Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
557 am EST sun Nov 29 2015
high pressure over the southern Great Lakes will lead to a drying
trend across the Ohio Valley today into tonight. A chance of
showers will then return for Monday into Tuesday as a cold front
pushes east through the region.
Near term /until 6 PM this evening/...
areas of rain have actually been filling in over the last few
hours from central Indiana up into west central Ohio. This is in
addition to the more widespread precipitation that has been persisting
elsewhere across southern portions of our forecast area this morning. This
precipitation is associated primarily with some isentropic lift...although
it does appear that some of the precipitation that has filled in across
our far north may be more associated with a weak deformation axis.
At any rate...isentropic downglide is forecast to develop north
to south across our area later this morning and into early afternoon
and this should allow for the precipitation to finally taper off across our
area. Temperatures will remain on the cool side today...with highs
in the 40s.
Short term /6 PM this evening through Tuesday/...
weak surface high pressure will try to build down from the north
tonight and this could allow for at least some partial clearing
across parts of our far north. Meanwhile...any precipitation associated
with the stalled out boundary across the Tennessee Valley should
mainly remain to our south...but will hang on to some slight
chance probability of precipitation across our far southern tier to cover the lower end
Low level flow will swing back around to the south during the day
on Monday and this will lead to developing isentropic lift across
the area. There are some model differences with the timing
and placement of the better isentropic lift though...so will keep
probability of precipitation in the chance category through the day. A better chance of
showers will then develop Monday night into Tuesday morning as a
cold front pushes east across the area. Increasing southerly flow
ahead of this front will lead to a bit of warmup for Monday with
highs ranging from the middle 40s north to lower 50s south. Temperatures
will then likely not drop off all that much Monday night with
early highs on Tuesday ahead of the front in the middle to upper 50s.
Long term /Tuesday night through Saturday/...
colder air will work for Tuesday night dropping temperatures back
into the 30s. On Wednesday as 500 mb low pushes east across the Great
Lakes...cold air advection and wrap around precipitation will work into the forecast area. Once again
the GFS is a little stronger with the 500 mb low and more developed
with the wrap around. Actually prefer this solution for Wednesday.
Critical thicknesses will be low enough for some rain/snow mix
Wednesday morning. Highs will be more seasonal on
Wednesday...randing in the 40s.
Large surface high pressure then takes control for the rest of the
forecast period. A warming trend will occur for the later half of
the week...with highs in the upper 40s to lower 50s
Thursday into Saturday.
Aviation /12z Sunday through Thursday/...
slightly drier low level air has started to work into the northern
terminals this morning allowing IFR ceilings to lift to MVFR. Across
the southern terminals light rain and IFR ceilings remain. Rap low
level relative humidity fields show this drier air slowly moving south through
the day allowing most sites to go VFR by later this afternoon.
Rain across the southern taf sites should also be coming to an end
early this morning as upglide transitions to downglide.
This evening forecast soundings show moist low level air quickly
starting to make a return for the southern terminals as a
stationary front to the south begins to wash out. The NAM is also
hinting at the potential for some fog development. Given the
widespread cloud cover have decided to not mention fog at this
time (gfs does not show this). At the end of the taf period high
res models are then split on whether or not rain will move back
north Monday morning. At this time confidence is low as there is a
general split between holding the rain off until later Monday and
bringing an initial band across the area Monday morning. For now
have leaned towards the drier solution.
Outlook...IFR ceilings and MVFR visibilities are likely Monday
night into Tuesday. MVFR ceilings and visibilities are possible
again Wednesday afternoon into Thursday morning.