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FXUS63 KPAH 251131

Area Forecast Discussion
National Weather Service Paducah KY
631 AM CDT Sun Jun 25 2017

.SHORT TERM...(Today through Tuesday night)
Issued at 246 AM CDT Sun Jun 25 2017

Forecast confidence for the Monday/Monday Night weather system is
above 60 percent, with the only caveat being the timing of the
greatest coverage of precipitation across the WFO PAH forecast

The signal for the entrance and passage of precipitation across
the for late Monday and Monday night remains consistent. However,
the challenge for precipitation coverage lies with the evolution
of the sharpening trough rotating around the Great Lakes low
during the aforementioned time period. The blended model guidance
initialization did generate a higher PoP (probability of
precipitation) within the WFO PAH forecast area. Given the
sharpening of the baroclinic zone ahead of the middle/upper level
trough, had to consider raising PoP chances across a broader area
Monday evening, closer to the Canadian model solution.

Regardless of the model guidance used, there does not seem to be
much of a surface reflection of the upper trough, in fact, surface
high pressure remains dominant. Instability is also a factor. Used
a blend of GFS/Canadian lifted index values from Surface to 850 mb
bases to find most unstable air. This suggests that lapse rate
changes will be focused along channeled vorticity zones with the
cyclonic flow aloft.

Given the elevated nature of the precipitation, amounts should
remain relatively light across most of the WFO PAH forecast area.

Adjusted the regionally blended model guidance for sensible
weather elements to include a little more weighting from the NAM-
WRF model families, the Canadian, and GFS guidance. 

.LONG TERM...(Wednesday through Saturday)
Issued at 246 AM CDT Sun Jun 25 2017

Decreasing confidence in the extended as a very unsettled weather 
pattern is starting to take shape. 

We start out the extended with fairly high confidence with respect 
to temperature...humidity and lack of precip. After Wednesday 
however confidence decreases mainly with precip chances and duration 
of precip. Amounts are still meager so medium confidence with that 
parameter. By Wednesday the upper high continues to drift off the 
southeast coast of the US. While the flow aloft remains near zonal 
until friday and Saturday when a subtle trough aloft will rotate 
through the area. This will be our best chance of significant 
rainfall. There is also a surface cold front to our northwest but at 
this time it does not appear to make it through the it 
appears to lose intensity and southward progress. However with the 
Gulf wide open for business this will allow for moisture to pool 
over our area late this week and through the weekend. So there will 
be thunderstorms over the area at least at times. Most likely during 
the heat of the day but there is elevated instability overnight as 
well. Wind shear remain fairly unidirectional through the weekend 
and not all that strong with strongest winds 25 knots through most 
of the column Friday. They decrease but remain unidirectional 
through the weekend. Capes will range from 2-3k j/kg during the 
afternoon hours this weekend...but decrease to 1k in the overnight 
hours. In addition PW's range from one and half to better than 2" 
inches. So they will be very efficient rain producers where ever 
they form. A severe storm cant be ruled out toward weeks 
end...widespread severe is not anticipated at this time. Also with 
freezing levels 15k feet and higher most any hail will melt before 
reaching the surface. Finally trimmed pops back to chance category 
for days 6 and 7.


Issued at 629 AM CDT Sun Jun 25 2017

VFR forecast still remains intact for the 12z Sunday issuance of
the WFO PAH TAF's. Periodic middle level clouds will move across
each of the TAF locations. Wind shift from the west to
northwest/north will occur during the period across the TAF



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