Flooding in Ohio, September 8, 2018

Area Forecast Discussion
National Weather Service Wilmington OH
437 AM EDT Sat Sep 8 2018

.SYNOPSIS...
The remnants of a tropical system will interact with a stalled
boundary across the Ohio Valley to produce periods of heavy rain
today through Sunday. Extensive cloud cover and heavy rain will
keep temperatures below normal until early next week. A drier
and warmer weather pattern will develop towards the middle of
next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Deformation zone induced banded rain will near and north of the
I-70 corridor through sunrise as a better push of heavier rain
begins to impact portions of east-central Indiana and western
Ohio through mid-morning. In fact, a gradual increase in both
coverage and intensity of both stratiform and convective rain is
expected through mid-morning, particularly for the western ad
northern halves or so of the ILN FA. Although rates during this
time are expected to stay below thresholds that would induce or
at the very least increase the risk for flash flooding, this
rain will act to prime the soils/ground for later heavier
rainfall. This being said, some locations may pick up an inch of
rain or slightly more before noon.

By mid-morning, there will likely be two main areas of rain --
one oriented approximately parallel and just north of the I-70
corridor and another pivoting northeast across the Tri-State
area. The latter area of activity is expected to progress
north/east through the afternoon hours before merging/congealing
with the more stratiform rain further north stretching from
east-central Indiana through central Ohio. By mid-afternoon,
coverage may briefly become more scattered in nature,
particularly south/east of the I-71 corridor before the better
influx of heavy rain pushes east toward the local area towards
the very end of the near term period.

Total rainfall through the near term period will generally range
from one half inch to possibly an inch and a half -- especially
in the more convective type showers/storms where rates will be
the highest. Localized flash flooding will be possible during
the afternoon hours, although the greater threat will likely
hold off until late in the evening into the overnight hours.

Temperatures will be held well below seasonal norms along/north
of the Ohio River today, with highs ranging from the upper 60s
to the lower 70s in these areas. South of the river, highs may
approach 80 degrees -- particularly in locations that receive
larger/longer breaks in the cloud cover.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
By this evening, there will be a tremendous increase in deep-
layer moisture as better forcing arrives from the west. The
remnant low center from Gordon is expected to track
approximately parallel to the western segment of the Ohio River
this evening into the overnight hours. As it does so, a
tropical-like airmass -- characterized by PWATS near or
exceeding 2" -- will overspread the area as broad-scale
forcing/ascent increases. This is expected to manifest itself in
a large semi-cohesive band of heavy rain which will track east
across the heart of the ILN FA late this evening through the
overnight hours. It is during this time period where widespread
heavy rain /and the potential for 1-2" per hour for several
hours in a row/ will exist. In a psuedo-tropical environment
such as this, with deep warm cloud depths and ample forcing,
rain rates will be extremely efficient. Confidence is increasing
that most areas within the flash flood watch area will receive
at least 2-3," with widespread 4-6" possible, particularly near
and perhaps just south of the I-70 corridor. If convective rain
rates are able to set up and train over the same areas, these
totals may end up being even higher. Do think that the high risk
of excessive rainfall from WPC is well-warranted given this
setup, as the potential for widespread flooding is likely to
evolve, particularly overnight tonight into Sunday morning.

The band of heavy to potentially very heavy rain will likely be
tracking east through central Ohio by mid-morning Sunday, with
more scattered coverage expected back further west towards parts
of east-central Indiana and the Tri-State area. At this point,
the surface low pressure center is likely to be somewhere in the
vicinity of Louisville as it continues to track northeast into
the local area by the afternoon. With this track, and
considering the diurnal-timing of this setup, some instby may
try to work north into south-central Ohio and eastern parts of
northern Kentucky during the afternoon hours. These areas will
still be east of the surface low, with activity expected to once
again become increasingly convective in nature Sunday afternoon
into the evening. Should the instby materialize as some hi-res
guidance suggests it may, thunderstorm chances would increase
Sunday afternoon/evening across the southeastern third or so of
the ILN FA. Any of the stronger storms that develops could very
well pose a low-end severe threat, so will mention this
potential threat in the HWO.

Highs on Sunday will vary considerably -- from the upper 60s in
east-central Indiana and west-central Ohio to the lower 80s in
southern portions of the lower Scioto Valley and northeastern
Kentucky.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
The remnant low from Gordon will be situated over northwest Ohio
early Sunday evening with a trailing cold front pushing east into
western portions of our area. Fairly widespread pcpn will likely
still be ongoing across at least eastern portions of our fa. With
most of our area still in the warm sector, a few embedded
thunderstorms may also persist into early evening, especially across
our far southeast. The low will then lift quickly northeast across
the lower Great Lakes Sunday night into Monday and weaken as it
does. This will allow for pcpn to taper off from west to east across
our area later Sunday night and into the day on Monday.  With a
cooler airmass in place, highs on Monday will only range from the
upper 60s northwest to the lower 70s across the south.

Surface high pressure will build down across the southern Great
Lakes and Ohio Valley Tuesday into Wednesday, helping to keep our
area generally dry. Meanwhile, temperatures will gradually moderate
with highs on Tuesday in the mid to upper 70s and then highs on
Wednesday in the upper 70s to lower 80s. Some weak mid level energy
between the ridge over the Southern Plains and a ridge nosing into
the mid Atlantic States, may try to squeeze up across the mid Ohio
Valley Wednesday into Thursday. There is quite a bit of uncertainty
with this so will just continue with some lower end pops Wednesday
night into Thursday. The forecast beyond that will be at least
somewhat dependent on where Florence ends up going. For now will
just continue with some lower end pops across mainly our eastern
areas for Friday. Temperatures will continue to moderate through the
end of the long term period with highs by Friday well into the mid
80s.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
Although the initial band of precipitation has set up north of
the local terminals, expect that the shield of SHRA/RA should
fill in rather rapidly toward daybreak. In the meantime, expect
on-and-off SHRA for western terminals of KDAY, KLUK, and KDAY
through sunrise with eastern terminals of KILN, KCMH, and KLCK
expected to stay drier through the first several hours of the
period.

Mainly IFR CIGs are expected overnight with some brief LIFR CIGs
possible with heaviest pockets of pcpn through the morning
hours, particularly at KDAY. However, prevailing CIGs should
remain IFR as SHRA/RA gradually increases in coverage and
overspreads terminals through the morning hours. Activity may
briefly become a bit more scattered during the afternoon hours,
particularly for southern/eastern sites of KCVG, KLUK, KCMH,
and KLCK, although lack of confidence on timing of any breaks in
the SHRA/RA precluded trying to depict in TAFs at this time.
With any steadier precipitation will come reductions in VSBYs,
although with saturation of the column as it is, MVFR VSBYs may
persist even outside of pcpn. And although thunder cannot be
completely ruled out, particularly for southern sites of KCVG,
and KLUK, did not include at this time due to expected lack of
coverage.

CIGs should improve during the afternoon, although only very
slightly. Nevertheless, CIGs may end up staying IFR even
during/after the diurnal-driven lifting.

Main item of interest for the period will be the influx/arrival
of heavy rain for the final part of the valid TAF period. This
will initially affect western sites of KCVG, KDAY, and KLUK
around/shortly after 00z before activity spreads east through
the remaining hours of the TAF period. With this activity, IFR
CIGs may briefly go LIFR and VSBYs may also go IFR or even lower
at times toward 06z.

Winds will remain out of the northeast through the period, with
a gradual increase in sustained wind and gusts through the next
24 hours or so. Winds of around 10 kts by daybreak will increase
to around 15kts with gusts to 25kts or so by sunset. Sustained
winds may approach 20kts towards 06z Sunday.

OUTLOOK...Thunderstorms will remain possible at times into
Sunday night. Prevailing MVFR ceilings are also possible on
Sunday and Monday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Flash Flood Watch from noon EDT today through Monday morning
     for OHZ026-034-035-042>046-051>056-060>065-070>074-
     077>080-082.
KY...Flash Flood Watch from noon EDT today through Monday morning
     for KYZ089>093.
IN...Flash Flood Watch from noon EDT today through Monday morning
     for INZ050-058-059-066-073>075-080.

&&

SYNOPSIS...KC
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...JGL
AVIATION...KC

Hazardous Weather Outlook
National Weather Service Wilmington OH
427 AM EDT Sat Sep 8 2018

KYZ098>100-OHZ081-088-090830-
Robertson-Mason-Lewis-Adams-Scioto-
427 AM EDT Sat Sep 8 2018

This Hazardous Weather Outlook is for Northeast Kentucky, Northern
Kentucky and South Central Ohio.

.DAY ONE...Today and Tonight.

Showers and thunderstorms today and tonight may produce locally heavy
rainfall. Isolated flooding and flash flooding will be possible.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Scattered showers and thunderstorms are expected Sunday afternoon and
evening. These storms may produce locally heavy rainfall as well as
gusty winds. An isolated tornado cannot be completely ruled out.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required.

INZ050-058-059-066-073>075-080-KYZ089>097-OHZ026-034-035-042>046-
051>056-060>065-070>074-077>080-082-090830-
Wayne-Fayette IN-Union IN-Franklin IN-Ripley-Dearborn-Ohio-
Switzerland-Carroll-Gallatin-Boone-Kenton-Campbell-Owen-Grant-
Pendleton-Bracken-Hardin-Mercer-Auglaize-Darke-Shelby-Logan-Union OH-
Delaware-Miami-Champaign-Clark-Madison-Franklin OH-Licking-Preble-
Montgomery-Greene-Fayette OH-Pickaway-Fairfield-Butler-Warren-
Clinton-Ross-Hocking-Hamilton-Clermont-Brown-Highland-Pike-
427 AM EDT Sat Sep 8 2018

...FLASH FLOOD WATCH IN EFFECT FROM NOON EDT TODAY THROUGH MONDAY
MORNING...

This Hazardous Weather Outlook is for East Central Indiana,
Southeast Indiana, Northern Kentucky, Central Ohio, South Central
Ohio, Southwest Ohio and West Central Ohio.

.DAY ONE...Today and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.

Areas of heavy rain with embedded thunderstorms may produce flooding
and flash flooding. Rainfall today and tonight will range from 2 to 5
inches. Rises on area creeks and streams will be likely.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.

Flash Flood Watch.

Areas of heavy rain with embedded thunderstorms may produce flooding
and flash flooding. Additional rainfall of 1 to 3 inches will be
possible Sunday and Sunday night. Rises on area creeks and streams
will be likely.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be required.