Area Forecast Discussion
Issued by NWS Wilmington, OH-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KILN 280621
Area Forecast Discussion
National Weather Service Wilmington OH
221 AM EDT THU JUL 28 2016
A stalled frontal boundary near the Ohio River will provide a
chance for scattered showers and thunderstorms through this
evening. A wave of low pressure traveling along the front will
bring an increased likelihood for showers and thunderstorms
Thursday into Friday. Unsettled weather will continue into the
weekend as several disturbances aloft interact with a persistently
moist and unstable airmass.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Mid/high level clouds continue to stream northward into area as
convection has fired along and south of a weak stationary front
oriented west to east across KY and extreme southern Ohio. Mid
level energy will lift northeast into Ohio Valley late tonight,
allowing for moisture to surge northward as frontal boundary
begins to pivot northward as a warm front. As this occurs, shower
and thunderstorm activity will move ENE into southern parts of FA
around and after 06z. Expect that with limited instby across
northern half of FA, any thunderstorm activity should be
constrained to far south parts of area. With high PWATs forecast
to be around/in excess of 2 inches, have continued Flash Flood
Watch for southeastern parts of FA, and have expanded watch to
include 5 additional Kentucky counties. Although activity tonight
will be developing in a moist environment, it appears it should be
fairly progressive, helping limit the potential for flash flooding
in the near term. Forecast lows are still on track for tonight,
with upper 60s in the north and lower 70s in the south.
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
Main concern on Thursday will be a higher potential for some flash
flooding across mainly south-central Ohio and northeast Kentucky
as a potent shortwave crosses the ILN CWA and interacts with a
very moist airmass. This shortwave energy will develop a couple
weak surface lows that will lift through eastern KY into south-
central OH in a moisture rich environment with PWATs of 2 to 2.2
inches (2-3 sigma above normal for this time of year). Warm cloud
depths will be >4km and a modest LLJ will lead to favorable
moisture transport across our southeast, though conditions will be
most favorable just outside of the ILN CWA. Given bulk shear
vectors from the southwest, do expect potential for training
cells over southern Ohio and northern KY. Synoptic models are in
pretty good agreement with the axis of heaviest precip setting up
over our southeast, so have issued a flash flood watch for this
area. At this time expect 1.5 to 2 inches of rainfall within the
watch area with locally higher amounts possible. Later shifts will
have to monitor whether the better forcing and axis of heaviest
precip may shift further west, though. While 0-6km wind shear
across our south will range from 25-35 knots, forecast soundings
show a nearly saturated column through the mid levels with tall
skinny CAPE <1000 J/kg. Thus, severe potential should be limited.
Precip chances will decrease Thursday night as the best forcing
Cloud cover and rain will keep temperatures down across our
southeast, where highs will likely struggle to reach 80. It will
be warmer northwest of I-71 where temperatures will climb into the
low to mid 80s. Lows Thursday night will be in the mid to upper
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
The long term will start with a series of upper level disturbances
moving across the area along with a front stalled out. This will
help to keep the chance of rain in the forecast almost through the
entire extended until Tuesday when weak mid-level ridging moves into
Looking more into the details, Friday will open up with a shortwave
moving across the region and the leftover frontal boundary from
earlier in the week still across the area. Upper level lift is
sufficient with weak PVA moving across and moisture values remain
above average for this time of year with PWATs forecasted to be
around 1.70". Instability is also present with ML CAPE values around
500 J/kg. As the shortwave exits Friday PoPs will slowly taper off
due to weak subsidence behind the wave.
Saturday through Sunday another weak shortwave trough will remain in
close proximity to the area with a surface front located across the
CWA. This will help to bring the chance of rain right back to the
area. Given the weak upper level trough quickly pulling east the
cold front stalling across the area seems likely. Given the chance
of showers and thunderstorms during the day have kept high
temperatures near climo. Monday into Tuesday as the shortwave trough
exits weak mid-level ridging will then build overhead as mid-level
high pressure builds over the central United States. There still
remains timing differences on when the high will build and how far
it will build east. For now have just trended PoPs down.
.AVIATION /06Z THURSDAY THROUGH MONDAY/...
Upper level trof over the lower Mississippi valley will lift
northeast today. As a result, a surface wave of low pressure will
develop and track northeast through the Ohio valley this
afternoon. A surge of tropical moisture overspread the region
ahead of the sfc wave as the weak sfc boundary pivots north into
the area. Showers and thunderstorms will overspread the southern
TAF sites early this morning. The preciptiation activity will
increase in coverage after 12z, with best coverage expected along
and south of the I-71 corridor. Deepest moisture to shift east of
TAF sites this aftn, so expect pcpn to become widely scattered.
Due lagging upper level support and unstbl airmass have kept VCTS
until early evening.
OUTLOOK...Thunderstorms likely Thursday night through Saturday.
OH...Flash Flood Watch through Friday morning for OHZ079-081-082-
KY...Flash Flood Watch through Friday morning for KYZ089-090-