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Posted at 7:00 PM ET, 01/29/2008

Area's Drought Continues

By Steve Scolnik

Moderate precipitation deficit persists into 2008

precip_small.2007.jpg
Chart by Capital Weather Gang. Click on image to enlarge.

While enough to get you wet without rain gear, today's semi-springlike showers have done little to dampen the impact of a prolonged dry spell in the Washington metro area. Rainfall amounts of around a tenth of an inch or less have barely equalled the long-term daily average, although more rain is possible tonight. With only two days left in the month, there have been only six days, counting today, with measurable precipitation (0.01" or more). That is less than two-thirds the average of 9.8 rainy/snowy days in the average January in the base period of 1971-2000. Total precipitation for the month is less than 50 percent of the "normal" (long-term average).

The regional 30-day precipitation percentage of average from the National Weather Service (NWS) Precipitation Analysis shows a lot of sub-average yellows and oranges, with the near to above-average grays and greens mostly limited to parts of the Northern Neck of Virginia and southern Maryland. The intensity of the dryness increases generally northward and westward of the Beltway, with Montgomery, Fairfax, and Loudoun Counties faring the worst within the near 'burbosphere.

Looking back at the last six months, the picture isn't any better, with large areas in the range of 75 percent or less of average. A sizable chunk of central Loudoun County is in the 25-50 percent bracket (and we're not talking tax cut proposals in this primary season). Outside of far western Maryland, there's virtually no above-average area south of the Mason-Dixon line.

The dry conditions have prevailed into this year from an also very dry 2007. The chart at the top of this post shows the monthly percentage excess or deficit of precipitation. Only April (+50%) and October (+103%) were substantially wetter than usual. Although October was quite wet, by far the greatest portion of the rainfall came in the four inches that fell on the 26th-27th. That two-day amount was nearly one-eighth of the total for the entire year. The number of rainy days was only 5, compared with 7.2 in an average October. August and December were marginally above average, but the other eight months all contributed significantly to the yearly deficit of 16 percent, especially the consecutive months of May, June and July.

Fortunately, the situation hasn't reached the magnitude of the "Exceptional Drought" classification as it has in the interior Southeast, but large portions of Virginia and central and southern Maryland are in the Moderate Drought category. Since it's clearly too warm right now for the white stuff, disappointed snow fans might want to consider doing a rain dance instead. The effects will be less obvious now that stuff isn't growing, but your lawn, shrubs, trees and water supply will thank you in the spring.

By Steve Scolnik  | January 29, 2008; 7:00 PM ET
Categories:  Droughts, Local Climate  
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Comments

On avarage, we are supposed to get, give or take, 3" of rain per month, every month, every year. That's 0.75" per week!!! I've lived in this area for almost 20 years and during the last 3-4 years I've missed REAL rain. Regular rainy days when it rains in the morning, afternoon and evening. Not just a shallow front moving thru in the afternoon. I miss regular NE storms from the south, "drowning" us with an inch or two. What we have now, every month, are a couple of 30% chance rains, fizzling out to nothing when it reaches Annapolis.

I hate those Bermuda Highs or whatever. My garden, that was here way before me, and the generation before me is dying away in front of my eyes.

But tonite we have 100% showers!!!!!

Posted by: Larry | January 29, 2008 8:10 PM | Report abuse

There's always a lot of variability that goes into those averages, but recently the variability has been more on the down side.

Posted by: Steve, Capital Weather Gang | January 29, 2008 9:20 PM | Report abuse

I miss the rain too. On the rare occasions lately when it's fallen hard enough to actually hear it, I've stayed up late to listen to it on the roof.

Posted by: ~sg | January 29, 2008 9:31 PM | Report abuse

I wish to thank Steve for giving attention to this developing crisis.

I have posted twice during the past week on this situation, and do not wish to be repetitive, but actual riverflows within the Potomac basin from the USGS may help to expose the gravity.

These flows are valid today:
Normal flow rates are established from 45 to 77 years of data.
South River at Waynesboro - 28% of normal flow.
Shenandoah River at Luray - 41% of normal.
Potomac River at Little Falls - 45% of normal. The normal flow at Little Falls for this date is 9430 cubic ft. per sec. The flow today was only 4,230 cfs.

If the pattern that has predominated for more than a year persists, does anyone care to guess what the flow of the Potomac at Little Falls will be in July ??

Posted by: Augusta Jim | January 29, 2008 9:43 PM | Report abuse

Augusta Jim/Steve,
thanks for this info, the drought had truly slipped my mind, and yes I too miss the sound of a steady rain. I like a cool rain on a Saturday that allows you to not feel guilty doing nothing but building a fire and reading the Post*

*unintentional host plug

Posted by: Curtis | January 30, 2008 12:34 AM | Report abuse

Does anyone know if there's data out there about how this is impacting the native fish populations? And how far west? (West Virginia streams too?)

Posted by: missy | January 30, 2008 7:35 AM | Report abuse

Missy,

I would think fish and wildlife might have that info. When I lived in WV there was also the Isaac Walton League.

Posted by: Sara in Oakton | January 30, 2008 11:19 AM | Report abuse

I don't miss the rain at all if it comes when I'm trying to commute. Friday morning could be a REAL HASSLE. That said, we are in a significant deficit mode; same goes for snowfall.

Last night I was expecting rain so brought an umbrella with me to the Clarendon Ballroom. Didn't feel a drop between 8 and 11 PM, though the forecast had been for heavier rain during evening and nighttime hours. Radar keeps showing that rain keeps passing north of the Metro area. I wonder what's responsible for this effect. (jet stream???)

Posted by: El Bombo | January 30, 2008 2:00 PM | Report abuse

The comments to this entry are closed.

 
 
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