7:00 AM | Hot and humid for the next several days, but there is a cold front on the horizon

6-Day Forecast

Today

Mostly sunny, humid, becoming hot, highs near 90 degrees

Tonight

Partly cloudy, mild, muggy, an isolated shower or thunderstorm, lows in the upper 60’s

Thursday

Mostly sunny, hot and humid, low 90’s

Thursday Night

Partly cloudy, humid and mild, upper 60’s

Friday

Mostly sunny, hot and humid, low 90’s

Saturday

Mostly sunny, hot and humid, low 90's

Sunday

Partly sunny, chance for showers and thunderstorms late in the day or at night, very warm and humid, upper 80’s

Monday

Mostly cloudy, cooler, showers and thunderstorms possible, near 80

Discussion

It’ll turn hot and humid today following the passage of a warm front that caused yesterday’s scattered showers and thunderstorms. Temperatures will jump this afternoon to near 90 degrees and should climb just pass 90 on Thursday, Friday and Saturday along with summer-like humidity values. A cold front will then approach the region late in the weekend raising the chances for showers and thunderstorms by Sunday night and temperatures will get knocked down some early next week following the passage of the front.

Elsewhere, a clash of air masses will likely produce severe weather later today and tonight across the mid-section of the country and this will include the risk for tornadoes in places like Oklahoma and Kansas. Some snow is now falling in the highest elevations of Colorado and Wyoming and this colder air mass is sweeping towards very warm and humid air in the central US setting the stage for late day severe weather and that threat will likely continue on Thursday as well in the nation's mid-section.

Video

httpv://youtu.be/XVgLNs0w-gk

1:10 PM | Atlantic tropical season about to get underway

Discussion

The 2013 Atlantic tropical season officially begins this Saturday, June 1st, and continues until November 30th. Of course, this timetable is a “man-made” one and Mother Nature can begin and end any time she wants to with respect to the formation of Atlantic tropical storms, but all-in-all, these are pretty reasonable choices for the beginning and end dates of the tropical season based on historical data.

Fortunately, it has been nearly 8 years since a major hurricane (i.e., category 3, 4 or 5) has struck the US which is the longest such period since the Civil War. In fact, Hurricane Wilma was the last major hurricane to hit the US back in October of 2005, the year that was the most active Atlantic hurricane season in recorded history and featured seven major hurricanes. Unfortunately, 2013 promises to be an active tropical season and the US east coast is vulnerable to a major hurricane hit based on some similarities in oceanic temperature patterns to analog years that were very active along the coast. Specifically, the current sea surface temperature anomalies in the northern Pacific (cold phase, negative Pacific Decadal Oscillation) and northern Atlantic (warm phase, positive Atlantic Multidecadal Oscillation) resemble closely many of the years in the decade of the 1950’s and there were numerous major hurricane hits during that time period. For example, in just the time between August 1954 and September 1955, there were five major hurricanes that struck the US east coast – Carol, Edna, Hazel, Connie and Ione. This certainly raises a red flag of warning along the east coast for the upcoming tropical season, and perhaps for the next few years as well.

I believe that the tropical season has a good chance of getting underway fairly quickly during the month of June – perhaps even as early as next week there could be some activity in the Caribbean Sea. Sea surface temperatures continue to be largely above normal across much of the tropical Atlantic and this is a primary cause of concern for an active season. (For more details on the tropical and Mid-Atlantic summertime outlooks and a comprehensive video discussion go to "Seasonal Forecasts" on the right panel).

Here is a list of the names for the 2013 tropical season (some interesting names on the list including the one for the 4th storm):

Andrea Barry Chantal Dorian Erin Fernand Gabrielle Humberto Ingrid Jerry Karen Lorenzo Melissa Nestor Olga Pablo Rebekah Sebastien Tanya Van Wendy

7:00 AM | Transition to heat and humidity today should bring scattered showers and thunderstorms; especially, to the north of the District

6-Day Forecast

Today

Mostly cloudy, mild, scattered showers and possible thunderstorms with the greatest chance for rain to the north of the District, highs in the low 80's

Tonight

Mostly cloudy, mild, showers likely and possibly a thunderstorm or two, lows around 65 degrees

Wednesday

Becoming mostly sunny, very warm and humid, near 90

Wednesday Night

Partly cloudy, humid and mild, mid 60’s

Thursday

Mostly sunny, hot and humid, low 90's

Friday

Mostly sunny, hot and humid, near 90

Saturday

Mostly sunny, hot and humid, near 90

Sunday

Partly sunny, chance for showers and thunderstorms late in the day or at night, very warm and humid, upper 80’s

Discussion

It’ll turn hot and humid by tomorrow afternoon, and the transition today from the weekend dry and cool conditions will bring us the chance for scattered showers and thunderstorms; especially, on the north side of the District . It’ll get milder today, but the real heat and humidity will be more noticeable on Wednesday after a warm front works its way to our north. This frontal passage will set the stage for a hot and humid period from Thursday through Saturday. By later Sunday, a cold front will approach from the west increasing our chances again for more shower and thunderstorm activity at the end of the upcoming weekend.

Video

httpv://youtu.be/KFm10UY5k3U

7:00 AM | Much cooler air has moved in and there will be occasional showers to close out the week

6-Day Forecast

Today

Mostly cloudy, windy, much cooler with lingering showers, highs in the mid 60’s early this morning

Tonight

Mostly cloudy, windy, chilly, chance for more showers, lows in the mid 40’s

Saturday

Becoming partly sunny, windy, cool, mid-to-upper 60’s

Saturday Night

Partly cloudy, chilly, mid 40’s

Sunday

Mostly sunny, breezy, cool, near 70

Monday

Mostly sunny, milder, mid 70’s

Tuesday

Partly sunny, even milder, upper 70’s

Wednesday

Variable clouds, warm, chance for showers and thunderstorms, low 80’s

Discussion

A strong cold front has passed through the region ushering in much cooler air for today and the weekend, and weather conditions will remain quite unsettled as a coastal low pressure system forms along the now stalled out front. Showers will linger around here through tonight as a slow-moving nor’easter strengthens along the frontal boundary zone over the next 24 hours or so and it'll remain quite windy and cool. In fact, the air will actually be cold enough farther north for some snow to fall from this coastal low in the interior higher elevations of the Northeast US. Strong Canadian high pressure will take better control of our weather on Sunday and Monday with plenty of sunshine expected both days, but it’ll still be rather cool for this time of year. Milder air works its way to the Mid-Atlantic region by the middle of next week with the 80's likely again later next week.

Video

httpv://youtu.be/r2WELwFaD4Y

7:00 AM | Strong storms possible as powerful cold front reaches the coast by tonight; nor'easter forms along front and affects our early weekend weather

6-Day Forecast

Today

Mostly cloudy, still warm and humid, but not quite as warm as yesterday, occasional showers and possible afternoon thunderstorms, any shower can be heavy and some of the PM thunderstorms can be strong-to-severe with heavy rainfall, strong wind gusts and hail, highs near 80 degrees

Tonight

Mostly cloudy, mild early, turning cooler late, occasional rain and a couple of thunderstorms possible, some of the rain can be heavy at times and any storm can be strong-to-severe with heavy rain, strong gusty winds and hail, lows in the upper 50’s by morning

Friday

Mostly cloudy, windy, much cooler, lingering showers likely, mid 60’s

Friday Night

Mostly cloudy, chilly, still the chance for showers, mid-to-upper 40’s

Saturday

Still some clouds, breezy, cool, chance for a lingering shower or two; especially, north and east of the District, upper 60’s

Sunday

Mostly sunny, breezy, cool, low 70’s

Monday

Mostly sunny, pleasant, low-to-mid 70's

Tuesday

Mostly cloudy, milder, mid-to-upper 70’s

Discussion

Big changes are on the way for the Mid-Atlantic region over the next couple of days as the pattern transitions from summer-like to rather winter-like by early this weekend with a full-fledged nor'easter developing off the Northeast US coastline. The transition from summer's warmth and humidity to yet another chilly air mass has actually already begun as the peak in the heat occurred yesterday with highs in the upper 80's in many parts of the DC metro region. Temperatures will actually drop more than 40 degrees over the next couple of days from yesterday's highs in the upper 80's to weekend lows in the middle 40's. As a powerhouse cold frontal system approaches the east coast today, there will be occasional showers and thunderstorms. Any shower can contain heavy rainfall and any thunderstorm that forms this afternoon and evening can reach strong-to-severe levels with heavy rain, strong gusty winds and hail. In fact, there will likely be scattered strong-to-severe thunderstorms up and down the east coast later today from the Carolinas to New England as this strong cold front heads to the coast.

Once the cold front reaches the east coast later tonight, a strong upper level low will dig into the Mid-Atlantic coastal region, and this will to cause the frontal system to grind to a halt as a nor’easter-type of coastal storm develops at the same time much chillier air pours into the region. As a result, Friday will turn out to be breezy and much cooler than today in the Mid-Atlantic region with lots of clouds and residual showers and, as the coastal storm only slowly pulls away to the northeast, Saturday will likely also turn out to be somewhat unsettled with some clouds, breezy and cool conditions with a lingering shower or two possible; especially, in areas to the north and east of the District. Farther north, the colder air mass will actually allow for the possibility for snowflakes to fall in some of the interior, higher elevation (>2000 feet) locations of the Mid-Atlantic and Northeast US early this weekend (e.g., Adirondacks, Green and White mountains). By Sunday, strong Canadian high pressure should finally take control of the weather and there will be plenty of sunshine around and that pattern will continue on Monday as well, however, both days will remain cooler-than-normal (normal high is now 77 degrees).

Video

httpv://youtu.be/pveInhfqsV0

1:10 PM | Big changes coming to the Mid-Atlantic over the next few days as summer-like pattern becomes kind of winter-like; heavy rainfall, and possible strong storms, to occur during the transition between tonight and the weekend

Discussion

To say it doesn't look like beach weather for this upcoming holiday weekend is looking more and more like quite an understatement for the Mid-Atlantic region and the Northeast US. Big changes are coming to the Mid-Atlantic region and Northeast US over the next few days as the weather changes from today’s summer-like pattern to one that is actually kind of winter-like - and strong-to-severe thunderstorms with heavy rainfall are likely during the transition between later tonight and the early weekend. Summer-like weather continues today in the Mid-Atlantic region with high humidity and temperatures well up in the 80’s in Philly and DC, and well up in the 70’s across the NYC metro region. This sultry air mass can help to spark some shower and thunderstorm activity later tonight and any storm that forms can be on the strong side. An even better chance for heavy rainfall and strong thunderstorms will occur later tomorrow and tomorrow night as a powerhouse cold front heads to the east coast. In fact, strong-to-severe thunderstorms are likely later tomorrow from New England to the Carolinas associated with this strong frontal system.

Once the cold front reaches the east coast later tomorrow night, a strong upper level low will dig into the Mid-Atlantic region, and this will to cause the frontal system to grind to a halt as a nor’easter-type of coastal storm develops at the same time much chillier air pours into the region. As a result, Friday will turn out to be breezy and much cooler than Thursday in the Mid-Atlantic region with lots of clouds and residual showers and, as the coastal storm only slowly pulls away to the northeast, Saturday may also turn out to be quite cloudy, windy and cool with the continued threat for showers; especially, from eastern Pennsylvania and New Jersey to points north and east to New England. In fact, it's starting to look like a lost weekend for places up the northeastern coast such as in Boston, MA where rain and wind could hang on through Sunday. The colder air mass will actually allow for the possibility for snowflakes to fall in some of the higher elevation (>2000 feet), interior locations of the Mid-Atlantic and Northeast US early this weekend (e.g., Adirondacks, Green and White mountains). By Sunday and Monday, strong Canadian high pressure should finally take control of the weather, but temperatures will remain well below normal for this time of year.

7:00 AM | Another summerlike day with heat and humidity; strong storms possible today and tomorrow; much cooler this weekend

6-Day Forecast

Today

Clouds this morning then partial sunshine this afternoon, very warm and humid, chance for showers and thunderstorms this afternoon and any storm that forms can be strong, highs in the mid-to-upper 80’s

Tonight

Mostly cloudy, mild, chance for showers and thunderstorms and any storm that forms can be strong, mid-to-upper 60’s

Thursday

Mostly cloudy, warm and humid, showers and thunderstorms likely and some of the storms can be strong-to-severe, near 80

Thursday Night

Mostly cloudy, mild early, turning cooler late, chance for showers and thunderstorms, upper 50’s by morning

Friday

Mostly cloudy, breezy, cooler, chance for a lingering morning shower, upper 60's

Saturday

Partly sunny, breezy, cool, near 70

Sunday

Mostly sunny, cool, near 70

Monday

Increasing clouds, still on the cool side, near 70

Discussion

A taste of summer will continue today in the Mid-Atlantic region as temperatures will climb well up into the 80’s in most locations and humidity levels will stay on the high side. Dew points climbed into the middle 60’s on Monday in the Mid-Atlantic region and then they reached the even more stifling upper 60’s on Tuesday to go along with summerlike temperatures. Showers and thunderstorms can break out at just about any time this afternoon and evening although much of the time will be rain-free. Any storm that forms this afternoon or evening can be on the strong side with some briefly heavy rainfall and perhaps some hail and high wind gusts. By tomorrow, a strong cold front will be moving through the Ohio Valley on its way to the east coast and this will enhance the chances for shower and thunderstorm activity in the DC metro region and there is a decent chance that strong-to-severe storms will develop later tomorrow and tomorrow night in the entire region between the Carolinas and New England.

Once the cold front reaches the east coast by early Friday, it will tend to slow down a bit and this will allow for mostly cloudy skies to continue on Friday along with cooler conditions and the threat for a residual morning shower. By the weekend, strong Canadian high pressure will slowly build into the Mid-Atlantic region and, similar to many previous springtime scenarios, much colder-than-normal air will spread to the eastern states with this high pressure system. As a result, it does not look at all like a “beach-type” weekend for coastal locations in the Mid-Atlantic and Northeast US, and frost is actually not out of the question for some interior, higher elevation locations. Cool and dry weather is likely to continue into the latter part of the Memorial Day weekend though clouds should thicken up on Monday as moisture heads our way from our southwest.

One final note: the tornado that struck Oklahoma on Monday has now been upgraded to an "EF-5" classification level which is the most intense type on the "Enhanced Fugita" scale and it is suggestive of 200+ mph winds.

Video

httpv://youtu.be/phbiaaLwpZk

12:45 PM | More on the Monday "EF-4 ?" tornado in Oklahoma

Discussion

Tornadoes require clashes of air masses to form generally to include cold, dry air in the upper atmosphere and very warm and humid air in the lower atmosphere. For much of the spring, the missing ingredient for this scenario in the US was the influx of very warm and humid air from the Gulf of Mexico thanks in large part to the persistent cold pattern in the central and eastern US that acted to inhibit Gulf of Mexico air from advancing northward. The cold air masses, however, began to retreat a couple of weeks ago and subsequently, dew points, which are a true measure of moisture content in the air, have consistently climbed in the central and eastern US and this increased dramatically the prospects for severe weather.

Indeed, the combination of very warm and humid low-level air with a vigorous cold upper-level low pressure trough on Monday helped to spawn the powerful tornado that struck portions of Oklahoma with a major impact on Moore, a heavily populated (50,000 residents) suburb of Oklahoma City some twenty miles to its south. The preliminary estimate is that the one-to-two mile wide tornado that struck the town of Moore reached EF-4 status on the “Enhanced Fugita” scale (5 being the most intense) with winds of nearly 200 mph, but these estimates will be re-evaluated over the next several days/weeks as tornado experts on the ground closely assess the damage and I think it may very well end up being classified as an EF-5. The tornado lasted for about 40 minutes causing destruction over a 20 mile swath.

The overall weather pattern that helped to produce the severe weather yesterday (i.e., warm, humid low level air, strong cold upper-level low with a powerful jet streak, strong surface cold front) will continue for the next couple of days with the severe weather threat zone slowly shifting eastward. There is a threat today for severe weather from the southern Plains to the Upper Midwest, and then likely in the Ohio Valley on Wednesday, and then perhaps in the Mid-Atlantic and Northeast US late Thursday as a strong cold front approaches the east coast. Strong-to-severe thunderstorms are possible later Thursday in the region from the Carolinas to New England as all the atmospheric dynamics shifts towards the east coast. This afternoon’s video includes some time-lapse video of yesterday’s tornado and a detailed discussion as to why the previously quiet tornado season has ended.

Video

httpv://youtu.be/XWgG6npVG_0

7:00 AM | A taste of summer through Thursday with a daily threat for shower and storms; cool weekend shaping up for the Mid-Atlantic

6-Day Forecast

Today

Partly sunny, very warm and humid, chance for showers and thunderstorms this afternoon, but most of the day will be rain-free, highs in the mid-to-upper 80’s

Tonight

Mostly cloudy, mild, chance for showers and thunderstorms, upper 60’s

Wednesday

Partly sunny, very warm and humid, chance for showers and thunderstorms, mid 80’s

Wednesday Night

Mostly cloudy, mild, chance for showers and thunderstorms, mid-to-upper 60’s

Thursday

Mostly cloudy, warm and humid, showers and thunderstorms likely and some of the storms can be strong-to-severe, near 80

Friday

Partly sunny, cooler, low 70’s

Saturday

Mostly sunny, cool, low 70’s

Sunday

Partly sunny, cool, low 70’s

Discussion

A taste of summer will occur in the Mid-Atlantic region today, tomorrow and Thursday as temperatures will climb well up into the 80’s in many locations and humidity levels will become more reminiscent of the summertime. One of the main ingredients necessary for severe weather to occur in the central and eastern US is moisture-laden air from the Gulf of Mexico and that has been largely missing from this part of the country during the spring until the last several days. In fact, dew points on Monday climbed well up into the 60’s in the Mid-Atlantic region and they will hold at those rather high levels from today through Thursday. At the same time, a strong upper level feature will slide slowly eastward to the eastern states during the next few days and this combination of humid air with strong upper level support will generate severe weather today from the southern Plains to the Upper Midwest, in the Ohio Valley on Wednesday, and then perhaps in the Mid-Atlantic region later Thursday. A strong surface cold front will approach the east coast late Thursday and this will likely spark the formation of strong-to-severe thunderstorms from the Carolinas to New England.

Once the cold front passes off the east coast on Friday, strong Canadian high pressure will build into the Mid-Atlantic region and, similar to many previous springtime scenarios, colder-than-normal air will spread to the east with this high pressure system. As a result, it does not look like a warm "beach-type" weekend for coastal locations in the Mid-Atlantic and Northeast, and frost is not out of the question for some interior, higher elevation locations of the Northeast US. Generally cool and dry weather is likely to continue into the latter part of the Memorial Day weekend.

Video

httpv://youtu.be/cU7GdZBRwBU

7:00 AM | A warm, humid and unsettled period with plenty of chances for showers and thunderstorms

6-Day Forecast

Today

Mostly cloudy, becoming warmer, chance for showers and thunderstorms, highs near 80 degrees

Tonight

Mostly cloudy, mild, chance for showers and thunderstorms, lows in the mid 60’s

Tuesday

Partly sunny, very warm and humid, slight chance for showers and thunderstorms, mid-to-upper 80’s

Tuesday Night

Mostly cloudy, mild, slight chance for showers and thunderstorms, upper 60’s

Wednesday

Partly sunny, very warm and humid, chance for showers and thunderstorms, low-to-mid 80’s

Thursday

Mostly cloudy, warm and humid, showers and thunderstorms likely and some of the storms can be strong-to-severe, low 80’s

Friday

Partly sunny, cooler, chance for showers and thunderstorms, mid 70’s

Saturday

Partly sunny, cool, low 70’s

Discussion

A frontal system continues to hang around the Mid-Atlantic region this morning as it has for the past several days and this front will combine with a couple of other fronts to make the next few days quite unsettled around here. After a damp and dreary start to the week this morning, the afternoon may feature some brightening skies, but a few PM showers are possible and maybe even a thunderstorm. It'll turn very warm and humid on Tuesday and that summer-like weather will continue through Thursday along with a daily threat for showers and thunderstorms. In fact, the thunderstorms that threaten the Mid-Atlantic region later Thursday could become strong-to-severe as a strong cold front sweeps to the east from the Midwest at that time and it'll have strong upper level support associated with the surface frontal system. This same upper level low will continue to cause severe weather today and Tuesday in portions of the Upper Midwest and central Plains before it slides to the east by later Thursday. Following the strong cold frontal passage Thursday night, high pressure will build into the Mid-Atlantic region and, from this vantage point, the Memorial Day weekend looks to be generally cool and dry.

Video

httpv://youtu.be/1I_gT1PXSWM