7:00 AM The weather becomes unsettled this weekend and there can be strong thunderstorms

6-Day Forecast

Today

Mostly sunny, nice, highs in the low-to-mid 80’s (normal high at DCA is 88 degrees)

Tonight

Mostly clear, comfortable, lows by morning near 65 degrees

Saturday

A mix of clouds and sun, a bit warmer, cannot rule out a few showers and possibly a thunderstorm, upper 80’s

Saturday Night

Mostly cloudy, mild, muggy, chance for showers and thunderstorms, near 70

Sunday

Mostly cloudy, warm, humid, occasional showers and thunderstorms, some of the storms can be quite strong, mid-to-upper 80’s

Monday

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

Tuesday

Mostly sunny, quite cool for this time of year, upper 70’s

Wednesday

Mostly sunny, still very pleasant, near 80

Discussion

High pressure will provide a nice end to the work week, but the weather becomes unsettled this weekend and there is a good chance for occasional showers and thunderstorms from Saturday night into Monday and some of the storms can be quite strong with torrential downpours, damaging winds and possible hail. Low pressure will move across the Upper Midwest on Saturday and into the Mid-Atlantic region by late Saturday night before pushing to our north on Sunday. A cold front will then approach on Monday as it moves west-to-east and this will continue the threat for occasional showers and thunderstorms as we begin the new work week. Cooler air anchored by strong Canadian high pressure and well below normal for this time of year will arrive by Tuesday and we’ll stay very comfortable into mid-week.

Video

httpv://youtu.be/vjtOCyUyGBU

7:00 AM | Yesterday's heat and humidity being replaced by another refreshing air mass for this time of year

6-Day Forecast

Today

Mostly cloudy, not as warm, still the chance for a couple of scattered showers, lowering humidity will become noticeable later today, highs in the low 80’s

Tonight

Becoming partly cloudy, turning cooler late, lows by morning in the lower 60’s

Friday

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

Friday Night

Mostly clear, cool, low-to-mid 60’s

Saturday

Partly sunny, warmer, cannot rule out a shower or thunderstorm late in the day or at night, upper 80’s

Sunday

Mostly cloudy, quite warm, more humid, showers and thunderstorms likely, upper 80’s

Monday

Partly sunny, not as warm, humid, chance for showers and thunderstorms, mid 80’s

Tuesday

Partly sunny, a bit cooler, near 80

Discussion

A cold front arrived in the region last night with scattered showers and thunderstorms and it will grudgingly push off the east coast today. As a result, clouds will linger for much of today and a scattered shower is still possible, but less humid air will move in by tonight and conditions will be quite pleasant overnight and on Friday. The weekend will gradually become more unsettled with an isolated shower or thunderstorm late Saturday and then more numerous showers and thunderstorms are likely on Sunday. Cooler weather returns to the region by Tuesday and Wednesday of next week.

7:00 AM | Strong storms early tonight as cold front arrives

6-Day Forecast

Today

Partly-to-mostly sunny, hot, humid, chance for showers and thunderstorms at the end of the day, highs in the low 90’s

Tonight

Showers and thunderstorms likely, some of the storms can be strong with torrential downpours, frequent lightning and possible hail, lows in the lower 70’s

Thursday

Mostly cloudy, not as warm, still the chance for showers and thunderstorms, low 80’s

Thursday Night

Mostly cloudy early with a lingering shower possible, some clearing and turning cooler late, near 60

Friday

Mostly sunny, comfortably warm, mid 80’s

Saturday

Partly sunny, warm, mid-to-upper 80’s

Sunday

Partly sunny, warm, more humid, chance for showers and thunderstorms, upper 80’s

Monday

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

Discussion

A cold front will arrive tonight and it should be accompanied by scattered showers and thunderstorms and some of the storms can be on the strong side. The best chance for showers and thunderstorms will be in the period between 4pm and midnight. The threat for showers and thunderstorms will linger for awhile on Thursday, but humidity will lower noticeably later in the day. High pressure will fill in behind the front on Friday and Saturday with comfortably warm conditions, but then the weather turns unsettled on Sunday with the threat for more showers and thunderstorms. The unsettled weather will continue early next week as a deep upper level trough sets up over the Great Lakes region.

Video

httpv://youtu.be/ATEg03pm7mk

2:45 PM | Another chilly air mass for this time of year coming next week

[Euro 500 mb height anomaly map for next Wednesday; courtesy Weather Bell Analytics at weatherbell.com]

Discussion

The same overall weather pattern that produced a colder-than-normal winter in much of the eastern half of the nation and an impressive cool shot last week will produce another cool shot during the first half of next week in the same general area. Once again, it appears that the pattern is unfolding to allow for the development of a significant trough in the upper atmosphere early next week in the eastern part of the nation and it will be centered on the Upper Midwest. This will produce below normal temperatures for several days in this part of the country with the biggest departure from normal once again focused on the Upper Midwest. Yesterday’s European computer forecast model run for the middle of next week suggests there will be a deep trough of low pressure for this time of year centered over the Upper Midwest – the same type of pattern that we’ve experienced frequently during the past several months (map courtesy Weather Bell analytics at weatherbell.com).

[Temperature records courtesy NOAA]

Last week’s widespread cool shot was impressive indeed with 2085 cold temperature records set across the nation in the past 7 days as compared with 281 warm temperature records (data courtesy NOAA). It is too early to tell if this next shot of cool air will produce widespread record-breaking chill, but below normal temperatures are very likely (NOAA 6-10 forecast temperature anomaly map shown below for the period July 27th through July 31st).

7:00 AM | More humid today; cold front arrives in the region tomorrow night with possible strong storms

6-Day Forecast

Today

More clouds than sun, quite warm, more humid, highs in the upper 80’s

Tonight

Partly cloudy, muggy, mild, some fog possible late, lows in the lower 70’s

Wednesday

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

Wednesday Night

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

Thursday

Mostly cloudy, not as warm, showers and thunderstorms still possible, low 80’s

Friday

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

Saturday

Mostly sunny, pleasantly warm, mid 80’s

Sunday

Partly sunny, warm, showers and thunderstorms likely, mid 80’s

Discussion

High pressure has slipped off the northeast US coastline and more humid air is now pushing into the Mid-Atlantic region. A cold front is dropping southeastward today across the Northern Plains/Upper Midwest and this front will increase our chances for showers and thunderstorms late tomorrow as it arrives in the region and some of the storms can be on the strong side. As the front drifts to our southeast, more refreshing air should return to the region by the end of the work week. After a pleasantly warm day on Saturday, the weather will become unsettled on Sunday and continuing into early next week with the threat for showers and thunderstorms. A cool pattern will become re-established by the middle of next week throughout much of the eastern half of the nation.

Video

httpv://youtu.be/00eC8GcPCiI

7:00 AM | Heats up by mid-week, but relief returns by the end of the week

6-Day Forecast

Today

More clouds than sun, still on the cool side of normal temperature-wise, chance for a shower or thunderstorm, highs in the low-to-mid 80’s

Tonight

Mostly cloudy, mild, chance for a shower, lows near 70 degrees

Tuesday

Partly sunny, warmer, humid, chance for a shower or thunderstorm, upper 80’s

Tuesday Night

Partly cloudy, mild, some fog possible late, low 70's

Wednesday

Partly sunny, very warm, humid, chance for showers and thunderstorms late, near 90

Thursday

Partly sunny, not quite as warm, showers and thunderstorms likely, mid 80’s

Friday

Mostly sunny, more comfortable, low-to-mid 80’s

Saturday

Mostly sunny, pleasant, mid 80’s

Discussion

High pressure that controlled our weather this weekend has slipped off the east coast and this will allow somewhat warmer and more humid air to return to the Mid-Atlantic region over the next couple of days following our spell of refreshing weather. A cold front will approach the Great Lakes region by mid-week and then head towards the Mid-Atlantic later this week. High pressure returns at the end of the week to bring in another refreshing air mass to the Mid-Atlantic region.

Video

httpv://youtu.be/9KwN7_gJUR4

7:00 AM | Comfortable weather continues today; clouds dominate this weekend

6-Day Forecast

Today

A mix of sun and clouds, pleasant, highs in the low-to-mid 80’s

Tonight

Partly cloudy, comfortable, lows in the mid 60’s

Saturday

Mostly cloudy, still comfortable, low 80’s

Saturday Night

Mostly cloudy, mild, mid 60’s

Sunday

Mostly cloudy, still comfortable, cannot rule out a shower or two, low-to-mid 80’s

Monday

Partly sunny, warm, more humid, maybe a shower or thunderstorm, mid 80’s

Tuesday

Partly sunny, quite warm, chance for showers and thunderstorms, upper 80’s

Wednesday

Partly sunny, humid, very warm, chance for showers and thunderstorms, near 90

Discussion

A refreshing air mass with low humidity has established itself in the Mid-Atlantic region and it should remain rather comfortable through the weekend. After a mix of sun and clouds today, clouds will tend to dominate the scene this weekend and then it'll turn warmer and more humid as we begin the new work week. Some record lows have been broken or tied this morning in the Mid-Atlantic region in such locations as the following: Fort Meade, MD; Baltimore, MD; Harrisburg, PA; Latrobe, PA and Franklin, PA.

Video

httpv://youtu.be/51OK6KHVygE

1:00 PM | Impressive record-breaking chill from an air mass that originated in the Arctic Circle

Discussion

On this date one year ago, the high temperature reached 96 degrees in Philadelphia, 97 degrees in Washington, D.C. and 97 degrees at Central Park in New York City in what turned out to be the hottest week of the summer. What a difference a year makes!

A chilly air mass for this time of year moved late yesterday from the Upper Midwest/Great Lakes region to the Mid-Atlantic and indeed there record lows were tied or broken this morning in the following nearby locations (new record, year of previous record):

Pittsburgh, PA (52, 1970) Dubois, PA (49, 2003) Dulles, VA (55, 1976)

In addition to these nearby locations, record lows were tied or broken this morning all the way into the Deep South in such cities as Atlanta, GA; Pensacola, FL; Jackson, KY; Mobile, AL and Vicksburg, MS. Yesterday morning saw numerous records tied or broken throughout the middle part of the country:

Temperatures late tonight/early tomorrow should drop into the 50’s in the suburbs of Philly and New York City and into the 40’s across higher terrain locations in upstate Pennsylvania (e.g. Poconos).

The air mass creating this chill across the eastern half of the nation had its origins in northern Canada several days ago. In fact, using computer forecast models, NOAA’s Air Resources Laboratory can calculate the approximate trajectory of an air mass and the map shown above indeed shows that the origin region of the air mass now entrenched in the Mid-Atlantic region is just north of the Arctic Circle. This NOAA model called "HYSPLIT" is a complete system for computing simple air parcel trajectories.

7:00 AM | Comfortable weather continues right through the weekend

6-Day Forecast

Today

Mostly sunny, pleasant, highs in the low 80’s

Tonight

Mostly clear, comfortable, lows near 60 degrees

Friday

Mostly sunny, nice, low-to-mid 80’s

Friday Night

Mostly cloudy, mild, mid-to-upper 60’s

Saturday

Mostly cloudy, still on the cool side, low 80’s

Sunday

Mostly cloudy, still on the cool side, low 80’s

Monday

Partly sunny, pleasantly warm, mid 80’s

Tuesday

Partly sunny, slightly warmer, slight chance for showers and thunderstorms, mid-to-upper 80’s

Discussion

A refreshing air mass with low humidity has established itself in the Mid-Atlantic region and it should remain rather comfortable through the weekend and right into next week with no serious heat or rain threat in sight.

7:00 AM | Big changes today as a refreshing air mass moves into the region

6-Day Forecast

Today

Morning clouds will be followed by increasing amounts of sunshine and noticeably lower humidity values, highs holding in the low 80’s

Tonight

Mostly clear, comfortably cool, lows not far from 60 degrees

Thursday

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

Thursday Night

Partly cloudy, cool, low 60’s

Friday

Partly sunny, still on the cool side, low 80’s

Saturday

Mostly cloudy, still on the cool side of normal, maybe a shower or thunderstorm late, near 80

Sunday

Mostly cloudy, more humid, still below-normal temperatures, chance for showers and thunderstorms, low 80’s

Monday

Mostly cloudy, more humid, still below-normal temperatures, chance for showers and thunderstorms, low 80’s

Discussion

After the recent heavy rainfall and strong thunderstorms, the weather is about to change dramatically for the better. A refreshing air mass will push into the region today with a very noticeable drop in overall humidity levels. Temperatures will hold at below-normal levels for the rest of the week to go along with the comfortable humidity levels. After nice days on Thursday and Friday, there is a chance for a shower or thunderstorm late Saturday, but the vast majority of the time between now and then will be rain-free as this refreshing air mass becomes well-established in the Mid-Atlantic region. Elsewhere, an impressive widespread area in the heartland this morning with record or near record lows (map above courtesy coolwx.com).

Video

httpv://youtu.be/ht76fcgqJko