Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 202045
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
245 PM CST Mon Feb 20 2017

.SHORT TERM...(Tonight through Wednesday night)
Issued at 245 PM CST Mon Feb 20 2017

Average confidence in the short term due to so-so model agreement.

At the time of this writing a deep N-S H5 trough is slowly pushing a
storm system/front out of the plains. With the approach of this
system, precipitation will begin to progress eastward across our CWA
starting this evening. In the process the trough evolves into a
split flow regime where the northern stream pushes the front across
the Great lakes region while in the southern stream the southern
part of the trough will become a closed low thus slowing down its
eastward progress. In addition, with the deepening of the low,
models are showing a surface low being induced on the front just to
the south of our area which will also slow its eastward progress.
What that means for our area is precipitation lingering across the
area longer. Precipitation chances should be greatest late tonight
into early Tuesday morning, then begin to slowly decrease from west
to east from Tuesday afternoon through the overnight hours before
ending. Minimal surface instability tonight so included isolated
thunder chances.

In the wake of this system, the area should remain dry through
Wednesday evening. Late Wednesday night models are showing a short
wave coming out of the plains tapping into a bit of deeper moisture
and cranking a sliver of QPF along the far eastern sections of our
CWA.

.LONG TERM...(Thursday through Monday)
Issued at 245 PM CST Mon Feb 20 2017

The above normal temperature trend will likely continue from
Thursday into Friday with near record maximum and minimum
temperatures prior to the frontal passage through the WFO PAH
forecast region early Saturday morning.

Recent runs of the medium range model guidance have suggested a
variety of longitudinal solutions with the Gulf of Mexico closed low
Wednesday and Thursday. The constant has been the slowing of
moisture moisture return/advection behind the closed low and ahead
of the broad western U.S. trough.

For Thursday...the Canadian and European guidance have been hinting
and a low to middle level ridging building north into the WFO PAH
forecast area, shifting the baroclinic zone and impressed warm
frontal zone north of the area limiting convective activity. At this
time, maximum temperatures may still be too cool, so may have to
consider temperatures in the middle 70s as time goes by.

For Friday, timing will be everything for instability and
thunderstorm coverage ahead of the cold front. Upper level wind and
thermal instability will be in the vicinity.  The question will be
how much deep layer moisture can envelope the WFO PAH forecast area
to support long and sustained buoyancy to produce impressive
updrafts and storm organization. The preferred CMCnh and ECMWF
guidance are still somewhat marginal in this area. The SPC outlook
area for Friday may still be feasible, especially around the Noon to
6 pm time period on Friday.

A return to near, but slightly above normal will occur post-frontal
on Saturday, with a gradual warm-up through early next week above
normal. At this time, there is low confidence on the system early
next week but at least 50% confidence on the Friday weather system.

&&

.AVIATION...
Issued at 1148 AM CST Mon Feb 20 2017

Conditions will begin to slowly deteriorate as a storm system
approaches the region tonight. After midnight the possibility of
showers increases along with small chances of thunder. The frontal
boundary hangs up over the TAF sites so during the last 6 hours of
the period chances for precipitation will be greatest. Ceilings
should eventually come down to at least MVFR levels as the rain
arrives along with the deeper moisture. Winds early will generally be
out of the southeast AOB 10 knots with a few higher gusts possible
at KCGI, then variable AOB 5 knots through the rest of the period.

&&

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

$$

SHORT TERM/AVIATION...JP
LONG TERM...Smith



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