Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
629 am EST Friday Nov 28 2014
high pressure over the Ohio Valley will move east of the region
late in the day. The high will continue east tonight into
Saturday. Southerly flow on the back side of the high will allow
for a warm up over the weekend. Also...increasing low level
moisture out of the Gulf will bring cloudy skies and the likelihood
for light rain Saturday night into Sunday. For Sunday night into
Monday...a cold front will slowly move southeast through the region.
Colder air will filter back into the area behind this front.
Near term /until 6 PM this evening/...
surface high pressure will build into the Ohio Valley this
morning...then it will begin to move east of the area this
afternoon. Despite the high...low level moisture in association
with the departing cold pool of air aloft will bring a few
flurries to the area during the morning hours. Not much break in
the cloud cover is expected as warm air advection will be on the heals of the
departing cold pool with middle clouds spilling into the region.
Temperatures will remain cold today with highs ranging from the
lower to middle 30s.
Short term /6 PM this evening through Monday night/...
upper level flow will transition over to a more zonal configuration
tonight and Saturday. A weak disturbance rippling southeast
within this flow tonight should remain to our north and east along
with its associated precipitation. Otherwise...skies will range from partly
to mostly cloudy. With southerly flow increasing overnight...we
should see temperatures bottom out early...then become steady or
show a slight rise toward morning. On Saturday...models continue
to advertise that a moist low level flow will develop out of the
Gulf and will pivot northeast into our region. This will allow
clouds of the lower variety to increase quite rapidly through the
day. The moisture is shallow...and with some weak lift...some
light rain or light drizzle may develop toward evening. On
increasing southerly flow...highs on Saturday will range from the
middle 40s north to around 50 south.
For Saturday night into Sunday...again...a decent moist...low
level flow will continue to feed northeast into the Ohio Valley
from the Gulf. Models have been advertising that with the warm air advection/low
level lift...precipitation will increase in coverage but will be on the
light side due to the lack of deep moisture. In fact...model
soundings indicate that the moisture will be mainly 850 mb and
lower. Despite this...believe that the airmass will become
saturated...and despite shallow moisture...there will be enough
lift to generate light precipitation. As a result...have gone with likely
probability of precipitation as models suggest the precipitation will measure. Have used a rarity
in the public zones which is to qualify the rain as light instead
of wording it as just rain. Another thing to consider during this
period is the chance for visibilities to lower despite stiff south
winds. Sref probabilities indicate visibilities may drop to less
than 1 mile...and this could conceivably happen with low ceilings
and persistent light precipitation. Will continue to monitor and add
mist/fog should it become necessary. Lows Saturday night will drop
slightly in the evening then slowly rise overnight. Highs on
Sunday will be mild despite overcast skies and light precipitation. Highs
will range from the upper 50s to near 60.
For Sunday night into Monday...there are some minor timing
differences amongst the models in regards to a cold front that
will drop southeast and slowly move through the region. Have taken
a blend of the 00z European model (ecmwf) (slightly slower) and the 00z GFS
(slightly faster) as a solution. Front will be slowly pushed
southeast by a middle level trough traversing the Great Lakes into
New England. Increasing frontal convergence and a little more
deeper moisture will bring higher chances for precipitation to the region.
Colder air will filter into the region behind the front late
Sunday night and continuing into Monday. It looks like there
could be a brief period of rain and now mixed before drier air
pushes into the area. Right now...am not expecting much in the
way of accumulations. Temperatures during the period will be non
By Monday night...the front will sag south of the region while
high pressure passes across the Great Lakes. Precipitation will come to an
end and skies will become mostly clear. Temperatures will fall
into the lower and middle 20s by Tuesday morning.
Long term /Tuesday through Thursday/...
there are quite a few model differences for the Tuesday through
Thursday time period. Models continue to agree to disagree for
this time period. Continued forecast thinking from yesterday and
went close to the European model (ecmwf) for this time period.
Another disturbance will move through Tuesday into Wednesday. This
system is expected to bring mainly a threat of rain to the area as
temperatures rebound some. High pressure will work into the
region by Wednesday night. Southerly flow begins to develop once
again by Thursday allowing for temperatures on Thursday to be
similar to those on Wednesday.
Aviation /12z Friday through Tuesday/...
although a brief MVFR ceiling will still be possible over the next
couple hours...for the most part the low-level clouds have begun
to break apart...with patches of overcast (generally at 2500-4000
feet) and clear spots in between. A layer of middle-level clouds is
expected to move over the taf sites this morning...with a few
4000-5000 foot clouds still possible through the day. There may be
a chance for some very light snow (or just flurries) at the Dayton
and Columbus taf sites this afternoon...but no impact to aviation
Winds today will shift from west-northwest to south-southwest...increasing to around 10
knots...with perhaps a few gusts slightly higher. South-southwest winds will
begin to increase in strength by early Saturday morning...with
some gusts to near 20 knots possible at the end of the forecast period.
Although clouds should remain in the VFR range today and
tonight...a gradual lowering early Saturday morning will lead to
the possibility of MVFR conditions just beyond the end of the
Outlook...MVFR ceilings are expected to develop from Saturday
through Sunday night...and a period of IFR ceilings and MVFR
visibilities will also be possible on Saturday night and into