Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 200734
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
334 AM EDT Sat Jul 20 2019

.SYNOPSIS...
Warm and humid conditions will continue through the weekend with
increased rain and storm chances from Sunday through Monday as
a cold front slowly pushes through the region. This will allow
for much cooler and drier air to filter into the Ohio Valley
Monday night through most of the upcoming workweek.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Tranquil weather conditions continue across the local area as
the warm and muggy airmass remains entrenched across the
region. In fact, as of this writing at 3 AM, there are many
sites in the ILN FA with temperatures still hovering around 80
degrees. Do anticipate that lows will eventually bottom out in
the mid/upper 70s area-wide, with quiet conditions continuing
through the morning hours with some cirrus debris from
convection across the Great Lakes spilling southeast into the
area during this time.

Some patchy lower clouds may also develop as was the case on
Friday, but am not seeing as strong of a signal for this to
develop, so it may end up being a bit more scattered in nature,
with most of the area waking up to sunny skies with just the
aforementioned convectively-driven cirrus debris sagging south
through the morning hours before it will inevitably thin out by
the afternoon -- at least to some degree.

Today will probably end up being the best chance of any day
during the recent stretch of higher heat and humidity to reach
widespread excessive heat warning criteria, although certainly
the signal is not as strong as once was the case. As often
occurs in setups like these, various contributors such as
cirrus/cloud cover, surface winds, and antecedent soil
conditions can all have subtle and sometimes countering effects
on the inevitable temp and dewpoint traces. Although it will
still feel hot and humid out there today, do think that
widespread heat indices may end up closer to 105 opposed to 110.
And this, too, may only be for a short period of time before
dewpoints mix down several degrees during the peak heating of
the afternoon. Most locations will spend late morning through
early evening with heat indices between 100 and 105 degrees,
with a few spots briefly exceeding the 105 degree mark --
especially in more rural areas where evapotranspiration from
corn crop will allow for higher dewpoints in the upper 70s to be
maintained.

Once again do expect most /if not all/ of the area to remain dry
today as the center of the mid/upper level ridge briefly
meanders a bit further east over the Ohio Valley this morning
through early afternoon. This will occur despite ongoing
convectively-induced outflows and other areas of midlevel energy
propagate southeast in the extreme eastern Ohio Valley --
keeping the chances for isolated storms in the fcst a bit to the
north/east of the local area.

The best chance for a stray shower/storm to work into the local
area will likely hold off until after sunset as another midlevel
disturbance races through the northern Ohio Valley, allowing for
one or more clusters of storms to once again develop across the
Great Lakes before migrating south toward the lower area by
midnight or so.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
There remains the possibility of a weakening cluster of storms
to graze extreme northern/northeastern portions of the ILN FA
towards midnight tonight before the activity inevitably
dissipates altogether as it encounters a less favorable
environment locally. However, as is often the case with these
types of setups, CAMS often show a weakening/dissipation faster
than can sometimes be the case owing to the fact that any
convection is likely to pivot toward the higher axis of
instability pooling to the south/southwest. So while any
activity is expected to be in a weakening phase should it
meander into the local area late this evening, it will certainly
be watched to see if it can be maintained a bit further south
than is currently being depicted by some of the guidance.

Tonight is likely to be the most uncomfortable night of the
stretch with an increase in cloud cover helping keep
temperatures even a bit warmer. Lows tonight will bottom out in
the mid to upper 70s area-wide.

By Sunday, the center of the impressive and expansive mid/upper
level ridge will begin to retrograde, allowing for height
falls/suppression of the ridge across the Ohio Valley --
especially as troughing becomes more pronounced in the Upper
Midwest as it propagates/digs southeast late Sunday into Monday.
Recent model guidance has shown a slightly slower progression of
the frontal boundary through the local area, with rain and storm
chances likely to linger into the day on Monday before the
onset of cooler and drier conditions begins by Monday night.

One or more clusters of scattered storms is likely to develop by
Sunday afternoon (initially potentially in the CLE/IWX/IND CWAs)
amidst an environment with seasonably high instability and a
subtle increase/enhancement in low/mid level flow fields. This
being said, there is still not much overlap being depicted by
some of the models between the best instability and shear
fields, suggesting that while a few strong to severe storms may
be possible, organized convection may not be as favored.
Certainly gusty winds will still be possible in the strongest
cores, especially if the convection is able to become somewhat
cold-pool driven, but this may end up being more isolated in
nature -- especially as convection moves further away from the
focused forcing immediately along/ahead of the front draped from
near CLE west through north-central IN). Did maintain the
threat for a few strong to severe storms during this time period
in the HWO, especially as SPC Day 2 SWO has included nearly the
entire area in a MRGL risk for Sunday.

Warm and humid conditions may again lead to heat indices near
100 degrees for parts of the local area on Sunday afternoon --
particularly for areas which are able to remain
cloud/convection-free the longest. However, did not have
confidence enough at this time given inherent uncertainties in
clouds/precipitation to go with a heat advisory at this time.
Additionally, the setup for such heat indices to be met or
exceeded once again will be a bit more on the marginal side.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A cold front will push south into the area Sunday night. There will
likely be an area of showers and thunderstorms ongoing along and
ahead of the front early Sunday evening. These storms should then
push south across our area and likely weaken as we lose the daytime
heating/better instability. Nonetheless, will allow for likely pops
into Sunday night and then taper back to a chance late
Sunday night into early Monday.

The front will continue to sag slowly south on Monday, but a surface
wave/low is forecast to ride east along it. This will likely slow
the front up and keep fairly high pcpn chances going across our area
through much of the day on Monday. Strengthening mid level wind
fields and the possibility of a surface low moving east along the
front, will lead to a chance for at least a few severe storms on
Monday. Highs on Monday will range from the upper 70s in the
northwest to the lower 80s across the southeast.

High pressure and a drier airmass will settle into the Ohio Valley
through the remainder of the week. Highs on Tuesday will only be in
the mid to upper 70s. Temperatures will then slowly moderate through
the rest of the week with highs by Friday into the mid 80s.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions will prevail at all local sites through the TAF
period, with the lone exception being a several hour period
around/after sunrise where patchy SCT to BKN MVFR clouds will
once again be possible, particularly for southern sites of KCVG,
KLUK, and KILN. By 15z, expect that any lingering lower clouds
should begin to scatter out/lift, yielding just some VFR Cu for
the afternoon hours.

Steady southwest wind of about 6-8kts will increase to around
10-12kts during the afternoon before subsiding again somewhat
towards sunset this afternoon. Additionally, there is the
potential for a weakening cluster of storms to work into central
Ohio towards the very end of the period -- with the full
expectation that this potential activity will weaken
considerably by the time it potentially reach KCMH and KLCK.
Did add in a VC for these sites starting at 03z to account for
this potential.

OUTLOOK...Thunderstorms possible Sunday into Monday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Excessive Heat Warning until 8 PM EDT this evening for OHZ026-
     034-035-042>046-051>056-060>065-070>074-077>082-088.
KY...Excessive Heat Warning until 8 PM EDT this evening for
     KYZ089>100.
IN...Excessive Heat Warning until 8 PM EDT this evening for INZ050-
     058-059-066-073>075-080.

&&

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



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