3:25 PM | Warm air surge at the end of the week does not signal a longer-term trend of warmer-than-normal weather in the Mid-Atlantic region

[map courtesy WeatherBell Analytics]

Discussion

A warm front will advance northeastward into the Mid-Atlantic region tomorrow night and warm air should surge into the DC metro region on Thursday following the frontal passage. The warm air, however, only grudgingly continues its northeastward expansion after that and this will result in a shorter period of warm weather as one heads farther and farther to the northeast. Temperatures in DC should reach 80+ degrees on Thursday, Friday and Saturday; Philly should approach 80 degrees on Friday (although this is still not a guarantee for Friday) and also on Saturday; New York City should climb to the mid-to-upper 70’s on Saturday following another day in the 60’s on Friday. The transition to the warm weather will be accompanied by showers and thunderstorms on Wednesday Night/Thursday and there can be additional showers and storms on Friday and Saturday as well in the Mid-Atlantic region.

The surge of warmth that arrives by the end of the week in the I-95 corridor does not look like it will signal a prolonged period of above-normal temperatures for the region. In fact, the latest 12Z GFS computer forecast model run suggests that a warmer-than-normal 5-day period from May 7-12th will be followed by a colder-than-normal period of weather in the eastern US from May 14-May 19th (map courtesy WeatherBell Analytics at weatherbell.com).

7:00 AM | 80's on the way for later this week

6-Day Forecast

Today

Clouds early today will give way to mostly sunny skies, comfortable, highs near 70 degrees

Tonight

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

Wednesday

Becoming mostly cloudy, comfortable, chance for late day showers, maybe a thunderstorm or two, mid-to-upper 60’s

Wednesday Night

Mostly cloudy, mild, a few showers likely and maybe a thunderstorm, near 55

Thursday

Becoming partly sunny, warmer, low 80’s

Friday

Partly sunny, warm, chance for a shower or thunderstorm, low-to-mid 80’s

Saturday

Mainly cloudy, still warm, showers likely, maybe a thunderstorm, near 80

Sunday

Partly sunny, warm, showers possible, upper 70’s

Discussion

Much warmer air has been expanding in the southern portion of the country over the last few days and it is now making a slow advancement to the north and east. A warm front will reach the the Mid-Atlantic region tomorrow night likely accompanied by some shower and thunderstorm activity. The DC metro region will be the first location along the I-95 corridor to experience a surge in temperatures as temperatures there on Thursday afternoon are likely reach or even slightly surpass the 80 degree mark. The Philly metro region is likely to experience the warm air surge on Friday afternoon with high temperatures possibly flirting with the 80 degree mark as we close out the work week. There is a small chance, however, that the warm air surge into Philly gets delayed a day and doesn't arrive with full force until Saturday. New York City is likely to not see a noticeable increase in temperatures until Saturday at which time highs up there should reach the mid-to-upper 70's.

7:00 AM | The 80's are likely later this week

6-Day Forecast

Today

Sunshine followed by increasing clouds, breezy, still on the cool side, highs in the mid-to-upper 60’s

Tonight

Mainly cloudy, chilly, showers likely, lows in the mid-to-upper 40’s

Tuesday

Becoming partly sunny after an early morning shower or two, not quite as cool, near 70

Tuesday Night

Partly cloudy, chilly, upper 40’s

Wednesday

Partly sunny, a bit on the cool side, a shower or thunderstorm possible late in the day or at night, upper 60’s

Thursday

Partly sunny, warmer, a shower or thunderstorm possible, low 80's

Friday

Partly sunny, still quite warm, low-to-mid 80’s

Saturday

Mainly cloudy, still warm, showers possible, low 80’s

Discussion

A cold front slipped through the region on Sunday and this front will stall out well to our south today as we begin the new week. High pressure will build into the region behind the front providing us with some sunshine for awhile today along with slightly cooler-than-normal temperatures; however, a weak disturbance will slide just to our south tonight and this system could generate a few nighttime and early morning showers around here. The stalled out cold frontal system will then turn around and head back to the north as a warm front later this week bringing with it the threat for a few showers and scattered thunderstorms during the transition to much warmer conditions. Once that warm front passes through our region, temperatures should jump into the 80's by Thursday afternoon and Friday to close out the work week.

Video

httpv://youtu.be/_WbXclE-F3U

12:30 PM | While mainly rain-free, the weekend will not be without showers in the Mid-Atlantic region

[Strong upper level low in the Northeast US by Sunday morning]

Discussion

The current synoptic setup is dominated by an upper-level trough situated over southern Canada that will amplify this weekend as it slides eastward across the Great Lakes region. As this trough intensifies and heads closer to our part of the country this weekend, it will send enough short wave energy into the Mid-Atlantic region to generate showers on both weekend days. The best chance for showers this weekend in the Mid-Atlantic region will be during the afternoon and early evening hours on Saturday and during the mid-day, afternoon and early evening hours on Sunday with a focus of the shower threat in areas north and east of the PA/MD border. In addition, as colder air moves into the upper part of the atmosphere this weekend, there will even be the chance for scattered thunderstorms to form in the Mid-Atlantic region on both weekend days. A west-to-northwest breeze is likely to stiffen noticeably during the day on Sunday as cooler air begins to move into the area - wind gusts up to 30 mph possible by afternoon.

7:00 AM | A nice finish to the work week and a decent weekend

6-Day Forecast

Today

Partly sunny, breezy, seasonably mild, highs near 70 degrees

Tonight

Becoming mostly cloudy, chilly, lows in the upper 40’s

Saturday

Partly sunny, seasonably mild, slight chance for an afternoon shower across the northern suburbs, near 70

Saturday Night

Partly cloudy, cool, upper 40’s

Sunday

Partly sunny, quite breezy, seasonably mild, couple of showers are possible, near 70

Monday

Mainly sunny, breezy, a bit cooler, mid 60’s

Tuesday

Partly sunny, still a bit on the cool side, maybe a couple of showers, mid 60’s

Wednesday

Partly sunny, milder, near 70

Discussion

A weak area of high pressure will build into the region today as we close out the work week. Low pressure tracking to our north on Saturday will drag a cool front through our region by Sunday and then high pressure will take control again early next week. The weekend cool frontal system could cause a smattering of shower activity in the Mid-Atlantic later Saturday and on Sunday; especially, during afternoon hours in areas close to the PA/MD border.

7:00 AM | Deluge is over with many areas receiving more than 5 inches; slow improvement today which will intensify tomorrow; weekend looks pretty decent

6-Day Forecast

Today

Mostly cloudy during the morning hours with a lingering shower possible then becoming partly sunny, noticeably milder and a bit on the muggy side, highs in the mid 70’s

Tonight

An evening shower or thunderstorm possible then becoming partly cloudy and turning cooler late, lows in the upper 40’s by morning

Friday

Mostly sunny, breezy, seasonably mild, near 70

Friday Night

Mostly cloudy, chilly, mid-to-upper 40’s

Saturday

Partly sunny, seasonably mild, an afternoon shower possible, near 70

Sunday

Partly sunny, breezy, comfortable, maybe a shower or two, near 70

Monday

Partly sunny, a bit cooler, mid-to-upper 60's

Tuesday

Partly sunny, still a bit on the cool side, upper 60's

Discussion

Our major rain event is now over with many spots in the DC metro region receiving more than 5 inches of rainfall during the past 24 hours or so (e.g., Columbia, MD 6.81", Oakton, VA 6.09", Germantown, MD 5.65"). While there can be a shower or two at just about any time today and an isolated thunderstorm early tonight, the steady and heavy rain has shifted well to our north and east. Significant improvement will take place on Friday in the Mid-Atlantic region with sunshine, seasonably mild conditions and dry weather expected. The weekend looks pretty decent overall; however, the same slow-moving upper-level low pressure system that has been affecting much of the eastern half of the nation during the past few days will be close enough to our area to produce some clouds and even the slight chance for an isolated shower or two on both weekend days.

Video

httpv://youtu.be/Hxc61WN0G6k

4:00 PM | **Torrential rain will continue for several more hours along the I-95 corridor from DC-to-Philly-to-NYC and there is a threat for strong-to-severe thunderstorms**

[Latest infrared satellite image showing moisture stream from Gulf of Mexico riding right up the east coast; image courtesy University of Wisconsin - SSEC]

Discussion

Very heavy rain will continue to fall along the I-95 corridor from DC-to-Philly-to-NYC over the next several hours as a deep plume of tropical moisture from the Gulf of Mexico continues to surge up the east coast. In addition to the heavy rainfall, there is a chance for strong-to-severe thunderstorms tonight that could produce damaging wind gusts, hail and even a few isolated tornadoes. Lightning strikes have been detected just south of the PA/MD border in northern Maryland over the last couple of hours and this trend for “convection” will surge northward during the evening hours along with an influx of warmer air. Temperatures have already jumped in the DC metro region to 60 degrees and will hold steady or rise through the night along the I-95 corridor - perhaps reaching the 60’s by morning as far north as the Philly metro region. Many roadways are flooded in the Mid-Atlantic region – do not attempt to drive into the water. More than 4" of rain has already been reported in many sections of the I-95 corridor and there are several hours to go with this major rain event.

7:00 AM | **Heavy rain and the threat for strong-to-severe thunderstorms**

6-Day Forecast

Today

Cloudy, breezy with periods of rain, heavy at times, maybe a strong-to-severe thunderstorm or two, temperatures this morning should hold primarily in the 50's, but then rise into the 60's this afternoon

Tonight

Cloudy, breezy, mild, periods of rain, heavy at times, maybe a strong-to-severe thunderstorm or two, temperatures holding steady in the 60's

Thursday

Mostly cloudy early, partly sunny late, mild, still the chance for showers and maybe a thunderstorm, low-to-mid 70’s

Thursday Night

Partly cloudy, cool, near 50

Friday

Partly sunny, mild, near 70

Saturday

Partly, mild, slight chance for a PM shower, near 70

Sunday

Partly sunny, breezy, mild, near 70

Monday

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

Discussion

All of the ingredients are in place for more heavy rain to occur in the Mid-Atlantic region today and tonight and there could be the development of some nasty thunderstorms as well. Low pressure will meander near the Great Lakes region today and a warm front will gradually lift northward across the Mid-Atlantic later today and tonight. Copious amounts of moisture will ride northward from the Gulf of Mexico region into the Mid-Atlantic adding fuel to the atmospheric fire. The advancement of the warmer and moisture-rich air will be accompanied by an outbreak of thunderstorms as it will help to destabilize the atmosphere. A cold front is forecast to then slide across our area on Thursday bringing an end to this heavy rain event. Much improvement is likely on Friday with some sunshine and mild conditions and much of the weekend should be pretty decent as well although a shower or two cannot be ruled out.

Video

httpv://youtu.be/wPQZxEWiviY

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]

7:00 AM | **Heavy rainfall and strong thunderstorm potential from later tonight through tomorrow**

6-Day Forecast

Today

Cloudy, breezy and very cool for this time of year, occasional rain or drizzle, highs only reaching the mid-to-upper 50’s (normal high is now 70 degrees)

Tonight

Cloudy, breezy, chilly, occasional rain becoming heavier and steadier as the night progresses, maybe a strong thunderstorm or two, lows in the low 50’s

Wednesday

Cloudy, breezy, milder, rain, heavy at times, maybe a strong thunderstorm or two, near 70

Wednesday Night

Cloudy, breezy, remaining on the mild side, rain, heavy at times, maybe a strong thunderstorm or two, near 60

Thursday

More clouds than sun, mild, still the chance for showers, maybe a thunderstorm, mid 70’s

Friday

Partly sunny, mild, upper 60’s

Saturday

Mostly cloudy, mild, PM showers possible, mid-to-upper 60’s

Sunday

Partly sunny, breezy, a bit cooler, low-to-mid 60’s

Discussion

Large low pressure in the middle of the country will slowly inch its way to the region bringing with it periods of rain into Thursday with the heaviest rainfall destined to fall from later tonight through tomorrow night. In fact, the heavy rainfall from later tonight into Wednesday night can generate localized flooding problems with more than three inches possible by the time the low pressure pushes into Canada later Thursday. There can be a few strong thunderstorms mixed into the picture as well during the heavy rain event and any of these storms can be associated with torrential downpours and gusty winds. While the steadiest rain moves away from the region on Thursday, there can still be a few more showers and perhaps an isolated thunderstorm or two. Mainly dry weather on Friday will be followed by somewhat unstable weather on Saturday in the Mid-Atlantic region with PM showers possible as a strong upper low moves nearby.

Elsewhere, another serious outbreak of tornadoes on Monday brought the two-day total number of reports to at least one hundred which doubled the still below-normal yearly amounts reported by NOAA in the entire preceding part of 2014. Yesterday's tornadoes focused on the Lower Mississippi Valley region which was slightly to the east of the area that was hit hard on Sunday. Today's tornado threat - slightly diminished compared to the past couple of days - will again take place across Mississippi, but will also include areas to the east such as Alabama and Georgia. Strong thunderstorms will be possible in the Mid-Atlantic region on Wednesday and quieter weather will return to the Deep South later this week.

Video

httpv://youtu.be/YwhV2LzB1YU