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Area forecast discussion 
National Weather Service Wilmington Ohio
420 PM EST Monday Jan 26 2015

surface high pressure will build into the Ohio Valley through the
middle of the week. An area of low pressure and a cold front will
move across the region on Thursday...bringing a chance of mixed
precipitation. Cold high pressure will move in again on Friday.


Near term /until 6 am Tuesday morning/...
a trough of low pressure is moving away from the region to the
east. Upstream...a weak and further weakening shortwave is moving
rapidly southeast out of the northern Mississippi Valley. A surface low
is weakening just as quickly...and is forecast to essentially
dissipate as it moves across the Ohio Valley tonight. There will
be a short period of time in which somewhat-favorable jet dynamics
help support some light snow to the southwest of the iln forecast
area...with possible accumulations over parts of southern Indiana
and central Kentucky. However...the iln County Warning Area appears unlikely to
receive much precipitation. A chance of flurries was inserted into
the grids...mainly south and west of Cincinnati.

Along the path of this weak cover should remain at
the high end of the scale. However...925mb/850mb moisture is not
expected to be as prevalent across the rest of the forecast
area...particularly in the northern and northeastern areas. With a
snow pack in place...and with winds that will become lighter
through the night...a solid amount of radiational cooling should
occur. This will allow temperatures to drop to around 10
degrees...and outlying or low areas may get well into the single


Short term /6 am Tuesday morning through Wednesday/...
the short term forecast period should be fairly quiet...with no
chances for precipitation. Temperatures will be the biggest
challenge...with surface high pressure sitting over the Ohio
Valley...and generally weak advection patterns setting up through
Wednesday. With gradually clearing skies...Tuesday may end up a
degree or two warmer than Monday...but there is no reason to
forecast a big swing in temperatures. For Tuesday night...clearing
skies and light winds will set up some very favorable radiational
cooling conditions...and the entire model suite has taken a
downward trend with temperatures. This forecast represents a drop
of several degrees from the previous min temperature grid...but even a
simple GFS/NAM consensus blend would result in cooler this forecast still has room for additional
downward adjustment.

On Wednesday...there are signs that some warm advection could
begin...though mainly just off the surface (at least through the
daytime hours). At 925mb...a ridge axis will have to cross east
through the region...before the low-level flow turns from north-northeast to
south-southwest. Though diurnal temperatures were used in the is
possible that maximum temperatures could be slightly later than on a typical
day. With the boundary between snow pack and snow-lack cutting
across the County Warning Area...if any warm advection can combine with the
plentiful insolation on could have a big impact on
the final numbers. This is a low-confidence temperature
forecast...especially with a fairly tight gradient in the
grids...and a model blend was used to get the numbers into
reasonable position. However...the extremely cold values in the
Canadian model were discarded.


Long term /Wednesday night through Monday/...
for the period Wednesday night into Thursday night...the European model (ecmwf) and
the GFS still differ a bit on the timing of a tandem of S/waves to
affect the region...along with an associated low pressure/cold
front. The European model (ecmwf) is slight slower and little more sharper with the
second shortwave while the GFS is faster. Have continued with the GFS
timing at this time to keep continuity from previous forecast. With
return flow...temperatures will begin to warm some late Wednesday
night into Thursday. There will be a race between how fast it warms
compared to when the onset of precipitation begins. It looks like there will
be a threat for a wintry mix...snow...sleet or freezing rain for
locations along and north of the Ohio River late Wednesday night
into Thursday morning. Best chance will be from east central Indiana
into central Ohio and points north. Minor snow...sleet...or ice
accumulations will be possible given a cold start...any freezing
rain will pose a hazard to travel so we will continue to monitor
this system. Have mentioned the threat in the severe weather potential statement product. Precipitation is
expected to change to all rain by Thursday afternoon as it warms
above freezing. Precipitation should change back to snow Thursday night in
the wake of the cold front before ending by Friday morning.

For Friday into Friday night...high pressure will once again build
into the region. Temperatures will cool back down to below seasonal

Long range models disagree on how shortwave energy from the northern branch of
the jet stream will either phase or not phase with southern stream shortwave
energy. As a result...have gone with wpc forecast which is an
ensemble mean of solutions. This brings a cold front through the
region Saturday night into Sunday with a chance of snow. Colder
air...of the Arctic variety...should push into the region Sunday
into Monday.


Aviation /21z Monday through Saturday/...
pronounced dry punch in the lower levels is digging into western
Ohio this afternoon and will likely keep lower MVFR cloud deck out
of western taf sites. There appears to be a slight westward
backbuilding in north central Ohio that will keep the low stratus
deck over central Ohio with a brief break expected later this
afternoon and early evening. Stratus will build back in overnight
in central Ohio but the northerly flow originating from Michigan
should keep western taf sites away from low stratus ceilings tonight.

Upper level cloud cover will stream over the region on north-
northwest winds...but a break should be in the offing at the end
of the valid taf period as the stacked low over the East Coast
wraps around some drier air in the Ohio Valley from the upper
levels of the atmosphere.

Visibilities should be VFR through the period.

Outlook...MVFR ceilings and visibilities possible Thursday.


Iln watches/warnings/advisories...


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

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