Posted: 4:10 pm Wednesday, May 16th, 2018
By Kirk Mellish
Following the morning rain the atmosphere around Atlanta has stabilized so there’s much less rain with peaks of sun. Showers and an isolated thundershower will redevelop to end the day then diminish overnight.
As I pointed out on the radio the other day, in tropical air masses the computer models have a well known bias of over exaggerating the rain threat and amounts. This leads those web pages and phone APPS and other things you look at with cute weather symbols showing endless days of rain and lightning symbols and dire warnings of flooding. And yet much of Tuesday was dry even where it rained, and lots of areas got zero.
The models have a problem with all the moisture and so tend to show it as ALL rain instead of mostly clouds with some rain. I’ve seen it hundreds of times over many decades.
Yes, rain is LIKELY at times. At times the next 7 days with scattered coverage any given day.
Amounts the next 3-days expected to average around 1 inch, but some spots could get double or triple that while others hardly get anything. Where that could be will vary each day.
When rain amounts are forecast I say “will average”, if you are unfamiliar with how averages work you can google it.
The surface and upper level low pressure system in the Gulf of Mexico will continue to pump gulf and Atlantic moisture into the region over the next 7 days. So rain will be possible anywhere anytime through the period. However, plenty of dry areas and dry hours in-between as you look at the next 7 days as a whole. Expect muggy conditions in the soupy air mass with dew points summer-like in the 60s to low 70s, with limited sun from breaks in the clouds at times through the period.
As of Wednesday afternoon ADDITIONAL rainfall amounts look to average less than .75 of an inch through the day Thursday.
The peak coverage of rain and isolated thunderstorms (most days anyway) will come in the afternoons and early evenings next 7 days. Temperatures will range from 78-84 with lows 64-68 through the weekend.
So for outdoor activities just know rain is possible on a daily basis along with isolated thunder and lightning. If you hear thunder you are in danger of being struck by lightning so get inside.
The rain will not be continuous with good breaks between showers most days and the sun will be out at times with a tropical sky.
Much of the rain will be light to moderate, but with some spots getting heavy downpours.
An interesting part of tropical rain bands in systems like this is “high efficiency”, the raindrops tend to be very large leading to quick accumulations.
Severe weather is not expected as of now.
Sometimes the sky will open up with little or no advanced warning due to the nature of this weather system.
Some areas will have more persistent rain than others, with some lucky (or unlikely depending on your needs) areas getting mostly missed. No way to tell in advance which spots will be which thanks to random nature, that’s what radar is for.
It’s impossible to give specific stop and start times for rain or thunder at any given spot due to the random nature of the hit and miss coverage across a huge area like Metro Atlanta. Some people mistakenly think Metro Atlanta is just in and right near the perimeter or it’s only where they live or work lol.
At any give time the weather is doing completely different things at the very same time across the region, as anyone who’s ever driven around here has witnessed for themselves. Or looked at the radar instead of just out the window.
500-MB CHART JET STREAM FLOW:
SURFACE WEATHER CHART NEXT 5 DAYS:
EXCESSIVE RAIN OUTLOOK WEDNESDAY:
RAINFALL ESTIMATE IN 24-HOUR INCREMENTS NEXT 3 DAYS:
ESTIMATED RAIN TOTALS OVER THE 5-DAY PERIOD ENDING LATE SUNDAY:
REMEMBER, these are average amounts, localized spot amounts will vary.
The European Ensemble shows 200-500% above normal rainfall in much of Georgia over the next 5 days!
You can see the “tropical connection” of our source of weather in the rain anomaly map:
Backward trajectories clearly show the source of our air mass:
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