Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
626 am EST Wednesday Dec 11 2013
a cold front will cross the Ohio Valley today and produce
scattered snow showers as it moves east. High pressure building in
the Midwest will exert northwest winds over the region and usher
in the coldest air of the season. The high will slide south of the
Ohio Valley on Thursday and flow will turn back to the southwest.
This will allow moist and warmer air into the region ahead of the
next system that is expected to bring the next wintery mix early
Near term /until 6 PM this evening/...
shortwave moving through the lower Great Lakes region will be at
its apex in Northwest Ohio this evening...and mark the tail end of
any snow showers that are occurring with the surface cold
front/wind shift late today. With the cold airmass...any source of
lift and moisture will eke out some scattered snow showers and
flurries. These showers may drop a quick half inch to inch of
snow this afternoon and early evening...primarily north of the
I-70 corridor. High temperature forecast today stands a chance of
being too warm with the expected frontal passage and cloud cover.
Short term /6 PM this evening through Friday/...
dry air infiltrating the Ohio Valley on northwest winds behind the
front will mark and end to any lingering snow showers and flurries
this evening. Axis of the ridge of the high will be over the
region at 12z Thursday and bring another morning of single digit
low temperatures to the area...even slightly cooler than this mornings
Flow is weak and turns southwest as the high settles over Kentucky/Tennessee
Thursday and works to the middle Atlantic by daybreak Friday. This weak
southwest flow will hold off on runaway cold temperatures but
still allow lower teens to prevail over the region Friday morning.
Weak southwest flow at the surface combined with zonal flow aloft
will prime the region with moisture. This will occur ahead of the
next inverted trough of low pressure that is slated to wring out
this moisture as early as late Friday night...more so on Saturday.
Temperature forecast aloft and thicknesses are still in question
with this system...but another wintery mix appears to be in the
offing for the region. Southern County Warning Area will stand the best chance of
being plain rain overnight Friday. North of the Ohio River will
see a rain/snow mix and the I-70 corridor will be primarily snow.
Long term /Friday night through Tuesday/...
a middle level short wave moving out of The Rockies Friday night will
combine with a stronger southern stream system lifting out of the
Gulf states Saturday into Saturday night. This will make for a
complicated forecast across our area as there is some uncertainty as
to exactly how these two systems will phase together. Both the 12z
GFS and 12z European model (ecmwf) are suggesting a developing surface low/wave will
lift up into the middle Ohio Valley Saturday before better energy
begins to Transfer off to the East Coast Saturday night into Sunday.
In a developing warm air advection ahead of this...expect precipitation to develop/spread
into the region Friday night and then continue through the day on
Saturday. How much warm air is pulled up ahead of this and the exact
track/placement of the surface wave will ultimately dictate the
precipitation type. Right now it does appear that we will warm up
enough in the lower levels to allow for at least a mix across about
the southeast half of our forecast area on Saturday...possibly going over to
all rain across our far south/southeast. Across our
northwest...there is a better chance of precipitation remaining primarily
snow and if this is the case...some accumulations will be possible
through Saturday. In warm air advection pattern do not expect temperatures to drop off all
that much Friday night...and then they should work up above freezing
across at least the southeast half of our forecast area on Saturday.
Precipitation will continue into Saturday evening before tapering off from
the west overnight. Good cold air advection will develop on the backside of the
system and with some lingering low level moisture...expect scattered
snow showers on Sunday...especially across our northern areas. Highs
on Saturday will be in the middle to upper 20s and only the low to middle
20s for Monday. It also looks like we could get into a fetch off of
Lake Michigan which would possibly linger a few snow showers across
parts of our north Sunday night into Monday. The 12z European model (ecmwf) is
stronger and a little faster than the the 12z GFS with the short
wave dropping down across the northern plains on Tuesday. Will go
ahead and bring some slight chance probability of precipitation in through the
afternoon...but it looks like the better chance for any precipitation would
be Tuesday night.
Aviation /11z Wednesday through Sunday/...
middle clouds associated with a system in the Great Lakes have
already worked into the tafs this morning. Models drag a cold front
through the tafs this afternoon. Some periods of MVFR ceiling are
possible...but confidence wasnt high enough at this time to go more
than a tempo MVFR ceilings at the northern tafs after 20z. Also only went
with a vicinity shsn at the northern tafs as the best chances of snow should
be a little further north.
Behind the fnt the winds turn northwest again and the models pool some
low level moisture. Kept a tempo MVFR ceiling at the northern tafs until
06z...before going only with scattered clouds as high pressure builds in.
Outlook...MVFR/IFR conditions are possible Friday night into