Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 092012

Area Forecast Discussion
National Weather Service Paducah KY
212 PM CST Fri Dec 9 2016

.SHORT TERM...(Tonight through Sunday night)
Issued at 212 PM CST Fri Dec 9 2016

Lots of clear sky and very light winds will be ideal for
radiational cooling tonight. A strong surface high is forecast to
be centered directly over the Lower Ohio Valley tonight. Lows will
be in the teens. Low cloudiness over southwest Indiana has been
stubbornly hanging in there, but satellite loops indicate the
clearing line is still edging northeastward.

Mid-level cloudiness will increase on Saturday and Saturday night
ahead of the next system. Winds will become southeast as the
high pressure system retreats to our east. Highs will be in the
mid to upper 30s Saturday.

Strong warm advection will develop aloft on Sunday as 850 mb
southwest winds increase to around 50 knots. Eventually the
atmosphere will moisten enough for precip to reach the ground.
By the time precip starts, the models indicate the cold air will
be dislodged. The precip type will remain all liquid with this
forecast. Pops will increase to the likely category in the

Rain will become widespread Sunday night as the surface cold front
passes across our region. The parent surface low is forecast to
move northeast across Missouri and Illinois to the Great Lakes
region. Following the cold front, temps will fall back into the
mid and upper 30s as the precip ends.

.LONG TERM...(Monday through Friday)
Issued at 212 PM CST Fri Dec 9 2016

The long term begins with a cold front making its final passage,
and thus offers the first forecast target of opportunity. The new
12Z GFS, 12Z NAM, and old 00Z Euro all say no QPF for us after 12Z
Monday. So after collab agreement, have eliminated the previous
and blended production of Monday morning Pops/QPF.

There is not much thermal change after this first front`s passage.
The mean overall flow is zonal at this stage. Monday`s highs/lows
wont be too far off climo actually.

A weak front/trof of lower pressure develops between two areas of
surface high pressure Tuesday, and makes a swift passage across the
Mississippi and Wabash river valleys. The new models suggest the
environment is moisture starved, and leads to our next forecast
target of opportunity for Tue pm/evening. Recognizing the pattern
and model (esp blend) bias tendency, and with support from all new
model data, and collab agreement, we similarly eliminated the scant
pop mentions and light qpf that was inherited/produced by the
blended init.

Pre frontal/trof temps Tuesday warm into/thru the 40s, then some
post frontal/trof cooling that occurs Tue night takes Lows back to
the 20s.

The main impact portion of the forecast is the Day 6 (Wed-Wed night)
Pcpn chance, and there is significant model difference. The 00z
guidance is drier and slower, the 06z and 12z guidance is largely
faster and wetter. The colder airmass brought in Tue night leads
into Wed for mainly frozen pcpn for our north, and a potential of a
change-over or mix for our south. We fine tuned our pcpn areas based
on 850 mb temps, sounding dendrite growth temps, and surface temps,
to collaborate as best we could on the either/or (mix/change) area
south with the all frozen pcpn north for Wed AM and PM time periods.
We further honed in on Wed pm to capture the strong cold advection
occurring with this more robust cold air advection reinforcement air
mass. All considered, the pic aligns well with our neighbors, and
the impact with light QPF is minimal for now. This could change/is
something to watch to see which direction the models go with regard
to speed/moisture, as that will have a significant correlation to
pcpn/amounts. Post system draw down temps are not too dissimilar
from what we just experienced, maybe even a few degrees colder with
20s for highs and teens for lows by the end of the package.


Issued at 212 PM CST Fri Dec 9 2016

Cold advection deck of MVFR to low VFR clouds may continue to impact
the KEVV and KOWB terminals thru the early evening hours. Advise a
close monitor thru early night hours to see if advertized scour out
(already running behind schedule) is thorough enough to warrant
elimination, or if overnight lingering may occur. Otherwise model
time/height cross sections suggest a dry lower trop with some mid
and high cover starting to spread over the terminals later tonight
into tmrw.




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