Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
358 am EST Tuesday Dec 10 2013
Short term /today through Wednesday/...
short term models are in good agreement for the most part although
some discrepancies noted...NAM/sref faster and GFS/European model (ecmwf) slower to
push front through forecast area today. Rap has initialized well
and is handling the rain band over northwest Georgia fairly well and
is in line with faster solutions. Temperatures remain in the lower
40s across northwest Georgia and with slow progress of colder air to
the north do not expect wintry precipitation in the forecast area. Colder
air will filter into portions of north Georgia by middle-late
morning...and models are trying to scatter/clear skies rapidly
behind the front. This will result in maximum temperatures across
north Georgia...including the Atlanta metropolitan area...this morning.
Cold air advection behind the front is not impressive...but should
be enough to offset any heating by the scattering clouds which
will result in several hours of near steady temperatures across
north Georgia. 1000-850 winds will increase behind the front with
gusts of 25-30mph expected by late morning in north
Georgia...spreading southward into central Georgia by early
afternoon and continuing through early this evening. Drier air
filtering into the forecast area by tonight...but wind speeds will
remain in the 5-10mph range overnight which will keep temperatures
from radiating out as much as they could...however temperatures will
drop to lower to middle 20s north Georgia and in the middle 30s over
central Georgia by morning. Temperatures will moderate on Wednesday
to near normal as dry weather and mostly clear skies set up across
Long term /Wednesday night through Monday/...
extended begins with longwave trough dominating the eastern half
of the country...with another shortwave diving through the Central
Plains. This dry wave will push into the southeast Thursday
morning but will bring a reinforcing shot of cool air to the
region. Weak ridging builds in aloft Friday ahead of a strong
system over the Desert Southwest. Surface low will push into the
Southern Plains Friday night...with strong southerlies pumping
Gulf moisture back into the southeast. Precipitation overspreads the area
Friday night and especially Saturday...and given agreement between
GFS and European model (ecmwf) as well as run-to-run consistency...have increased
probability of precipitation to categorical on Saturday. Looks like easily another inch of
rain across the area. There may be enough instability creeping
into southern zones Saturday afternoon to warrant adding thunder
to the forecast...but have left it out for now.
Complicating factor is diabatically enhanced classical cad
developing Friday night and early Saturday...though right now
thicknesses across Georgia for the most part look too warm for any
wintry precipitation...but later forecasts will have to be reevaluated.
Did add a brief rain/snow mix extreme north Sunday morning as the
cold front pushes through. GFS is just a tad faster than the European model (ecmwf)
by this point so uncertainty is increasing. Cool and windy behind
the front but clearing into early next week.
IFR to MVFR conditions will deteriorate to IFR...some LIFR at taf
sites. Light rain moving across taf sites mainly this morning will
aid in improving ceilings to MVFR. Colder air filtering in may stall
clearing skies but will go VFR after 18-20z. Winds will increase
out of northwest 10-15kts with gusts to 27kts expected.
//Atl confidence...06z update...
medium confidence all elements.
Preliminary point temps/pops...
Athens 53 28 55 29 / 80 0 5 5
Atlanta 50 30 55 31 / 80 0 5 5
Blairsville 47 22 52 23 / 60 0 5 5
Cartersville 48 24 53 26 / 70 0 5 5
Columbus 59 32 59 36 / 50 0 5 5
Gainesville 50 29 53 31 / 80 0 5 5
Macon 61 28 58 30 / 80 0 5 5
Rome 47 22 52 25 / 50 0 5 5
Peachtree City 49 25 55 28 / 80 0 5 5
Vidalia 69 39 59 40 / 70 5 5 5