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Information is from the NWS Wilmington, OH Office

ILN Area Forecast Discussion/SKEW-T

FXUS61 KILN 240200

Area Forecast Discussion
National Weather Service Wilmington OH
1000 PM EDT Fri Mar 23 2018

Low pressure traveling from the west will bring hazardous
winter weather to southern locations late tonight through
Saturday. Drier weather will arrive Sunday and Monday with high
pressure. A slow moving cold front is forecast to provide
several rounds of showers Tuesday through Friday.


All attention is on the winter storm moving into the
southwestern portion of the forecast area tomorrow. Even as the
axis of greatest forcing has become more consistently defined
within the various models, the extreme sensitivity of the
thermal situation in the lowest 3km of the atmosphere is
continuing to provide forecast challenges, and a low confidence
in precipitation type forecasts. NAM/RAP cross sections depict
a consistent sloping frontogenesis signal, with lift near the
surface in the far southwestern CWA and then more elevated (and
in a less favorable thermodynamic environment) near the center
of the CWA. Forcing in the low levels will be maximized in a
moist and near-isothermal environment at just a couple degrees
Celsius below the freezing mark. After the 12Z model suite
(including the ECMWF) suggested the best conditions for snow
were lining up slightly further south than previously indicated,
18Z GFS/NAM runs were just a tiny bit further to the north.
With this slight oscillation, the best course of action is to
make no major changes to the going forecast. The best signal for
the heaviest snow still appears likely for a portion of the
southwestern ILN forecast area -- particularly from Ripley
County IN through Pendleton County KY. To the south of this
axis, even when snow becomes the dominant p-type for a time
(there will likely be some mix with rain and sleet) much of it
may melt on contact. To the north, the gradient in overall
precipitation amounts will be sharp, resulting in a snowfall
forecast that -- as of this writing -- ranges as much as 3-4
inches from one corner of a county to the opposite corner of the
same county.

Overall, the forecast thinking described below is largely
unchanged. The actual axis of heaviest snow may still be
narrower/sharper than the even what is in the ILN forecast
grids right now. If forcing can be maximized for a couple hours
along a swath where temperatures are just cold enough for all
snow, there is still the potential for a narrow (carefully-
measured) 6" wet snowfall. No changes are needed for the current
warning/advisory layout.

Previous discussion >
High pressure will move east tonight, ending a period of
tranquil weather. Low pressure currently entering Kansas will
move to Missouri by Saturday morning, before dropping southeast
toward Tennessee Saturday evening. A large swath of moisture,
short wave energy and isentropic lift ahead of the low will push
in after Midnight tonight. Models have trended a bit slower and
farther south with respect to track and effects of this system.
Still expect precip to develop late tonight in far southwest
counties, then move across southern counties Saturday morning
and afternoon. Main effects will be along and south of the Ohio
River, impacting Cincinnati, Williamstown, and Vanceburg.
Residents of Wilmington can expect to be on the edge of
accumulating precip, while Dayton and Columbus may escape any
measurable precip.

After evaluating model precip forecasts and temperature
profiles, main form of precip is expected to be wet snow. Sleet
and rain will probably mix in, especially along the southern
edge of the precip. Snow accumulations of 3 to 5 inches are
forecast for parts of Southeast Indiana, Northern Kentucky and
Southwest Ohio, including Cincinnati and its southern and
western suburbs. These amounts require a Winter Storm Warning.
The next tier of counties to the north are expected to receive 2
to 4 inches of accumulation, warranting a Winter Weather
Advisory. Wilmington may record an inch of snow accumulation,
and little to no accumulation may be observed at Dayton and
Columbus. High sun angle and marginally cold temperatures rising
to the mid 30s even while snow is occurring should limit
hazards from this system, with travel not affected as much as it
would be compared to mid winter. However, gusty east winds may
bring down snow-laden branches that could cause scattered power


Low pressure and associated moisture and forcing will be
traveling southeast Saturday night. This will bring an end to
the winter storm as high pressure and drier air build across the
Great Lakes. As skies become partly cloudy, cold advection and
snow cover will help temperatures fall into the 20s for
overnight lows.


High pressure centered over Southeast Canada will extend into the
Great Lakes and Ohio Valley on Sunday. Dry weather along with
sunshine are forecast. There will still be a stiff east/northeast
wind with some gusts expected. Temperatures will range from the
lower to mid 40s, which is still cool for late March.

For Sunday night into Monday, surface ridge axis will begin to move
east while a low amplitude mid level ridge pushes into the Great
Lakes and Ohio Valley. Clouds will increase as low level moisture
return occurs. In fact, a few showers may develop by afternoon
across the far western zones.

The pattern from mid to late week will then transition to a wet one.
The mid level ridge will move east Monday night into Tuesday. Moist
southwesterly flow on the back side of the ridge, along with
embedded disturbances, will increase the threat for showers. By mid
to late week, a slow moving front will move into the region and
perhaps sag southeast of the area by Wednesday/Wednesday night,
followed by a wave of low pressure across the middle/upper Ohio
River Valley Thursday/Thursday night. This will keep the threat for
showers going. Drier weather may return later Friday and into the
first part of the weekend as high pressure and zonal flow aloft move
into the area.

As for temperatures through the period, they will moderate into the
50s and lower 60s through mid week, then cool a little by Friday in
the wake of the wave of low pressure.


VFR will continue across forecast area this evening and into
tonight as high pressure moves east. Low pressure traveling just
south of the Ohio River will bring rapidly deteriorating flight
conditions to CVG and LUK toward sunrise as precipitation and
lower clouds move in lasting through the end of the TAF period.
CVG may see LIFR visibility during moderate snow around 15z
Saturday, while LUK could have IFR in lighter snow. Lesser
effects will be felt at ILN where snow and rain may occur in the
vicinity, with northern sites DAY CMH and LCK should avoid the
storm and remain VFR being outside of precip. Conditions should
rapidly improve at CVG and LUK by late Saturday evening as low
and moisture pull off to the east. East winds will also be an
issue, with gusts over 20 knots expected.

OUTLOOK...MVFR ceilings are possible Monday and Tuesday.


OH...Winter Weather Advisory from 2 AM Saturday to 2 AM EDT Sunday
     for OHZ070-078-079-081-088.
     Winter Storm Warning from 2 AM Saturday to 2 AM EDT Sunday for
KY...Winter Storm Warning from 2 AM Saturday to 2 AM EDT Sunday for
IN...Winter Weather Advisory from 2 AM Saturday to 2 AM EDT Sunday
     for INZ058-059.
     Winter Storm Warning from 2 AM Saturday to 2 AM EDT Sunday for


NEAR TERM...Coniglio/Hatzos
SHORT TERM...Coniglio
LONG TERM...Hickman


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