Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 130137

837 PM CDT Fri Sep 12 2014

Issued at 836 PM CDT FRI SEP 12 2014

Advancement of a sheared shortwave vorticity axis coincident with
decent low level moisture in the 306-311K isentropic layer across
the WFO PAH forecast area. Improved condensation pressure
deficits and local pressure derivatives of up to 1
microbars/second are forecast to move across the Southeast
Missouri Delta, the Purchase Area and Pennyrile areas of West
Kentucky between 02z-10z per the NMM version of the 4km NAM-WRF,
the 13km RAP, and 3km HRRR guidance.

With this in mind, adjusted the gridded forecast to enhances some
area with a mixture of measurable PoP/Weather (very light rain)
and patchy/areas of trace precipitation (drizzle) overnight. There
may be a miss for some areas, but attempted to use the high
resolution guidance to focus on those areas from late evening to
the early morning hours on Saturday for rain chances.

To accommodate (non-diabatic) sensible weather changes with these
enhanced precipitation areas, minor tweaks to temperature,
dewpoint, and winds were also modified for the evening. Dry air
advection with time at the lower levels should limit any
measurable visibility restrictions due to the precipitation overnight.

Given the short temporal (time) and spatial (space) impacts of the
precipitation, these adjustments will show up more in the gridded
forecast (available through the point and click forecast on the
NWS Paducah web page) and tabular forecast versus the general text
forecast for specific forecast locations overnight.


.SHORT TERM...(Tonight through Sunday night)
Issued at 250 PM CDT FRI SEP 12 2014

The upper-level storm system is currently moving eastward through
Minnesota, and the trough trails to the southwest into the central
Plains. Some light showers are trying to move northeast out of
central Arkansas and toward the four state region. The general
consensus of the 12Z guidance is that the precipitation will
dissipate before reaching our region. The lone exception appears
to be the NAM which drags some light showers or drizzle northeast
through the Pennyrile region of Kentucky in the late evening and
early morning hours. Decided to keep a slight chance of showers in
the far east in that time period, but kept the rest of the area
dry tonight. There has been an increase in drizzly echoes to the
south and southeast of KPAH in the last hour, so also added patchy
drizzle over the southern half of the forecast area through 06Z.

The models continue to indicate a rapid clearing trend late
tonight and Saturday morning, as the upper system passes by and
the surface high really begins to surge across the area. Some
locations may test record min max temperatures Saturday. The
record min max at KPAH today is going to be shattered, but
Saturday will be with full sunshine. Gusty north winds will make
it feel even cooler Saturday afternoon.

Surface high pressure will slowly settle over the region, and
winds over much of the area may drop to near calm. This will
likely lead to good radiational cooling, and with dewpoints well
into the 40s throughout the area, some record lows may be tested
Sunday morning. Some moderation is expected in both temperatures
and dewpoints Sunday, but guidance may be a bit aggressive with
those trends.

.LONG TERM...(Monday through Friday)
Issued at 250 PM CDT FRI SEP 12 2014

For the upcoming work week, the weather appears to be fairly quiet.
The only real challenge will be Monday-Tuesday when decisions have
to be made on the likelihood of rain with an incoming frontal
boundary. Lower level moisture will be lacking for much of Monday,
with the bulk of it to our northwest. Therefore, believe that much
of the area will be dry.

As we head into Monday night into Tuesday, low level moisture will
be increasing from the north and settle into the area. The 00Z ECMWF
stays the course of its past runs and shows the moisture blasting on
through here and exiting by Tuesday morning, not bringing us much of
anything in the way of precip. The GFS a slower solution and
indicates better chances for precip after midnight Monday night in
the northwestern half. This is also supported by a few members of
the GFS precip ensembles. However, the moisture is slow to move
through, so it is possible to see a few lingering showers into
Tuesday, but will leave mainly dry for now. After watching the
behavior of the last several runs of the GFS, it has definitely been
favoring this scenario, unlike the faster Euro.

Nevertheless, by Wednesday, high pressure will build in and
northwest flow aloft will take over...with no big signals of any
other systems to deal with for the rest of the week.


Issued at 637 PM CDT FRI SEP 12 2014

With moisture still trapped below the inversion, IFR/MVFR cigs will
continue through 14-16Z, then VFR. Northerly winds AOB 10 knots
will continue through 14Z, then veer around to the north northeast
around 15Z at 10 knots with gusts up to 18-20 knots at KCGI/KPAH.




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