Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 191419
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1019 AM EDT Sat Oct 19 2019

.SYNOPSIS...
High pressure will drift east of the region today, allowing for
slightly warmer temperatures to filter into the region. Above
normal temperatures are expected through Monday before a strong
storm system progresses through the area Monday afternoon
through Monday night. Cooler air will return to the Ohio Valley
by Tuesday following the frontal passage Monday night.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
High pressure in low levels has shifted far enough to the east
to bring about light southeasterly return flow across much of
the region this morning. This, along with sunrise, has warmed
temperatures quickly and ended any frost/freeze threat. The
remainder of the morning will see continued warming under mostly
clear skies and light southeasterly to southerly winds.

With this in mind, stuck with temps a couple degrees above model
blends today under WAA and mostly sunny skies. Did increase
cloud cover a bit in the far southeast this afternoon to match
with satellite presentation and movement of tropical low in the
Deep South.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
By tonight, the local area will be positioned between a system
to the north/west and another to the south/east, the latter of
which is the remnants of Nestor as it tracks through the
Carolinas. With relatively dry air still in place in the low
levels, do think that even with an increase in cloud cover and
forcing for ascent tonight, we should stay dry. As such, did
remove even slight chance PoPs for tonight into early Sunday
morning -- even though we may see some returns on composite
imagery at times late this evening through the overnight period.
Moreover, the best WAA-induced isentropic lift should stay far
enough north and west as to keep the ILN FA dry even through the
short term period.

With more cloud cover and winds that are not completely calm,
will likely see lows tonight 6-8 degrees warmer across the board
than has been the case the past several mornings. Temps will
start off in the lower 40s in the east and the upper 40s to
around 50 degrees in the south/west.

Despite a bit more cloud cover to contend with on Sunday, highs
will still top out in the lower 70s area-wide. More robust WAA
associated with a rapidly tightening pressure
gradient/strengthening wind fields will hold off until Sunday
night into Monday.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A deepening trough and surface low pressure over the central US
become the main features to watch as the new work week begins. The
intensifying surface low moves northeastward during the day on
Monday, pushing a cold front into the area by late Monday night.
With the newest 00Z guidance in, there remains modest uncertainty as
to the timing of the heaviest precipitation as the GFS/NAM is much
faster with the bulk of the rain compared to the ECMWF/CMC. The
first group keeps the majority of the heavy rain ahead of the cold
front and within the warm sector Monday afternoon while the later
group has the bulk of the precip along the cold front as it moves
through overnight.

When examining why the timing differs so greatly, it felt reasonable
to assume that there were probably differences in the dynamic
forcing, however, both the GFS and Euro rotate a secondary vort max
through the base of the occluding low during the overnight period.
The timing of this secondary source of lift is fairly similar
between the two operational runs, but there is a clear absence of
overall moisture within the GFS solution. The occluded low
progresses slightly further east by 06Z Tuesday, pushing the
abundant moisture through the forecast area. With the further west
occlusion, there remains a longer window of modest moisture
favoring not only warm sector showers/thunderstorms but also more
precipitation with the actual surface front. Despite the forcing,
the GFS has very little additional rainfall with the frontal
passage. With these discrepancies in mind, decided to gradually ramp
PoPs up through Monday afternoon with the highest PoPs toward late
evening and overnight with the front. While instability is rather
marginal during this time period, the dynamics in place raise some
concern for damaging wind gusts and isolated tornadoes. SPC has
placed parts of the area (south of I-70) in a marginal risk for
Monday. As the event draws closer, additional tuning of timing
and severity will likely be needed.

Precipitation tapers off fairly quickly from west to east early
Tuesday morning as drier air moves in behind the cold front. It does
look like some wrap around moisture may work back into perhaps our
far northern areas through the day on Tuesday. Will therefore allow
for the possibility of a few showers across the north Tuesday
afternoon. In good CAA, it will be breezy and cool with highs on
Tuesday ranging from the upper 50s in the northwest to the lower 60s
in the southeast.

For the second half of the extended, Wednesday and Thursday look dry
with a very weak ridge in place over the southeast US. The ridge
breaks down on Friday as a weaker upper level shortwave drops into
the central US. Global model guidance differs greatly in the
location and timing of the wave through the Ohio Valley. GFS is much
further south, delaying rainfall till next weekend, however the
ECMWF brings in the next chance for rain by Friday. Decided to limit
PoPs to 20% for Friday and Saturday given the uncertainty at this
time.

Regarding temperatures, the warmest temps of the extended can be
expected at the beginning, with many areas in the mid to upper 70s
ahead of the approaching cold front. Post frontal passage,
temperatures are a few degrees above or below average through the
rest of the week under climatologically normal 500 mb heights/850 mb
temperatures.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
After VSBY restrictions at KLUK rapidly improve shortly after
the beginning of the period, high pressure will provide
generally VFR conditions through tonight, even as clouds
increase toward the very end of the TAF period.

Light/calm winds will go more southerly and increase to about
5-7kts this afternoon. Cirrus will be on the increase this
morning through this afternoon with even some BKN cloud cover
possible. However, do not expect much (if any) in the way of
additional clouds (other than cirrus) through 00z.

Midlevel clouds with even some 5kft clouds will be on the
increase from the southwest toward/beyond 06z Sunday. Setup for
BR/FG tonight will be much less favorable -- although still
cannot rule out brief MVFR VSBYs at KLUK late.

OUTLOOK...MVFR conditions and gusty winds are likely Monday
into Monday night.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...KC
NEAR TERM...Hogue
SHORT TERM...KC
LONG TERM...McGinnis
AVIATION...KC


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