Midnight update: Flash flood warning issued for central Fairfax County and Fairfax city until 3 a.m. Flash flooding has been reported in Fairfax city where doppler radar has indicated more than 2” has fallen in a short time. The National Weather Service indicates a police report of cars submerged at Roberts and Forest Avenue.
Additional thundershowers are possible through pre-dawn. Remember, never try to cross a flooded roadway in your vehicle. Turn around, don’t drown.
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10:45 p.m. update: Three bits of good news: 1) Although there are strong storms with torrential rain rates (2”+/hour) around Falls Church and Annandale, none of the storms in the area right now are severe 2) Areas needing rain like NW DC and southern Montgomery county are getting it from the current thundershowers, 3) More thundershowers still lie to the west, and may bring additional beneficial rain to parts of the area over the next few hours. This will be the last update of the evening unless something particularly severe develops - however, we’ll have some updates on the Twitter feed above which you can re-load for the latest. Thank the heavens for this “polite” rain. Continue monitoring the storms in the tracking center below or on the interactive and static radar views at PostWeather.com, and comment with your storm reports.
10:10 p.m. update: Storms are into central Fairfax and southwest Montgomery county, and about to move inside the beltway on the west side. Main impacts will be heavy downpours and lightning. Storms will probably arrive in the District and rest of southern Montgomery county in next 30 mins and eastern suburbs after 11 p.m.
9:20 p.m. update: A line of strong to severe storms has developed over south central Fauquier county into northwest Prince William county. Quarter-sized hail and winds to 60 mph are possible with this storm (for which a severe thunderstorm warning continues through 9:30 p.m.) This line should advance into the Fairfax county over the next 30-45 minutes, and, if it holds together, into the District and Montgomery county between 10:00 and 11 p.m. We’ll keep you posted.
From 3:40 p.m.: A front crawling into the region today, and taking much of tomorrow to get out of our hair, will trigger occasional showers and thunderstorms. They will tend to be hit or miss, and most numerous this evening. An increase in sunshine Friday should boost temperatures 5-8 degrees warmer than this afternoon’s highs near 80.
Through Tonight: Widely scattered showers this afternoon probably become a bit more concentrated this evening before slowly decreasing after 9 or 10 p.m. The GFS model wants to give us a deluge, whereas the NAM model is far less generous. I’m favoring the drier NAM, but still think about half of the region sees measurable rain. A strong thunderstorm or two is possible, but more likely well to the northwest.
Tomorrow (Friday): As the cold front passes just to our east, rain chances decline. Still, the front’s within close enough proximity to generate a 30% chance of a shower or thunderstorm - best odds in the eastern suburbs. Sunshine is more prevalent than today, with highs in the mid-80s - maybe even upper 80s.
Pollen update: From Walter Reed: “Tree pollen is LOW (NAB range) at 4.79 gr/cubic meter, MODERATE for our local area count data. Grass pollen is LOW (NAB range) at 4.47 gr/cubic meter which is also MODERATE for our local grass counts. Weed pollen is LOW at 1.92 gr/cubic meter and mold spores are in the LOW range at 3644.51 spores/cubic meter.”
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