Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 192236

Area Forecast Discussion
National Weather Service Paducah KY
436 PM CST Mon Feb 19 2018

Issued at 433 PM CST Mon Feb 19 2018

Updated Aviation discussion for 00Z TAF Issuance.


.SHORT TERM...(Tonight through Wednesday night)
Issued at 329 PM CST Mon Feb 19 2018

Aside from the breezy and record warm conditions, the main story
in the near term is the high precipitable water levels and
therefore heavy rain potential, mainly Tuesday night. In the
meantime, however, shortwave energy will continue to eject out of
the mean longwave trof out in the western CONUS, while an
anomalously strong western Atlantic upper high holds firm. This
setup will tend to keep pcpn out of the southeast half of the PAH
forecast area, though the aforementioned energy should cause an
minor eastward surge in shower and possible tstm activity
overnight and early Tue. Record high and record warm low records may
fall Tue.

In response to more mid level shortwave energy, a cold front is
progged to sink through the region Tue night, providing large
scale lift of copious moisture, more fit for early spring than
late winter. This is expected to provide over an inch of rainfall,
(possibly higher) for mainly southeastern MO and southern IL,
after midnight. This rainfall rate should translate to mainly
western KY after daybreak Wed. Some tstm activity is possible Tue
night. WPC does have parts of southeastern MO (west of the
Bootheel) under a moderate risk of excessive rainfall. Taking into
account the drought conditions in southeastern MO, at this time
we held off on issuing a Flood Watch. However, with what`s coming
at us later in the week, a Flood Watch may eventually happen.
Through Wed night, moisture will continue to ride up over the
wedge of colder air near the surface, keeping a decent PoP and
(QPF) in the forecast through then. The higher elevations of the
Ozark Foothills may receive spotty icing Wed and Wed night as
colder air surges in.

.LONG TERM...(Thursday through Monday)
Issued at 329 PM CST Mon Feb 19 2018

Forecast confidence is high. A very wet pattern is still forecast
Thursday night through Saturday night.

We will remain in southwest flow aloft, caught between high pressure
anchored off the southeast Atlantic Coast and a trough over the
western U.S. A series of minor impulses will stream northeast across
the region bringing rounds of potentially heavy rainfall to the Quad
State. The surface boundary will be nearly parallel to the upper
flow, and is likely to lift a bit northward as each impulse
approaches and then drop south a bit behind them.

Extreme low-level moisture is forecast to interact with the boundary
and each impulse across our region, resulting in multiple rounds of
heavy rainfall. Model precipitable water values are around 1.5" near
the boundary throughout the period. This is well above the
climatological maximum for February, March and even April! The stage
is definitely set for a major heavy rainfall and flood event.

The western upper-level trough is forecast to eventually lift out
and move toward our region. It will weaken considerably as it gets
assimilated into the southwest flow aloft, but the 12Z models still
have a surface reflection moving through our region Saturday night,
with a cold front trailing to the south of it.

The cold front will bring an end to this prolonged period of heavy
rainfall and flooding. Unfortunately, it will bring the most
concentrated threat of convective rain rates which will likely
create the most significant flash flooding across our region. Prior
impulses will likely lead to at least some areal flooding and serve
to really prime the area for a flash flood event with the cold
front/surface low Saturday evening.

The cold front also could lead to some more intense convection.
SPC`s Day 6 outlook keeps the a slight risk just to our south, but
if we can get some heating ahead of the cold front, we might eek out
enough instability to support a severe weather threat. 12Z GFS
soundings do not show much instability due to a lack of surface
heating and steep mid-level lapse rates. We continue to mention a
slight chance of thunderstorms near and south of the surface frontal
boundary through the period.

Temperatures will remain very mild through the entire period, even
behind the cold front Sunday and Monday.


Issued at 433 PM CST Mon Feb 19 2018

Satellite reveals a few lingering bases in the MVFR range, but
mostly, VFR base clouds/cigs, and we anticipate that to continue
into/thru the first half of the night. Bases will lower later
tonight/toward morning, with rain chances incoming from the west,
so we reintroduce MVFR cigs for that time range, keeping vsbys vfr
even with chance/showers. Gusty southerlies will pick up again



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