Tuesday, September 15, 2009

Wet pattern may continue into the weekend

5-Day Total Precip Forecast
The latest computer model extended forecasts are indicating that the current weather pattern over this region of the country may remain stagnant throughout the week and into the weekend. The pattern consists of a vertically-stacked low pressure system (meaning low pressure at levels of the atmosphere) that is sitting over the ArkLaTex (Arkansas-Louisiana-Texas border region) and moving very little. With southerly wind on the east side of the system, moisture is streaming north from the Gulf of Mexico into the Mid-South, southeast U.S., and Lower Mississippi Valley, producing very cloudy and muggy conditions and plenty of shower activity, along with some embedded thunderstorms.
With no stronger systems approaching from the west to push this system on, the low moves very little and conditions don't improve. This has prompted the issuance of Flash Flood Watches for the entire region and occasional Flash Flood Warnings in areas where heavy showers occur. The map above shows the rainfall potential for the remainder of the week - the Memphis metro area could see 3-4" of rain over the next 5 days, following many reports of 2-3" on Monday.

As we head towards the weekend and the low weakens slightly, I expect shower activity to become more diurnal in nature, meaning that more rain will be around during the daytime hours than at night. In addition, there will probably be more breaks in the clouds, which could promote heating of the lower atmosphere and additional lift, resulting in more thunderstorms versus showers.
Extended computer models are also identifying a potential fall season cold front, with a strong push of cooler air behind it, to arrive early next week, which would pick up whatever is left of the persistent low and move it on, allowing skies to clear out and rain chances to dwindle. We'll hang on to that hope and, in the meantime, deal with soggy conditions for the next several days! Keep the umbrella handy, remember not to drive into areas where water covers the road, and always use headlights when windshield wipers are on.

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