Area Forecast Discussion
Issued by NWS Atlanta, GA
FXUS62 KFFC 190921
Area Forecast Discussion
National Weather Service Peachtree City GA
421 AM EST Thu Jan 19 2017
.SHORT TERM /Today through Friday/...
Recent water vapor loop still reveals a large trough of low
pressure across central US with several notable
perturbations/shortwave troughs rotating within. The shortwaves
currently located across TX Big Bend and S Nebraska, respectively,
will be the main sensible weather makers/enhancers later today.
Current sfc analysis reveals a stationary boundary draped across
Gulf coast states into the CWA...with a sfc wave developing along
this boundary in SE TX/W LA in response to Big Bend shortwave.
This sfc wave will continue to develop today as shortwave moves
east and help push our stationary boundary north as a warm front.
Weak sfc high north of stationary boundary will set up weak wedge
across NE Ga.
Today: Axis of diabatically induced shortwave ridge will slide to
our east with time as aforementioned perturbations to our west drive
drive large trough eastward. This large trough has tapped into
copious amounts of subtropical Pacific moisture...and this will
increase across the state today as deeper SW flow pushes in. With
sfc wave development...moisture from Gulf will increase
/evident in moisture transport vectors/ which will work in tandem
with subtropical Pacific plume of moisture. This all points to Round
1 of an upcoming active weather pattern. Expect activity to really
kick up across LA/MS and spread east this afternoon. Already seeing
returns on radar moving across AL this morning which will skirt
across W Central and NW Ga early in the day in the form of light
showers. With rich boundary layer moisture in
place...destabilization will commence across the SE this
afternoon despite rather warm mid level temps/poor lapse rates.
This causes a concern for thunder later today. All in all...0-6km
shear values of 30-40kts amidst modest CAPE points to development
of a semi-organized line along developing cold frontal boundary to
our west. This line will push into W Ga at the end of the day
today...but will likely weaken as better dynamics push north and
front starts to fizzle. Not out of the question this line could
pose a damaging wind/brief tornado threat across W Georgia before
weakening...but main severe threat should remain to our west
Tonight and Friday: Disorganized line/cluster of leftover thunder
and rain will push north and east as main shortwaves eject into OH
Valley. Should see a lull in activity Friday morning into Friday
evening with just some scattered showers roaming around. By day`s
end on Friday...a VERY impressive 170kt+ 300mb jet will be digging
into W Mexico from the Pacific. This will be responsible for the
development of Round 2 of active weather (and eventually Round
3)...as energy aloft taps into the subtropical moisture plume en
route to the SE. This next batch will move in just outside of short-
Temps will continue well-above normal through the short term with
highs generally in the 70s and lows in the 50s.
.LONG TERM /Friday Night through Wednesday/...
General trend of long term looks the same...several short waves
crossing the southeast states with increasing chances of showers
and thunderstorms. Southwest flow aloft will keep moisture and
a warm air mass over the region. Rain chances increase rapidly
again Friday night into Saturday and continue into Sunday. By that
time...the upper closed low will be moving from the lower MS
valley into the Southern Appalachians. There are some timing
differences between the GFS and ECMWF. However categorical showers
and scattered thunderstorms looks reasonable for Saturday into
Sunday. Timing of the upper low will affect rain chances on Monday
but precipitation should be ending during the day. Brief break on
Tuesday with ridge building aloft...rain returning late
Wednesday. A few strong to severe storms are possible Saturday and
again Sunday into Sunday night. The risk for severe will depend
on several factors...including existing cloudiness and ongoing
rain...combined with lapse rates and shear.
Daytime Temperatures will remain warm throughout...however cooler
nights are expected for the beginning of the week. For the period
including tonight through Sunday...rainfall totals should average
two to three inches. No hydrology issues anticipated at this time
since rain will be spread over several days.
VFR conditions continue at all sites and expect this trend to
continue towards daybreak. It is possible MVFR ceilings could
develop early Thursday morning across northern sites but
confidence is not high based on upstream obs. Fog will be possible
a CSG once again with some MVFR vsbys. Do expect all sites to
return to VFR in the afternoon before a decent shot of rain and
thunderstorms arrive Thursday evening...where ceilings tank and
PROB30s have been introduced. NW winds will shift east Thursday
morning remaining 10kts or less through the period.
//ATL Confidence...06Z Update...
Low on MVFR ceilings
High on all other elements
.PRELIMINARY POINT TEMPS/POPS...
Athens 67 55 71 57 / 20 80 50 30
Atlanta 70 59 72 59 / 50 90 50 40
Blairsville 62 50 66 52 / 40 90 50 20
Cartersville 69 56 70 56 / 60 90 50 30
Columbus 73 59 74 61 / 50 80 40 30
Gainesville 65 54 69 56 / 30 90 50 30
Macon 73 58 75 61 / 20 70 40 40
Rome 68 56 71 56 / 70 90 40 20
Peachtree City 71 54 72 57 / 50 90 40 30
Vidalia 76 60 76 62 / 5 40 30 40