Scientific Forecaster Discussion
fxus62 kffc 171453
Area forecast discussion...updated
National Weather Service Peachtree City Georgia
1050 am EDT Sat Aug 17 2019
no changes planned for the forecast.
Previous discussion... /issued 411 am EDT Sat Aug 17 2019/
Short term /today through Sunday/...
Current satellite loop shows moisture plume associated with the old
frontal boundary extending from just off the mid Atlantic coast down
the Georgia coast and across north/central Florida. This moisture should stay
in place one more day as a much drier air mass across north and
central Georgia keeps things mostly dry today. Areas south and east of
Macon will see some increased moisture today so included a slight
chance of afternoon showers and thunderstorms today. Instability
indices stay fairly low today so any showers and thunderstorms that
develop will stay below severe limits.
Moisture begins to increase across the entire area from the south
and north Sunday which is definitely evident in the precipitable
waters. Pws go from 0.9-1.2 inches today to 1.4-1.5 inches Sunday.
Instabilities also increase with MUCAPES getting into the 1700 j/kg
range. Lifted indices and shear values stay fairly weak so not
looking for much in the way of severe storms but would expect to see
some strong storms Sunday.
Heat index values will get into the 98-102 deg range over much of
central Georgia on today...but should remain below advisory criteria.
Forecast high temperatures should continue mostly above normal
areawide for today and Sunday.
Long term /Sunday night through Friday/...
As the extended period begins, broad upper-level ridging will be in
place to the west of the forecast across the central Continental U.S. And to
the east of the area over the western Atlantic. A transition in the
pattern will be ongoing by Sunday night as weak troughing will be
building in between the two ridges. This upper-level troughing
will allow for a gradual moistening of the airmass, northward
advection of the deeper moisture, and an overall more unsettled
pattern through the remainder of the period. At the surface, a
dissipating frontal boundary will remain stalled across central
Georgia on Sunday night, providing a focus for some lingering
isolated showers and thunderstorms in central Georgia.
The persistent trough and increase in deep moisture will allow for
greater coverage of diurnally driven convection during the afternoon
hours each day in the coming week. Primarily chance to low-end
likely pops are expected across the area each afternoon and evening
starting Monday. With precipitable water values approaching 2 inches
by Tuesday, there is a possibility that some of the stronger
thunderstorms could produce locally heavy rainfall each day. Late in
the period, a deep longwave trough extending from the Great Lakes
region is anticipated to drop another cold front towards the
forecast area, providing a chance for some more organized
convection. However, model guidance remains inconsistent with the
handling of this feature at this time. The increase in convective
coverage and clouds during the extended period will also somewhat
moderate temperatures. Highs are thus expected to return to near
or just above climatological normals, in the upper 80s to low 90s
VFR conditions expected to continue with no precipitation or
restrictions to vsbys. Winds are light and variable this morning.
Will see speeds pick up into the 4-7kt range by 16-18z out of the
northwest. Winds will turn to the east by 00z then to the SW by 08z
//Atl confidence...12z update...
confidence high on all elements
Preliminary point temps/pops...
Athens 97 72 95 72 / 10 10 20 20
Atlanta 97 74 94 74 / 5 5 20 20
Blairsville 89 66 87 66 / 10 5 40 20
Cartersville 98 71 96 72 / 0 5 20 20
Columbus 99 74 95 75 / 0 10 30 20
Gainesville 94 71 93 72 / 5 5 30 20
Macon 98 73 94 73 / 10 20 40 20
Rome 98 71 97 72 / 0 0 20 10
Peachtree City 98 72 95 73 / 0 10 20 20
Vidalia 94 74 93 73 / 40 20 50 20