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Posted at 05:00 AM ET, 08/25/2011

Forecast: Heavy t’storms likely in afternoon, Irene looms for Saturday/Sunday

Flash flood watch noon thru evening (non-hurricane related)
Hurricane Tracking Center with Tweets from NHC
(originally posted at 5 a.m., updated at 8:30 a.m.)

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EXPRESS FORECAST

Today: Increasing humidity with p.m. t’storms. 87-92. | Tonight: T’showers end early. 67-73. | Tomorrow: Mostly sunny, not quite as humid. 86-91. | Get Express Forecast by E-mail

FORECAST IN DETAIL

Don’t lose sight of today’s weather looking off toward Irene and the weekend. There is a good chance of storms and some could be pretty strong with very heavy rain. If Irene were just a little closer she would actually squelch them as the air descends around the outer edges of a hurricane and inhibits thunderstorm activity. However, no such luck and traffic, while nothing like “earthquake day”, could be messy in the afternoon. The weekend starts out nice, albeit humid, but is likely to go downhill in a hurry Saturday night if Irene gets as close as the most recent models suggest. She is no gentle lady.

Today (Thursday): A partly sunny start to the day allows a quick warm up - although isolated storms are possible north and west of town. The rising humidity provides some juice for afternoon storms. Winds from the southwest at 10-20 mph get your attention. Skies should quickly begin clouding up in the afternoon as a line of t’storms is likely to be coming off the Blue Ridge by mid-afternoon. Severe storms are possible (highest chance northeast of D.C.) including gusty winds and heavy downpours. One to two inches of rain are possible throughout the region, falling in a short time, and there is a risk of flash flooding. Most likely timing would be 3 to 7 p.m. with a 70% chance of storms where you are. Highs reach the mid-80s to lower 90s but should come off notably with the showers. Confidence: Medium

Tonight: Showers should be tapering off early with only a 40% chance of lingering rain after 8 p.m.Humidity is still noticeable even after the showers move away. Readings should slip from the low 80s to the upper 70s for the evening activities. Overnight lows should only fall to the upper 60s to lower 70s. Confidence: Medium-High

Keep reading for the forecast through the weekend...

Tomorrow (Friday): Clouds quickly scuttle out of the area in the morning. It should still be refreshing behind the front with a little less humidity. However, we are likely to be transitioning to a tropical environment by the afternoon. Humidity starts ratcheting up and the sun blazes through mostly sunny skies. Highs are likely to jump right back up to the upper 80s to near 90. This enhanced warming is typical on the edges of strong tropical systems. Breezes are very light as we are still far away from Irene. Confidence: Medium-High

Tomorrow night: There should still be a starry evening to enjoy. Humidity is steadily climbing with only a light breeze from the east to help with the cooling as readings remain in the low-to-mid 80s. A few quick moving showers are possible after midnight. These are set off by the tropical storm but are not part of the storm itself. The chance of getting one is only 20% and any should be brief. Overnight lows reach the low-to-mid 70s. Confidence: Medium

A LOOK AHEAD

NOTE: THE SATURDAY AND SUNDAY FORECAST ARE DEPENDENT ON THE EXACT TRACK OF IRENE. A TRACK FARTHER WEST WOULD BRING HEAVIER RAIN AND STRONGER WINDS (FOR A LONGER TIME AND OVER A LARGER AREA), A TRACK FARTHER EAST THE OPPOSITE.

Saturday dawns with Irene approaching the Outer Banks of North Carolina. Because this is such a big system, high clouds should be steadily increasing. Breezes only slowly pick up with winds from the northeast at 5-10 mph in the morning and 10-15 mph in the afternoon with infrequent gusts to 25 mph. Another band of showers well ahead of the system is again possible (40% chance). Highs are still able to make mid-to-upper 80s. By evening, some of the outer bands of Irene may start to push through but the main rains are likely (near 100% chance) after midnight with 2” possible in the city and heavier to the east. Winds steadily increase from 10-20 mph in the early evening to 15-30 mph overnight. Gusts to 45 mph are possible when stronger rain bands move through. Lows will be low-to-mid 70s. Confidence: Low-Medium

LATEST GUIDANCE SUGGESTS WEATHER AT THE MD/DE/VA BEACHES *MAY* BE DANGEROUS, WITH TORRENTIAL RAIN, SEVERE COASTAL FLOODING AND DAMAGING WINDS. WE WILL HAVE MORE DETAILS IN POSTS LATER TODAY.

Sunday starts out with very strong winds out of the north at 15-25 mph gusting to 40 mph. Despite Irene being at its closest early in the day most of the rains are quickly pushing to the north and rain chances at 70% in the morning decrease to 30% by afternoon. In fact, do not be surprised at all to see sunny skies some time in the afternoon. Be sure to look for the deep blue skies! This is due to all that more oxygenated surface air that the hurricane pumps into the atmosphere. Winds shift to the southwest at 15 to 25 mph and highs are likely to jump again on the edge of the storm to mid-to-upper 80s. Lows slip to the mid-to-upper 60s. Confidence: Low-Medium

Monday is the calm after the storm with clear skies, light winds, lower humidity and highs only in the low-to-mid 80s. Here’s to hoping we have minimal clean up duty! Confidence: Low-Medium

By  |  05:00 AM ET, 08/25/2011

Categories:  Forecasts

 
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