Saturday, July 22, 2006
Significant Severe Thunderstorm Threat Today...
Jason Samenow @ 1:00 PM
2pm update: Storms look to occur a bit later than estimated earlier. Closer to 4-5pm far western suburbs, 6-8pm immediate DC area and east.
Atmospheric conditions may be conducive for dangerous thunderstorms.
Not everyone will experience storms or severe storms, but the potential exists for storms with damaging winds and even tornadoes in some areas.
A number of ingredients could come together today for a significant severe thunderstorm outbreak in the Mid Atlantic. While it will not rain most of the day, given the severe weather potential this afternoon and evening, tomorrow offers better promise for (relatively) worry-free outdoor activities.
Notable severe thunderstorm threat. The following is my best guess as to the possible sequence of events today (caveat: it is VERY difficult to forecast the timing of thunderstorms):
Why possibly severe storms? These ingredients are in place:
According to a Special Weather Statement from the National Weather Service Forecast Office in Sterling:
A factor that may prevent a widespread severe thunderstorm outbreak is cloudiness. If it's cloudy, the atmosphere may not destabilize sufficiently for severe storms to form. But if it's sunny when you're out late in the morning and early in the afternoon, be concerned. Monitor the area above this post to see if watches/warnings are issued for your county. Also, keep an eye to the sky and check the radar periodically. Report your storm observations in our comments area.
Pictured: The sun appears as a thunderstorm moves to the south and east of Fairfax, VA yesterday. By CapitalWeather.com photographer Kevin Ambrose.
Overnight, there will be gradual clearing and it will be a bit cooler, with lows in the low 70s (downtown) and upper 60s in the cooler suburbs.
Lower humidity, much improved. Humidity will drop noticeably and sunshine will likely be more abundant -- although there will be scattered cloud cover. High temperatures will be in the low to mid 80s and dewpoints will only be in the low 60s -- so it will feel more comfortable. There's just a slight (20%) chance of an isolated thunderstorm due to some cold air aloft.
Atmospheric conditions may be conducive for dangerous thunderstorms.
Not everyone will experience storms or severe storms, but the potential exists for storms with damaging winds and even tornadoes in some areas.
A number of ingredients could come together today for a significant severe thunderstorm outbreak in the Mid Atlantic. While it will not rain most of the day, given the severe weather potential this afternoon and evening, tomorrow offers better promise for (relatively) worry-free outdoor activities.
Today
Notable severe thunderstorm threat. The following is my best guess as to the possible sequence of events today (caveat: it is VERY difficult to forecast the timing of thunderstorms):- 7am to 1pm: Variably cloudy and muggy, with temperatures rising from the mid 70s to near 80
- 1pm to 4pm: Partly sunny and humid, storms approach western suburbs around 4-5pm. Temperatures in the mid 80s.
- 4pm-8pm: Storms in the immediate DC area between 5pm and 8pm, moving into the eastern suburbs towards dark. Temperatures falling into the upper 70s.
Why possibly severe storms? These ingredients are in place:- A warm, moist and unstable airmass brought about by strong southerly flow at the surface. Humidity levels are very high (you can feel it) with dewpoints in the low 70s.
- An approaching cold front to serve as a focusing mechanism for the storms
- An approaching upper level trough (or area of low pressure) will help destabilize the atmosphere and cause the winds to turn with height.
According to a Special Weather Statement from the National Weather Service Forecast Office in Sterling:
ENVIRONMENTAL WINDS ARE ALSO EXPECTED TO BECOME SUPPORTIVE OF SEVERE THUNDERSTORMS INCLUDING SUPERCELLS WITH A THREAT OF DAMAGING WINDS...HEAVY RAINFALL AND TORNADOES. AT THIS TIME...THE GREATEST RISK FOR SEVERE WEATHER EXIST OVER NORTHERN VIRGINIA...WESTERN AND NORTH CENTRAL MARYLAND INCLUDING THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS. THE TIME FOR SEVERE WEATHER MOST LIKELY TO OCCUR IS BETWEEN 1 PM AND 8 PM.NOAA's Storm Prediction Center has placed our area under a "slight risk" of severe storms. It identifies for our region:
- A 30% chance of wind damage
- A 5% chance of tornadoes
- A 5% chance of large hail
A factor that may prevent a widespread severe thunderstorm outbreak is cloudiness. If it's cloudy, the atmosphere may not destabilize sufficiently for severe storms to form. But if it's sunny when you're out late in the morning and early in the afternoon, be concerned. Monitor the area above this post to see if watches/warnings are issued for your county. Also, keep an eye to the sky and check the radar periodically. Report your storm observations in our comments area.Pictured: The sun appears as a thunderstorm moves to the south and east of Fairfax, VA yesterday. By CapitalWeather.com photographer Kevin Ambrose.
Overnight, there will be gradual clearing and it will be a bit cooler, with lows in the low 70s (downtown) and upper 60s in the cooler suburbs.
Tomorrow
Lower humidity, much improved. Humidity will drop noticeably and sunshine will likely be more abundant -- although there will be scattered cloud cover. High temperatures will be in the low to mid 80s and dewpoints will only be in the low 60s -- so it will feel more comfortable. There's just a slight (20%) chance of an isolated thunderstorm due to some cold air aloft.
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