FXUS61 KILN 190837

Area Forecast Discussion
National Weather Service Wilmington OH
437 AM EDT Mon Mar 19 2018

Today will start off dry, before an area of low pressure brings
rain to the area Monday evening into Tuesday. Tuesday night into
Wednesday surface low pressure will form over West Virgina
bringing accumulating snow to the region.


Most of today will be dry across Ohio as the region remains in
between two systems. The system that brought beautiful weather
Sunday to the area will be located off the east coast with a
potent mid level low centered over the Kansas/ Oklahoma border.
Weak low level WAA will commence this afternoon, but clouds will
remain thick across the region. Due to this think high
temperatures will be very similar today as they were yesterday.
By late this afternoon the mid level low will be located across
southeastern Missouri with surface low pressure located over
western Kentucky. Looking at GFS and NAM forecast soundings
there will still be plenty of low level dry air in place with
light returns probably confined to northern Kentucky and eastern
Indiana. This means some of the light returns will probably
start out as virga.


This evening precipitation will begin to overspread the region
as the low levels finally moisten up and condensation pressure
deficits approach 0 MB. The mid level low will also begin to
open up over Indiana late this evening allowing PV to wash over
the region. In the upper levels the feature will try to take on
a negative title with upper level diffluence occurring across
Kentucky and far southern Ohio. The surface low itself will
track across central Kentucky with the ILN forecast area
remaining on the northern cold side.

As the surface low tracks northeast towards Charleston, WV the
deformation band will begin to pivot over the area. Early
Tuesday morning the deformation band will be setup west/east
across southern Ohio and northern Kentucky and will begin to
orient southwest/ northeast into the afternoon. The northern
edge of the deformation axis will likely have a sharp cutoff
with drier air just north. This means our southern counties will
likely see rain Tuesday morning with Dayton possibly having to
wait until late morning before observing precipitation.

As the precipitation heads north Tuesday morning the NAM is
indicating a small window where freezing rain might occur on the
northern fringe (such as Dayton). As of now the NAM appears to
be the outlier. Overall thinking is that by the time the
northern edge of the precipitation makes it north surface
temperatures will be above freezing. Temperatures Tuesday
afternoon will likely remain in the upper 30s to around 40 with
the widespread cold rain.

Late Tuesday afternoon into early evening a reinforcing shot of
cold air will begin to push southeast out of Canada in the form
of another shortwave. As this happens rain will start to mix
with snow northwest of Dayton.


A broad upper level trough will shift slowly east across the region
Tuesday night through Wednesday night. As it does a weak 850 mb
low/wave will move east across the upper Ohio Valley with an
inverted surface trough nosing northwest into our area. The models
have been fairly consistent with the broader features with this
system over the last several runs, but the 00Z deterministic models
continue to shift around quite a bit with their exact location and
amounts of heavier QPF Tuesday night into Wednesday. Complicating
matters is that given the time of year, the thermal profiles will be
somewhat difficult to forecast, particularly during the daytime
hours and ground temperatures will likely start off relatively warm.

Widespread precipitation is expected across our area Tuesday night
and likely lingering into at least Wednesday morning before beginning
to taper off from the northwest through Wednesday afternoon. Expect
the precipitation to start off as mainly rain early Tuesday
evening, but then change over to snow fairly quickly as we begin to
cool off and lose some of the diurnal enhancement. Expect
precipitation then to remain mainly snow through the remainder of the
event, even into Wednesday as boundary level temperatures should
remain cool enough to support mainly snow.

The 00Z NAM remains the wettest and snowiest, with a decent axis of
heavier snow forecast to set up across northern portions of our area
while the 00Z ECMWF has also trended quite a bit wetter/cooler and
is also indicating the possibility for some decent snowfall with
warning criteria type totals across parts of our area. However, the
00Z GFS and CMC are less impressive, but still suggesting possibly
some higher end advisory type totals across parts of the area. The
GEFS mean across our area is somewhat lower, generally in the 3 to 4
inch range with similar numbers from the 00Z EPS mean. Considered
possibly going with a watch for at least part of our central
forecast area where we have the lower 4 inch criteria, but confidence
is just not high enough at this time given all of the uncertainties.
As a result have opted go with snow amounts generally in the 2 to 4
inch range with amounts closer to 4 inches across parts of our

High pressure and a drier air mass will build across the area
Wednesday night into Thursday. We will remain well below normal
though with highs on Thursday only ranging from the upper 30s in the
north to the mid 40s across the south. Mid level ridging across the
area on Friday will quickly break down as short wave energy pushes
in from the northwest. This will allow for a surface low to move
east across the Ohio Valley Friday night through Saturday night.
This will result in an increasing chance of precipitation Friday
night into Saturday before tapering off through Saturday night.
Ptype will again be an issue with this system with at least a
rain/snow mix possible across northern portions of our area and
mainly rain across our south. Highs through the weekend will be in
the 40s with overnight lows mainly in the 30s.


All TAF sites are currently VFR this morning with surface high
pressure off to the east. During the day today a mid level low
will approach from the west with the pressure gradient slowly
increasing. Finally by late tonight bands of precipitation will
move in from the south. Ceilings will slowly fall from VFR to
MVFR by Tuesday morning.

OUTLOOK...MVFR/IFR ceilings and visibilities are possible
Tuesday through Wednesday.




NEAR TERM...Haines
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