Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wilmington Ohio
411 PM EST Thursday Jan 29 2015
scattered snow showers will be possible tonight as an Arctic cold
front moves through the area. A cold high pressure system will
slide east across the area Friday into Saturday. Accumulating snow
is expected to develop Saturday night and continue into Sunday as
a low pressure system moves through the Tennessee Valley.
Near term /until 6 am Friday morning/...
the cold front is currently pushing across eastern portions of our
forecast area and should be east of the area within the next hour or so.
In developing cold air advection behind the front...lower stratus is overspreading our
area along with some scattered rain showers and drizzle. Forecast
soundings are keeping US nearly saturated below 2 km through 00z
before partially drying out the boundary layer from the northwest
overnight. The top of the saturated layer remains right around -10
celsius through at least early evening so think we will continue
to see a mix of drizzle and showers as we head into this evening.
With colder air moving in from the northwest...expect rain
showers to mix with/change to snow showers and we could even end
up with a period of freezing drizzle.
As we progress through the night...we start to get into a fetch
off of Lake Michigan as a secondary middle level short wave and
an associated cold front drops down through the area. The btv snow
squall parameter off the NAM is indicating some increasing
instability working down northwest to southeast across our area in
the 06 to 12z time frame and this coincides with a favorable pv
anomaly. As a result...think we will see an uptick in scattered
snow shower activity later tonight...with the highest probability
running from our northwest through our southeast. Will allow for
some light snow accumulations...generally less than a half an
Short term /6 am Friday morning through Saturday night/...
any lingering snow shower activity should taper off through Friday
morning as short wave energy moves off to the southeast. Good cold air advection
will continue at least through Friday morning and do not expect
much of a rise in temperatures through the day with highs ranging
from near 20 in the north to around 30 in the south. Surface high
pressure will begin to build in from the west Friday night and
slide east across the area through the day on Saturday. As we get
into some return flow through the day on Saturday...highs will
bump up into the upper 20s to middle 30s for highs. Isentropic lift
will increase from the west Saturday night ahead of a developing
low pressure system. This will allow for snow to develop from west
to east through the night.
Long term /Sunday through Thursday/...
focus in the immediate long term will be on the low pressure system
moving through the Tennessee Valley on Sunday...then east toward the
middle Atlantic region Sunday night. Meanwhile...an Arctic front will
be pushing southward through the region. Isentropic lift and
frontogenesis will bring categorical probability of precipitation to the region Sunday. This
will result in mainly snow north of the Ohio River with snow mixing
with rain along and south of the Ohio River as temperatures creep
above freezing here. This system has the potential to be a decent
snow producer...especially where it stays all snow. We will have to
watch in later forecast model runs whether the low becomes
stronger...moves farther north...or maintains a more east to west
track. This will have an effect as to how far north the rain/snow
mixture may move which will cut into snowfall amounts. In either
case...once colder air moves in on the back side of the low...all
locations will see some snow accumulation. Based on current model
consensus...the potential exists for a 6"+ snowfall event north of
the Ohio River with lesser amounts south (4 inches or less as a
first forecast amount). Precipitation will be tapering off Sunday night into
Monday morning as the system moves off to the east. Will continue to
highlight this winter weather threat in the severe weather potential statement product.
For Monday into Monday night...Arctic high pressure will traverse
the region. Temperatures will not warm that much from Monday morning
lows...ranging from the lower teens north to near 20 south.
Temperatures will drop Monday night as skies become mostly clear
early...followed by some increasing clouds from the west overnight.
Some locations will go below zero with single digits along and south
of the Ohio River. Winds will increase and some wind chill values
will likely drop into the 10 below to 20 below zero range in the
For the remainder of the extended...the GFS and European model (ecmwf) are fairly
similar with synoptic systems except for Tuesday where the GFS tries
to spread isentropically driven precipitation into the region. Have gone with
the dry European model (ecmwf) solution. Another Arctic front is expected to arrive
by middle week. Some warming will occur ahead of the front with
temperatures returning to cold values behind it. There will be a
chance of rain/snow Tuesday night into Wednesday with a return to
dry weather and Arctic high pressure by Thursday.
Aviation /20z Thursday through Tuesday/...
middle level short wave trough to move through the Great Lakes today/tonight. Associated
surface low over lower Michigan to lift NE with southward trailing cold front
over Indiana sweeping east through the taf sites this afternoon. MVFR ceilings will
develop with this frontal passage of this front. The development
of a few showers will also be possible. Due to lack of widespread coverage
have limited mention to vcsh. Have ceilings drop to IFR for a period late
this afternoon at kday. Expect MVFR ceilings through the night with a few snow
showers possible off Lake Michigan. These snow showers could
affect the western taf sites but due to limited coverage have
omitted the mention at this time. Ceilings to improve to VFR by Friday
afternoon as surface high pressure builds in.
Southwest winds will gust up to 28kts and veer to the west this
afternoon. These west winds will continue to gust up to 24 kts and veer
Outlook...IFR ceilings and visibilities likely Sunday into Sunday
night with MVFR conditions possibly continuing into Monday.