Fri evening, Nov 22, 2013 Area Forecast Discussion

A minor lake effect snow event is forecast in northeast Ohio.

fxus61 kcle 222348
afdcle
area forecast discussion
national weather service cleveland oh
648 pm est fri nov 22 2013

synopsis...
cold front will exit east of the area this evening with a ridge
building in from the west. an arctic cold front will push south
across the area on saturday with lake effect snow developing. strong
high pressure will build east across the ohio valley late sunday.
&&

near term /until 6 am saturday morning/...
update...forecast on track. no significant changes.
original...area radars continue to show a light drizzle across ne
ohio/nw pa late this afternoon. will carry drizzle in the forecast
for a few hours with conditions drying out behind the cold front
this evening.
suface analysis shows one area of low pressure over quebec with a
seondary low developing developing north of lake superior. the first
low will exit to the northeast tonight with a ridge sharply building
into the low levels in advance of the second system. satellite
imagery shows the clearing line moving across western lower michigan
and will push into nw ohio during the evening. skies will clear
except for ne oh/nw pa where enhanced troughing downwind of the lake
will aid lake effect cloud developement. temperatures will fall into
the upper 20s for inland areas...holding near 30 along the lake.
&&

short term /6 am saturday morning through sunday night/...
upper level trough seen on water vapor imagery over canada will
surge south over the great lakes region on saturday...pushing an
arctic cold front south across the area. the 850mb temperature at
churchill manitoba was down to -24c this morning and models are in
agreement that the h850 temperature will drop to near -18c by sunday
morning. the initial frontal passage will lack moisture and will
just carry chance pops for most areas except downwind of lake erie.
those areas will see a quick burst of snow with the front and could
result in up to an inch of snow accumulation over the higher
terrain.
a break is expected before the lake effect snow ramps up during the
evening as the moisture depth increases with the passage of the
upper level trough. the combination of extreme instability over the
lake and upslope northwesterly flow will allow lake effect snow
showers to fill in across the snow belt. the heaviest accumulations
are expected in nw pa where models indicate we will establish a lake
huron connection. snowfall rates beneath this band could be 2 inches
per hour but hard to define exactly where this band will set. it
looks like fairly high chances of it impacting erie and crawford pa.
the airmass is cold enough that not expecting the lake to reduce
accumulations enough to leave the lakeshore areas out.
accumulations in nw pa will exceed 6 inches in many areas but
local amounts could exceed a foot by the time the snow ends if the
band becomes stationary.
have expanded the les watch to include geauga county where the
upslope component will cause enough enhancement for accumulations of
4 to 8 inches. the bulk of this will fall on saturday night with the
passage of the upper level trough. the rest of the snow belt will
see accumulating snow and lake effect snow advisories may be needed
in periphery counties. northwest winds will contribute to blusterly
conditions with speeds of 15 to 25 mph and gusts to 35 mph. the snow
will have a high snow/liquid ratio (15:1 or even 18:1) given the
cold airmass and will blow around easily.
strong high pressure over the midwest will expand over the ohio
valley on sunday and will be accompanied by very dry air. dewpoints
fall into the single digits and teens and snow will decrease in
coverage from west to east as this dry air intrudes. the
complicating factor of this forecast is how long it will take for
snow to decrease...given the limited moisture with the system.
decided to let the watches continue for another forecast package to
allow additional time to consider the moisture quality and placement
of lake effect snow bands before making determination on
warnings/advisories. heavy snow also not expected to develop until
saturday night.
&&

long term /monday through friday/...
very few changes to the long term today as the period looks cold
with occasional snow showers. will try to start the period off dry
on monday. a system will pass to the north on tuesday and drag a
cold front across the region. some warm air advection precip could
occur as early as monday night but better chances for measurable
precip will come with the front. winds will become favorable for
lake effect snow late tuesday through wednesday night. moisture
appears to be somewhat limited as it will be a dry airmass. as a
result...no more than chance pops for the time being. the surface
ridge will move just to east of the area on thursday and then linger
on friday. this will prevent an airmass change. high temps the
entire week will be a good 10 to 15 degrees below normal.
&&

aviation /23z saturday through wednesday/...
difficult forecast for the overnight hours. significant
drying...at least at midlevels will be coming in overnight.
evening nw gusts will subside some and the winds will back more
westerly as temporary ridging nudges toward the area. questions
will be what will happen with the current ifr/mvfr ceilings. most
model guidance wants to clear or scatter that out leaving vfr
conditions for morning. one model...the hrrr would like to
redevelop at least an mvfr ceiling across the west after 09z and
never really get rid of a non-vfr ceiling across the east. have
trended the forecast in this more pessimistic direction. models
have been too fast all day...and our current ceiling situation has
hung on longer than it was suppose to.
for saturday...next trough will drop south across the area for the
afternoon hours. some scattered snow activity possible with
this...the snow showers likely for the snowbelt. this will return
conditions to mvfr or lower. winds will also be gusty
saturday...with 25 knots for most...30 knots for some. for the
extended portion of the cle taf...winds will remain gusty even
after 00z sun.
outlook...non vfr mainly over ne oh and nw pa saturday night through
sunday because of lake effect. non vfr returning late monday night
into tuesday and continuing across ne oh/nw pa on wednesday.
&&

marine...
with the exception of a few hours later tonight will likely see
small craft conditions the entire period. nw flow will continue
tonight through sunday. speeds will increase late saturday as a
secondary cold front crosses the lake. could get sustained winds in
the 25 to 30 knot range for several hours behind the front. winds
will become sw on monday as surface ridge crosses the lake. speeds
will remain up with sustained winds of at least 20 knots. another
cold front will cross the lake on tuesday causing the flow to return
to the nw. strong north to nw flow will then continue through
wednesday.
&&

cle watches/warnings/advisories...
oh...lake effect snow watch from saturday evening through sunday
evening for ohz013-014-089.
pa...lake effect snow watch from saturday evening through sunday
evening for paz001>003.
marine...small craft advisory until 7 pm est sunday for lez142>149.
&&
$$
synopsis...kec
near term...kec/tk
short term...kec
long term...kubina
aviation...oudeman
marine...kubina

#weather - #lakeerie