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Area forecast discussion 
National Weather Service Paducah Kentucky
848 PM CST Mon Dec 5 2016

Update...
issued at 848 PM CST Mon Dec 5 2016

Delayed the onset of precip by a few hrs given recent radar trends
and hi-res short term models. Rain should develop in earnest
by around 05-07z across southeast MO, western Kentucky and far southern
Illinois and quickly spread northeast across the area thru the
overnight hrs. The northwest edge of the precip shield may end up
setting up shop near our northwest counties from near Perryville,
MO to Mount Vernon, Illinois. Thus this area may end up not picking up
much measurable precip. Other sensible weather elements appear on
track with temperatures holding steady or even rising a few
degrees through the overnight hours.

Update issued at 602 PM CST Mon Dec 5 2016

Updated the aviation discussion for the 00z taf issuance.

&&

Short term...(tonight through Wednesday night)
issued at 236 PM CST Mon Dec 5 2016

Well it is still looking wet tonight into Tuesday, but the 12z
model consensus now has the Arctic surge coming through dry
Wednesday night.

The 12z models continue to open up a closed low over Texas as it
moves into our region by 12z Tuesday. The associated surface low
will lift from southern Louisiana to middle Tennessee by 12z
Tuesday, and should stay to our southeast. This storm system will
tap plentiful moisture from the Gulf, but the trend has been to
slow down the arrival of the showers until later this evening, and
then ramp them up in the 03z-06z period. Not sure where the back
edge of the precipitation will be, but it could be right along our
northwestern border.

The greatest precipitation should fall over the southern pennyrile,
where over an inch will be possible. This forecast is likely to
end up on the wet side, but the 12z consensus quantitative precipitation forecast has already been
lowered over much of the area. Decided to pull out thunder, as the
MUCAPE was very low and splotchy. Cannot rule out a stray rumble
of thunder, but the overall lightning threat is low. It still
looks like the precipitation should push east of the area shortly
after 15z, and the entire area should be dry by 18z.

Looking ahead to the Arctic surge Wednesday night, the 12z
consensus has any associated precipitation drying up before
reaching the area. The only outlier at this point, is the CMC
which has a hundredth or so reaching southeast Missouri and
southern Illinois in the evening, and then is dry for the entire
area overnight. Will leave a slight chance of rain or snow or a mix
for these areas in the evening, just to make sure the models don't
reverse their drying trend tonight.

As for temperatures, generally accepted consensus after tonight.
With MVFR ceilings over much of the area at sunset, and increasing
moisture through the night, really feel that temperatures are not
likely to fall much if at all tonight. Winds will back from east
southeast this afternoon to north by morning, but there should
not be any tangible cool advection. Tricky part for tonight is
where will temperatures be at 01z when the mint period begins?
Some guidance options have warmer lows than the observed 20z
temperature. Gave it a shot, but may not be mild enough.

Long term...(thursday through monday)
issued at 236 PM CST Mon Dec 5 2016

The first push of modified Arctic air of the season will continue
through the end of the workweek. The associated surface high will
sink southeast from the Canadian prairie provinces to the lower Ohio
Valley by Friday night. The impressive 1048 mb high will weaken as
it moves southeast, but it will still be around 1035 mb Friday
evening. 850 mb temps are forecast to average around minus 10c on
Friday, which is by far the coldest air so far this season. Despite
very dry air and plenty of Sun, afternoon highs will struggle to
reach 32 on Friday. The lowest wind chills of the week are likely to
occur early Friday morning, possibly in the 5 to 10 above range.

Over the weekend, moisture will increase as a low amplitude 500 mb
shortwave moves eastward in the fast zonal flow. A southerly flow of
milder air will increase ahead of a surface low over the plains. The
12z GFS generates fairly widespread qpf in the strong warm advection
pattern Saturday night. The 12z ecwmf is slower with the 500 mb
shortwave and the arrival of precip. The forecast will call for
increasing clouds Saturday, followed by a slight chance of precip
Saturday night. The lower levels are forecast to be nearly
isothermal, right around freezing. Any precip that reaches the
ground would likely be a mixture of snow, sleet, or freezing rain.

Precipitation chances will increase rapidly on Sunday as a weakening
cold front moves into the Mississippi Valley by evening. Continued
warm advection on Sunday will result in mainly liquid precip. There
could still be a mixture early in the day, mainly across southwest
in and NW Kentucky. Highs will be mainly in the 40s.

Sunday night and Monday should be on the damp and chilly side. The
cold front will stall or dissipate over our region, preventing any
significant drying. Lows will be in the 30s with highs in the 40s.

&&

Aviation...
issued at 602 PM CST Mon Dec 5 2016

As a system lifting northeast out of the deep south approaches
and tracks just southeast of the taf sites, cigs/vsbys will
deteriorate to MVFR/IFR along with dz/rain through at least the
first half of the period. Conditions will slowly improve and the
precipitation will end from west to east during the latter
portions of the period. Easterly winds at or below 10 knots will slowly
back around to the northwest in the wake of the system, then
become gusty with gusts up to 22-24 knots during the last third of
the period.



&&

Pah watches/warnings/advisories...
Illinois...none.
MO...none.
In...none.
Kentucky...none.
&&

$$

Update...snow pellets
short term...drs
long term...my
aviation...jp

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