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000 
FXUS63 KPAH 122030
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
230 PM CST Thu Dec 12 2019

.SHORT TERM...(Tonight through Saturday)
Issued at 200 PM CST Thu Dec 12 2019

In the immediate term, models were having difficulty handling the
dry air at the surface this pm. Dew points remain largely in the
20s and there's even some upper teens around, which may be
suspect. The models appear better synchronized with clouds that are
largely mid and high variety and winds, with some gustiness, that
are higher closer to the tighter gradient in our northwest tier of
counties.

Beyond the immediate term, gridded time/height cross sections show we
should see a continuation of the very dry air in the lower trop 
thru the day Friday. This should work to preclude (most) precipitation
chances from slinging much back into the FA, as moisture overruns
a boundary that is well to our south and east. But it looks like
we may carry a collaborative small pop in our far east, into 
Friday evening. Pops there (east) should diminish late Friday 
night, as upper trof energy swings thru. However, a 2ndary punch
of clipper wave energy will bring its own sling of moisture down 
the nwly pike, and the blend has consistently picked up on 
smallish pops with its track, across basically our northeast half 
of the FA. We'll stay with these ensembled assembly of smallish 
pops for late Friday night thru Saturday, but overall QPF is 
scarce, and boundary layer temps just warm enough, so they should
offer minimal impacts.

.LONG TERM...(Saturday night through Thursday)
Issued at 200 PM CST Thu Dec 12 2019

As a surface high builds into the Midwest and western Great Lakes
region Saturday night/Sunday, isentropic lift should get going by
Sunday afternoon east of a mid level trof out over the southern 
Rockies. This may be able to generate some light precipitation 
along and to the north of a west-east oriented sfc boundary 
located from the western Gulf Coast states ne into the lower TN 
River Valley. Precip chances will then increase Sunday night into 
Monday as a surface low develops on the frontal boundary and 
begins to strengthen and head northeast. 

It seems as though enough cold air will be in place on Sunday into 
Sunday night for any precipitation to fall in the form of snow or a 
rain/snow mix, especially north of the OH River. Would not be 
surprised to see some accumulations during the late afternoon and 
night-time hours, but the qpf forecast is a bit problematic and 
of lower confidence. For now, will compromise with a qpf close to 
WPC numbers, but it should be noted that there are some models, 
including the 12z ECMWF, that triple the WPC qpf. Of course, that 
would translate into higher snow totals than we currently have in 
the official forecast. In addition, there may well be a narrow 
band of mixed wintry precip along or somewhere near the OH River. 
Stay tuned. 

On Monday, surface low pressure will rise northeast along the 
frontal boundary. Though models have converged somewhat on the track 
of the low, there is still uncertainty as to whether the track is 
right up the OH River, or farther southeast toward the Nashville TN 
area. For now, looking like consensus is to lean more toward the 
farther south solution. This is important because if the low track 
were to end up farther nw, then we could be dealing with a 
convective risk too, as more instability would become available 
along/east of the low track.  

Thinking now is that just enough warming will take place during the 
daylight hours Monday across our northern counties to allow any snow 
to change over to a cold rain, which could dig into any snow totals. 
In addition, it is now looking as though any deformation snows 
wrapping around the back side of the system on Monday evening will 
miss our forecast area to the nw and north, but not by much. 
However, any lingering precip that does last into Monday night would 
likely turn back over to a little light snow or flurries before 
ending later in the evening.  

Another shot of very cold, Canadian air will spill into the region 
behind the system Tue/Wed, with high temps holding in the 30s to 
near 40 and overnight lows down into the teens to lower 20s. Some 
moderation should begin to take place by Thursday, but readings 
should still be below seasonal norms. 

&&

.AVIATION...
Issued at 200 PM CST Thu Dec 12 2019

Time/height cross sections show dry air wedged below 700 MB, so
cloud bases should remain mid and high VFR variety, even with 
cigs, thru the first half of the forecast at least. During the 
latter half, some saturation down begins to occur, so during the 
planning period and beyond, we may see lower but probably still 
VFR bases enter the forecast picture. Southerlies prevail thru the
package.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.

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