Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
629 PM EST Thursday Nov 27 2014
a weak Alberta clipper storm system will move east away from the
area this evening. The low will drag a cold front through the area
this afternoon and a trough of low pressure this evening. Colder air
will follow the front and the trough will bring another round of
snow to the region. High pressure will build east across the Ohio
Valley Friday and to the East Coast on Saturday. A warm front will
lift northeast across the area Saturday as a low pressure system
moves northeast across Lake Superior. A cold front will move east
across the area Sunday night.
Near term /until 6 am Friday morning/...
no major changes to forecast. Bumped up probability of precipitation to likely or
categorical over most of east as it is snow over most of eastern
County Warning Area. Snowfall amounts look reasonable.
Alberta clipper will slide east of the area dragging the cold front
south followed by a surface trough this evening. The trough in
association with some fairly strong positive vorticity advection
will cause some snow to develop over the area. Lake enhancement will
take place over northeast Ohio and northwest Pennsylvania as wind
flow becomes oriented around 320 degrees. The flow gradually shifts
overnight into tomorrow morning to a 270 degree direction.
Cold air will take place behind the cold front tonight helping to
support the lake effect snow showers overnight. Right now I am
thinking a snow accumulation of 1 to 3 inches in the snowbelt areas
and an inch or less elsewhere. As trough pulls out to the
East...Lake effect will be the primary source of precipitation
overnight into tomorrow. Otherwise...mainly cloudy to mostly cloudy
skies can be expected overnight. Drier air will push into Northwest
Ohio by morning and it is possible that they could go partly cloudy
before day break.
Cold air advection takes place overnight behind the cold front and
expecting temperatures to drop into the lower 20s near the lake and
upper teens elsewhere. Air mass to the northwest of the area gave
overnight lows down around zero in some places.
Short term /6 am Friday morning through Sunday night/...
upper level pattern trending toward a more zonal flow at this time
going into the weekend. A weak very broad upper level ridge builds
in over the region Saturday. At this time...another trough will
begin to dig in over the Canadian prairies by Sunday and head our
way for early next week.
In the mean time...drier air pushes into the forecast area as high
pressure builds east. This should begin to turn the flow to a
westerly and then southwesterly direction on Friday. The change in
the air flow will also gradually cut off the lake effect snow to the
northeast. Overall totals could reach 6 inches in the higher
elevations of Erie and Crawford counties in Pennsylvania by the time
this snow event is done. The snow accumulations will be drawn out
over a long period and will have a minimal impact.
The high will shift east to the eastern Seaboard by Saturday morning
but a warm front will lift northeast across the region. The warm air
advection with the front will initially start out the precipitation
as some light snow Saturday morning and then transition over to
showers. Will keep a mention of a chance of showers in the warm
sector on Saturday but I anticipate much of the day should remain
Cold front lumbers its way southeast toward the region and arrives
Sunday evening into the forecast area. Expecting showers to develop
along the cold front through Sunday night. Weak waves of low
pressure will move northeast along the frontal boundary as well.
Warm air advection will take place in earnest on Saturday and
continue through Sunday in the warm sector. Should start to see some
cold air advection take place Sunday night with the passage of the
Long term /Monday through Thursday/...
still some question on the speed of the cold front early in the
week. The GFS remains the fastest...zipping the front through the
area Sunday night. The European model (ecmwf) and the Gem have slowed and do not
bring the front through until early Monday. This seems a bit slow
given the lack of a big trough or wave on the front but will
compromise for the Monday forecast. Will keep a chance of showers I
the forecast Monday morning. It will probably stay warm enough for
the majority of the precipitation to be rain but some wet snow is
possible across Northwest Ohio by Monday morning.
Canadian high pressure will slide by to the north on Tuesday. The
models have been trending colder with the Monday night and Tuesday
forecast and will nudge forecast temperatures down a degree or two. I will
hold off the warm advection precipitation until Tuesday night to stay
consistent with the current forecast. The European model (ecmwf) is faster and
farther south with the next cold front on Wednesday while the GFS
just wants to give a glancing blow. Do not want to to be too slow
given the rather zonal pattern but also do not want to be too cold.
Will stay closer to the current forecast with temperatures near
normal middle week.
Aviation /00z Friday through Tuesday/...
trough/secondary cold front dropping across the area through the
evening hours depicted by west winds turning northwest. Trough is
near a ktol-kdfi line at 23z and will exit east by 06z. Expecting
snow showers and MVFR conditions across the area through the
evening hours with improvement from the west after 04z-06z.
Concerned however for kfdy where snow showers off Lake Michigan
could hold MVFR conditions in past 06z. Elsewhere lake effect off
of Lake Erie will continue to affect kcle Keri kyng and kcak
through the evening and early overnight although with changeable
winds bands should be disrupted from time to time. After about 08z
drier air begins to move in which should cause bands to
weaken/dissipate. Mainly VFR Friday.
Outlook...non-VFR possible Friday night into Saturday NE Ohio/northwest
PA. Non-VFR developing again Sunday continuing into Monday with
-shra with the next front.
the Small Craft Advisory will be in effect tonight into Friday. It
may be able to be cancelled early on Friday especially the western
basin...as the surface high should build in quickly. The winds will
come around from the south on Friday as the ridge moves east. The
south flow will increase over the weekend ahead of the next cold
front. We may be able to get away without having a Small Craft
Advisory since the larger waves and wind will be out on the Open
Lake and the Canadian side. The front should drop across the lake
Sunday night and winds will come around from the northwest on Monday
at which point the Small Craft Advisory will likely be needed
Marine...Small Craft Advisory until 10 am EST Friday for lez142>149.