Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
1020 am EST Monday Dec 29 2014
Current grids in good shape and not much change anticipated. Main
adjustment was to bump up southeast corner probability of precipitation through early
afternoon as nice rain shield has set up along frontal boundary.
Kept patchy fog in the grids for a few more hours with scattered
sites still seeing reductions to visibility at this hour.
Remainder of the short term forecast is on track.
Previous discussion... /issued 631 am EST Monday Dec 29 2014/
Short term /today through Tuesday/...
/issued at 333 am EST Monday Dec 29 2014/
latest surface analysis shows a cold front near a La Grange to
Milledgeville line and prognosticated by models to push south of the
forecast area during the afternoon. Regional radars show a large
area of mostly light rain...with a few spots of embedded moderate
rain across north and parts of central Georgia this morning. This rain is
being enhanced by an upper short wave tracking across the southeast states
this morning. A back edge to the rain shield was noted over northwest Alabama
and timing tool suggest this back edge will reach northwest Georgia around 7-8
am... Atlanta around 10-11 am... and maybe an Athens to Columbus
line around 1-2 PM this afternoon. Associated rainfall amounts are
generally light... with expected widespread rainfall amounts today
less than 1/2 inch across north Georgia... and generally less than 1/4
inch across central Georgia before the rain ends. Area streams and rivers
should be able to handle these amounts without any significant
threat of widespread flooding. Therefore... plan to cancel the Flood
Watch with the new 4 am forecast issuance this morning.
Short term models show a series of disturbances tracking across
mainly the Tennessee Valley region through tonight... serving to help hold
clouds over the area today and tonight... and warrant a slight
chance of light rain over parts of the eastern and southern zones at
least through this evening. At this time... expect clearing on
Tuesday as surface ridge builds from the north and drier air spreads
in from the west.
As for temperatures... leaned slightly cooler than guidance for high today
with clouds and light rain... then took a mav and met blend for
tonight and Tuesday.
Long term /Tuesday night through Sunday/...
/issued at 333 am EST Monday Dec 29 2014/
next system begins to increase deep moisture late Thursday night
into Friday morning. Potential for a light rain/freezing rain mix
over the far north counties with low temperatures running 30 to 32.
Model blends currently indicating only low potential for measurable
precipitation. However...low temperatures could very easily be before any
precipitation onset and rise some the last portion of the night. There still
could be some cold air trapped in the valleys.
Model blends then indicating best rain potential over north and portions
of central Georgia through Saturday night with an overrunning flow and
moist SW flow aloft. Slight chance for thunderstorms Saturday with
and a chance of thunderstorms Saturday night with MUCAPE below 500.
Cold front moves into the area Sunday with a warm front moving north
ahead of it. Severe potential has not really changed with cape of
500 to 1000 over the central Georgia Sunday afternoon with best shear
remaining to the north. GFS and European handle the surface low much
different and this will be significant from a low level shear
Models consistent with the cold front exiting the area Sunday night
with rain chances diminishing quickly.
expect current VFR ceilings to occasionally lower to IFR levels through
14z... then settle to prevailing MVFR ceilings that persist through much
of today. Could see VFR conditions later this afternoon... as GFS
MOS shows VFR by 18z today... while NAM MOS guidance holds onto
IFR/MVFR ceilings today and tonight. Both models agree on IFR ceilings
returning by 06z tonight... with improvement to MVFR or VFR by 15-
16z Tuesday. Expect northwest winds at 5-7 kts today and tonight... then 10-
12 kts on Tuesday.
//Atl confidence...12z update...
medium on IFR ceilings this morning and MVFR ceilings through the afternoon.
High on all other elements.
Preliminary point temps/pops...
Athens 61 44 59 37 / 80 20 10 10
Atlanta 62 46 57 35 / 70 10 5 10
Blairsville 57 40 51 30 / 60 20 20 10
Cartersville 59 41 53 33 / 60 10 5 5
Columbus 66 48 63 39 / 80 20 5 5
Gainesville 59 44 54 35 / 70 20 10 10
Macon 65 46 63 40 / 80 20 5 10
Rome 58 41 52 31 / 50 10 5 5
Peachtree City 63 40 58 35 / 70 10 5 5
Vidalia 67 51 65 44 / 100 40 10 10