Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
659 am EST Thursday Dec 18 2014
a weakening upper level disturbance moving through the Ohio Valley
will lead to a few snow flurries this afternoon into this evening.
Weak surface high pressure will then push slowly east across the
region through the weekend...leading to primarily dry conditions
and near normal temperatures.
Near term /until 6 PM this evening/...
plenty of low clouds remain in place across the area early this
morning...although we are seeing perhaps a bit of erosion in these just
off to our southwest. This is in the area of some advancing middle
level moisture that will work east across our area later this
morning and into this afternoon in association with a weakening
middle level short wave. As a result...would expect any dissipation
in the lower level clouds to be overcome by the middle level
clouds...resulting in cloudy skies through the day. Models are
suggesting some weak lift at and above 700 mb developing through
early afternoon and expect this to result in some flurry or
possibly even some snow shower activity this afternoon. There is
actually a period from about 18z to 21z this afternoon where the
dendritic growth zone is maximized in the area of best lift
across parts of our southern forecast area. However...given that the moisture
is pretty limited and rather dry between about 950 mb and 700
mb...will continue with just a chance of flurries this afternoon.
Given the combination of the clouds and mainly neutral low level
temperature advection through the day...only expect a few degree
bump up in temperatures through this afternoon with highs
generally in the low to possibly middle 30s.
Short term /6 PM this evening through Saturday/...
we could see a few flurries linger into this evening...but for the
most part expect dry conditions tonight through Friday as a weak
area of high pressure builds across the Great Lakes region. The
models continue to trend farther south with the low pressure
system moving through the southeastern United States Friday night
into Saturday. With the better forcing generally remaining to our
southeast...will trim back probability of precipitation and just allow for a token slight
chance into our far southeast through the day on Saturday. With
this farther south solution...we would be cold enough for any precipitation
to be all snow. Fairly seasonable temperatures are expected through the
end of the week...with highs both Friday and Saturday in the middle to
Long term /Saturday night through Wednesday/...
high pressure and a cool airmass should allow dry weather on
Sunday. Light precipitation will be possible Monday extending from a
trough along the East Coast.
We may begin to feel the effects of a powerful low pressure system
on Tuesday. Have less than average amount of confidence due to model
differences from run to run. At this point it appears the low will
develop over the Southern Plains on Tuesday...before lifting through
Ohio to the Great Lakes on Wednesday. The low may feature a very
tight pressure gradient surrounding its deep center...producing
strong winds. Copious moisture feeding from the tropics and from the
Atlantic Ocean could advect around the low. Current temperature
forecast allows rain Tuesday into Wednesday...changing to snow later
Wednesday as colder air wraps in behind the low.
Temperatures will be relatively close to normal for the most part.
Highs will be a couple degrees warmer for Sunday and Monday under
neutral to weak warm advection. Readings on Tuesday and Wednesday
will be dependent on the position of the anticipated strong low.
Warm advection ahead of the low could bring highs up into the middle
40s on Tuesday...or even higher if the warmer mex guidance
verifies. Highs could slip to around 40 on Wednesday in cold
advection behind the low.
Aviation /12z Thursday through Monday/...
a persistent MVFR cloud deck is likely to remain in place across
the taf sites into the afternoon. At that time the deck should
break...becoming VFR....as a weak upper level system approaches
the area with its associated middle and high clouds. After this there
continues to be major disagreement in the numerical guidance. Several
models bring MVFR ceilings back into the area this evening while
others continue with a deck of VFR ceilings between fl050 and 070. Have
chosen to go with the rap solution which seems to have
somewhat...although not perfect handle on the situation. While
moisture with this next system will be lacking in terms of
precipitation...flurries are expected this afternoon and evening. Since no
visibility restrictions are expected and the timing during this period
will be variable have not included this mention in the forecast.
West winds of under 10 knots are expected through the forecast period.
Outlook...MVFR ceilings may continue into Friday. MVFR ceilings
and visibilities are possible on Saturday.