Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
333 PM EST Monday Feb 8 2016
..accumulating snow and black ice potential continues for
portions of north Georgia through Tuesday along with dangerous
wind chill values for far northeast Georgia beginning Tuesday
Short term /tonight through Tuesday night/...
Complicated forecast given the environment of strong broad upper
low and shallow unstable layer providing convective rain/snow
shower generation with low quantitative precipitation forecast and precipitable waters . Main areas of impact
with accumulating snow continues to be the higher elevations of
far north Georgia as light snow continues to be observed though
thermal profile transition shows quick sub-freezing column
farther south that battles a drier near-surface layer. All in all
still looking at 1-2 inches in higher elevations with locally
higher before forcing/moisture translates away through Tuesday
night. Some light snow shower or flurry potential overnight for
all of north Georgia including the Atlanta metropolitan area and as far
south as northwest portions of central Georgia with little to no
accumulation expected...although the bigger concern may be if a
light band of snow sets up farther south in portions of north
Georgia midday Tuesday into afternoon...which cannot rule out a
quarter inch or less accumulation. This has had some run to run
consistency in the short term guidance so will need to closely
monitor for additional impacts. Will be likely covering areas
farther south from Winter Weather Advisory zone with Special
To add more wintry hazards in the mix...the bitter cold airmass
advecting into the area along with gradient winds result in wind
chill values within advisory level for the far northeast mountains
/below 5 degrees/...and actually approach the upper end of wind
chill warning criteria /near 10 below/ by Thursday morning. The
current Wind Chill Advisory area /just issued with afternoon
package/ will likely be extended farther west and south as the
cold gets further reinforced through midweek. Please monitor
updates as changes are likely.
Long term /Wednesday through Monday/...
strong high pressure building into the southeast middle week. A short
wave moving through the southeast Thursday night into Friday may
bring a chance for precipitation during that time. GFS/European model (ecmwf) still
differ on location and amount of moisture with this system. Have
continued with low probability of precipitation for Friday into Friday night...but added a
chance extreme northeast Thursday night. Have tried to tweak
precipitation type based on temperatures. European model (ecmwf) showing colder for the
weekend and temperatures were trended down a bit. Previous
discussion is included below.
Previous discussion... /issued 620 am EST Monday Feb 8 2016/
long term /Tuesday night through Sunday/... 500mb trough and
strong shortwave energy will begin to shift off to the east
Tuesday night. So any lingering isolated/scattered snow showers will taper
off during this period. Since the atmos is pretty dry at this
point and very little additional snow is anticipated.
The forecast should remain dry for Wednesday and Thursday as high
pressure settles over the area and the middle levels remain fairly
quiet. County warning forecast area will remain in northwest flow for much of the remainder of the
The GFS and European model (ecmwf) are progging a pretty good shortwave to dig down
in the flow for the end of the week. This is also coincident with a
low pressure wave moving east across the southeast states. An old
frontal boundary across the northern Gulf/Florida Panhandle will
start pushing north later Thursday into Friday. The wave of low
pressure is prognosticated to develop further west and move east along the
boundary through late Friday. Isentropic lift along and north of the
boundary may produce some light precipitation. Models have
consistently kept probability of precipitation at 20 percent or less during this period.
However...the latest European model (ecmwf) is coming in a little wetter than
previous runs. The system is still a little far out...so will go
with persistence for now and keep probability of precipitation capped at 20 percent or less
Friday and Friday night.
Ptype may be an issue with the Friday system. During the day
Friday...temperatures look warm enough for all rain. However...Friday night
will be a little trickier. The precipitation may end as a wintry mix
of precipitation. Model soundings are showing some potential for
light freezing rain/drizzle...mainly across northern Georgia. Its still
too far out to nail down exact ptypes...so will go with rain or snow.
Interested parties should remain weather aware...especially since
ptype issues are involved.
The weekend looks dry as strong high pressure builds over the area.
The next front may begin to impact the County warning forecast area by early next week.
initial low end VFR ceilings for northern sites should lower to MVFR
overnight and persist into Tuesday. Chance for precipitation is tricky
but looks like enough to warrant a tempo for initial -shra then
transition to -shsn after near 05z in prob30 groups for katl and
nearby sites. Any development is expected to have little to no
accumulation and there is more uncertainty with a possible light
band of snow forming near midday Tuesday into the afternoon as far
south as katl as well. Will need to keep monitoring for updates as
warranted. Otherwise winds west to west-northwest 7-10 kts with gusts 18-25
//Atl confidence...18z update...
low on -shsn chance/coverage.
High on all else.
Preliminary point temps/pops...
Athens 29 39 23 38 / 30 10 5 5
Atlanta 29 36 23 37 / 20 30 20 5
Blairsville 24 30 17 28 / 60 60 30 10
Cartersville 28 35 22 35 / 30 30 30 5
Columbus 32 43 25 44 / 10 10 5 5
Gainesville 28 34 22 33 / 30 20 20 5
Macon 31 43 25 44 / 20 5 5 5
Rome 28 35 21 35 / 30 40 30 5
Peachtree City 29 38 23 38 / 20 20 5 5
Vidalia 34 46 28 47 / 20 5 0 5
Wind Chill Advisory from 4 am Tuesday to 10 am EST Thursday for
the following zones: Dawson...Fannin...Gilmer...Lumpkin...
Winter Weather Advisory until 10 am EST Wednesday for the
following zones: Catoosa...Dawson...Fannin...Gilmer...Lumpkin...