Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Peachtree City Georgia
646 am EST Sat Feb 28 2015
Previous discussion... /issued 338 am EST Sat Feb 28 2015/
.Freezing Rain Advisory for small portion of NE mountains late
Short term /today through Sunday/...
what would a middle shift be without more winter weather concerns?
Will get to that in a moment but first...starting off the night
with a strong high pressure system over the Ohio Valley at this
time with ridging all the way down toward the Gulf Coast so this
high has a wide influence. Temperatures generally in the lower to middle
30s across the are but temperature fall has been curbed slightly
for the northwest sections by infiltrating cloud deck. This middle deck is
part of a large plume of middle level moisture moving northward from
the Gulf Coast through the Mississippi Valley this morning but
effects should be limited local to aforementioned northwest zones.
For today...high shifts east and begin to see wedge setup over
eastern Seaboard through the Lee side of the Carolinas and
eventually into Georgia by this afternoon. Meanwhile...developing
southerly flow from 3k through about 10k will enhance isentropic
upglide beginning in southern sections of the forecast area today.
Enough moisture and lift present along with support from hires
models like the local WRF and 4km NAM to warrant increased probability of precipitation
with 40 percent for the southern zones. If some of the hires runs
are correct...even this may be too low and will need to be
monitored closely for possible changes.
Biggest forecast challenge emerges tonight as low level moisture
increases and expands northward aided by developing 35 knots jet that
should maximize isentropic ascent by 06z tonight. Meanwhile...our
friend...mr 1045mb high...has taken positioned itself along the NE
coast with 1040 mb as far south as Virginia. Thinking combination
of wedge placement and strength along with residual snow cover
over the NC mountains may allow temperatures tonight to be below guidance
despite an abundance of clouds. Regardless...temperature curve
will be decidedly non diurnal with min temperatures likely reached
between 02z and 06z before rising through daybreak. The
combination of isentropic induced light rain and drizzle along
with a brief period of sub freezing temperatures in the valleys of the NE
mountains provides another opportunity for winter weather. Carrying
light freezing rain and drizzle in the current grid set but only
indicating a light glaze for most locations. Still...this is
enough for a Freezing Rain Advisory and will issue with the
morning package. May see temperatures rise above freezing well prior to
daybreak for these areas and no issues anticipated as we get into
For the remainder of the area...although quantitative precipitation forecast will be
light....light rain and drizzle looks like a good bet for most
areas the balance of the day Sunday with eastern sections favored.
Have small areas of likely probability of precipitation advertised but these may need to
be ramped up should model trends continue with increased
isentropic upglide over the area.
Long term /Sunday night through Friday/...
warmer pattern setting up across the region for the majority of the
extended forecast period with persistent southwesterly upper flow.
This pattern also leans wetter. Minor focus for more organized
precipitation Monday as a weak frontal boundary sags into the state
and washes out. Little upper support and minimal instability so I am
inclined to remove the slight chance for thunder we currently have
for the daytime period Monday. Better chances for thunder Wednesday
into Wednesday night as a much stronger front sweeps into the state
ahead of a fairly strong short wave. Instability is noticeably
better with this system...and with a strong low-level jet prognosticated
across the southeastern U.S. We will need to keep an eye out for
possible severe weather with this system. Cooler weather fills in
behind this system heading into next weekend...but flattening upper
pattern shunts the best cold air east well north of the state.
latest satellite imagery shows middle clouds having now infiltrated
most of the state. Low clouds that were anticipated to form
across eastern portions and move into ahn are just simply not
there and model guidance has backed off on their development
through daybreak. Have done likewise in the latest taf sets with
just scattered advertised for the lower cloud decks. By tonight
however...more certainty in a prolonged low cloud event with MVFR
and some potential for IFR and LIFR into Sunday as well with -ra
and dz developing.
//Atl confidence...12z update...
medium on ceiling this morning.
High on remaining elements.
Preliminary point temps/pops...
Athens 50 35 47 42 / 10 60 60 50
Atlanta 49 37 51 43 / 5 50 50 50
Blairsville 44 31 49 40 / 5 60 60 60
Cartersville 47 36 50 43 / 5 40 50 60
Columbus 54 41 56 48 / 20 40 30 40
Gainesville 45 33 47 41 / 5 60 60 50
Macon 51 39 51 45 / 30 50 40 40
Rome 49 35 50 43 / 5 30 40 60
Peachtree City 52 38 52 44 / 10 40 40 50
Vidalia 48 38 53 49 / 40 50 40 30
Freezing Rain Advisory from 10 PM this evening to 7 am EST
Sunday for the following zones: Fannin...Lumpkin...towns...