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Good afternoon. This is Keith Stellman with the National Weather Service in Peachtree
City GA with a briefing on rainy conditions today through next week.
Water Vapor Satellite imagery from 7 AM this morning shows the weak short wave moving through
the region today as well as the system moving through the upper mid-west. These two systems
will combine over the next 24 hours off the east coast resulting in a significant snow
storm for the Northeast US. For us here in GA, once the southern wave moves through late
tonight, conditions will improve for Friday and Saturday.
Total Rainfall forecast for the region through Friday shown here. Heaviest rainfall amounts
are expected across the southern portion of the area from Columbus to Macon to Augusta.
North GA will generally receive less than 1” with this first system.
Slide 4 This is the graphic
Weather conditions through the weekend for the most part will be near normal and pleasant.
Highs on both Saturday and Sunday will range from the upper 50s across north GA to the
lower and middle 60s across central and south GA.
The upper level and surface weather pattern are shown here from the GFS model for Saturday
AM. An upper level ridge of high pressure will dominate the center of the country meanwhile
the noreaster off the New England coast will be producing heavy snow for that region. Our
attention will shift to the upper level low across the western US as it will be our next
weather maker
By Sunday AM, the upper ridge shifts east as the upper level low over the southwest
lifts north and east toward the great lakes. At the surface, high pressure will shift east
with a gradual increase in south winds ahead of a front that will be moving through the
lower mississippi valley region toward us.
By late Sunday in Monday, the upper level low formerly in the southwest will be located
over the great lakes and the cold front associated with it will be slowing down or stalling across
our region. This front is forecast to stall over us due upper level winds above the front
becoming nearly parallel to it as noted by the green lines in this graphic showing the
upper level pattern as of Monday AM. Note that the winds aloft will be moving parallel
to the green lines which is parallel to the surface front.
Total rainfall forecast for the period starting Sunday through Tuesday. This rainfall will
be primarily associated with the stalled or slow moving cold front. The heaviest rainfall
is expected along the I85 corridor.
The Tuesday AM weather pattern shows that the front will have made very little progress
south and east as we await the upper level low across the western us to kick the front
out. The rainfall focus will shift on Tuesday from north and north central GA to south and
southeast GA as the front slowly works that direction. There are still some model uncertainties
with timing as the solution shown here is a bit faster than other models we have to
look at.
Total rainfall forecast for Tuesday through Wednesday showing the shift to the south and
east with the precipitation. These areas will be able to handle this rainfall a little better
as they have been in a longer term drought as compared to north GA.
This graphic depicts several different model total rainfall forecast through next Wednesday.
Top left is the 00z Feb 7 Run of the GFS, top right is the 06Z Feb 7 run of the GFS
and the bottom left is the 00z Feb 7 run of the ECMWF model. All of the models differ
slightly in their amounts but all are consistent in suggesting that heavy rainfall is coming
and in a general swath across a large portion of GA. The worst case is the ECMWF in the
lower left showing a little over 6” across Central GA.
This is the total 7 day official rainfall forecast from the Hydromet Prediction Center
from 7 AM Thu Feb 7. Highest amounts are shown in pink across east-Central GA where 6”
– 7” is possible. The area in red from Athens to Lagrange to Columbus to Vidalia
indicates where 5” – 6” will be possible. Areas of north GA are currently forecast to
have the lowest amounts ranging from 2” -4”, however, as you’ll see on the next
slide, that area has had the most rain so far this year and is much above normal.
This graphic shows the total rainfall accumulations for January 2013. More than 10”+ have fallen
across the north GA counties with more than 5”+ in an area north and west of the I85
corridor. Because of these wet conditions leading into this next rainfall, flooding
will be a concern across the entire area.
At this point, we have a high confidence that flooding will occur across the region especially
beginning late Monday through the middle of next week. Because of the uncertainty of how
quickly the rainfall will occur, for example the rainfall rates, we only have a medium
confidence in flash flooding. However, the greatest likelihood will be across the metro
areas and in the hillier terrain of north ga due to the wet antecedent conditions.
Due to the widespread nature of these heavier amounts, there will be the possibility of
some significant flooding. That is, there could be some moderate to major flooding at
a few river and creek locations due the these heavy amounts of rainfall. By moderate or
major flooding, we mean some impact to roads or structures. It is too early to tell at
this point which areas will have the greatest impact, but we will keep you posted through
the weekend as this event unfolds.
In summary, we are looking at a very wet week ahead with two different systems affecting
GA. The first is today and Friday where 1” to as much as 2” will be possible across
the southern half of the region. The second and larger system will begin to affect the
region late Sunday night through Wednesday where widespread 3-5” will be possible.
Flash flooding and Flooding will certainly be likely across the region, particularly
Monday and Tuesday.
Late Friday through the early part of Sunday look to be near normal in terms of temperatures
with generally pleasant conditions across area.