Scientific Forecaster Discussion
fxus63 kpah 250435
Area forecast discussion
National Weather Service Paducah Kentucky
1135 PM CDT Sat Aug 24 2019
Short term...(tonight through Monday night)
issued at 251 PM CDT Sat Aug 24 2019
High pressure centered over the Great Lakes into eastern Canada
continues to make its presence felt, with comfortable east-northeast flow
across the area offering tolerable dew points and afternoon temps in
the mid 70s to near 80. Pesky showers over the Ozarks continued to
make it as far east as Carter and Ripley counties. Will carry
limited pops into this evening generally west of Highway 67, with
increasing clouds east of the MS river. Generally used the hrrr for
precip trends into the evening.
Overnight, mainly late, pops should increase over the southwest 1/2
of the area, especially semo into far west KY, the southern tip of
Illinois. Showers and isolated thunderstorms expected, with the best
chance of storms toward Tennessee/Arkansas state lines. Sunday, good chance pops
for convection, driven by an evolving 500 mb trof to our west that will
strengthen south-southwest moist flow over the area, along with providing lift
and instability. Those chances will continue Sunday night into
Monday as heights fall with the 500 mb trof axis moving overhead. Should
see a decrease in pops by afternoon and early evening. This will be
in advance of an approaching cold front to our northwest that will
offer up yet another chance of convection late. More on that (for
tuesday), in the long term section.
Temperatures were generally a MOS/nbm blend. We went a couple of
degrees cooler for Sunday and Monday given the expected clouds and
Long term...(tuesday through saturday)
issued at 251 PM CDT Sat Aug 24 2019
The medium range models continued to have a solid signal for a
surface cold frontal passage during the day Tue, driven by a lobe of
shortwave energy to the southeast of a vortex centered near Hudson
Bay. Showers will be likely across the pah forecast area, with at
least scattered thunderstorms moving through. The deeper moisture
should be scoured out by evening, thus pcpn coverage will wane
significantly Tue night.
A reinforcing shot of dry air is progged by the models to sweep into
the region on Wed. The initialization blend, modified with 50%
consall data, supported a small possibility of an isolated shower or
two, with a few lightning strikes, popping up mainly in the southern
third of the region on Wed afternoon. After that, the extended
forecast looks essentially dry under west-northwest flow aloft and
high surface pressure.
For Fri/Sat (days 6&7), some models indicated another mid level
shortwave may drive another mostly dry surface cold front through
the region. There were significant timing differences with this
feature, thus any confidence of associated pcpn during this time
frame is low. If it was to rain anywhere, it would be in the
northwestern fringe of the region.
Once the high-dewpoint air is out of our region (starting Tue
night), expect mild conditions for this time of year, with dewpoints
mainly in the 60s.
issued at 1134 PM CDT Sat Aug 24 2019
For the 06z Sunday weather forecast office pah taf issuance, the forecast becomes
quite challenging for the kcgi and kpah taf locations after 18z
Forecast guidance suggest that ceilings will drop marked into the
IFR/MVFR category for kcgi and kpah locations as the frontal
boundary moves over these locations. The greatest uncertainty is
with visibilities and is dependent on the rainfall in and around
the taf locations. For now, given the rainfall probability, kept a
vicinity shower mention with VFR category visibility. However,
would not be surprised to see brief periods of MVFR visibility.
Anticipate a slow decline in ceilings for kmvn, kevv, and kowb.
MVFR ceilings may not occur until the last few hours of this
forecast issuance (03z-06z).