National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KILN 210212
AFDILN

AREA FORECAST DISCUSSION
National Weather Service Wilmington OH
1012 PM EDT Mon May 20 2019

.SYNOPSIS...
High pressure will build south into the Ohio Valley tonight.
A mid level disturbance may bring a chance of light rain across
west central Ohio on Tuesday, otherwise it will be partly to
mostly cloudy. As the the high moves to the east of the area on
Tuesday night, a warm front will begin to move northeast toward
the Ohio Valley. This warm front will push northeast across the
region on Wednesday, bringing a chance of showers and thunderstorms.
Cool conditions on Tuesday will transition to warm and more
humid weather on Wednesday.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A mixture of low and high clouds are affecting the region this
evening. Stratocu continue to linger in portions of central and
west central Ohio. Meanwhile a cirrus shield is affecting
southern portions of the fa. These high clouds are forecast to
continue to spread east throughout the night.

Temperatures will drop down to the mid 40s in the north to the
upper 40s around the Ohio River.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
On Tuesday, the center of surface ridge will move east toward
the eastern Great Lakes. Meanwhile, a mid level ridge will begin
to build northward into the Ohio Valley. Embedded disturbances
riding this ridge, along with mid level forcing (various models
show a 700 mb jet/convergent focus) may bring a chance of rain
to west central Ohio. Have placed 20/30 PoPs here. Otherwise,
considerable mid and high level clouds will gradually lift to
the north during the afternoon while locations along and south
of the Ohio River scatter. Winds will have shifted to the east
around 10 knots. Given a cool start, easterly flow, and
considerable clouds, temperatures across the north will remain
on the cool side, while afternoon sun across the south will
allow for warmer temperatures. Highs will range from near 60 far
north to the lower 70s along and south of the Ohio River.

A strong occluding system will lift north toward the central
Plains Tuesday night while the mid level ridge continues to
build north. This will allow a warm front to our southwest to
begin to push northeast. Ongoing convection well to our west
across the mid Mississippi River Valley will move east
overnight, but should weaken as it does. We could see a shower
or thunderstorm encroach our western zones late from the
weakening convection. Overnight lows will occur by early morning
Tuesday night, then begin to rise some toward sunrise Wednesday.
Lows will range from the lower 50 to mid 50s north with mid to
upper 50s expected along and south of the Ohio River.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
By Tuesday night into early Wednesday, the remnants of what
once was a cohesive and well-formed convective line across the
mid-Missouri Valley will nudge eastward closer to the local area
but will most likely do so in a weakening state as the source
impulse/disturbance essentially becomes sheared-out as it
progresses into an increasingly hostile environment
characterized by a midlevel ridge axis centered from eastern TN
northward into eastern MI. As such, precipitation chances will
decrease west to east Wednesday morning with the nudging of the
pseudo-warm front east across the area, with just chance PoPs
during the day as the remnants of the disturbance push east
through the region. Increasing low-level instby during the
afternoon hours, attendant with the influx of BL moisture-rich
air, will occur with at least the potential for a remnant
outflow/storm- scale boundary lingering about the area -- which
may provide a focus for re-initiation of storms during the
afternoon hours across central and western portions of the ILN
FA. With relatively weak forcing overall, however, the coverage
is expected to remain isolated to scattered in nature even
during peak diurnal heating.

Even with the inherent uncertainties in convective re-
initiation locations on Wednesday afternoon, the expansion of
the ridge across the Gulf States and southeast U.S. will yield
an increasingly large, warm, and humid airmass across both the
Tennessee and Ohio Valleys midweek and beyond.

By Thursday, the upper level ridge across the southeast will
strengthen considerably -- and this has been, and continues to
be, supported both in deterministic and ensemble datasets among
multiple synoptic-based modeling systems. However, a midlevel
disturbance progressing eastward along the northern periphery of
this ridge may provide enough focus for ascent to allow for
scattered showers and storms again during the day on Thursday.
This being said, there remains considerable variations in the
global model suite handling of this system and the potential
implications on convective coverage locally. However, with at
least some focus for ascent and more than enough surface-based
instby, do think that storm activity will be more widespread
Thursday (especially compared to Wednesday). And even after the
midlevel impulse moves through, a very weak front will likely
become laid out in a west-east orientation across the northern
Ohio Valley -- which in and of itself may provide enough surface
convergence to keep scattered storm activity going further into
the overnight period into very early Friday morning --
especially across central Ohio and points northward.

The positioning of the strong ridge over the southeast U.S.
will undoubtedly have implications on the sensible weather
locally for the end of the workweek into the upcoming weekend --
as it at the very least appears like the center of the ridge
will stay well south of the Ohio Valley. This setup does lend
itself to the potential for embedded disturbances riding along
the northern fringes of the ridge, which would act to keep a
daily chance of showers and thunderstorms in the forecast
(especially across the northern reaches of the Ohio Valley)
opposed to going with a hotter/drier solution for Friday through
the end of the long term period. This being said, the
oscillation of the weak frontal boundary about the northern Ohio
Valley is not being handled well at this time by long range
guidance in terms of its orientation and associated
progressions/retreats from Friday through early next week. The
ECMWF continues to show a further north mean frontal position
/with attendant corridor of favored repeated rounds of
showers/storms/ while the GFS trend of a wetter/stormier pattern
for the local area continues from run-to-run. Am leaning right
now toward the GFS solution of daily chances of showers/storms
being maintained in the ILN FA with the Ohio Valley positioned
more squarely on the fringes of the ridge. Although these kinds
of patterns can be deceivingly active for us here locally, did
not want to jump too much on precipitation chances given
inherent uncertainties in timing and placement of the
aforementioned oscillating front -- the evolution of which will
be dictated by the expanse (or lack thereof) midlevel ridging
northward into the region. Nevertheless, the pattern for the end
of the week into the weekend may very well feature multiple
rounds of storms for the Ohio Valley -- the specifics of which
may not come into better focus for at least several days.
Nevertheless, the prospect of having midlevel disturbances pivot
about the ridge axis amidst an inherently unstable airmass will
be watched in the coming days for the potential for episodic
thunderstorms for an extended period of time late in the week.

With all of this being said, confidence remains high in a very
warm and humid airmass building into the region from Wednesday
through the end of the long term period -- with highs in the
80s/near 90 and lows in the 60s. These temperature trends of
course will inevitably be augmented by associated complexes of
storms at times during this period. However, the overall pattern
supports an extended stretch of above normal temperatures for
much of the region.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
VFR stratocu deck that has affected the northern tafs this
afternoon is breaking up leaving high clouds aloft. Expect these
to linger throughout the night as upper level energy is lifted
up the west side of the upper ridge. High pressure will drop in
from the north, allowing the winds to drop to less than 6 kts.

Between 06-12Z, mid level isentropic lift will increase across
Indiana into NW Ohio. This will bring a mid deck into the
northern tafs by 12Z. There could be a sprinkle out of this mid
deck in the northern tafs, but left it out for now.

After 12Z Tuesday, the center of surface ridge will retreat
into the ern Great Lakes. By 18Z the isentropic lift weakens and
the mid deck should go scattered, leaving scattered mid and
high clouds.

Winds will begin to increase late in the period as a strong
surface low in the plains begins to increase the pressure
gradient even over our region.

OUTLOOK...Thunderstorms possible Wednesday and Thursday, and
again Saturday.

&&

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

&&

$$
SYNOPSIS...Hickman
NEAR TERM...Sites
SHORT TERM...Hickman
LONG TERM...KC
AVIATION...Sites