WRAL WeatherCenter Blog

Relief - But Brief?

Posted November 21, 2005

For several days we've watched the coming development of what appeared to be a widespread, soaking, and much-needed rain for drought-parched central NC. There were enough variations among computer models in the particulars of the system on hand that no guarantees were possible, but we've been expecting somewhere between one half and two inches of rain for the past two to three days, and in the end the nature delivered nicely today, with rainfall amounts settling neatly into that range for much of the WRAL viewing area and even running in the 3 inch range across southeastern parts of the state. At my home in Apex, the total as of late this afternoon has been 1.2 inches, and some other representative values from the area include about 1.7 inches at RDU, just over an inch at the Fayetteville airport, and about .8 inch at Greensboro.

A large rain shield with embedded areas of moderate to high rainfall rate during the morning to midday hours accounted for most of these totals, but there should be at least some modest additions tonight with the passage of a trailing mid-upper level low that will open into a progressive trough and sweep northeast across the state. It appears the most substantial totals with this portion of the storm will fall across the western Piedmont, mountains, and foothills, perhaps finishing off with some accumulating snow (trace to around three inches) in the western mountains as colder air encroaches. For us, a few lingering sprinkles or light showers by early Tuesday should give way rapidly to a mix of clouds and sun, with a cold, blustery northwest wind.

The kind of system we're experiencing now is just what we need for drought relief, and it would be nice if we could expect repeat performances every three or four days for a while. Unfortunately, this may have been a one-off event for the time being, as the next week or two appear to be dominated by a cold trough over the eastern U.S. that will leave the deepest moisture and best lift (needed for persistent, widespread rains) off to our east. Barring a pattern shift, we could be left instead with occasional "clipper" type systems that dive in from the northwest, offering up only a few clouds, occasional brief rounds of light precipitation, and reinforcing shots of cold, dry air. That possibility is reflected in medium range outlooks from NOAA's Climate Prediction Center, showing a tendency toward below normal temperatures and precipitation over the eastern U.S. in the 6- to 14-day period. See the associated graphics at:

http://www.cpc.ncep.noaa.gov/products/predictions/610day/

and

http://www.cpc.ncep.noaa.gov/products/predictions/814day/

Likewise, the longer range outlook for the winter season ahead, while not leaning toward either a drier or wetter than normal pattern due to the lack of clear long-term moderating influences, doesn't offer great hope for a rapid recovery from dry conditions, as indicated in the winter outlook and the latest seasonal drought outlook extending through February. You can see those products at the addresses below:

http://www.noaanews.noaa.gov/stories2005/s2534.htm

and

http://www.cpc.ncep.noaa.gov/products/expert_assessment/seasonal_drought.html

Of course, long range predictions are subject to large uncertainties, so while the outlook isn't very promising, we can at least cross our fingers and hope that a more active precipitation regime manages to develop over the region in spite of the current lack of positive indicators. That, and conserve water where we can just in case...
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