Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
648 PM EST Sat Nov 28 2015
Previous discussion... /issued 149 PM EST Sat Nov 28 2015/
Short term /tonight through Sunday night/...
Southeast Ridge continues to weaken as prevailing flow becomes more
zonal to SW along with the approach of an elongated frontal system
slow to progress from the northwest. Have trended probability of precipitation to be slight to
chance in the far north by late tonight and likely to categorical by
Sunday and Sunday night. Gradient of moisture still looks to be
rather tight across the County Warning Area as the greater chance probability of precipitation stay mainly
along and north of the I-20 corridor with little to no chance across
most of central Georgia. Prognosticated instability is close to none through the
period so have kept just shower mention. Quantitative precipitation forecast results in upwards of 1-
1.5 inches through Sunday night in the far northern tier so cannot rule
out some isolated minor flooding potential. Based on type of forcing
and being less convective in nature...thinking it should be a rather
steady light to moderate rain and no so much of heavy dumpers.
For temperatures...despite increase in cloud coverage and precipitation potential
there should still be a rather warm airmass in place with Sunday
highs still near 10 degrees above norms and overnight mins 10-15
degrees above /many areas only getting down to middle 50s Sunday night/.
Long term /Monday through Saturday/...
mainly only tweaks to the long term based on the lastest
Previous discussion... surface front sinks into the Tennessee Valley by
the start of the long term as upper ridge weakens. Looks like the
front stalls over that area into the first of the week as it
becomes generally parallel to the upper flow. The deeper moisture
remains over north Georgia and have continued with the highest probability of precipitation in
that area through Tuesday night. Closed upper low moving through
the Great Lakes should push the front southward into the state and
models indicate some drying for Wednesday night and Thursday.
Differences show up for Thursday as the GFS wants to develop an
upper low over Texas and spread moisture back into Georgia Thursday night
and Friday. The European model (ecmwf) does not show this and keeps the southeast
dry through the end of the week. To compromise...have continued
with low probability of precipitation Thursday night and Friday.
VFR will slowly deteriorate to MVFR conditions in the
morning...with MVFR ceilings expected just before the showers. Showers
look to hang up north of the taf sites until after 00z on Monday.
Light and variable winds will favor the southeast until 08z when they
will shift back from the SW...with speeds at 5 kts or less.
//Atl confidence...00z update...
medium confidence in timing of weather.
Medium to high confidence all other elements.
Preliminary point temps/pops...
Athens 51 70 54 65 / 5 30 60 60
Atlanta 53 69 56 67 / 10 40 50 60
Blairsville 50 62 53 60 / 20 80 80 100
Cartersville 52 66 55 65 / 20 60 70 80
Columbus 52 74 56 73 / 5 10 10 10
Gainesville 53 65 54 62 / 10 60 70 80
Macon 48 74 53 73 / 5 10 10 10
Rome 53 65 55 65 / 30 70 80 80
Peachtree City 50 70 54 69 / 5 30 30 30
Vidalia 51 74 54 75 / 5 5 5 10