Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 232003

303 PM CDT Wed Apr 23 2014

.SHORT TERM...(Tonight through Friday night)
Issued at 302 PM CDT WED APR 23 2014

The surface high has really held down warming this afternoon,
despite plenty of sunshine. It will continue to dominate the
region tonight with relatively light east southeast winds and
mostly clear skies expected in most locations. Temperatures will
be tricky, with potential for radiation cooling to drive
temperatures below guidance. With warm advection aloft, will go
close to guidance, and let the evening shift monitor for
potentially cooler temperatures overnight.

Winds will eventually veer to due south by Thursday afternoon, as
the surface high finally loosens its grip on the region. The 12Z
NAM and the high-resolution WRF runs have slowed down the arrival
and progression of the convection through the area Thursday
afternoon and evening, and they have been followed closely for
timing. Just about all 12Z models have a more intense mid/upper
trough swinging through the area Thursday evening. This will
result in greater forcing than expected yesterday, but the quality
of the low-level moisture and lapse rates aloft are still

The slightly slower passage of the front will allow a bit more
time for lower 60s surface dewpoints to reach at least southern
portions of the area, but surface-based instability will still be
highly dependent on the forcing to be released. This should result
in a more linear event, with damaging winds the main concern, but
a stray brief tornado cannot be ruled out even within the line or
line segment.

A supercell or two cannot be ruled out initially as
the convection develops over southeast Missouri around 21Z, and
there could also be an embedded supercell structure within the
line or a line segment into the evening. The mid-level storm-
relative flow will still be rather weak, which would be
detrimental to the persistence of any supercell structures, and a
more robust severe weather event.

Look for scattered to numerous thunderstorms to develop over
southeast Missouri between 21Z and 00Z, and then move across the
remainder of the area as a line or series of line segments
through 06Z. In general, the severe weather threat will weaken as
it moves eastward through the evening. Any heavy rainfall should
be short-lived enough to prevent any major flash flooding
potential with this event.

Winds will become west or west northwest behind the front and
remain west or southwest Friday and Friday night. As for
temperatures, will generally side with the warmer MAV guidance for
highs Thursday and Friday. Leaned toward the milder MET guidance
for lows Thursday night and stayed close to guidance for lows
Friday night.

.LONG TERM...(Saturday through Wednesday)
Issued at 302 PM CDT WED APR 23 2014

The extended period will begin with a sharp ridge aloft and srly
boundary layer flow over the PAH forecast area. Srly low level flow
will be on the increase Sun as a large, nearly stacked, low pressure
system approaches from the Central Plains. There will probably be
enough moisture influx/instability/divergence aloft ahead of the
system to trigger scattered tstms by Sun afternoon across much of
the region. The system should progress ewd Sun night, making
rainfall likely, with perhaps scattered lightning. By Mon, ample
vertical motion/moisture influx/instability is forecast to continue
through the day, with the added forcing of a sfc warm front lifting
nwd through the region, and inducing plentiful tstm activity into
Mon evening.

As to the severe weather possibility, at this time, the med range
models were in reasonable agreement that there will be robust wind
shear aloft by daybreak Mon. However, instability is forecast to be
somewhat limited, and the phasing of best lapse rates and best upper
jet winds do not appear to be ideal in the PAH forecast area, but it
should be better just to the west. Still, this does not rule out
some severe tstm development here, especially during Mon afternoon/

After Monday, the GFS ensemble members began to spread apart a bit
regarding the placement of the mid level and sfc lows, along with
the deterministic runs of the med range models. Tue should yield
showery conditions with the low pressure system somewhere in the
vicinity, with lesser QPF and still some lightning activity as sfc
winds finally turn to the nw late in the day. By Wed, if the model
solutions remain stable, a mid level trof in the nern conus will
have merged with the low over the PAH forecast area, dropping
heights a significant amount, meaning much cooler temps, and
continued cloudy, showery conditions through Day 7.


Issued at 1213 PM CDT WED APR 23 2014

Surface high pressure will continue to dominate the region through
tonight. East northeast winds this afternoon will veer to east
southeast and become light this evening. As a strong storm system
and cold front approaches Thursday, winds will increase from the
south. Some gusts up to near 20kts will be possible at KCGI by
18Z, but elsewhere the gusts should hold off until after 18Z. A
batch of mid clouds will stream across the area tonight, otherwise
skies will generally be clear.




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