Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 120456

1155 PM CDT Fri Jul 11 2014

Issued at 1155 PM CDT Fri Jul 11 2014

Updated aviation discussion only for the 06Z issuance.


.SHORT TERM...(Tonight through Sunday night)
Issued at 259 PM CDT FRI JUL 11 2014

The area of high pressure that has kept the area`s weather a bit
more tolerable for the past few days will retreat eastward tonight.
This will allow a stationary frontal boundary to our south and west
to retreat northward as a warm front.

The warm front is forecast to be in the vicinity of the northeast
sections of our CWA Saturday morning. This combined with increasing
low level moisture and a weak short wave aloft may produce scattered
showers and thunderstorms generally north and east of a line from
Mount Vernon Illinois to Evansville to Rockport Indiana during the
morning hours. During the afternoon the front and the short wave
will have moved out of our area, so it looks dry for the moment.

Precipitation chances make their way into the far northern sections
of our CWA late Saturday night with the approach of a frontal
system. Chances will increase from north to south across the area
Sunday into Sunday night as the frontal boundary draws nearer.

The SPC has outlooked part of our area (north of a line from
Perryville MO to Owensboro KY) for Sunday. In addition to the
approach of the front, the atmosphere will be quite unstable with
decent mid level lapse rates and strengthening mid level diffluent
flow. However, with little to no shear and freezing levels expected
to be AOA 15K feet, the primary hazard from any storm that becomes
severe should be damaging winds. Model soundings showing a decent
mid level capping inversion over the southern portions of our CWA on
Sunday so not sure if anything will fire there.

.LONG TERM...(Monday through Friday)
Issued at 259 PM CDT FRI JUL 11 2014

A marked cooldown is anticipated in the long term. A
climatologically rare...deep upper level low will descend as far
south as the Great Lakes region on Tuesday. The 12z ecmwf indicates
a central height of 555 dm over Lower Michigan at 18z Tuesday. 850
mb temps will fall into the single digits during the middle of the
week as far south as the Ohio River...and possibly to the Tennessee
Valley. 850 mb temps will be as low as 3 standard deviations lower
than climatology over Missouri on Tuesday evening...and 2 to 3 sd
from climatology over a wide area for a few days.

As far as the daily details...
The timing of the cold front varies considerably from model to
model. The models may not be helpful in this case...since the
influence of convective systems will probably determine the
effective frontal position. A realistic scenario not depicted by any
global model is that a convective complex will cross our region
Sunday night...effectively relocating the frontal boundary to our
south by Monday. The 12z ecmwf is the slowest model...taking the
cold front across the Lower Ohio Valley late Monday night.

The forecast will continue to indicate 50 to 60 percent pops Monday
into Monday night due to the proximity of the frontal boundary. The
potential for strong to severe convection will be heavily influenced
by the presence of any convective systems early Monday. If the
atmosphere is not raked over early Monday...there is some potential
for severe weather later in the day into the night. Temps will of
course depend on outflow boundaries and convective activity.

The forecast is more clear cut the rest of the week. A
climatologically rare blast of cool air will arrive Tuesday and last
through most of the week. The cooler ecmwf guidance has been quite
consistent...and performed very well during the early month cool air
intrusion. Therefore...will trend toward this guidance as opposed to
the warmer gfs guidance and the all blend. The coverage of
cloudiness will be a factor with temps. There may end up being quite
a bit of diurnal cumulus given steep lapse rates and deep cyclonic
flow around the Great Lakes low.

By the end of the week...the models indicate residual upper
troughing lingering down into the Lower Ohio Valley. The 12z ecmwf
and 12z gfs ensemble mean show a surface warm front lifting north
across Tennessee...with some qpf reaching into western KY. Will keep
the forecast dry after collaboration with neighboring offices and a
look at the dry 12z gfs.


Issued at 1155 PM CDT FRI JUL 11 2014

A warm front will continue to lift newd through the PAH forecast
area over the next 24 hours. With the exception of MVFR fog at
KCGI/KPAH between 08-12Z, VFR conditions should prevail through the
period. Some showers are possible after 15Z mainly along the I-64
corridor (including KEVV/KOWB) near the aforementioned frontal
boundary. Light and variable to calm winds will continue at all
sites through 14-15Z, then pick up out of the south southwest at 5-7




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