Area forecast discussion
National Weather Service Peachtree City Georgia
326 PM EDT Sat may 18 2013
Short term /tonight through Sunday/...
weak upper low over the Tennessee Valley is slowly pulling east.
Weak disturbances rotating through the flow over Alabama and Georgia was
producing scattered showers/tstorms. The precipitation should diminish this
evening...but as another weak wave moves into southeast Tennessee
late tonight...expect convection to increase across north Georgia and
spread south and east Sunday. Models are rather conservative with
the probability of precipitation and have continued with likely probability of precipitation for Sunday. At this
time expect a few storms to be strong and an isolated severe storm
is still not out of the question Sunday afternoon...mainly across
west central Georgia. There remains plenty of isentropic lift and k-index
values are quite high and therefore expect some heavy rain in some
of the stronger storms. With little surface wind tonight and plenty
of surface moisture...expect fog/stratus to develop across west
central Georgia which should spread north and east late tonight.
17
No changes needed to the previous extended forecast rationale.
16
Long term /Sunday night through Saturday/...
have adjusted probability of precipitation upward for Sunday night across the County warning forecast area.
Models are showing signs of an mesoscale convective system developing in the northwest flow and
affecting the County warning forecast area. Strong surface instability and very steep
lapse rates will help sustain convection and continue the
possibility of severe storms at least through midnight.
For Monday...a 500mb trough/shear axis sets up right along the southeast
coast. This feature should serve to focus any convective activity
for Monday and Monday evening. Do think rain showers/thunderstorms and rain will be more
diurnal in nature. Kept the trend of highest probability of precipitation in the east...with
only isolated activity to the west.
Weak shear axis/500mb trough moves off the coast on Tuesday with
ridging building aloft across the County warning forecast area. Any convection should be
isolated in nature...surface instability will be present but no
discernible surface mechanism to focus precipitation is noted. Precipitation
should be diurnal.
Uncertainty begins to creep into the forecast by Wednesday. Earlier
model runs prognosticated a cold front to move through the County warning forecast area during the
latter half of the week. The European model (ecmwf) now keeps the front to the
north...while the GFS does move the boundary through slowly Friday
through Saturday. Have opted to go persistence for this period due
to low confidence.
Nlistemaa
Aviation...
18z update...
MVFR ceilings across atl/ahn areas should continue to lift with areas
going VFR by 21z and remaining VFR until late tonight. Scattered
convection will be possible through the afternoon. Any convection
that does develop should diminish to showers late this evening. A
second short wave will move into north Georgia late tonight and spread
into central Georgia Sunday bringing an increasing chance of convection
through the day. Winds will remain southwest less than 10kts through
the forecast.
//Atl confidence...18z update...
medium confidence on all elements on cigs/vsbys.
Low to medium on timing of convection.
17
&&
Preliminary point temps/pops...
Athens 63 77 65 84 / 50 60 60 40
Atlanta 65 81 66 86 / 50 60 60 20
Blairsville 62 76 60 82 / 60 70 70 40
Cartersville 64 81 65 88 / 60 60 50 20
Columbus 67 86 67 89 / 30 40 50 10
Gainesville 63 77 63 84 / 60 70 60 40
Macon 64 83 66 87 / 40 60 60 30
Rome 66 82 65 89 / 60 60 40 10
Peachtree City 64 82 65 87 / 50 60 60 20
Vidalia 68 86 68 84 / 40 60 60 40
&&
Ffc watches/warnings/advisories...
none.
&&
$$
Short term...17
long term....16
aviation...17
