Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kpah 182328 

Area forecast discussion
National Weather Service Paducah Kentucky
628 PM CDT sun Aug 18 2019

issued at 623 PM CDT sun Aug 18 2019

Updated aviation discussion for 00z tafs.


Short term...(tonight through Tuesday night)
issued at 200 PM CDT sun Aug 18 2019

Several outflow boundaries seen on satellite today, along with a
weak front that was poised to our northwest. A weak upper level
disturbance will continue to move east into the area this afternoon
and allow for continued scattered convection. Exactly how widespread
and how far east to take pops is the main question right now.

Looking at the latest data, it appears the northern half of the area
has the best chances to see more widespread coverage the rest of
this afternoon through about mid evening. Deep moisture is
definitely lacking over western Kentucky and this is evident in the upper
60s dewpoints, so chances there appear low at this time. Spc's day
one outlook confirms this. However, depending on how organized the
storms become, we could see activity cross over into west Kentucky if the
thunderstorm outflows become strong enough. There is slight better
shear parameters up in the northern sections of the area, therefore
storm organization will be increased in S. Illinois/SW in and parts of
semo, which is likely why the upgrade to slight risk was made to a
small part of the area and an expansion of the marginal risk, with
the late morning Storm Prediction Center day 1 update. In fact, a Severe Thunderstorm
Watch for parts of semo/S. Illinois GOES until 700pm, so a few strong to
possibly severe storms are likely. Will analyze latest
satellite/radar trends and make last minute decisions on how to
handle pops for the rest of this afternoon.

How much and exactly where convection will linger into this evening
will be most likely driven by outflow boundaries from this
afternoon's storms, as the upper level disturbance will be moving
off to the east by late evening. Will linger chances until about 03z
and then taper off pops for the rest of the night. The Fly in the
ointment will be the fact that various guidance is indicating the
possibility of additional activity in the unsettled northwest flow
aloft later tonight into Monday morning. This isolated to scattered
activity will be with US throughout the day on Monday as we continue
to deal with minor perturbations in the northwest flow aloft.
Meanwhile, the front that was mentioned earlier, will continue to
slowly sink southward and by Monday night, could be laying across
our northern counties. Coverage of any shower or thunderstorm
activity on Tuesday appears to be rather low, but chances will be
increasing late Tuesday night and especially as we head into
midweek, as another front sags south toward the area.

The heat will continue on Monday as a strong ridge of high pressure
develops in the south Central Plains and noses into our area.
Expecting lower 90s for highs on Monday and Tuesday, with some mid
90s possible especially out west on Tuesday. These types of
temperatures combined with 70 to 75 degree dew points will likely
lead to 100 to 105 degree heat indices which for most US has been
the status quo lately. If we see indications that we will reach much
higher than that, an advisory will be needed.

Long term...(wednesday through sunday)
issued at 200 PM CDT sun Aug 18 2019

The models are really changing alot with how they handle the mid
week front and its entrance/passage. The ensemble/blend is now
hanging it up over the area, offering pretty good chances thru
Thursday, and then washing it out and while it does cool and dry a
little off the peaks, it is not really offering The Plunge of
drier/cooler air to the degree that just one day ago, it was
suggesting. As a result, have some skepticism with the blend, esp
considering the 12z GFS now oscillates back a little more toward
yesterday's output.

Nevertheless, am not comfortable with the outlier changes, so will
stick with The Middle Ground active/pops scenario thru Wed/Thu.,
Then hope to fine tune it over the next 24-48 hours. That means
triple digit heat indices are possible Wed., With peak pops Wed-
Thu., Waning to smaller mainly diurnal chance mentionable pops
finishing out the forecast. Highs in the 90s Wed will curb back to
the 80s thereafter, but dew points will remain in the upper 60s to
lower 70s as their fall off, with lows mirroring that, except in the
north, where the drier/cooler air has a little better chance of
reaching down.


issued at 623 PM CDT sun Aug 18 2019

Scattered convection still working through portions of the region,
but it should continue to dwindle over next several hours. Best
chance at any ts activity affecting a terminal would probably be
at kowb and back into southeast Missouri near Arkansas border
through 02z. Otherwise, main concern during overnight/early
morning period will be the potential for fog development in areas
that received rain today. Included tempo mention for now at
kcgi/kmvn and may eventually be needed at kevv as well. Slight
chances for convection return during the day tomorrow, but
confidence too low to include in any terminal at this time.


Pah watches/warnings/advisories...


National Weather Service Glossary of Abbreviations