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Good afternoon. This is Vaughn Smith with the National Weather Service here in Peachtree
City GA with a briefing on potential wintry weather this Afternoon and Tonight. There
is still some uncertainty with the forecast but confidence is increasing in accumulating
snowfall for the Georgia mountains and widespread travel impacts due to a brief period of black
ice.
I would like to start off by talking about the recent rainfall amounts. We will get to
the specifics of this winter weather scenario in a moment, but let’s take a look at the
current situation as relates to rainfall amounts. This graphic shows the rainfall accumulations
we have received over the past 7 days. Across far north Georgia already 5-7 inches of rain
has fallen, with pockets of 8 plus inches. You can see the tight gradient of rainfall
where the amounts go to zero quickly across southern sections of the forecast area. So
how much more rain are we going to get?
We are currently expecting additional precipitation through Friday morning. This is liquid equivalent
amounts, so it includes both rain and the liquid equivalent of snow. North Georgia could
see an additional 1 to 2 inches of rain. Central Georgia will continue to see the lower amounts.
This additional precipitation could result in additional rivers going into minor flood
and a few rivers already in flood going into moderate flood. A flood watch still remains
in effect for much of North Georgia.
This graphic shows How the recent rains have weakened the Drought across North Georgia.
The Graphic on the left shows the severity of the drought as of January 8th. The Graphic
on the Right shows it as of January 15th. You can see just how much the rainfall over
the past 7 days have weakened the hold the drought had on North Georgia.
This graphic is showing the sustained win speeds across the area. Winds will continue
to increase today then slowly decrease tonight through Friday morning. This is important
to show due to the recent rainfall. With North Georgia having received 4-8 inches of rain
over the past few days…the ground is very moist. With wind speeds expected in the 15-20mph
range and gusting to 30 mph…some trees may be blown over due to the loose soil.
We are still looking for the main feature to be a cold upper level storm system that
will shift east from Alabama and move through Georgia This afternoon and tonight. Typically
systems like these produce isolated pockets of brief moderate snowfall which is why we
are expecting as much as we are over such a short time frame.
Lets take a look at some of the model guidance. This is the WRF model Reflectivity forecast.
This is basically showing what the Radar Reflectivity should look like as this system moves through
our area. This is 1 pm today…and you can see rain moving east through Georgia with
cold wrap around moisture over Mississippi and Alabama where it is currently snowing.
This is the same model by 7p tonight. You see the main line of showers has moved into
South Carolina with the cold wrap around moisture now over North and portions of Central Georgia.
By 10 pm…the wrap around moisture is still over North and Central Georgia with cooler
air infiltrating the state from the north.
By 1 am Friday…The bulk of the moisture will be east of the area but we should still
see some light show showers or flurries through 3-4am across eastern portions of the state.
This is the GFS Total Snowfall Accumulations Map. This Model is showing a 4 inch bulls
eye across Northeast Georgia with 1-2 inches across most of the northern Atlanta suburbs.
Areas South of Atlanta would see less than an inch.
The SREF Model is showing a little bit less…with a 2.25 inch snowfall bulls eye across Northeast
Georgia through Friday morning.
The NAM Model is showing a 4-5 inch snowfall Bulls eye across Northeast Georgia. I wanted
to show that even through all the models are showing a different snowfall total…They
are all showing the majority of the snow falling across North Georgia tonight.
The Hydrological Predictions Center (HPC) has taken a blend of the forecast models and
this is what they are predicting as snowfall totals across Georgia tonight.
So lets put it all together….The north Georgia mountains continue to have the potential for
the largest amounts of accumulating snowfall with 1 to 3 inches...up to 4 inches in the
higher elevations. For areas South of a Rome to Helen line you can generally expect to
get and inch or less of accumulating snow tonight. For area south of a Carrollton to
Athens line should only see a dusting if anything. All of these areas, generally north of a Columbus
to Macon to Washington line have the potential for black ice Thursday night and Friday morning.
Based on these expected accumulation values and transportation impacts due to the black
ice, a winter storm warning and a winter storm Advisory has been issued.
Here are the locations for the current Winter Storm Warning…and Advisory through Friday
Morning.
As air temperatures drop below freezing and the roadways become wet, black ice is a concern
across north and portions of central Georgia. The area highlighted in the light blue box
shows the below freezing temperatures expected for the Atlanta metro area. Temperatures should
drop below 32 degrees around midnight and increase above freezing by 9am. This time
will be delayed in the mountains where it could take a little longer to warm up.
Overall, warm soil temperatures will keep snow from initially sticking, however as the
ground begins to cool, snow will begin accumulating on surfaces. Soil temperatures have been coolest
across northwest Georgia, where values are in the 40s. This indicates the area where
snow will accumulate the quickest.
Temperatures Friday will get above freezing by 9am and continue to rise into the 40s and
50s across the area. Any frozen precipitation should all melt away by Friday morning and
afternoon.
Once this winter weather scenario is over…we are not expecting any more precipitation through
the weekend and into early next week. We are looking at a Very Cold Artic ridge building
into the region and bringing a Cold air mass to the area. Temperatures Tuesday morning
area expected to get down into the 20s and lower 30s.
Temperatures Tuesday will warm up a bit but only expecting to see readings in the 40s
and 50s.
So in summary, confidence is beginning to increase with this event of rain changing
to snow This afternoon into Tonight. The greatest snowfall amounts are expected to be across
the north Georgia mountains with the potential of 2 to 4 inches of snow. Amounts will decrease
south of there to little or no accumulation. Impacts will continue into Friday morning
as black ice is expected across north Georgia and portions of central Georgia. This will
cause widespread travel impacts. Finally…a cold air mass will move into the region through
next week dropping temperatures into the 20s and 30s.