The SI Weather
21Jul/14Mon

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

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18Jul/14Fri

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

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17Jul/14Thu

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

bck_traj

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.

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17Jul/14Thu

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.

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