Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 231718
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
1218 PM EST Tue Jan 23 2018

.SYNOPSIS...
Cloudy skies and cold air will be the resultant weather behind
the cold front that crossed the region last night. A weak upper
level trough will keep cloudy skies and a threat for light snow
in the forecast through early Wednesday. Dry conditions will
occur as the high pressure builds through Thursday, along with
a return to warmer temperatures for the end of the week and into
the weekend.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Current observations show that surface low pressure is centered
near Owen Sound ON, well occluded from a frontal boundary that
is now moving across Pennsylvania. Consistent WSW flow through
the boundary layer will continue to cold advect through the day,
leading to a well mixed temperature profile through the lowest
3000-4000 feet. Combined with cold air aloft, this will keep the
atmosphere favorable for cloudy skies and occasional light
precipitation, even after the axis of the 500mb trough passes
the area in the next couple hours. Based on current obs,
as temperatures fall below about 38 degrees, snow is starting to
mix in with the rain. For a while at NWS ILN near 900AM,
distinct snowflakes and rain drops were falling at the same
time, though precipitation has stopped at the time of this
discussion (940AM). A mix of light rain and snow (maybe better
described as sprinkles and flurries) will eventually switch to
snow as temperatures aloft continue to fall (and temperatures at
the surface essentially remain steady through afternoon before
falling tonight). Not expecting any accumulations, but chances
for precipitation were extended a little further into the night
than with the previous forecast.

Previous discussion >
Showers will skirt the northwest portion of the CWA early this
morning. Afterwards, the cold air pushing into the region will
interact with a moist lower atmosphere to produce scattered
showers that will quickly mix with and change to snow showers
this morning and early afternoon. Temperatures will be
experiencing a slow drop through the day as the atmosphere cools
from aloft. Even if surface readings are around 36-38 degrees,
the warm layer will be fairly shallow and most of the region
would be seeing scattered snow showers and flurries by the
afternoon. Accumulation is expected to be on the order of a
tenth to a quarter inch and not be a strong impact as the ground
will be warm to begin with and inhibit accumulation on
roadways.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
Cold air will continue to push in tonight, with a very weak
secondary trough aloft being enough to keep some flurries in the
forecast through the overnight hours. A stronger upper trough
will cross late Wednesday but the atmosphere will have dried out
enough to not produce any snow shower activity with the feature,
just more cloudy skies. Wednesday highs will only be about 5-7
deg warmer than the overnight lows and top out in the lower
30s with continued cold advection.

Cloud cover overnight Wednesday will help keep temperatures from
falling past the middle and upper 20s. Return flow on Thursday
will permit readings to rise into the 40s with a clearing trend
in sky cover. By Friday, readings should be topping out in the
50s once again with continued dry conditions.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Did not make any significant change to the extended forecast.
Warm air pooling ahead of a cold front will help wring out
shower activity beginning early Saturday, maxing out in the
afternoon with colder and drier air working in overnight and
Sunday. Temperatures will then cool and return to just above
their seasonal normals for next week.

&&

.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
Broken/overcast MVFR ceilings are common over the TAF sites this
morning and this looks to continue through the bulk of the
upcoming TAF cycle. Cyclonic flow, low level cold advection
steepening the lapse rate, and abundant moisture observed on
KILN and forecast soundings this morning all but ensure a rather
pessimistic cloud forecast in terms of lower ceilings. Most
uncertainty lies with potential for IFR ceilings and/or
visibilities with any rain/mixed/snow showers over the next 12
hours. Of most concern is a rather concentrated area of IFR
cigs and MVFR vsbys over central Indiana seemingly tied to weak
vertical motion along a subtle shortwave trough. Forecast
soundings do show that as this feature rotates east, low level
moisture depth deepens toward 2km, suggesting some light snow or
rain /drizzle/ may develop late this afternoon and evening in
some areas. Have put ceilings down to lower MVFR categories
during this timeframe but will need to watch for IFR potential
especially evening into early overnight with the deepest
moisture. Do not think vsby restrictions will be widespread - so
keeping these unrestricted given that cloud forecasts are
already in the lower half of MVFR, and amendments can be handled
on as-needed basis as areas of drizzle/rain/snow present
themselves later this afternoon into the evening.

OUTLOOK...MVFR ceilings likely to linger into Wednesday. MVFR
ceilings and visibilities possible Saturday.

&&

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

&&

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


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