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000 
FXUS63 KPAH 160923
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
323 AM CST Sat Dec 16 2017

.SHORT TERM...(Today through Monday night)
Issued at 323 AM CST Sat Dec 16 2017

High pressure over the northern Gulf states will bring plenty of
sunshine and breezy southwest winds to the region today.
Temperatures will respond by jumping into the lower to mid 50s
this afternoon. 

Tonight, a dampening mid level short wave will begin to eject 
northeast from the Southern Plains. This feature will then 
continue to lift northeast through the Ohio Valley on Sunday. 
Light rains will begin over southeast MO after midnight, then 
spread northeast across the forecast area Sunday morning. The 
precipitation will move east of the region by Sunday evening as 
the short wave moves away. Though rain chances will be quite high 
with this system, it will be weakening as it moves through, and 
overall rain amounts should be light, generally less than 1/4 
inch. 

The rest of of the short term is expected to be precipitation
free as ridging takes place. Even so, low clouds will likely be
tough to get rid of Monday and Monday night as moisture remains
trapped beneath a sharp low level temperature inversion. With
southwesterly low level flow, temperatures will still manage to
make it into the 50s. 

.LONG TERM...(Tuesday through Friday)
Issued at 323 AM CST Sat Dec 16 2017

In the early part of the extended forecast period, both the 
deterministic 00z Saturday GFS and ECMWF advertise the closed low 
(currently over northwestern Mexico, just east of the southern Baja) 
to eject into eastern TX/OK by 12z (6am CST) Wednesday. The actual 
placement of the this vertically stacked mid/upper level low will 
determine if there is enough moisture advection and lift ahead of 
the low to support a small chance for rain late Tuesday night 
through the daytime hours on Wednesday. Given potential timing and 
placement issues inherent in the ejection of the closed low, opted 
to use the model blend initialization as the forecast solution with 
this package.

The passage of the aforementioned low will work to set the stage for 
a transition to west to east flow into a southwesterly flow aloft by 
midday next Friday. 

An elongated shortwave developing along the northern tier of the 
U.S., combined with a slower wave over the desert southwest late 
Thursday will lead to some baroclinic enhancement (surface frontal 
zone reflection) late Thursday night into Friday, suggesting a small 
chance for rain later Thursday night into Friday morning. 

The continued translation of the northern shortwave across the 
Middle Mississippi Valley and the Ohio River Valley will continue to 
support cold air advection aloft over the area. 

looking beyond the forecast period, the eventual translation of the 
desert low shortwave next Friday will ultimately determine the 
chances for precipitation into the weekend and on Christmas Day. The 
degree of impact that this shortwave has on increasing moisture 
advection north of the Lower Mississippi Valley will determine 
whether or not the WFO PAH forecast area will have any over-running 
precipitation. The ECMWF and GFS are similar on the low level 
thermal profile, with 850 temperatures below zero across the area 
from late Friday night through Christmas Day.  The translation of 
the shortwave will determine whether or not the WFO PAH forecast 
area will see 1) precipitation, and 2) whether it will be a wintry 
mix. 

The 00z GFS has a further north solution with overrunning next 
weekend, while the ECMWF is much further south and away from the WFO 
PAH forecast area.  Although the signal remains, timing and 
intensity issues limit any potential for significant winter weather 
for the local area around Christmas Day.  Will need to monitor for 
continuity of thermal and mass fields the next few days to determine 
any weather impact for holiday travelers.

&&

.AVIATION...
Issued at 1157 PM CST Fri Dec 15 2017

Clear skies expected through most of the TAF period at all sites,
with maybe just a few high clouds at the end of the period. Winds
will be from southwest to south around 5 kts overnight, increasing
to around 10 kts with gusts around 15 kts after 14z. No vsby 
restrictions.


&&

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

$$

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