Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 132054
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
254 PM CST Sat Dec 13 2014

.SHORT TERM...(Tonight through Monday night)
Issued at 253 PM CST SAT DEC 13 2014

A warm front was located just southwest of the area mainly across
northeast Arkansas. South of the boundary, skies were partly cloudy
and dewpoints were near 50. Unfortunately, its progress northeast
toward our region is likely to slow down significantly with loss
of mixing in the next hour or two. Cannot completely rule out some
clearing over portions of Ripley county, but otherwise, most of
the region is socked in and ceilings are actually lowering this
afternoon.

There are some breaks along I-64, and likewise, that scattering
process is likely to stop with loss of heating/mixing soon. Would
expect clouds to quickly spread back across that area by 00Z.

The 12Z models do not push that warm front through the area
tonight, so ceilings should continue to lower, and areas of drizzle
and fog are a good bet throughout the area. Guidance seems too low
for lows tonight.

Dewpoints should surge through the 40s Sunday. Not sure how much
clearing/scattering there will be, but would expect it to be
confined to the western half of the area. Guidance seems
reasonable over most areas, with the exception of the far east,
where the cooler end of guidance should be closer.

The 12Z models continue to take the upper low northeast from
Kansas to Iowa Sunday night into Monday. Ahead of it, they
continue to be very consistent in pushing a solid band of showers
east/northeast through our region very late Sunday night and
Monday morning. None of the models generate any tangible
elevated instability, so thunder will not be mentioned.

Jumped PoPs up to categorical, but the main question is how far
east it will get by 12Z Monday? The 12Z models seem to be trending
slower with this band, but they also keep there relative biases.
Generally followed HPC QPF for this forecast, which seems to be
most in line with the 12Z GFS timing.

All bets are off for precipitation chances beyond 18Z Monday. Any
deep saturation is gone by Monday afternoon, so it would be more
of drizzle chance Monday afternoon. The only chance for deeper
saturation to occur will be Monday evening as the southern
periphery of the main upper low/trough swings rapidly eastward
across the region. This will also push the cold front through the
region. Will keep PoPs up to 50% in the northeast and east Monday
afternoon and night, but southeast Missouri may stay dry for this
entire period.

As for temperatures, it should be fairly mild, generally above
guidance, Sunday night, and would not be at all surprised to see
some 60 degree readings in southeast Missouri Monday.

.LONG TERM...(Tuesday through Saturday)
Issued at 253 PM CST SAT DEC 13 2014

The overall trend during the long term period will be toward
increasing precipitation. The models are in good agreement that a
moist southern branch of the jet will ensure at least one organized
precip event. As usual, the devil is in the details. The timing of
the event (or events) and the type of precip are highly variable
from model run to model run.

As far as the daily specifics...
On Tuesday, a colder and drier northwest wind flow will prevail on
the back side of a departing surface low. Given the relatively mild
start to the day and the potential for partial sunshine, highs may
end up being in the upper 40s in many locations.

On Tuesday night and Wednesday, a 1028 mb surface ridge will move
east across the middle and upper Mississippi Valley. This ridge will
bring rather cold and dry air in the low levels. However, mid and
high clouds will increase as the upper level flow becomes westerly.

On Wednesday night and Thursday, model differences become more
significant. The 12z gefs (gfs ensemble) develops a northeast
surface wind as the 850 to 500 mb layer flow becomes southwest. A
rather large area of light qpf breaks out, most likely tied to the
overrunning of shallow cold air. The ecmwf maintains dry conditions
through Thursday due to its slower and stronger upper level ridge.
Given the model differences, will maintain small 20 to 30 percent
pops Wed night into Thursday. Precip type could be just about
anything in the north, and most likely rain or a mix in the south.

Thursday night and beyond, there is strong agreement that a moist
upper level shortwave will eject east-northeast from the southern
Plains. However, the track and timing of the system varies
considerably from run to run. For example, the new 12z ecmwf is
about 12 hours slower with the system than the 12z gefs. The ecmwf
is also further south with the track of the system. The differences
in track and timing yield differences in the location of the
rain/snow line. It appears the precip event will be partially or
mostly snow northwest of the Ohio River, based on the 12z model
suite.

&&

.AVIATION...
Issued at 1140 AM CST SAT DEC 13 2014

Low VFR ceilings cover the entire area late this morning, and
satellite imagery shows no signs of the overcast breaking. Would
not be surprised to see any location drop to MVFR levels through
the afternoon, but that seems most likely at KCGI. The latest
guidance continues to indicate at least IFR conditions with drizzle
and fog late tonight. Not sure how quickly or gradual ceilings
will lower through the night, but certainly should see MVFR
ceilings at all locations by 06Z. Some clearing or decent lifting
at KCGI and KPAH is possible in the last few hours of the
forecast, but conditions are not likely to improve at all through
midday in the northeast.


&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
MO...NONE.
IN...NONE.
KY...NONE.
&&

$$

SHORT TERM...DRS
LONG TERM...MY
AVIATION...DRS






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