Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
303 PM EDT Tuesday Mar 31 2015
to add Haralson and Carroll counties to Severe Thunderstorm Watch
number 9 that GOES until 8 PM this evening. Strong storms
developing in north Alabama have a trajectory that may track them
into these counties between around 5-6 PM if they hold together.
Short term /tonight through Wednesday night/...
/issued at 249 PM EDT Tuesday Mar 31 2015/
Storm Prediction Center has posted a Severe Thunderstorm Watch for areas generally
along and south of a Franklin to fayettevile to Swainsboro line
until 8 PM this evening...but think we will likely see this threat
go a bit longer into the evening. Latest analysis and hires model
data continue to support the potential for isolated severe storms
from late this afternoon into the middle evening hours... as an upper
disturbance interacts with increasing instability and an old
boundary stalled across central Georgia. A few of thunderstorms have
the potential to become severe... with steep middle level lapse
rates... cold air aloft and middle level dry air all supporting the
potential for large hail... strong downburst winds and frequent
lightning with the stronger storms. Expect the main severe storm
threat to be between 4 PM and 10 PM today... and generally in and
around the watch area...which means Atlanta metropolitan area is close...
so cannot rule out a severe storm brushing the downtown Atlanta
area. All interest are encouraged to closely monitor storm
development through the evening. Have updated zones to headline
Otherwise... the upper disturbance pushes east tonight... which
will increase ridging overhead for Wednesday. This will help
reduce any threat of thunderstorms on Wednesday... except maybe
down along the far southern reaches in central Georgia during the
afternoon. Will hold onto a low chance near Columbus to Macon and
southward Wednesday afternoon... but suspect the greater chances
will be south of the forecast area on Wednesday. An upper
disturbance approaching late Wednesday night will warrant a low
chance of showers and thunderstorms across the northwest zones
after midnight Wednesday night... with increasing chances into
A mav and met blend on temperatures looked good through the short term...
so did not stray far.
Long term /Thursday through Tuesday/...
/issued at 249 PM EDT Tuesday Mar 31 2015/
no changes planned to extended portions. Models are in fairly
good agreement with some discrepancies noted with system Friday
night into Saturday. For next week GFS bullish on bringing Gulf
moisture back across the area on Monday with diurnally driven probability of precipitation
across the area once again.
Previous forecast discussion appended below...
Previous long term discussion.../issued 434 am EDT Tuesday Mar 31 2015/
Long term /Wednesday night through Monday/...
the extended starts off with weakening high pressure moving off
the Carolina coast Wednesday night setting up a Bermuda like ridge over
the area through Friday. This will set up near zonal southwesterly
flow Thursday and Friday. With decent diurnal driven instability and
available moisture expecting showers and thunderstorms with the
possibility of isolated severe storms Thursday and Friday. By Friday
night a closed low center moving east through the upper
Mississippi and Ohio River valleys pulls a trailing cold front
into northwest Georgia by 06z Sat. This frontal system has decent moisture
and instability associated with it but its a very fast moving
front. It moves almost completely through our County Warning Area by 18z Sat. Will
see showers and isolated thunderstorms from this front but not to
sure about the severe threat as it moves through mainly at night.
Strong high pressure ridge builds into the area right behind this
front Sat with the state clearing our from northwest to southeast during the
day. This ridge keeps things mostly clear through Easter sun
before it pushes off the eastern Seaboard Sunday night. Temperatures will
near to slightly above seasonal norms through the extended.
/issued at 137 PM EDT Tuesday Mar 31 2015/
VFR conditions to persist through the period. An upper disturbance
will move across that state late this afternoon and evening... with
scattered showers and thunderstorms expected to develop from near
Rome to around Atlanta and down east of Macon. A few storms could be
strong with wind gusts to 35kts or greater... mainly between 20z Tuesday
to 03z Wednesday. Expect the convection to push east and south of atl by
04-05z... with middle level ceilings scattering by 09z tonight. Expect scattered
middle clouds by 16-18z Wednesday with afternoon heating. West winds this
afternoon and evening will become northwest tonight and persist on Wednesday.
Speeds around 10-12kts this afternoon... then 5-8kts tonight and
//Atl confidence...18z update...
high confidence all elements.
Preliminary point temps/pops...
Athens 53 79 53 72 / 20 10 20 50
Atlanta 55 77 57 72 / 40 20 30 50
Blairsville 48 73 49 62 / 20 10 30 60
Cartersville 51 78 56 73 / 40 20 30 60
Columbus 57 80 57 80 / 50 30 20 20
Gainesville 53 76 53 67 / 30 10 30 50
Macon 56 81 54 77 / 40 20 20 40
Rome 52 78 54 74 / 40 20 30 60
Peachtree City 53 79 53 75 / 50 20 30 40
Vidalia 59 80 58 79 / 40 20 10 30
Severe Thunderstorm Watch until 8 PM EDT this evening for the
following zones: Bibb...Bleckley...Carroll...Chattahoochee...