This weekend’s thunderstorms didn’t bring much drought relief to Gwinnett county, despite the tempting red splotches on the radar all around. Saturday morning brought less than a tenth of an inch at my house, and then nothing for the rest of the weekend.

Other locations did see a reasonable amount of precipitation, though. A storm passing through early Sunday morning and some afternoon rainfall brought .78 inches of rain to Covington–the most rain recorded in North Georgia on Sunday. Meanwhile rainfall amounts varied a lot, even at relatively close distances. Marietta recorded .73 inches on Sunday, while nearby Charlie Brown Airport in Atlanta got not a drop. In Cartersville, they had a quarter of an inch, while Rome received only trace precipitation. Atlanta, which has recorded a scant .23 inches of rain for all of June ended Sunday with only 1/100 of an inch of rain.

The weather over the last week or so has featured an upper level trough over the east coast that has tended to keep tropical air from the Gulf of Mexico away. Thus dew points have been relatively low, making it harder to generate thunderstorms. The rain we’ve had has been caused by small disturbances traveling on the edge of the trough. That is likely to change later in the week, as the trough moves out and moist air returns. However after this evening, we’re not likely to have a good chance for precipitation until the weekend.

It looks like we could have a record cold temperature this evening/Wednesday morning.  The current record low for April 30th is 40 degrees set back in 1969.  Forecasters are calling for a low of 36 in Lawrenceville, but only 42 for Hartsfield Airport, so it’s going to be close.  The Weather Service has issued a frost advisory for most of the state north of Macon.

The cold air is caused by Canadian high pressure sweeping into the area following last weekend’s rain.  Usually these cold blasts end around the first of April because developing high pressure off the Atlantic Coast (the proverbial Bermuda High) strengthens enough to counteract the approach of the cold front from the north.  Between this round and the cold weather back in the middle of the month, we’re likely to end April with below normal temperatures for the month.  You can be glad you’re not in Chicago or as far south as West Virginia, which have had a late season snowfall.

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I got a comment from Matt asking how we’re doing with the drought, given the recent rainfall, and rather than answering his question in another comment, I decided to do a new post.

In reality, with 9.79 inches of Atlanta is still behind what would be ‘normal’ rainfall by 2.44 inches as of yesterday, and some of that deficit has been reduced by today’s storms.  However, we are doing better than as of this time last year.  In 2007, Atlanta had recorded only 7.71 inches by March 14th, 2.08 inches less than in 2008.  In Gainesville, which has had 10.74 inches of rain so far, they are ahead by 2.17 inches.  Here in Lawrenceville, I’m only showing .86 inches more rain than this time last year, but keep in mind I don’t have an ‘official’ rain gauge.

Even though actual rainfall varies across the metro area, it’s probably safe to say that we’re two inches ahead of where we were this time last year.  Plus, in 2007, the second half of March ended up being rain-free, so by the end of this month, we are likely to be even further ahead of 2007.

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It’s probably just coincidence that on the day with the most rainfall since last December, Gwinnett County clarified its plans for outdoor watering this spring. While the county has gone along with the state and allowed the filling of swimming pools, it has declined, at least for the moment, to go with the relaxed hand watering rules announced by the governor a few weeks ago.

In mid-December, the county commission passed a water conservation resolution (PDF) that set limits on outdoor watering that were more restrictive than the state’s level four watering restrictions in effect at the time.  The resolution limited the state’s exemption for watering of new or reconditioned landscape to watering on ten of the first 30 days following installation or reconditioning. The resolution also requires that exempted homeowners and businesses post a sign visible from the right of way stating the exempted area, the installation date, the firm doing the installation/reconditioning, and the property owner’s name.

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Back on Christmas, I posted that 2007 was not going to be the driest year ever recorded in Atlanta, given the Christmas rains. I also quoted the record as having been set in 1931.  Well, reviewing my sources, I found I was half right.  The 1931 amount was for rain through December 12th, not December 31st. They must have had more than two inches of rain in the last three weeks of December that year, because the actual record for the entire year is held by 1954, with 31.8 inches of rainfall.

With the good soaking we got on Friday, Atlanta’s rainfall total now stands at 30.55 inches for the year, or 1.26 fewer inches than the record amount of 1954.  There’s a reasonable chance that we’ll see that much tonight and tomorrow, but it really depends on where the bulk of the precipitation falls. Right now, a surface front lies across Georgia from southwest to northeast.  The exact position of the front will determine the amount of rainfall we see, but the HPC is calling for a band of two inch rainfall roughly between Columbus and Greenville, SC.  It may very well be that since Atlanta’s official rain gauge is at Hartsfield Airport on the southside, where more rain is expected, the record will be avoided.

In any case, the rain is welcome, although it’s going to be followed by colder weather to usher in the new year. Look for temperatures in the low 20s Wednesday morning, and highs only in the 40s on Wednesday.  By Thursday, we start returning to more normal temperatures, and even above normal temperatures for the first two weeks of the new year, with high temperatures reaching into the 60s, 15 degrees above normal. Lows should be in the 40s, also well above what we would expect to see in early January.

Meanwhile, tropical weather may be getting ready to make a late season appearance.  The National Hurricane Center is reporting that a low pressure system 950 miles southwest of the Azores is developing tropical characteristics, and could become a subtropical storm by Sunday morning.  We already had  Subtropical Storm Olga make a late appearance in mid December, so something is not out of the question.