Area Forecast Discussion
Issued by NWS Wilmington, OH

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330
FXUS61 KILN 231442
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
942 AM EST Fri Feb 23 2018

.SYNOPSIS...
An extremely moist airmass will remain over the region into
Saturday night. Multiple weather disturbances riding along a
slow moving front will produce periods of heavy rainfall.
Dry weather is expected with the arrival of high pressure
Sunday through Tuesday. Above normal temperatures are forecast
to persist through the period.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
An initial round of precipitation has exited the area to the
east this morning, but additional rainfall over Kentucky is
expected to move into the ILN CWA over the next few hours,
especially for the southern/southeastern third of the CWA.
Surface observations and KIND radar data show that a cold front
is currently crossing the state of Indiana. This front will get
into the ILN CWA to some extent, but as the parent surface low
moves further off to the northeast, the front will pivot and
slow as the day goes on. Though the surface front may eventually
get through much of the CWA, flow at 850mb and above will remain
southwesterly for the majority of the forecast area.

The KILN 12Z sounding sampled a new February record for
precipitable water (roughly 1.38" depending on which algorithm
is used for the calculation). This very moist air mass will
continue to support a threat for rainfall and flooding. With
that said, the next round coming through later this morning and
afternoon may be more of a steady moderate rainfall than
something more heavy and convective, which should at least limit
the threat for any significant flooding in the near term. As
has been consistently forecast, the flood threat will continue
to be exacerbated over additional rounds of rain over the next
couple days -- and the flood watch continues through Sunday
morning.

No big changes were needed to wind/sky/Td grids. Some
adjustments to temperatures were necessary, as the flow ahead
of the cold front has been a little warmer than anticipated.
PoPs were updated based on latest radar and HRRR trends, showing
an increase over parts of the CWA over the next 3-6 hours,
followed by a relative lull in precipitation potential during
the evening.

Previous discussion >
Broad southwesterly flow with embedded shortwaves is bringing
another round of rain to the region early this morning. Models
bring the highest PoPs across the region during the morning
hours, before shunting the pcpn off to the east and southeast
during the afternoon with the passage of a cold front. It looks
like there will be some elevated instability across the south
today, so kept a chance of thunderstorms.

Current Flood Watch footprint looks good as the heaviest QPF
looks like it will fall across the se half of the fa. QPF
amounts of around a inch are possible with today shot of rain.

Highs today will range from the upper 50s in West Central Ohio
to around 70 in the Lower Scioto Valley and ne KY.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Tonight the cdfnt will drop into KY before stalling. This should
bring a break in the precipitation across the north, with low
chances in the south. The boundary will linger around the Ohio
River on Saturday as a warm front as it waits for more mid
level energy to kick out Saturday night. Rain should overrun the
area on Saturday, so kept the 100 PoPs. There will be a big range
in highs for Saturday as the extreme northern counties will see
highs around 50, while the nrn Kentucky counties will see highs
in the 60s.

H5 s/w will kick out of the Rockies Saturday night, pushing a
surface low into the western Great Lakes, while a cold front
whips up the Ohio Valley. Large area of heavy rain will lift
across the region and will fall on already saturday grounds and
rivers which will be running high or are already in flood.
There could be a chance for some severe thunderstorms Saturday
night with such a dynamic atmosphere.

The front is expected to be pushing through the region Sunday
morning, bringing and end to the pcpn. Highs on Sunday will be
early highs with temperatures falling in the afternoon.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Surface high pressure will build across the Great Lakes
offering dry weather from Sunday night into the middle of next
week.

Temperatures to turn cooler but still above normal with highs Monday
from the upper 40s north to the mid 50s south. Temperatures Tuesday
look to be around 10 degrees above normal, with highs from the lower
50s north to the upper 50s south.

Model solution differences develop at mid week regarding how fast
moisture returns on the backside of retreating surface high
pressure. Will limit pops low chance Wednesday afternoon south and
then across the entire FA Thursday. Mild temperatures to continue
with highs in the 50s Wednesday and Thursday.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
Rain overspreading the region is improving cigs and vsbys across
the bulk of the TAF sites this morning. Low stratus and
IFR/LIFR conditions will be the general rule, but there appears
to be enough mixing with the to have at least a temporarily
higher cig that tickles the 3kft cutoff between MVFR and VFR
categories.

Generally tried to improve the TAF conditions with the thought
that west and northwest winds later tonight will mix in drier
air in the lower atmosphere. Regardless, any improvement will
then begin to tank late in the period when the next batch of
rain enters from the southwest. An area of convergence to the
northwest may see KDAY start raining before anyone else as the
axis of the next round of showers late tonight will be focused
here. Rain will be prevailing at KCVG towards daybreak Saturday.

Have only seen a handful of CG strikes south of KCVG and the
thunder threat for today seems to be better focused southeast of
the I-71 corridor and out of the TAF locations. Given a first
glance at the 12z radiosonde info, the low level jet that was
forecast to be near the region has not made it to ILN as yet.
Will continue to consider the threat of thunder and/or LLWS but
take a reactionary stance once a threat becomes apparent.

OUTLOOK...MVFR/IFR ceilings and visibilities are likely into
Saturday night. MVFR ceilings may linger Sunday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Flood Watch through Sunday morning for OHZ053>056-060>065-
     070>074-077>082-088.
KY...Flood Watch through Sunday morning for KYZ089>100.
IN...Flood Watch through Sunday morning for INZ050-058-059-066-
     073>075-080.

&&

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



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