Area Forecast Discussion
Issued by NWS Paducah, KY

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983
FXUS63 KPAH 161231
AFDPAH

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

.UPDATE...
Issued at 618 AM CST Sat Dec 16 2017

For aviation section.

&&

.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 618 AM CST Sat Dec 16 2017

VFR conditions are expected through much of the TAF period at all
sites, with maybe some mvfr cigs working into se MO after 08Z with
some light rain. Winds will be increasing to around 10-15 kts
with gusts 20-25 kts after 14z. No vsby restrictions.


&&

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

$$

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



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