Area forecast discussion...updated
National Weather Service Peachtree City Georgia
745 am EDT Monday may 20 2013
Short term /today through Tuesday night/...
the immediate short term will be spent dealing with results of a
nearly 24 hour long rainfall event which includes the development
of low clouds and fog. Genesis region for this is the Carolinas
and over the last several hours has spread west into the northeast
mountains and just now entering into the remainder of north
Georgia. Nam12 very bullish on fog development through this
morning with widespread condensation pressure deficit values right
around zero. GFS not nearly this aggressive but based on
observation...looks like nam12 is initializing better at this point and
will favor its solution.
Fog and low clouds to slowly lift during the morning hours but
enough low level moisture remains to maintain a ceiling deck for much
of the day. As far as probability of precipitation area concerned...models in agreement
that upper ridge axis will shift eastward...getting US out of the
belt of northwest flow and limiting effects from any impulses to our
extreme eastern sections. Am a little concerned that weak synoptic
wins will allow sea breeze and developing outflows propagate west
and bring showers and thunderstorms with them so have gone above
guidance form my southeast zones today. Hrrr shows separate
section developing during the afternoon. Although this region is
closer to upper ridge...strength of this feature is limited and
will need to carry at least slight chance probability of precipitation all zones.
Low clods and fog not quite as prominent in the models Tuesday
morning but satellite looks like decent development over the eastern
third of the region...especially the northeast mountains. This
will give way once again to improving sky conditions by afternoon
but probability of precipitation look to be on the increase again. Upper ridge axis
weakens slightly in response to approaching trough.
Meanwhile...low level instability and lapse rates will be on the
increase with cape values of near 3000 j/kg projected late
Tuesday. Given flow pattern...would expect development over the NE
mountains first and then propagating SW toward the Atlanta metropolitan.
Have gone a considerable amount above guidance for these areas.
Deese
Long term /Wednesday through Sunday/...
upper level trough approaching on Wednesday and combined with
associated moist and instability will give potential for numerous
showers and scattered thunderstorms across mainly north Georgia and mainly
scattered showers and storms for central Georgia. A weak cold front gets
into the area late Thursday...possibility associated with some upper
level support...will give the chance for showers and storms. Best
moisture and upper support drifting east on Friday allowing for only
a slight chance of showers and storms. Overall moisture and
instability appear lacking Saturday into Monday and while precipitation
potential is not zero it looks to be less than 20 percent at this
time. Temperatures running within 5 degrees of normal through the
period.
Bdl
&&
Aviation...12z update...
IFR/LIFR this morning should prevail at the terminal sites until at
least 14z...with improvement to VFR by 17z. Winds are tricky with
light easterly flow expected to last much of the morning then switch
to southwest 5 to 8 knots by afternoon. Convection should redevelop
this afternoon but will be widely scattered...so have not put in the
tafs at this time.
//Atl
confidence...12z update...
medium on ceilings and winds.
High on remaining elements.
41
&&
Preliminary point temps/pops...
Athens 84 65 86 64 / 20 5 40 40
Atlanta 85 68 86 67 / 20 5 30 30
Blairsville 82 58 83 63 / 20 5 30 30
Cartersville 86 65 87 66 / 20 5 20 20
Columbus 88 67 89 67 / 20 10 20 20
Gainesville 83 65 85 66 / 20 5 40 40
Macon 86 64 88 64 / 30 5 30 30
Rome 87 65 88 66 / 20 5 20 20
Peachtree City 86 62 87 63 / 20 5 30 30
Vidalia 85 66 87 69 / 40 20 30 30
&&
Ffc watches/warnings/advisories...
none.
&&
$$
Short term...deese
long term....bdl
aviation...deese
