Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 011729

1230 PM CDT Fri Aug 1 2014

Updated aviation section for the 18Z TAF issuance


.SHORT TERM...(Today through Sunday)
Issued at 305 AM CDT FRI AUG 1 2014

Will be monitoring the patchy and shallow dense fog across much of
the area again this morning. See no reason why it wouldn`t be
similar to yesterday`s development.

A sharper mid/upper level trough will develop within the broad
cyclonic flow over the region through tonight, but the 00Z models
are a bit weaker and farther east with it compared to yesterday`s
runs. It will push just east of the area by Saturday evening.

In the low-levels, weak warm advection is noted within the KPAH
VAD wind profile, but the surface pressure pattern is very flat. A
minor push of surface high pressure into the area is expected in
the wake of the upper trough late Saturday into Sunday.

The weak warm advection over southeast Missouri may result in some
isolated shower activity this morning. The NAM soundings in western
portions of southeast Missouri indicate a shallow layer of
instability based around 7kft, and the HRRR develops showers
northward into that area from the Boot Heel region and northeast
Arkansas through the morning. The soundings dry up by 18Z, but as
the mid/upper trough develops southward toward our region, a small
chance of deep convection exists across northern portions of
southern Illinois in the late afternoon and possibly into the
early evening. If a storm develops it should be short-lived and
rather weak.

With the upper trough over the eastern half of the region
Saturday, isolated diurnal showers and thunderstorms can be
expected generally along and east of the Mississippi River. Once
again any storms should be short-lived and rather weak.

As for temperatures, the consensus of rather tightly grouped guidance
looks pretty good through the period.

.LONG TERM...(Sunday Night through Friday Night)
Issued at 305 AM CDT FRI AUG 1 2014

High Pressure aloft dominates the WFO PAH forecast area through 12z
Thursday. effectively suppressing convection across the region.

Between 18z Wednesday and 18z Thursday, the latest 00z Friday medium
range model guidance begin to differ sharply in the position of a
deepening shortwave in the Upper Midwest/Northern Plains region.
This significantly impacts the rapidly evolving baroclinic zone to
the northwest of the WFO PAH forecast area. The ECMWF sets up a warm
advection flow with convection being developed along a warm front
developing over the Tri-State region (Southwest IN, Northwest
Kentucky, Southeast Illinois. The GFS keeps the WFO PAH forecast
area in the warm sector ahead of the impressed warm and cold fronts.

By Thursday, the movement and deepening of the Upper
Midwest/Northern Plains low continues to differ sharply with the
GFS/ECMWF/NAM guidance in locations and to a lesser degree timing of
upstream convection. Regardless of the latest solution, slowed down
the onset of convection into the area into Thursday.

Beyond Thursday, the east-southeast movement and deepening of the
Upper Midwest/Northern Plains shortwave transitions into an upper
Low over the Great Lakes by late Friday night. Although there is
some initial concern on the timing of the precipitation into the WFO
PAH CWA, this becomes a moot point Thursday into Friday as the
baroclinic zone becomes stretched across the area, prolonging rain
chances across the area.  In fact, several of the recent model runs
are consistent in keeping higher than normal PoPs/Weather in place
during this time period.

Therefore, PoPs and Weather have been included for the period from
next Thursday into Friday. All other forecast changes minor, with
the exception of those sensible weather elements impacted by the
forecast convection.


Issued at 1230 PM CDT FRI AUG 1 2014

For the southern terminals /kcgi and kpah/...mid level cigs around
10k feet will persist through this evening in advance of a
southeastward moving upper level disturbance. Once skies clear out
later tonight...there will likely be some fog as winds become calm.
Conditions should be similar to early this morning. The fog will
burn off quickly within a couple hours after sunrise.

For the northern terminals /kevv and kowb/...cumulus clouds will
gradually increase this afternoon but should remain scattered for
the most part. A mid level cloud deck will arrive early this evening
in advance of an upper level disturbance. Could not rule out some
showers this evening...but probabilities are too low to include in
tafs. Skies will clear out by early Saturday morning.




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