Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
720 PM EST Thursday Nov 20 2014
low pressure over southern Quebec will move east tonight but leave
a trough of low pressure extending southwest across the central
Great Lakes. High pressure will build across the Ohio Valley on
Friday. Sunday the high will move off the middle Atlantic coast
allowing deep low pressure to move into the Great Lakes region.
Near term /through tonight/...
Current forecast appears on track.
From 22z to 00z the lake snow bands and boundary layer flow
across Lake Erie has begun to veer which has allowed the snow
bands to come ashore over northwest PA and the snow belt NE of cle with
light accumulation thus far. Les cloud top temperatures have
cooled about 5c in places which somewhat corresponds with radar
reflectivity in the 30-35 dbz range. With sunset the boundary
layer will become more stable and should allow the snow bands to
become more uniform. Kcle radar hourly snow accumulation intensity
has gradually increased this evening with the region from Southern
Lake County into Ashtabula having rates of 0.75 to 1.25 inches per
hour. These rates will likely continue for the next few hours.
Acars soundings near cle show the inversion
height from 6500 to 7000 feet while the 00z DTX sounding has the
upstream inversion height near 7300 feet. This inversion height
should allow for moderate to heavy snow showers to persist for the
next few hours. For now we will not alter the snow accumulation
will continue winter weather headlines as they are. Forecast
still on track with radar showing increasing activity on the lake
in response to short wave energy moving toward the area from
Michigan...with the start of the bands now in vicinity of the islands.
Winds have backed just a bit through the late morning and early
afternoon as previously thought would happen. BUFKIT forecast
soundings however continue to show winds veering through the
evening which will bring snow onshore. Concern for the overnight
is that while the hrrr brings the band onshore the intensity also
decreases before new bands set up in more of a northwest flow.
Local models however develop more lift/radar return resulting in
better snow totals. Believe that with moderate to extreme
instability...low level lift and favorable snow growth
temperatures within the moist air...snow in the northwest bands
outcome will better resemble local model forecast. Outside of lake
effect not much more that flurries or light snow showers early.
Thinking that much of the cloud cover which developed with
afternoon heating will decrease through the evening and overnight.
Short term /Friday night through Sunday night/...
forecast begins with snow ongoing across northwestern PA and northestern Ohio
although dry air will be moving in fast to believe snow will be
coming to an end rather quickly from the west. End time of the
advisory still looks fine at 10am. Flow remains off the lake northwestern
PA but low level winds back and warm advection moves in at least
to the generation area of the bands so snow should taper/end
either late morning or early afternoon. High pressure over the
area Friday will move east Friday night bringing warm air Friday
night through Saturday. Models bring overrunning moisture north
across the Mississippi Valley into western Ohio late Friday night
and Saturday. Expect Friday night lows to be early with temperatures
rising overnight from the west. Main concern will be ptype as the
precipitation gets into the area either late Friday night or Saturday
morning. For now it looks as if there is a reasonable chance of
precipitation in the west before dawn. Temperatures also appear that they will
not move above freezing until 8-10am so put a chance of rain and
freezing rain in the forecast west. The rest of the weekend looks
mild to seasonal temperature wise with high chance to likely probability of precipitation.
Long term /Monday through Thursday/...
a cold front crossing the area and strong upper dynamics will
combine for a good chance for rain showers on Monday so will carry likely probability of precipitation.
Some drying will follow the front that should produce a lull in the
precipitation as temperatures turn colder and any precipitation that does occur changes
to snow Monday night into Tuesday. The models show wrap moisture working southeast
back into the area Tuesday with an upper short wave. Should see shsn in the
snowbelt with a chance for lighter shsn or flurries elsewhere.
The models start to differ some Wednesday into Thursday but in general there
should be a another short wave digging into the main upper trough that
induces a low to move out of the plains into the region by Thursday or
Thursday night. Will keep at least a small chance of pop in the forecast
through Thursday with emphasis on the snowbelt. Temperatures will be below normal
and kept cold enough for just snow as the precipitation type.
Aviation /00z Friday through Tuesday/...
a weak trough will drop southeast into the area this evening. This should
cause the lake effect shsn affecting eri to drop southeast which may lead
to some improvement later into the night at eri but will cause the
shsn to start to affect cle and yng and possibly even some light
shsn or flurries all the way south into cak. As usual with the
shsn...conditions can waver from VFR/MVFR to low IFR in short
distances and in short periods of time.
Winds gusting 25 to 30 knots will diminish early tonight for all but
eri where gusts of 20 to 25 knots may continue into Friday morning. The
higher wind gust will lead to some blowing and drifting of the snow.
Conditions should start to improve from west to east midday Friday as
drier air moves in from the west.
Outlook...non VFR conditions in lake effect snow in the snowbelt
will end west to east Friday afternoon into early Friday night. Areas of
non VFR should return Sat night and continue most of the time sun
winds will start to diminish tonight and diminish a little more on
Friday before backing to SW fro Friday night. Small Craft Advisory conditions and low water
problems should end on the west end of the lake late tonight into
Friday morning and the Small Craft Advisory may finally be allowed to end Friday evening on
the East Part of the lake. The winds may keep enough of a southerly
direction to keep 4 foot waves well offshore through sun but winds may
get into a 15 to 25 knot range anyway to require Small Craft Advisory advisories.
In any case...a fairly strong low moves NE across the upper lakes
Sun night and Monday pulling a cold front east across Lake Erie Monday.
Expect winds of at least 15 to 25 knots by Monday that turn more toward
the west behind the front for Monday night and Tuesday. This will allow
waves greater than 4 foot to get back into the nearshore waters so a
Small Craft Advisory looks almost definite for then.
Ohio...Lake effect Snow Advisory until 10 am EST Friday for ohz012-
Lake effect snow warning until 3 PM EST Friday for ohz014-089.
PA...lake effect snow warning until 3 PM EST Friday for paz001>003.
Marine...low water advisory until 4 am EST Friday for lez142>144-
Small Craft Advisory until 10 PM EST Friday for lez147>149.
Small Craft Advisory until 4 am EST Friday for lez142>144.
Small Craft Advisory until 10 am EST Friday for lez145-146.