Wednesday, June 21, 2006
10-Day Outlook: Unbearable Heat, then Much Cooler
Josh Larson @ 11:00 PM
Today's Weather
If we had a "Not-Nice Day Stamp," today would be a prime contender. Expect morning clouds giving way to afternoon sun, scorching afternoon highs from 92-96 and very high humidity levels producing dangerous Heat Indices from 100-105, especially in downtown areas. A cold front slowly approaching from the west may bring very widely scattered late afternoon thunderstorms, but most places will remain dry. Partly cloudy and sultry tonight, with uncomfortable lows from 72-76.The rest of the forecast, through the weekend and beyond, continues below after the Pattern Overview and Booz Allen forecast.
Pattern Overview
Thankfully, after today, the unbearable heat will begin to break -- which will lead to a period of cooler than average temperatures -- courtesy a slow-moving, indecisive cold front. That front, however, will be the reason that in addition to dramatically cooler temperatures in the upper 70s for highs this weekend, we'll see the potential for numerous, widespread showers and thunderstorms from Friday thorough Sunday.
Computer modeling suggests that, as occasionally happens around here, the approaching cold front will essentially stall out over the region this weekend, with several waves of low pressure riding up the nearly-stationary front. As such, we'll count on considerable cloud cover, high temperatures below 80, and significant chances for precipitation. While forecasting temperatures and precipitation in a stalled cold front scenario is typically tricky business, there is good model agreement at this time which leads to at least moderate confidence. In fact, some models (such as the GFS forecast model) suggest the potential for several inches of drought-busting rain this weekend, which would significantly cut into our year's deficit of rain, and please green thumbs, but might greatly dissapoint those keen on outdoor activities this weekend. In the wake of the cold front which will finally clear the area by early Monday, we'll look for widely scattered showers and thunderstorms lingering during the first half of next week, slightly cooler than normal temperatures -- courtesy a lingering trough over the Northeast -- and a return to mostly sunny skies.
Image above: the HPC's 5-day Total Forecast Precipitation, showing the potential for heavy rain over our area this weekend.
Booz Allen Forecast
High heat and humidity will be the big story as first round play begins today at the Booz Allen Classic in Potomac. Temperatures should be near 70 as the first groups tee off at 7am, but climbing into the low-to-mid 90s by afternoon. A stray, pop-up late afternoon shower or thunderstorm can't be ruled out, but it's more likely that precipitation will hold off until after play has finished for the day. The real threat, for both spectators and players, is the high humidity, which could produce dangerous heat indices above 100 degrees. The obvious advice: Drink lots of fluids.The next 5 days (June 22-26)
Forecast highs/lows: 83/69 (normal = 86/67)
Forecast precip: Much above normal
After today's scorching heat, we'll see more bearable temperatures on Friday, but with more cloudiness and pretty good chances for scattered late-day showers and thunderstorms, some of which may be heavy and gusty. Expect afternoon highs near 87, with scattered showers and thunderstorms lingering overnight and lows near 71. Saturday and Sunday will feature pretty much the same weather: mostly cloudy skies (with occasional peaks of sun) and widespread showers and thunderstorms through the daytime and nighttime hours, some of which may feature torrential rain. Expect much cooler highs both days in the upper 70s with overnight lows in the upper 60s. Monday will feature a return of party sunny skies, with a chance of more widely scattered showers and storms, and highs near 80. The following 5 days (June 27 - July 1)
Forecast highs/lows: 85/66 (normal = 87/68)
Forecast precip: Near normal
Computer models suggest that after the cold front finally clears the region on Monday, we can expect a period of rather benign weather from Tuesday through Saturday of next week. I anticipate that a weak trough will hang out over the Northeast, which will keep temperatures at slightly below normal levels as well, in addition to humidity (for late June). While widely scattered showers and thunderstorms cannot be ruled out for any day next week, no widespread precipitation events appear likely at this point. Most days will feature partly to mostly sunny skies with highs from 82-86 and overnight lows, for the most part, in the mid 60s.
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