Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
640 am EST sun Mar 1 2015
Previous discussion... /issued 255 am EST sun Mar 1 2015/
Short term /today through Monday/...
latest msas analysis across the area reveals a strong 1040mb wedge
in place over the eastern Carolinas with axis into the upstate of
South Carolina and northeast Georgia. Have been following
temperatures very carefully tonight as -ra and dz begin to push
into The Wedge at this hour. At the beginning of the overnight
period...the rtma analysis showed some temperatures right around
freezing but since then have seen some slight warming as winds
become more easterly as opposed to northeast. Not ready to call it
quits just yet on the advisory as there could be some cold pockets
left in the valleys where observations are sparse but may be able
to later this morning based on trends.
Otherwise...as temperatures rise this morning...it becomes just a
pop forecast the remainder of the day. So far...hires reflectivity
guidance along with the namdng5 have been verifying the best with
this event. Remains a low quantitative precipitation forecast but high pop scenario and have
followed suit with categorical probability of precipitation over east central Georgia this
morning with a large swath of likely to the west including the
Atlanta metropolitan. Again...much of this will be light rain or even
drizzle with meager quantitative precipitation forecast but should measure nonetheless. In
categorical areas...enough light rain should fall to allow for up
to a tenth of total precipitation through this afternoon.
With zonal flow aloft...surface wedge remains very progressive in
nature and is dissipated by late this evening. Next system begins
to move into the western zones at this same time with likely probability of precipitation
for the northwest corner with shortwave moving from north Alabama through
northwest Georgia. Not much southward push expected with this activity as
aforementioned zonal flow keeps storm systems moving more west to
east. Have therefore kept highest probability of precipitation in same northern zones for
the remainder of the short term period.
Long term /Monday night through Saturday/...
warm pattern still appears to be in store for the region to start
out the extended forecast period as upper-level flow becomes strong
southwesterly ahead of the western U.S. Trough. Cannot rule out some
chance for precipitation Monday night through Tuesday night with
ample moisture and the potential for weak middle/upper-level short
waves ejecting from the deep trough. However the lack of low-level
forcing and the uncertain nature of the timing any of these
transient middle/upper features leads ME to keep probability of precipitation chance at best
through that time frame. Strong surface trough associated with the
approaching upper trough Wednesday through Wednesday night brings
the best chances for organized precipitation to the forecast area
with sufficient instability for at least scattered thunderstorms.
Instability is waning some as the front pushes in but is high enough
when combined with relatively strong low/mid-level winds to keep US
on our toes for at least some marginal isolated severe potential.
Still too uncertain to include any mention right now. GFS...and to a
lesser extent the European model (ecmwf)...continue to bring in fairly cold air into
the forecast area Wednesday night while keeping some light quantitative precipitation forecast over
the region through Thursday. With the main upper trough lifting and
filling some as it sweeps through I am still a bit Leary that the
best cold air will make too big of an intrusion into the area vs
getting shunted off to the east. I have been leaning toward the
slightly warmer and drier European model (ecmwf) the past few runs and am inclined to
continue that trend in light of the latest couple of runs of the GFS
also showing this same trend in flattening the flow across the
region in the wake of the lifting upper trough.
latest plot of flight categories across the area shows LIFR
across most of south Georgia moving into the csg and mcn portions
of middle Georgia with all IFR to the north of this. Along with
the IFR is a good deal of -ra and dz across the area. Expecting
LIFR to IFR for most all of the day now as latest guidance a
little more pessimistic on improvement. Could be a brief
improvement late this evening as edge erodes and next front
approaches but prospects for this improvement look low. Additional
low cloud for Sun night with more chance of seeing reduced visibility as
well with some guidance indicating vlifr possible.
//Atl confidence...12z update...
medium on vlifr potential Sun night.
High on remaining elements.
Preliminary point temps/pops...
Athens 45 43 61 46 / 60 50 30 50
Atlanta 48 46 60 49 / 70 40 40 40
Blairsville 49 44 55 43 / 60 60 60 40
Cartersville 48 45 57 46 / 50 50 50 40
Columbus 53 48 67 51 / 50 30 30 30
Gainesville 46 44 60 45 / 60 50 50 50
Macon 49 45 68 48 / 60 40 30 30
Rome 48 45 55 45 / 40 60 60 40
Peachtree City 48 45 61 48 / 70 40 30 30
Vidalia 50 49 72 52 / 50 40 30 20
Freezing Rain Advisory until 8 am EST this morning for the
following zones: Dawson...Fannin...Hall...Lumpkin...towns...