains later next week. By the time we get to the end of next week, the combination of the rainfall expected during the next 36 hours and the significant rainfall expected next week in the developing blocking pattern, will likely result in at least a few inches of total rainfall over large portions of the central and eastern U.S. For more on “The Omega Block” check out video #15 at the “Meteorology 101” section of the weather web site.

7:00 AM | Rain later later today and tonight, maybe a thunderstorm or two; next week looks ugly with chilly, rainy weather for an extended period

6-Day Forecast

Today

A mix of clouds and sun through mid-day then cloudy skies this afternoon, a bit milder, showers likely for the late afternoon hours along with a thunderstorm or two, some of the rain can be heavy at times, highs in the mid-to-upper 60’s

Tonight

Periods of rain this evening, maybe a thunderstorm or two, some of the rain can be eavy at times, becoming windy late with some clearing possible, lows near 50 degrees

Saturday

Variable cloudiness, mild, breezy, good chance for afternoon showers, maybe a thunderstorm or two, low-to-mid 70’s

Saturday Night

Clouds with a shower possible early then becoming partly cloudy, breezy, colder late, low-to-mid 40’s

Sunday

Mainly sunny, breezy, cooler, mid 60’s

Monday

Partly sunny, cool, mid 60’s; showers likely at night

Tuesday

Cloudy, chilly, rain likely at times, mid 50’s

Wednesday

Cloudy, chilly, rain likely at times, mid 50’s

Discussion

It’ll turn milder today and more tranquil than recent days with some sunshine this morning, but clouds this afternoon will likely produce showers by late in the afternoon (after 4pm) and there will be periods of rain this evening with some heavy at times. A thunderstorm is also possible at any time from late this afternoon through the early part of the evening. A frontal system will approach the region on Saturday keeping us unstable and this should generate more showers during the afternoon hours and there can even be another thunderstorm or two mixed into the picture. It'll turn breezy and cooler on Sunday following the passage of this next frontal system.

Looking ahead to next week, it looks downright ugly with a large-scale upper level trough setting up shop in the eastern US for several days due to a developing blocking pattern in the upper atmosphere. As a result, there will be quite chilly and well-below normal weather for much of the week throughout the central and eastern U.S. with rain at times around here from Monday night into Friday.

Video

httpv://youtu.be/RW12TmbGWUI

7:00 AM | Still breezy and cool today; next week looks ugly

6-Day Forecast

Today

Mostly sunny, still breezy and on the cool side, highs in the mid 60’s

Tonight

Partly cloudy, lighter winds, chilly, lows near 45 degrees

Friday

Mostly cloudy, a bit milder, chance for a few showers, maybe a thunderstorm, low 70’s

Friday Night

Mostly cloudy, cool, chance for a shower, near 50

Saturday

Partly sunny, mild, a few showers possible, mid 70’s

Sunday

Mainly sunny, breezy, cooler, mid 60’s

Monday

Increasing clouds, breezy, cool, showers possible late in the day or at night, low-to-mid 60’s

Tuesday

Mostly cloudy, cool, rain likely, low 60's

Discussion

The breeze will continue to be quite noticeable today in the Mid-Atlantic region although it will not be as strong as yesterday. Along with the NW breeze, there will be plenty of sunshine and temperatures still on the cool side for this time of year. More tranquil conditions are in store for tomorrow as we close out the work week and it’ll become slightly milder, but there will also be the threat for a few showers. Saturday will be mild, but there is a chance for showers and then it’ll turn breezy and cooler on Sunday following the passage of another cold frontal system. Looking ahead to next week, it looks ugly with a large-scale upper level trough setting up shop in the eastern US and this will bring us the threat for showers over an extended period of time (late Monday into Thursday) along with cooler-than-normal temperatures.

7:00 AM | Much cooler today with strong NW winds; 30's again for lows in the overnight hours

6-Day Forecast

Today

Mostly sunny, windy and much cooler than yesterday, gusts up to 40 mph, highs in the low 60’s

Tonight

Mostly clear, breezy and cold, lows in the mid-to-upper 30’s

Thursday

Mostly sunny, still quite breezy and on the cool side, mid-to-upper 60’s

Thursday Night

Mostly clear, chilly, mid 40’s

Friday

Mainly cloudy, breezy, milder, chance for a few showers, low 70's

Saturday

Mainly sunny, breezy, quite mild, mid 70’s

Sunday

Mostly sunny, breezy, cooler, low-to-mid 60's

Monday

Mostly cloudy, cool, chance for showers at night, low 60’s

Discussion

The big weather story of the day will be the strong NW winds that can gust up to 40 mph or so at times. These winds will flood the Mid-Atlantic region with a much cooler air mass compared to yesterday following the passage of a strong cold frontal system late yesterday that brought with it numerous showers and thunderstorms. Temperatures will struggle to pass 60 degrees this afternoon despite some sunshine along with those stiff NW winds and low temperatures by early tomorrow morning will once again bottom out in the 30's in most areas. It’ll continue on the cool side on Thursday, but milder conditions are likely at the end of the work week and during the beginning of the upcoming weekend before it turns cooler again early next week.

Looking ahead and to put it simply - next week is looking ugly. A large-scale upper level trough will set up shop in the eastern U.S. by the middle-to-latter part of next week and this will lead to an extended period of cool and unsettled weather with the threat for rain over several days. In fact, it'll likely be cold enough later next week in parts of the central/northern Plains and Upper Midwest for some more late season snow to fall in those areas during next week's cool and unsettled weather pattern.

Video

httpv://youtu.be/KCMzpp1EdFw

7:00 AM | Front brings showers and possible thunderstorms to the region

6-Day Forecast

Today

Becoming mostly cloudy, breezy, quite mild, afternoon showers likely with a couple of thunderstorms possible, highs near 75 degrees (normal high is now 69 degrees at DCA)

Tonight

Early evening showers possible then becoming partly cloudy, windy, much cooler late, lows by morning in the low-to-mid 40’s

Wednesday

Mostly sunny, windy, much cooler, near 60

Wednesday Night

Mostly clear, breezy, cold, mid-to-upper 30’s

Thursday

Mainly sunny, quite breezy, still on the cool side, mid 60’s

Friday

A mix of clouds and sun, milder, chance for showers, low-to-mid 70’s

Saturday

Partly sunny, quite mild, maybe a shower, low-to-mid 70's

Sunday

Mostly sunny, breezy, cooler, low 60’s

Discussion

Strong high pressure will lose control of our weather today as a cold frontal system pushes towards the east coast. This front will generate afternoon and early evening showers in the Mid-Atlantic region and maybe even a thunderstorm or two. Behind the front, it’ll turn noticeably cooler on Wednesday along with a stiff NW wind and it should remain pretty cool and breezy on Thursday as well. Milder conditions will return to the area as we close out the work week, but so will a threat for showers.

Video

httpv://youtu.be/nn3hZROWj5A

7:00 AM | Nice to start the new week; showers later tomorrow and maybe a thunderstorm or two

6-Day Forecast

Today

Mostly sunny, milder, highs near 70 degrees

Tonight

Partly cloudy, cool, lows by morning in the upper 40’s

Tuesday

Mostly cloudy, mild, PM showers likely, maybe a thunderstorm or two, low-to-mid 70’s

Tuesday Night

After an early evening shower threat, clearing skies will set in, breezy and quite cool late, low-to-mid 40’s

Wednesday

Mostly sunny, windy, cooler, low 60’s

Thursday

Mainly sunny, breezy, cool, low-to-mid 60’s

Friday

Partly sunny, milder, chance for showers, low-to-mid 70’s

Saturday

Partly sunny, mild, near 70

Discussion

Strong high pressure will control our weather to begin the new work week, but a frontal system will approach the Mid-Atlantic region on Tuesday. This next cool front is likely to generate showers later tomorrow and tomorrow night, maybe a thunderstorm or two, and then cooler air will flow into the area on Wednesday riding in on stiff NW winds. Temperatures will remain cool on Thursday and then another frontal system could generate more showers around here at the end of the work week.

Video

httpv://youtu.be/5O4WbQam7Vs

7:00 AM | Decent weekend as temperatures continue to modify

6-Day Forecast

Today

Mostly cloudy, still cool with light E-SE winds, highs in the upper 50’s

Tonight

Mostly cloudy, chilly, lows by morning not far from 40 degrees

Saturday

Becoming mostly sunny, a bit milder, mid 60’s

Saturday Night

Partly cloudy, chilly, low 40’s

Sunday

Partly-to-mostly sunny, comfortable, upper 60’s

Monday

Partly sunny, milder, near 70

Tuesday

Mostly cloudy, mild, showers likely later in the day or at night, low-to-mid 70's

Wednesday

Mostly sunny, breezy, cooler, upper 60’s

Discussion

Strong high pressure just off the New England coastline has generated an ocean flow of air (low-level E-SE winds) in the region and this has resulted in clouds pushing in from the east. This rather moist flow of air will, in fact, help to keep copious amounts of clouds around the region right through tonight and temperatures will stay on the cool side as ocean temperatures are still quite chilly this time of year. A frontal system will cross the region early Saturday changing our wind direction and a new high pressure system will subsequently build into the region from eastern Canada for Sunday and Monday. Another frontal system will then approach on Tuesday bringing with it a good chance of showers for the Mid-Atlantic region. Looking ahead, it appears there will be another shot of cold air for the Northeast US as we work our way through the last week of the month.