Scientific Forecaster Discussion
Area forecast discussion...update
National Weather Service Peachtree City Georgia
1140 am EDT Tuesday Mar 31 2015
Late morning update...
main concern is the potential for isolated severe storms moving in
from Alabama this afternoon and spreading across parts of north Georgia
and much of central Georgia during the evening hours. Current thinking is
an upper disturbance will interact with increasing instability and a
stalled boundary across central Georgia to help produce scattered
thundestorms later this afternoon. A few of these thunderstorms have
the potential to become severe... based on morning soundings showing
steep middle level lapse rates... relatively low freezing levels and
some middle level dry air. These parameters would support the potential
for large hail... strong downburst winds and frequent lightning if a
few strong to severe storms are able to develop. The main threat at
this time appears to be mainly between 2 PM and 10 PM... and
generally along and west of a Summerville to Stone Mountain to
Swainsboro line... which includes the Atlanta metropolitan area. Have
updated zones to word for isolated severe storms for this area this
afernoon and evening. All interest are encouraged to monitor storms
closely later today and this evening. /39
Previous discussion... /issued 434 am EDT Tuesday Mar 31 2015/
Short term /today through Wednesday/...
unsettled weather will continue through the short term portion of
High pressure is centered across the Tennessee Valley...while yesterdays
cold front is situated across south-central Georgia. In the middle
levels...northwest flow will allow several pieces of shortwave energy to
move southeast across the County warning forecast area. The shortwave energy aloft will
interact with the old frontal boundary...leading to
isolated/scattered showers and thunderstorms through Tuesday.
Good low level moisture will pool along and south of the
boundary...and with strong heating...surface instability will
increase through the afternoon. The highest probability of precipitation will be situated
along and south of the old front. However...the shortwave will
supply steep middle level lapse rates. The good middle level forcing could
help fire rain showers/thunderstorms and rain on the north side of the boundary...but coverage
should remain more isolated in nature. The strong cold pool aloft
will also increase the likelihood of hail. Isolated severe storms are
possible...with large hail being the main severe component. Even sub-
severe thunderstorms will have the potential to produce small hail.
Storm coverage should lessen with the loss of surface heating.
Wednesdays set up will be a lot like today. However...the old
boundary should be a little further south. The isolated/scattered probability of precipitation should
be limited to the southern quarter of the County warning forecast area. Another piece of
shortwave energy is prognosticated to drop south in the northwest flow...so storms
will once again have the potential to be mainly hail producers.
Min and maximum temperatures will remain above normal.
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 diurnaly 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 724 am EDT Tuesday Mar 31 2015/
VFR conditions to persist through the period. An upper
disturbance will move through the region this afternoon...and some
isolated/scattered convection is possible. Models have backed off on the
low ceilings for tonight/early Wednesday. Will keep a few012 in the
taf. Best chances for any precipitation will be south of the terminals
//Atl confidence...12z update...
high confidence all elements.
Preliminary point temps/pops...
Athens 74 54 75 54 / 10 20 10 20
Atlanta 74 53 77 56 / 30 20 10 30
Blairsville 72 47 75 47 / 20 20 10 30
Cartersville 74 53 78 55 / 30 20 10 30
Columbus 77 53 77 58 / 40 30 30 20
Gainesville 71 53 72 53 / 20 20 10 30
Macon 77 56 79 56 / 30 20 20 20
Rome 74 51 78 54 / 40 20 10 30
Peachtree City 75 53 77 55 / 40 20 10 30
Vidalia 77 62 76 56 / 20 20 20 10