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000
FXUS63 KPAH 211125
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
625 AM CDT Sat Oct 21 2017

.UPDATE...
Issued at 625 AM CDT Sat Oct 21 2017

Updated for 12Z aviation forecast discussion.

&&

.SHORT TERM...(Today through Monday night)
Issued at 230 AM CDT Sat Oct 21 2017

Today will be our transition day, as we wait for the arrival of our
next cold front. This morning, we will continue to see moisture
increase especially out in our southeast Missouri counties, and
that is where we might encounter some sprinkles but nothing too
major.

By 18Z, the cold front will be situated from western Minnesota to
eastern Nebraska to the OK/TX panhandles. During the afternoon hours
the front will slide eastward. Mid to high clouds could knock a few
degrees off temperatures from what they have been the last few days,
but still expect highs in the upper 70s today. Again a few sprinkles
or a few light showers are not out of the question in SEMO during
the afternoon today. But most areas should remain dry.

We should see a marked increase in rain chances during the evening
hours but especially overnight tonight, as the frontal boundary
inches even closer the CWA. Prior to 12Z Sunday, the best rain
chances will be southeast MO, southwest IL and possibly far west KY.
Still appears to be a decent chance for rain and embedded storms
during the day on Sunday. The problem lies in just how far east the
precipitation will make it prior to 00Z Monday. During the day on
Sunday, an upper level low develops near the Arklatex region.
Models differ on where exactly this upper low travels through the
rest of the day on Sunday. This has some pretty substantial
implications on where any precipitation bands set up. Therefore,
we continue to see POP challenges for the Sunday-Sunday night
period. We will keep the categorical wording for areas further
west and early on in the period, but back off to chance to likely
wording further east as we head through the Sunday evening period.
High temperatures on Sunday will back off into the lower to mid
70s, although we could reach the upper 70s far eastern sections.

Heading into Monday, the forecast continues to hinge on the movement
of the aforementioned upper low. It does move east during the day on
Monday and we should see rain over a decent part of the area on the
northern side of this low. But again, placement of where the highest
POPs should be as well as QPF is still questionable because models
differ on the development of a new sfc low along the front as
well. Another fly in the ointment heading into Monday night is
that a northern stream upper trough will be heading southeast into
the area. Depending on how fast and deep this trough ends up
being, will dictate how quickly we shove this precipitation east
of our area. Right now, we will continue to show an eastward
progression of the precip probabilities during Monday evening and
overnight.

As far as severe potential...models seemed to have amped up the
instability overnight Saturday night into Sunday, especially over
SEMO. Decent shear will be in place there too along with good mid
level lapse rates. These parameters wane after 12Z Sunday. SPC is still
not overly excited about severe weather prospects however, so
chances will remain low for now. However, PWs still look rather
high so the threat for heavy rain does remain.

.LONG TERM...(Tuesday through Friday)
Issued at 230 AM CDT Sat Oct 21 2017

Medium confidence in the extended...high confidence in an unsettled
weather pattern with several fronts poised to move through the
region.

There are some significant discrepancies among the models for the
extended. As usual the GFS is faster and much cleaner with the start
and stop of the precip chances. The GFS creates a closed off low
that travels across the gulf states while the ECMWF keeps an open
low traveling through the great lakes region. The NAM however keeps
has a closed low moving through the gulf states but opens it up by
12z Tue. The Canadian is somewhere in the middle of these solutions.
The ECMWF is the slowest to move pops out of the area and the blend
is starting to diminish precip chances into tuesday. However one
thing they do agree on is that Tuesday will be a breezy day. Winds
on Tuesday will be northwest with gusts approaching 30 mph. This
will usher in much drier and colder air. In fact have introduced at
least patchy frost Wednesday morning. Although MOS differs a great
deal for highs Tuesday they come into agreement with overnight lows
in the 30s. Think strongly scattered frost will occur unless the
winds stay up. LI`s remain positive with CAPES in below a 100 j/kg2
and the K index briefly reaches 30. So for now will not introduce
thunder but will monitor for possible introduction at a later time.
As for temps the blend came in a bit cooler than the mex which we
think this is the right direction to go with such strong CAA and low
sun angle for this time of year.

&&

.AVIATION...
Issued at 625 AM CDT Sat Oct 21 2017

VFR conditions will persist across the region through the 24 hour
TAF period. Winds and moisture will be on the increase as
southerly flow strengthens in response to a cold front approaching
from the Plains. This will result in an increase and eventual
lowering of ceilings over the next 24 hours. Winds will pick up
from the south around 10 knots with some gusts to 15 to 20 knots
by this afternoon. Showers will be a possibility late in the
period.

&&

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

$$