Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 150400
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1000 PM CST Sat Jan 14 2017

.UPDATE...
Issued at 1000 PM CST Sat Jan 14 2017

As expected measurable rainfall has been very scarce this evening,
and will continue to be so into the overnight hours. An area of
rain over southwest Missouri is moving northeast and should not
reach our area until 09Z or so. Of course, the latest HRRR runs
are non-committal on whether or not it will reach our area. Held
PoPs at low chance levels until very late tonight before ramping
up to 50-60% in the northwest. Of course, this is where
temperatures will be right at the freezing mark, so will have a
mention of freezing rain. With temperatures expected right near
32F, figure any icing will be limited to elevated objects. With
little, if any, ice from yesterday left in these areas, the impact
should be nil. Have addressed this in the HWO and do not plan to
issue any extra products for this event.

There have been some very light echoes on area radars this
evening, and some lowered visibilities in METARs, indicative of
some light drizzle. With the rain in the forecast, just settled
for mentioning areas of fog, which is what we have seen here at
the office recently.

UPDATE Issued at 610 PM CST Sat Jan 14 2017

Updated aviation discussion.

&&

.SHORT TERM...(Tonight through Monday night)
Issued at 225 PM CST Sat Jan 14 2017

Have allowed winter/fog headlines to expire this afternoon as
vsbys have improved and surface temperatures have crept just above
the freezing mark over nw counties with precip shifting south
toward the OH River. Could be another batch or two of very light
rain or drizzle overnight tonight at many locations as the lower
atmosphere remains quite saturated. Not much forcing to work with
though, so any QPF should be quite light. Temperatures not
expected to fall off much during the night, but it would not take
much of a drop to get our northern/western counties of srn IL/se
MO back to near or just below freezing. Will need to monitor to
see how precip/temp trends go this evening up in those locations
for possible quick advisory for some freezing drizzle/light
freezing rain possibilities.

Weak mid level ridging on Sunday will also serve to keep any
significant amounts of precip out of the region, though will need
to leave some chance for a bit of very light precip, especially
along/north of the I-64 corridor. Again, would not be surprised to
see a touch of freezing precip in that corridor early in the day,
but will hold off on headlines at this time and handle with
HWO/possibly an SPS.

Next high chance of rain/isolated thunder looks to hold off until
later Mon/Monday night time frame as the next surface front and
associated H50 short wave approach from the west. Not too excited
at this time on strong/severe threat given overall lack of
instability. More likely just a few isolated rumbles of thunder
here and there. Could be some decent widespread rain amounts up
over 1/2 inch tho.

.LONG TERM...(Tuesday through Saturday)
Issued at 225 PM CST Sat Jan 14 2017

The northern hemispheric pattern has the center point of the wave
pattern shifted toward the Arctic circle northwest of Alaska at the
start of the extended forecast period, with the most dominant
meridional wave extending from the pole to east of Greenland and a
low amplitude, split trough over the Northern Pacific. The evolution
of the primary stable five wave pattern (per the ECMWF and GFS
guidance) into a 3-4 unstable wave pattern, suggest a more dynamic
and chaotic flow over the U.S. during the extended period. However,
the dominance of the mean trough east of Greenland/Northern
Atlantic, may mean greater heights upstream over the eastern U.S.,
pushing systems to the west of the WFO PAH forecast area further to
the west and north.

Although the GFS and ECMWF similarly handle the ejection of the Baja
California low into the western Great Lakes through Tuesday, the
similarity begins to wane with time, especially late in the week.
The 12z Saturday ECMWF is a little warmer aloft, but cooler at the
surface than the 12z Saturday GFS.  A blend of ECMWF/GFS seems to be
a more realistic solution.

For the WFO PAH forecast area, this would be mean that the weather
system on Tuesday should exit a little quicker, with the system
moving from the southwest Thursday into Friday should be shifted
more to the east with time in a more progressive flow.

Blended max/min temperatures upward slightly from the cooler ECMWF
values, but still lower than the GFS. In addition, kept PoPs in
place closer to the slightly faster and more eastern ECMWF than the
warmer and more unstable GFS.  There is lesser forecaster confidence
in the late week solution (40-50%) than the Tuesday weather system
(60-70%).

Otherwise, no significant changes in the other sensible weather
elements through the forecast period.

&&

.AVIATION...
Issued at 610 PM CST Sat Jan 14 2017

Weather conditions are expected once again to deteriorate overnight
with the diurnal cooling of the lower trop. Meanwhile, a wedge of
cool air near the surface will pivot eastward through the region,
causing some veering of the surface winds. IFR cigs are expected
soon, if not there already, and should go LIFR after midnight. Vsbys
should eventually go IFR sometime this evening in drizzle and fog,
with a chance of LIFR levels (not in TAFs currently). By mid morning
Sun, heights aloft will begin to rise, resulting in improving
conditions, albeit with rain showers, from southwest to northeast.
However, IFR cigs will probably remain through the end of the 00Z
TAF period.


&&

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

$$

UPDATE...DRS
SHORT TERM...GM
LONG TERM...Smith
AVIATION...DB



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