Small chances of storms tonight
While not as hot as last year’s record setting 102 degrees on this date, today’s been plenty warm - with highs reaching the mid-90s in most spots. A front draped across southern Pennsylvania separates our steamy airmass from the cooler, drier air lurking to the north. As the front drifts southward, shower and thunderstorm chances increase. We have a small chance of storms this evening, but a much better chance Friday afternoon with the front on top of us.
Through Tonight: Storms are most likely (50%-60% chance) between Baltimore and the Mason Dixon line, but a few could (30-40% chance) sneak south into the metro region - especially later this evening, between about 9 p.m. and midnight. Any storms that do move through will probably be slow moving, and thus, capable of producing heavy rainfall amounts over isolated areas. It’s downright muggy, with overnight lows 69-75 (suburbs-city).
Tomorrow (Friday): With the front in our immediate vicinity, expect mostly cloudy skies and only peeks of sun. Periodic showers and thunderstorms are likely, especially in the afternoon and evening. Note: it will not rain all the time and don’t be surprised if a few areas miss out on a lot of the rain. Cloud cover will probably hold high temperatures in the mid-to-upper 80s.
Where and when it falls, rainfall has the potential to be quite heavy, prompting the flash flood watch that was issued. Total amounts will be highly variable (depending on your location) but average amounts should be in the 0.5-1” range. However, slow-moving heavy rain storms have the potential to drop more than 2” of rain in a short time.
Pollen update: Walter Reed reports tree, grass, and weed pollen are all LOW.
90 degree days: Today marked our 19th 90+ degree day of 2011. The average number of 90+ days year to date is 11.6. Only 14 out of last 139 years (or 10%) have had more. 1979 did not have any. The record-setting 2010 had 27 through today. (h/t Ian Livingston)
Weather Gang Lab: In today’s video, I walk through the forecast through the weekend, recap June, and discuss the weather for the Atlantis launch. Watch it...