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Area forecast discussion 
National Weather Service Peachtree City Georgia
736 am EDT Friday Apr 18 2014

Previous discussion... /issued 406 am EDT Friday Apr 18 2014/

.Rainy and windy to end the week and kick off the weekend...

Short term /today through Saturday night/...
latest surface analysis over the southeast US shows strong late
season high pressure along the east Seaboard with wedging on the
Lee side of the Appalachians through north Georgia. Along the
Gulf Coast...a broad trough exists through the Panhandle of
Florida. South flow just above the surface transitioning to
southeast is allowing for excellent isentropic lift setup with
rapid expansion of rain shield into most of southwest Georgia at
this hour. Meanwhile...aloft...upper low beginning to move through
the lower Mississippi Valley with subtle shortwaves ahead of this
feature providing added support to developing rain shield. Thunder
continues to be prevalent from the northern Gulf of Mexico through
North Florida but decreases rapidly toward the local forecast area
and no plans for immediate inclusion in grids at this time.

Still some differences in the models in the short term as GFS
continues to be the most northern track of low while the Euro is
further south. Based on trends seen this morning and recent track
record in these types of systems...actually prefer a more northern
translation of higher rainfall amounts. This solution has some
backing from local WRF and hrrr solutions as well and will follow
for the placement of higher rainfall chances primarily. As far a
amounts...I do increase these as well to the north but certainly
will see some cutoff of moisture transport from Gulf convection so
no major changes planned in that regard.

As far as local thunder potential...sref now indicating some
MUCAPE easing into southeast sections of forecast area and strong
isentropic ascent should provide impetus for slight chance thunder
by this evening for southern and eastern tier. Given lightning is
already approaching southern sections of forecast area...this
portion of forecast will need to be monitored closely for possible
updates later this morning.

Winds look to be an issue as well and problematic in forecasting
given high advertised values and placement of wedge. By this
evening...nam12 actually indicates 52 knots at 925mb over southern
sections which is disturbing but not sure how much of this will
translate to the surface given wedge and inversion in place.
Models indicating surface winds should increase to at least 20 knots
sustained over southern tier by this afternoon and across north Georgia
this evening with gusts as high as 30 knots. Will therefore hoist
a segmented Wind Advisory for most of the area which will go
through Friday night.

Deese

Long term /Sunday through Thursday/...
main closed low just off the Georgia/Carolina coast stays fairly
stationary through sun and Monday before weakening and pushing
further out to sea Tuesday. Clouds will linger across the area sun
with maybe a few light showers Sun morning across southeastern
sections of the County Warning Area. Models are in very good agreement through
most of the extended with minor differences in timing and available
moisture with next system Tuesday.

00z Monday...a shortwave over the middle of the country develops into
a closed low center and moves over the Great Lake states by 00z
Tuesday. Its trailing colds front sweeps through the Mississippi River
valley and into na Georgia by 12z Tuesday. Will see shower and
thunderstorms sweep through the state Tuesday and could see some
fairly strong storms as instability indices are increasing model
run to model run. Temperatures will be a little above normal and with
dewpoints in the 50s and low 60s...MLCAPE values will be
sufficient for some strong storms. Deep shear will be somewhat
weak...0-6km bulk shear only 10 to 15 kts. Will continue to
monitor. This front should be east of the state by 00z to 06z Wednesday
with high pressure building back in for Wednesday and Thursday.

01

Hydrology...
still leaning toward HPC guidance for the first 24 hours and then
more local flavor added thereafter as I keep probability of precipitation in a little
longer than models suggest on Saturday. This increases anticipated
rainfall totals to in excess of 3 inches over portions of the
southeast where convective elements are more likely. More
importantly...2 inch contour is brought northward and will adjust
Flood Watch northward accordingly to account for this. Also
extended Flood Watch in time given slower retreat of rain on Saturday.

Climate...

Records for Friday April 18...

Maximum temperature min temperature
station high low high low
------- ---------- ---------- ---------- ----------
kahn 90 1942 54 1902 64 1969 32 1936
1927
katl 87 2002 50 1983 69 1927 33 1997
1937
1896
kcsg 91 2002 62 1983 69 2006 37 1962
1956
kmcn 90 1967 55 1921 66 1922 33 2001
1955

Records for Saturday April 19...

Maximum temperature min temperature
station high low high low
------- ---------- ---------- ---------- ----------
kahn 91 1917 51 1984 64 1927 30 1983
katl 88 1941 50 1983 66 1927 30 1983
kcsg 91 2002 59 1983 68 1995 33 1983
1953
kmcn 91 2002 59 1910 66 1927 31 1983
1976
1968

Aviation...
12z update... rain showers continues to work its way northward from the
Gulf Coast now impacting csg and mcn terminals followed soon by atl
area terminals. Ceilings following suit thus far with mainly VFR over
the local area but MVFR quickly developing within rain shield and
lifting north. Expect a quick transition to MVFR for all terminals
later this morning and then IFR by late this afternoon.
Advertising a later clearing trend than models indicate and keep
IFR throughout entire taf cycle. As far as winds...by this
afternoon and especially this evening into the overnight...could
see some high gusts to as high as 30 kts. Withing heavier
rain showers...these values could be even a little higher and will be
monitored closely.

//Atl confidence...12z update...
medium on IFR timing and wind gust potential.
High on remaining elements.

Deese

&&

Preliminary point temps/pops...
Athens 57 46 62 51 / 100 100 60 10
Atlanta 56 47 62 53 / 90 80 40 10
Blairsville 57 45 63 50 / 70 80 60 10
Cartersville 59 47 65 53 / 70 70 40 10
Columbus 57 49 65 56 / 100 70 30 10
Gainesville 54 47 61 51 / 80 80 60 10
Macon 55 50 64 53 / 100 90 30 20
Rome 61 47 67 54 / 60 70 40 10
Peachtree City 56 47 63 52 / 100 80 30 10
Vidalia 61 55 67 58 / 100 90 50 30

&&

Ffc watches/warnings/advisories...
Flood Watch through Saturday evening for the following zones:
Baldwin...Bibb...Bleckley...Butts...Chattahoochee...Crawford...
crisp...Dodge...Dooly...Emanuel...Glascock...Greene...Hancock...
Harris...Houston...Jasper...Jefferson...Johnson...Jones...
Lamar...Laurens...Macon...Marion...Monroe...Montgomery...
Morgan...Muscogee...Oglethorpe...Peach...Pulaski...Putnam...
Schley...Stewart...Sumter...Talbot...Taliaferro...Taylor...
Telfair...Toombs...Treutlen...Twiggs...Upson...Warren...
Washington...Webster...Wheeler...Wilcox...Wilkes...Wilkinson.

Wind Advisory from 1 PM this afternoon to 2 am EDT Saturday for
the following zones: Baldwin...Bibb...Bleckley...Chattahoochee...
Crawford...crisp...Dodge...Dooly...Emanuel...Glascock...
Hancock...Harris...Houston...Jefferson...Johnson...Jones...
Laurens...Macon...Marion...Monroe...Montgomery...Muscogee...
Peach...Pulaski...Schley...Stewart...Sumter...Talbot...Taylor...
Telfair...Toombs...Treutlen...Twiggs...Upson...Warren...
Washington...Webster...Wheeler...Wilcox...Wilkinson.

Wind Advisory from 6 PM this evening to 8 am EDT Saturday for
the following zones: banks...Barrow...Bartow...Butts...Carroll...
Cherokee...Clarke...Clayton...Cobb...Coweta...Dawson...DeKalb...
Douglas...Fayette...Floyd...Forsyth...Greene...Gwinnett...Hall...
Haralson...heard...Henry...Jackson...Jasper...Lamar...Lumpkin...
Madison...Meriwether...Morgan...Newton...north Fulton...Oconee...
Oglethorpe...Paulding...Pickens...Pike...Polk...Putnam...
Rockdale...South Fulton...Spalding...Taliaferro...Troup...
Walton...white...Wilkes.

&&

$$

Short term...deese
long term....01
aviation...deese