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Posted at 10:35 AM ET, 06/11/2009

Forecast: Another Day, Another Chance of Storms

By Josh Larson

* Severe T-Storm Watch til 8 PM | Flash Flood Watch til 4 AM Friday *
* Outside Right Now? See Radar & More: Weather Wall | NatCast *


Today: Mostly cloudy; PM storms. Low 80s. | Tonight: Storms early? Upper 60s. | Tomorrow: Mostly cloudy; PM storms. Mid-80s. | A Look Ahead


Here we go again. Over the next couple days we'll see rather warm and humid conditions, with increasing afternoon clouds producing scattered afternoon showers & thunderstorms just in time to snarl the evening's rush hour. Because the ground is saturated in many locations, heavy rains will continue to pose a flood risk. Conditions may somewhat improve this weekend.

Radar: Latest D.C. area radar loop shows movement of precipitation over past two hours. Powered by HAMweather. Refresh page to update. Click here or on image to enlarge. Or see radar bigger on our Weather Wall.

Today (Thursday): Today's weather will be very similar to yesterday's. Plan on mostly cloudy skies with rather humid-feeling afternoon highs in the low 80s. By afternoon scattered thunderstorms will develop -- a few of which may be severe (with the potential for damaging winds and hail) -- and last, in some spots, well into the evening hours. Confidence: Medium-High

Probability: 60%
Coverage: Scattered

Tonight: We'll see muggy conditions tonight with the aforementioned scattered storms lasting into the evening hours (and in a few spots perhaps even until after midnight). Localized flooding will be a possibility in heavier storms. Overnight lows will stay propped in the upper 60s. Confidence: Medium

Keep reading for the forecast through early next week...

Tomorrow (Friday): With a nearly stalled frontal boundary remaining over the region on Friday we can expect the same unsettled conditions we'll see today. Despite mostly cloudy skies, breezy southwesterly winds of 10-15 mph will boost high temperatures into the mid-80s before (can you guess?) scattered thunderstorms develop during the afternoon hours (50% chance). A few of these, again may last into the evening hours. Confidence: Medium-High

Tomorrow Night: There may be some widely scattered thundershowers over the region during the evening hours (though not as widespread as this evening), so have a umbrella handy just in case. By the overnight hours we can expect partly cloudy (and drying) conditions with overnight lows dropping to 60-65 (suburbs-city). Confidence: Medium


Conditions (at least from an outdoor-activity perspective) will begin to slowly improve on Saturday as the front pushes south. We're likely to have a little more in the way of sunshine than the previous two days but the front will be close enough to pose a 20% chance of afternoon or evening thundershowers. Any storms should be much less widespread than today and tomorrow. Highs will reach the low-to-mid 80s with overnight lows in the mid-60s (near 60 in the cooler suburbs). Confidence: Medium

The forecast for Sunday poses a bit of a conundrum. The storm-producing front may stay to our south or it may drift northward, providing another round of afternoon and evening storms. I'll call for a 30% chance of storms -- but this assessment may need to be adjusted upward (or downward). Temperatures are the easy part of the forecast, with highs likely around the low 80s. Confidence: Low

Monday's outlook is, again, somewhat uncertain depending on where the front is. I've got to leave a chance of showers/storms in the forecast (30%), with highs around 80 after morning lows in the 60s. Confidence: Low

By Josh Larson  | June 11, 2009; 10:35 AM ET
Categories:  Forecasts  
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Next: San Francisco's Summertime Stratus Deck


Why is it that thunderstorms always seem to show up at the same time of day? I had originally thought it was due to the extra heat at the end of the day but that doesn't synch with the fact that the fronts come from the West and therefore Pittsburgh gets its storms at 2pm, West Virginia at 3pm and Hagerstown at 4pm.

Someone help me understand.


Posted by: kriscolby | June 11, 2009 8:17 AM | Report abuse


Storms do tend most frequently occur during the late afternoon and evening (in most places) because of day time heating which acts as fuel for the storms. However, the timing of fronts and boundaries in the atmosphere that serve as triggers for storms also play a role... so storms can occur at other times.

Posted by: CapitalWeatherGang | June 11, 2009 10:30 AM | Report abuse


Also, we sometimes see storms develop earlier in the day toward and over the mountains than we do here on flatter terrain because air is pushed upward as it flows across the mountains (you need rising air to form showers and storms). Whereas in the valley we're more dependent on the buildup of daytime heating to get the air rising, especially in the absence of a frontal boundary, and often the heating doesn't reach the level needed for storm development until later in the afternoon.

Posted by: Dan-CapitalWeatherGang | June 11, 2009 10:54 AM | Report abuse

Dan, good answer :) Can't really add much to that. @kriscolby, at least there's some semblance of normalcy about around what time of day summer thunderstorms form around here...

Posted by: Josh-CapitalWeatherGang | June 11, 2009 11:02 AM | Report abuse

I don't know what's worse: 3-4 days of slow steady rain (2-3 inches) or getting dumped by the same amount of rain in a couple of hours, as happened in PG county and other parts of MD yesterday.

Posted by: jojo2008 | June 11, 2009 11:07 AM | Report abuse

Unfortunately my "dry" weekend is now being knocked out. The Weather Channel is now predicting rain EVERY DAY THROUGH MONDAY!!!

Betcha that even AugustaJim is inundated by this DELUGE.

Posted by: Bombo47jea | June 11, 2009 11:11 AM | Report abuse

C'mon Josh, no way are the suburbs cooler!!

Posted by: combedge | June 11, 2009 11:19 AM | Report abuse

the ground is already so saturated -- how many days of dry weather would it take to alleviate the risk of flash flooding with every little rainstorm?

neighbor's small tree (~6 feet) toppled yesterday. no damage, but it didn't have enough roots established to hold it into the soft mud.

Posted by: akva | June 11, 2009 12:11 PM | Report abuse

kriscolby - when I spent summers with my late mom in southern FL, it seemed you could set your watch by the daily 4 o'clock thundershower. It'd build out of blinding sunlight, pour for its fifteen minutes of dark fame, then vanish, leaving behind a sparkling bright afternoon and clear evening. It was as if the lower peninsula had an appointment to drive through an automatic car-wash every day.

Sadly, it seemed the evening news had a corresponding predictability, with the anchor invariably announcing the death of a local area man by lightning. The seniors said self-employed roofers and outdoor carpenters were loath to gather up tools and interrupt the flow of work for so brief a storm.

Posted by: jhbyer | June 11, 2009 6:22 PM | Report abuse

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