Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Wilmington Ohio
1256 am EST Tuesday Jan 27 2015

Synopsis...
surface high pressure will build into the Ohio Valley through the
middle of the week. An area of low pressure and a cold front will
move across the region on Thursday...bringing a chance of mixed
precipitation. Cold high pressure will move in again on Friday.

&&

Near term /until 6 am this morning/...
mostly clear skies across much of the region in combination with
light winds and a fresh snow pack has allowed temperatures to fall
rapidly. Lowered temperatures for a vast majority of the
region...but made the low temperatures a little after
midnight...then with slightly rising temperatures as clouds try
and work back in. Went 0-5 above in west central Ohio and single
digits for the rural areas of central Ohio and over to the Miami
Valley. Locations from Cincinnati southwestward should stay in
the 20s.

Looks like the chance of flurries that is associated with energy
dropping southeast through Indiana and into Kentucky will stay to the SW
of the forecast area...so dropped the mention of them in the tri-state
region.

&&

Short term /6 am this morning through 6 PM Wednesday/...
the short term forecast period should be fairly quiet...with no
chances for precipitation. Temperatures will be the biggest
challenge...with surface high pressure sitting over the Ohio
Valley...and generally weak advection patterns setting up through
Wednesday. With gradually clearing skies...Tuesday may end up a
degree or two warmer than Monday...but there is no reason to
forecast a big swing in temperatures. For Tuesday night...clearing
skies and light winds will set up some very favorable radiational
cooling conditions...and the entire model suite has taken a
downward trend with temperatures. This forecast represents a drop
of several degrees from the previous min temperature grid...but even a
simple GFS/NAM consensus blend would result in cooler
conditions...so this forecast still has room for additional
downward adjustment.

On Wednesday...there are signs that some warm advection could
begin...though mainly just off the surface (at least through the
daytime hours). At 925mb...a ridge axis will have to cross east
through the region...before the low-level flow turns from north-northeast to
south-southwest. Though diurnal temperatures were used in the forecast...it is
possible that maximum temperatures could be slightly later than on a typical
day. With the boundary between snow pack and snow-lack cutting
across the County Warning Area...if any warm advection can combine with the
plentiful insolation on Wednesday...it could have a big impact on
the final numbers. This is a low-confidence temperature
forecast...especially with a fairly tight gradient in the
grids...and a model blend was used to get the numbers into
reasonable position. However...the extremely cold values in the
Canadian model were discarded.

&&

Long term /Wednesday night through Monday/...
for the period Wednesday night into Thursday night...the European model (ecmwf) and
the GFS still differ a bit on the timing of a tandem of S/waves to
affect the region...along with an associated low pressure/cold
front. The European model (ecmwf) is slight slower and little more sharper with the
second shortwave while the GFS is faster. Have continued with the GFS
timing at this time to keep continuity from previous forecast. With
return flow...temperatures will begin to warm some late Wednesday
night into Thursday. There will be a race between how fast it warms
compared to when the onset of precipitation begins. It looks like there will
be a threat for a wintry mix...snow...sleet or freezing rain for
locations along and north of the Ohio River late Wednesday night
into Thursday morning. Best chance will be from east central Indiana
into central Ohio and points north. Minor snow...sleet...or ice
accumulations will be possible given a cold start...any freezing
rain will pose a hazard to travel so we will continue to monitor
this system. Have mentioned the threat in the severe weather potential statement product. Precipitation is
expected to change to all rain by Thursday afternoon as it warms
above freezing. Precipitation should change back to snow Thursday night in
the wake of the cold front before ending by Friday morning.

For Friday into Friday night...high pressure will once again build
into the region. Temperatures will cool back down to below seasonal
normals.

Long range models disagree on how shortwave energy from the northern branch of
the jet stream will either phase or not phase with southern stream shortwave
energy. As a result...have gone with wpc forecast which is an
ensemble mean of solutions. This brings a cold front through the
region Saturday night into Sunday with a chance of snow. Colder
air...of the Arctic variety...should push into the region Sunday
into Monday.

&&

Aviation /06z Tuesday through Saturday/...
Cincinnati terminals will be on the edge of low clouds from the
west and Columbus terminals on the edge of low clouds from the
east to start the taf period. After 12z expect low level moisture
to swing in from the northeast and persist through the day.
However it is not clear whether this will manifest itself as low
clouds. A bit higher confidence of MVFR ceilings during the day in
Columbus. Less so at kday and Kiln. At this point think Cincinnati
will be VFR after 12z. Low level moisture will slowly pull off to
the east late in the taf period which would put an end to any MVFR
ceilings.

Outlook...MVFR ceilings and visibilities along with a period of
freezing rain possible Thursday.

&&

Iln watches/warnings/advisories...
Ohio...none.
Kentucky...none.
In...none.

&&

$$
Synopsis...hatzos/sites
near term...sites
short term...hatzos
long term...Hickman
aviation...

National Weather Service Glossary of Abbreviations