Scientific Forecaster Discussion
Area forecast discussion...updated for aviation
National Weather Service Peachtree City Georgia
637 PM EST Mon Dec 5 2016
Short term /tonight through Tuesday night/...
an upper low across SW Texas will lift NE through the period, merging
with an upper trough swinging through the upper mid-west. Meanwhile,
an associated sfc low off the Louisiana coast will lift north and
west of the area through Tuesday afternoon. This will bring an
increase chance of precipitation as we approach the evening hours,
with the heaviest expected overnight and into the early morning
hours Tuesday. With a high to the north and The Wedge currently in
place across much of north and central GA, this will inhibit storm
development through the afternoon/early evening. However, we did
note lightning strikes across Alabama and thus placed much of the area in
schc thunder by the evening hours. The Wedge will retreat to the NE
as a warm front trapped across southern Georgia lifts north. However, the
extent of the northward progression of the front is still a bit
unclear. Confidence is increasing that the front will lift across
central Georgia Tuesday morning (perhaps approaching north ga) as the sfc
low exits to the north. It should also be noted that as The Wedge
retreats and the front approaches, the gradient will tighten with
winds becoming gusty at times. While instability is still marginal
with ample shear, we can not rule out strong to isolated severe
storms possible as we get into later this evening, overnight and
into the morning hours Tuesday (especially across central ga). High
pressure will build into the area late Tuesday allowing things to
dry out fairly rapidly. Also, anticipate gusty westerly flow Tuesday
afternoon behind the low.
Latest wpc and model guidances are suggesting the heaviest rainfall
axis will set up south of the I-85 corridor where rainfall amounts
of 1 to 3 inches are possible over the next 24 to 36 hours. These
amounts over this area should not be enough to cause any significant
flood concerns at this time, but if the heaviest rainfall axis
shifts northward, cannot rule out some brief minor flooding along
any of the typical flood prone creeks in the Atlanta area.
An atypical diurnal temperature pattern will set up tonight as The
Wedge retreats and the warm moist air to the south lifts north. This
will mean increasing temps through the overnight. Lows occurring
early in the evening in the mid 50s across the north to around 60
along central Georgia. Temps will continue to increase Tuesday with
highs around 60 across the higher elevations to the lower 70s down
toward central Georgia. With the low to the north of the area and northwest flow
bringing in drier and cooler air Tuesday night, expect temps to fall
quickly with lows in the low/mid 40s across north Georgia and upper 40s
Long term /Wednesday through Monday/...
only tweaks to the long term based on the latest guidance.
medium-range models remain in general agreement concerning the large
scale pattern through the extended forecast period...however there
continues to be noticeable differences between the GFS and European model (ecmwf)
concerning the timing and depth of the smaller scale details. With
this in mind I have continued the trend of generally going with a
blend through the period. Still looking at a major cold intrusion
behind the Wednesday/Thursday system. Precipitation is expected to be
over by the time the better cold advection overtakes the region and
no wintry precipitation is included in the forecast for the mid/late
week system at this time. Both the GFS and European model (ecmwf) are a bit slower
with the onset of precipitation associated with the weekend system.
Blended pops do not move into the northwest until late Sunday
allowing for more of a warm up. Latest temperature forecasts
Sunday night into Monday Point to a liquid event at this time.
expect IFR occasionally LIFR in rain and a few thunderstorms through
the night. Best chance for thunder still looks to be toward daybreak
into mid morning...ahead of the surface cold front with a few storms
possible severe. Winds remaining easterly 6 to 8 kt overnight
southwest after 14z. Some improvement to MVFR after that time.
//Atl confidence...00z update...
high on all elements...except medium on timing of cold front.
Preliminary point temps/pops...
Athens 51 59 44 61 / 100 100 10 5
Atlanta 52 68 45 59 / 100 100 10 5
Blairsville 50 58 39 56 / 100 100 10 10
Cartersville 53 65 42 57 / 100 100 10 10
Columbus 57 70 48 62 / 100 80 10 0
Gainesville 50 57 44 58 / 100 100 10 10
Macon 55 71 47 64 / 100 100 10 0
Rome 53 63 41 57 / 100 100 10 10
Peachtree City 54 67 43 60 / 100 100 10 0
Vidalia 59 77 51 67 / 100 80 10 0