Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
414 am EST Sat Jan 31 2015
Short term /today through Sunday/...
latest regional analysis continues to show a strong 1033mb high
north of the local area over the Ohio Valley with ridging SW
through the Tennessee Valley and lower Mississippi River valley.
This is providing an optimal setup for a light northerly drainage
flow conducive for an advective freeze for most all locations.
Most of the mountain locations are already in the middle to upper 20s
at this hour with upper 20s and lower 30s elsewhere with several
more hours of cooling to go. High clouds are ahead of schedule and
should push across prior to daybreak but with limited if any
effect on continued temperature drop across the local area.
Looking like a rather tranquil beginning to the short term with
just the aforementioned increase in clouds anticipated for today.
Thickening middle level deck may curb a degree or two off highs and
went just below model blends for the maximum T in the grids. Opposite
GOES for tonight as clouds should begin to curb diurnal trends as
should developing southerly flow late and have gone a few degrees
above guidance for this time period.
The first half of Sunday looks dry for the area...but southern
branch of the jet should put a quick end to this as moisture
increases rapidly off the Gulf of Mexico. A series of shortwave
impulses embedded in mean westerlies should provide necessary lift
for none probability of precipitation in the morning to quickly transition to categorical
by afternoon. Adiabatic Omega becomes maximized during this time
period over northwest Georgia as well adding to confidence in widespread
rain potential. Instability initially looks non existent but
40 to 50 kts of isentropic upglide may be enough to allow some
elevated convection. Chances too low for mention at this time but
will need to monitor closely.
Long term /Sunday night through Friday/...
short term rain event Sunday continues into the initial extended
periods. Models have backed off Monday morning wintry precipitation
chances...but given Monday morning lows in the north Georgia
mountains as wrap around moisture impacts the area...have opted to
continue with mention of snow or a wintry mix. Light accumulations
may be possible in the higher elevations and have continued with
mention of a quarter inch or less. The system exits quickly
Monday...and have tapered off probability of precipitation by late morning.
A quick reprieve in the rainy conditions expected on Tuesday
before another system approaches the area Wednesday morning.
Extended models continue to differ on timing and northward extent
of moisture with this next system as it draws Gulf moisture into
the region. Have generally gone with more of the European model (ecmwf) solution
initially and kept the highest probability of precipitation across central Georgia...then
continue to spread probability of precipitation further north. Given the discrepancies
between the models expect this forecast to change into next week.
Given the morning low temperatures on Thursday and Friday
mornings...have continued with mention of wintry precipitation. Thursday
morning looks like the best chance would be in the
mountains...while Friday morning appears to hold more of a chance
for the Atlanta metropolitan area. For now...accumulations appear minimal
and have not included any in the grids at this time.
The remainder of the extended forecast looks dry into next
with dry air in place...relative humidity values will dip into the lower to middle
20s for around 4 hours today. Given low fuel moisture...a Fire
Danger Statement is warranted for the entire area.
VFR conditions expected through this taf period with just an
increase in high clouds expected. 20k feet ceilings will gradually
transition to 15k feet by late in the period but no rain expected
until Sunday afternoon...outside of this taf period.
//Atl confidence...06z update...
high on all elements.
Preliminary point temps/pops...
Athens 52 33 56 45 / 0 5 60 90
Atlanta 53 39 55 40 / 0 5 80 90
Blairsville 53 34 46 37 / 0 5 80 90
Cartersville 53 36 54 39 / 0 5 100 90
Columbus 56 40 61 46 / 0 5 70 90
Gainesville 52 34 49 40 / 0 5 70 90
Macon 56 34 63 49 / 0 0 50 80
Rome 53 34 54 39 / 0 5 100 80
Peachtree City 54 33 58 42 / 0 0 80 90
Vidalia 58 34 68 55 / 0 5 20 80