Thursday, December 15, 2011: Rain For Everyone Today, SPLIT Forecast Tomorrow
Good Thursday morning, everybody. It's a soaking day with widespread rain sliding across the area. In general, most places will end up with close to 0.5" to 0.75" of rain today, which will take us about 1/3rd of the way to the annual rainfall record in Lexington. Showers will become lighter in the afternoon, and temperatures will plunge late this evening behind the late-day cold front.
Friday will be a very SPLIT FORECAST between the drier north and wetter south. A second area of low pressure will slide just to our south tomorrow, producing another round of rain in southern Kentucky on Friday. This will generally be a lighter rainfall. Temperatures will peak in the lower 40s tomorrow, on the heels of the cold front. While northern parts of the area may stay entirely dry (generally north of I-64) on Friday, several hours of southern KY rain may end with a few sleet pellets or wet snowflakes mixing in before precipitation totally exits.
Here is a small sampling of the SREF forecast for 7 PM tomorrow. SREF stands for Short Range Ensemble Forecast. Basically, a computer model is run many times, with a slight difference in initial conditions as input for each run ("ensemble member"). The slight differences in input can lead to a variety of differences in the member forecasts. This is a way of determining degree of confidence in one forecast solution vs. another forecast solution.

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Courtesy: Penn State Univ. Dept. Meteorology
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These maps represent a sampling of 9 of the ensemble member forecasts for precipitation type at 7 PM on Friday. This is the time frame when precipitation will become VERY LIGHT in southeastern Kentucky, if any is left in the area at all. Blue represents a snowfall forecast, green is rain and sleet / freezing rain are the reds and magentas in between.
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IMPORTANT NOTE: In a precipitation type forecast, there is no differentiation between extremely light precip and heavy precip. Drizzle or a snow flurry may appear as bold, with the same color coding, as torrential rain or heavy snow. Precipitation will be EXTREMELY LIGHT at 7 PM, if any is left in KY at that time on Friday.
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Dry weather will return for the weekend, and temperatures will be seasonable (highs in 40s, lows in 20s).
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A word on Herrington Lake's flooding situation: The lake continues to fall steadily this morning, and is now back to NEAR flood stage, after about 2 weeks of flooding.
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While there is some widespread rain falling right now and today, this should not be enough to significantly slow the fall of the lake level.
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Herrington Lake drains much of Boyle Garrard and Lincoln Counties, and some surrounding areas.
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Have a great day, and stay dry!
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Geoff