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Area forecast discussion 
National Weather Service Wilmington Ohio
647 PM EST Sat Feb 13 2016

as a large upper trough moves east of the region...Arctic high
pressure will build into the area this evening. A warm front will
start to move through the region on Sunday...bringing snow to the
area through Sunday night. Low pressure will move southeast of the
area on Monday...with additional precipitation. Another area of
low pressure will move into the area on Tuesday...with warmer
temperatures expected for the end of the week.


Near term /until 6 am Sunday morning/...
the current surface analysis indicates that an area of high
pressure is centered over Illinois. The southern Great Lakes and
Northern Ohio valley remain in a regime of northwesterly
flow...with low pressure (and a large upper trough) still to the
east of the area. Although there is no appreciable forcing this
afternoon...steep low-level lapse rates have developed (especially
downwind of the lakes)...leading to some enhanced stratocumulus
development. Flurries are expected across the northern County Warning Area on
occasion through evening...with just a slight chance of a
legitimate snow shower.

The diurnal clouds are expected to gradually diminish heading into
the the dry high pressure center moves closer to
the area...with very light winds. However...some high and middle
level clouds (potentially thick) will be moving in from the west
and southwest during the overnight hours as well. The timing of
this process will have an impact on the min temperatures
conditions are very favorable for significant drops in
temperature if skies remain clear. This should hold true for at
least a while in all but the far southwestern County Warning Area...and min temperatures
through the central part of the forecast area are expected to be
in the low single digits. Some outlying locations (as was the case
last night) may end up within a degree or two on either side of
zero. Thankfully...since winds will be very light (and perhaps
even completely calm)...wind chills will not be an issue.


Short term /6 am Sunday morning through Monday night/...
during the short term forecast period...two shortwaves will be
moving through the Ohio Valley...presenting an array of
forecasting concerns. Impacts from the first shortwave (snow on
Sunday / Sunday night) are coming into view with respectable
clarity...with decent agreement between models in the overall
setup. Confidence is also growing that impacts from the second
shortwave (largely a rain event for monday) will be minor...even
though the details of the actual meteorological factors remain
remarkably discombobulated.

On Sunday morning...surface high pressure will be moving to the
east of the iln County Warning Area. The shortwave in question will be moving
eastward through Iowa at around 12z. Ahead of the wave...surface
to 700mb flow will take on a southerly component...and elevated
warm frontal processes will begin (with notable convergence and
ascent at 850mb). A swath of snow (with the front edge oriented
northwest-to-se) is expected to develop and move into the iln forecast
area during the late morning to early afternoon. It may take some
time for the column to saturate...with quite a bit of dry air
(especially in the 5kft-10kft layer) to work through. Once it
occurs...the forcing type and overall setup favor a widespread
light snow for the entire forecast area...with some slightly
heavier rates in the southern third of the County Warning Area. Temperatures
through the lowest 10kft appear likely to warm up just enough to
not really support any significant dendrite snow
ratios may not end up being as high as the initially frigid
temperatures might otherwise suggest. Nonetheless...the prolonged
nature of the snow (perhaps up to 6-8 hours of steady light snow)
will allow for a gradual accumulation...especially in the southern
County Warning Area where deep-layer moisture will remain in place for a longer
period of time. Total accumulations of 2-3 inches can be expected
for the far southern counties...with around 2 inches near the
cutoff of the Winter Weather Advisory...and lesser amounts further
to the north. The advisory GOES into effect in two segments
tomorrow based on timing. However...the entire advisory will
remain active until Monday morning...allowing time for surface
temperatures to rise above freezing. Though not specifically
mentioned in the west-southwest product...there does appear to be some
potential for light precipitation to continue after the wave has
moved through...but moisture becomes extremely shallow during this
time frame (early Monday morning). Thus...freezing drizzle could
be a possibility...with ground conditions that will be very
susceptive for icing if that scenario were to occur.

The forecast for the second system on Monday remains notably
convoluted...with major differences between models in the
evolution of the next shortwave...and the surface low it helps to
develop. This wave (or at least its genesis) can be traced all the
way back to the southern British Columbia coast this
indication that it has a long way to travel before reaching the
Ohio Valley on Monday. The vast majority of 12z operational
guidance allows for a surface low to develop...remain somewhat
weak...and head east-northeast into the Middle-Atlantic States. The
European model (ecmwf) has remained the furthest west with regards to the low
track...and the strongest with regards to the low strength.
Looking at ensembles (gfs/sref)...even through an array of
perturbations...there appears to be little support for the European model (ecmwf)
solution. The expected weaker low track does still allow for
another increase in precipitation chances for the southeastern iln
County Warning Area...and perhaps a significant increase for Monday afternoon and
evening...with good forcing to the north of the low and plenty of
moisture to work with. However...there is a huge caveat to all of
the above...and that is the continued trend toward a warmer
solution across all available models Sans the NAM. This means
that much of the precipitation on Monday...and in particular any
potential for heavier precipitation...will fall as a cold rain.
So...despite the continued befuddling model differences in the
setup...a somewhat-reasonable level of confidence in the
temperature situation does provide for a slightly better idea that
this second system will produce little additional hazardous winter
weather impact. There remains a possibility that cooling
temperatures Monday evening could allow for some light snow on the
back side of the system...but given all the other uncertainties would be foolish to try to make an accumulation
forecast (if any snow occurs at all) at this point in the forecast

Temperatures were hand-edited non-diurnally through the entire
forecast period. Although conditions at the surface on Sunday will
only warm a little from Saturday (despite the start to a warm
advection pattern)...a more significant boundary layer warming
will begin on Sunday night. Temperatures will likely be rising
going into Monday morning...and will then go above freezing for
the entire County Warning Area by early Monday afternoon.


Long term /Tuesday through Saturday/...
a fast moving shortwave in a northwest flow aloft will be right on the
heels of departing system Monday night. This disturbance will be
associated with an area of surface low pressure. Models have the energy
in different spots with the NAM the farthest north and the European model (ecmwf) the
farthest south. Have gone with the middle of the Road GFS.
Regardless...all solutions suggest that warm air advection ahead of this system
should keep precipitation in the form of rain as it moves in on Tuesday. Have
used likely probability of precipitation. Temperatures will warm into the upper 30s to the
lower 40s.

For Tuesday night into the system quickly moves
east...colder air will filter into the region on the back
some mix with or a brief change over to snow is expected before
tapering off toward Wednesday morning. Any snow accumulations should
be across the far north and minor in nature...less than an inch. On
Wednesday...will go with a dry forecast...although considerable cold air advection
stratocumulus is expected.

For Wednesday night into Thursday...high pressure will build south
into the Ohio Valley. Skies are expected to become partly cloudy.
Models different on the extent of cold air filtering in the have sided with a wpc blended approach.

As the high moves east Thursday night...a warm front is forecast to
approach from the west. We should see an increase in warm air advection induced
clouds. As of now...any precipitation generated with the warm front is
expected to stay northwest of the area. Overnight lows will be early
followed by slowly rising temperatures as winds increase from the

For Friday into Friday night...low pressure will traverse the Great
Lakes as a cold front pushes in from the northwest. Models vary on
how much moisture will be pulled northward along and ahead of the
front system...along with the have gone with a chance of
rain. Friday certainly looks to be the warmest day of the extended
with temperatures rising into the 50s area wide.

On Saturday...front exits to the east...but cold air advection stratocumulus moves
into the region. Precipitation will move east as well. Temperatures will cool
into the middle 40s to lower 50s for highs.


Aviation /00z Sunday through Thursday/...
cold air advection cumulus is eroding with the loss of heating. Cirrus will work in overnight
while a surface high makes winds light and variable.

500 mb short wave will eastward out of the plains tomorrow. Ahead of it an area
of snow will develop...reaching kcvg around 17z. The snow will
spread over the rest of tafs by 21z. Ceilings and visibilities will drop to
MVFR in the snow with some IFR visibilities possible in the southern tafs.

Outlook...MVFR/IFR conditions are possible with precipitation
from Sunday through Tuesday.


Iln watches/warnings/advisories...
Ohio...Winter Weather Advisory from noon Sunday to 10 am EST Monday
for ohz077-078.
Winter Weather Advisory from 5 PM Sunday to 10 am EST Monday
for ohz079>082-088.
Kentucky...Winter Weather Advisory from noon Sunday to 10 am EST Monday
for kyz089>098.
Winter Weather Advisory from 5 PM Sunday to 10 am EST Monday
for kyz099-100.
In...Winter Weather Advisory from noon Sunday to 10 am EST Monday
for inz073>075-080.


near term...hatzos
short term...hatzos
long term...Hickman

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