Area Forecast Discussion
Issued by NWS Wilmington, OH

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376
FXUS61 KILN 231353
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
953 AM EDT Tue May 23 2017

.SYNOPSIS...
A ridge of high pressure will exit east of the region today.
Upper level low pressure in the Upper Midwest will strengthen as
it moves southeast to the Tennessee Valley by Thursday morning.
At the surface and lower levels, low pressure will be further
north and settle in the Ohio Valley during this time.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Surface high pressure is departing the region to the northeast,
with the ILN CWA currently in between two areas of greater
moisture -- one ahead of the upper low moving southward along
the Mississippi River, and the other moving through the
southwesterly flow off the Gulf coast. Outside of these areas,
the low-level flow remains fairly weak, so the advection
process is not occurring particularly quickly in the middle
Ohio Valley region. Generally light radar echoes have been
observed over Indiana, with just a few reports of light rain so
far. Over eastern Kentucky, an area of greater deep-layer
moisture is advecting northeast, and 06Z model runs suggest this
will clip the southeastern corner of the ILN CWA. There will be
no more than a slight chance of light rain in either case, so
most of the CWA will be kept dry in this forecast update. Some
slight upward adjustments were made to temperatures, based on
the current amount of clearing over the region, but clouds are
expected to increase in coverage through the day.

Previous discussion >
Generally cloudy conditions will prevail over the region today
with high clouds thickening and spilling in from the southwest.
With the exiting surface high pressure ridge, dry conditions
will be found. Temperatures will be fairly uniform and climb
into the middle 70s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
As the upper low digs south in the Upper Midwest tonight,
southerly flow in the lower levels of the atmosphere will bring
in moisture and wring it out in the broad upward motion found in
the region. Scattered showers will become more prevalent later
in the night and the increased chances will spread from west to
east. Overnight lows will also be somewhat uniform over the
region and drop to the middle and upper 50s.

By Wednesday, some daytime insolation will be added to the mix
and shortwave energy rotating north into Ohio will help to
initiate more widespread showers and some embedded
thunderstorms. Given the thicker cloud cover and expected
rainfall, temperatures will be hard pressed to move past the 70
degree mark.

Wednesday night should see precipitation move north as the upper
level circulation remains well south of the area and the surface
and lower level low circulation is along or just north of the
OH/MI border. Though rainfall will be on the decrease and not
much is expected, temperatures will once again drop into the
low to mid 50s. Deeper moisture and the re-emergence of shower
activity on Thursday will hamper temperatures once again, with
middle 60s expected. The low pressure system will orient itself
nw-se and move east of the region in the late day, with some
cold-pool scattered instability showers possible in its wake.
Ridging at the surface and aloft will take hold for Friday and a
general drying pattern will be found as temperatures begin to
rebound into the lower 70s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Models continue to trend on the quicker side both with the
departure of the upper low Thursday night and additional
precipitation chances beginning Friday night. Beyond that,
model spread remains somewhat high for the weekend forecast, as
a series of shortwaves is expected to move eastward across the
region in the pseudo-zonal flow. At least initially, it is
likely that some sort of surface boundary will exist across the
region, with greater theta-e just to the south. Though this may
eventually shift northward, this pattern is one that would
support multiple rounds of showers and storms within an
increasingly moist air mass. Thus, there will be at least some
potential for both stronger storms as well as heavy / repeated
rainfall for Saturday and Sunday. Within the GEFS suite and from
run- to-run of the operational ECMWF/GFS, there are still big
differences in wave amplitude/timing, negating the ability to
forecast the specifics. For now, lower-end PoPs will be
maintained through the entire weekend (though this has been
increased from the previous forecast), with slightly above
normal temperatures. This may come to an end with a cold frontal
passage late Sunday into Monday, leading to drier conditions to
start next week.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Surface ridge centered to the northeast will continue to
extend down across the tafs today. This will keep the low
levels dry. Stubborn cirrus will provide broken to overcast
ceilings into afternoon when it is expected to thin.

After 00Z, the low levels start to moisten as vort max swings
around the closed H5 low in the Mississippi Valley. There are
still timing differences as to when the pcpn will start. Went
with a consensus blend which brings scattered pcpn into the sw
tafs around 09Z, then a steadier rain in around 12Z.

OUTLOOK...MVFR ceilings and visibilities possible Wednesday
into Thursday, and again Saturday.

&&

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

&&

$$
SYNOPSIS...Franks
NEAR TERM...Franks/Hatzos
SHORT TERM...Franks
LONG TERM...Franks/Hatzos
AVIATION...Sites



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