Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 152039

Area Forecast Discussion
National Weather Service Paducah KY
239 PM CST Thu Nov 15 2018

.SHORT TERM...(Tonight through Saturday night)
Issued at 239 PM CST Thu Nov 15 2018

With fairly rapid increase in thicknesses and southwesterly flow
behind the winter storms, had to reconsider the potential for
advection/radiation fog over the snow cover this evening in parts
of southern Illinois and southeast Missouri. With a little
sharpening of the pressure gradient from the west this evening,
there may be enough turbulent surface mixing to saturate the
lowest 10 meters of the boundary layer to generate some patchy
fog. The Short range ensembles suggest at least a 35-40 percent
probability of seeing visibilities dropping into the 1-3 statute
mile range. Though it is a small probability, the ability of the
WFO PAH region winds to decouple would initially help to set up a
favorable thermal profile. As the winds pick up overnight, this
probability should diminish markedly overnight.

Decent warm air advection should continue through early Friday
morning as a broad ridge builds across the area. High resolution
guidance has been consistent in pushing maximum temperatures on
Friday from middle 40s north to lower 50s over southeast Missouri.
Given good insolation and evaporation, these high temperatures may
be achieved. At this point in time, am only 70% confident of these
maximum temperatures for Friday.

A very refined zone of channeled vorticity will develop and move
south from the upper Midwest and northern Plains Friday evening,
as the ridge flattens and the WFO PAH forecast area moves into a
zonal flow. This flattened shortwave will impress an weak frontal
zone over the area on Saturday, but anticipate only and increase
in cloud cover associated with its passage of the weak frontal
zone through the area Saturday afternoon and evening.

Despite the short term warm advection through the area through
Saturday, temperatures will still remain some five to ten degrees
below normal.

.LONG TERM...(Sunday through Thursday)
Issued at 239 PM CST Thu Nov 15 2018

In the extended forecast period, the medium range model solutions
were in reasonable agreement, especially for our vicinity. There
will be a persistent ridge-west/trof-east flow pattern aloft across
the CONUS, with periodic shortwaves temporarily suppressing the
ridge and moving through the mean trof.

In the northern stream, the mid/upper pattern will apparently split
into two shortwaves over the weekend, with one heading toward the
Great Lakes/Northeast and the other moving out of the central Plains
into our region by late in the weekend. The second shortwave is
expected to result in the only measurable pcpn for the PAH forecast
area during the extended period. A surface cold front will accompany
this feature, providing lift of moisture mainly in the 850-700 mb
layer. Less than a tenth of liquid pcpn is forecast. Profiles now
appear to be warm enough for mostly rain, but there continues to be
a possibility of a little sleet or freezing rain on the trailing
edge of the pcpn shield, with no impacts anticipated.

Next week, a couple of surface high pressure centers will pass
through our region, keeping our part of the country pcpn-free. Temps
are forecast to moderate to near seasonable averages, especially
toward Day 7. However, confidence in this temp forecast is not high
at this time, since below-average temps have been very common as of
late, and the GFS ensemble mean suggests the current flow pattern
over the CONUS may be reluctant to change.


Issued at 1138 AM CST Thu Nov 15 2018

Winter weather currently impacting at least three of the four WFO
PAH TAF sites as of 18z, with visibilities dropping down between
one and two statute miles.

For the 18z WFO PAH TAF issuance, will keep MVFR/IFR ceilings and
conditional IFR visibilities with the passage of the deformation
zone snow bands rotating around the upper low. At this point, do
not plan to go beyond 20z Thursday for KCGI and KPAH, but may
extend to 21-22z for KEVV and KOWB. By 00z Friday, a return to VFR
ceilings and visibilities will occur at all of the WFO PAH TAF




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