Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
940 am EST Sat Jan 31 2015
high pressure will move east today allowing low pressure to move
toward the region from the plains. This low will track along the
Ohio River valley Sunday night into Monday morning. Arctic high
pressure will return by Monday night.
Near term /until 6 PM this evening/...
cloudy in the east with warm air advection...should begin to scatter some this
afternoon. That said tweaked cloud cover. Temperatures look reasonable.
Warm advection is generating a bit more lift than anticipated and
has produced cloud cover. Have increased the cloud cover for
today. Since there will be less sunshine than expected earlier
this morning we will have to rely on warm advection to boost
temperatures. Had already gone on the cooler side of guidance so
will not adjust highs downward at this point.
today will be the lull before the storm as high pressure slowly
shifts to the east through the day. The high should reach the
middle Atlantic coast by this evening which will allow the plains
low to move closer.
We are slightly concerned that some weak convergence will persist
on the north side of the high pressure today. This area of
convergence would be located over the eastern third of Lake Erie
and clip portions of northwest PA. At this point any snow that develops
will be light and should not be anything more than flurries.
The region will have a cool start to the day with much of the
region in the single digits. A few locations will start out below
zero. Increased warm advection should nudge highs into the
20s...maybe even touch 30 degrees across the southwest County
Short term /6 PM this evening through Monday night/...
low pressure will move toward the area through the night and will
track along the Ohio River valley Sunday night. We have been
monitoring the path of the 800 mb low in each model run. Its track
will dictate where the heaviest snowfall occurs. For this forecast
we have leaned toward a European model (ecmwf)/GFS blend which takes the 800 mb low
from about Marion Sunday evening eastward to the Youngstown area
by early Monday morning. The heaviest swath of snow will likely
develop near and to the north of this track Sunday afternoon into
the evening. Later shifts will need to monitor where the best
frontogenetic forcing develops. However the latest indications
place it from Findlay to near Cleveland. Just keep in mind that
the location for the heavy snow will likely wobble around over the
next 24 hours and may not become evident until the heavy snow has
begun Sunday afternoon. In any event the accumulating snow across
the region will start after midnight tonight and continue into
Monday morning. The snow will taper off from west to east on
Monday. There is some concern that slightly warmer air will move
into the area south of the 800 mb low which will impact amounts. This
is the reason why the latest snow total graphics have lower
amounts across the south.
We did take a quick look at the cips data from St Louis University
which looks at the current weather pattern and gives output from
events of the past. It indicates that much of the area should see
4 or more inches with a swath of 6 to 8 inches common. While there
have been cases where around a foot of snow has occurred in this
pattern it is only indicating that this occurs 20 or so percent of
the time. So it should be difficult to get more than isolated
locations of around a foot.
So with all this said we will hold off on upgrading the watch at
this point. Still enough uncertainty in the track.
Highs on Sunday will range from the middle 20s north to the lower
30s south. The track of the low will have impacts on where to
place this gradient in temperatures. Arctic air will spill into
the region Sunday night into Monday with highs back into the teens
for highs on Monday. Gusty winds on the back side of the low will
cause wind chills to dip to 10 degrees below zero or colder late
Sunday night into Monday morning. Have added this mention into the
Winter Storm Watch.
If skies can clear Monday night lows will be able to dip below
zero for a large portion of the region.
Long term /Tuesday through Friday/...
a flattened ridge maintains itself across the West Coast while
disturbances from the northern Pacific and western Canada contribute
to a general broad trough for east of The Rockies through the end of
the week. This keeps US on the cool side...with a temporary surge of
colder air behind low pressure that tracks across the central Great
Lakes on Wednesday. This system brings the chances for snow to the
area for Wednesday and Wednesday night. High pressure follows in its
wake. Have lingered some snow shower chances into Thursday...but
position of the high will determine if the flow is more northerly or
west-northwesterly. 800 mb temperatures dip to colder than -14c...with
differences on how cold yet amongst the various models. Limited lake
influence with the ice coverage...but still could perpetuate
flurries/light snow showers. High pressure overhead Thursday night
and area could see sub-zero lows again. Thermal trough shifts east
and a slight warmup is forecast toward the weekend.
Aviation /12z Saturday through Wednesday/...
a VFR day today with a light south-southwest wind under 12kts as high pressure
shifts east. Conditions deteriorate rapidly later tonight as low
pressure from the plains merges with a cold front dropping south
across the Great Lakes. Snow will be on the radar for tol/fdy near
midnight spreading east through 12z Monday. It is very possible that
conditions will drop like a rock to IFR as soon as or very soon
after the snow starts. Winds to start will be light.
Outlook...non VFR conditions will occur Sunday into Monday in
snow. Snow may be heavy at times on Sunday afternoon and evening
across all of taf sites. Significant accumulations are possible.
Non VFR possible again Tuesday night into Wednesday.
light southwest flow will come around to the north-northeast by
Sunday morning as a cold front drops south across the Great Lakes.
Low pressure is expected to deepen as it crosses west to east across
the Ohio Valley. The northeast winds on Lake Erie will increase with
a tightening gradient by Sunday afternoon and may reach gale force
Sunday night as the low moves across southeast Ohio. On Monday winds
will veer from the north to the northwest while diminishing. The
winds Sunday night/early Monday morning will have the potential to
close shipping lanes and make for difficult navigation. Pressuring
and ridging will also be possible. Significant snow is also forecast
with this system. High pressure follows for Monday/Tuesday. The next
system on the horizon arrives middle week as low pressure moving
east-northeast across the Central Lakes and bringing a cold front
across Lake Erie Wednesday.
Ohio...Winter Storm Watch from late tonight through Monday morning
Winter Storm Watch from late tonight through Monday morning
PA...Winter Storm Watch from late tonight through Monday morning