Scientific Forecaster Discussion
fxus61 kcle 152110
Area forecast discussion
National Weather Service Cleveland Ohio
410 PM EST Fri Dec 15 2017
low pressure over Northern Lake Huron will move east into Quebec
tonight. A ridge will expand over the Ohio Valley on Saturday. Low
pressure will move out of the plains towards the central Great Lakes
on Sunday, lifting a warm front north across the area.
Near term /through Saturday/...
snow has been filling in on the south side of an area of low
pressure moving east across the central Great Lakes. Initially snow
has been developing in an area of warm advection within the
southwest flow. As the low moves towards Quebec overnight, a
prolonged period of westerly flow is expected to set up across Lake
Erie. This will set the stage for lake effect snow to develop. The
advisory has been expanded to Ashtabula County and a lake effect
snow warning has been issued for inland Erie County.
Snow is expected to intensify along the northeast Lakeshore this
evening as convergence increases while the trough moves onshore.
Areas closer to the Lakeshore will see a quick 1 to 3 inches through
the evening hours with locally higher amounts in the upslope
areas. The shifting flow with the passage of the trough will be
followed by a window of reorganization/lull in the snowfall
overnight. An area of drier mid-level air will also move
overhead. While this is ongoing aloft, favorable low level
conditions remain with flow down the long fetch of the lake.
Deeper moisture can be seen on satellite imagery upstream moving
into the Midwest. This moisture will overspread the lake for
the second half of the night with lake effect snow intensifying.
Interesting set-up for a lake effect event with the airmass
starting to warm late tonight. What the event lacks in lake
induced instability will likely be made up for by the synoptic
forcing and moisture. The backing low level flow is expected to
intensify low level convergence with the potential for a
dominant band producing high snowfall rates of 2- 3" per hour
late tonight into Saturday morning. Still some uncertainty as to
where this band will set up but the namdng, arw, and nmm all
place over an inch of quantitative precipitation forecast across primarily inland Erie County
PA. Expecting the favored upslope areas in the north half of the
County to see the highest accumulations of 7-9 inches through
midday Saturday. We will need to monitor the placement of the
heavier lake effect bands overnight and can not rule out needing
to upgrade an adjacent area to a warning, either the Lakeshore
areas of Ashtabula/Erie counties if the heavier band sets up
there, or across inland Crawford PA if the band pushes farther
Areas outside of the snowbelt will see a light accumulation of less
than an inch in NE Ohio this evening with additional light coating
possible prior to dawn. Lows will only drop off a couple degrees
tonight into the lower to mid 20s. A gradual warming trend will
continue on Saturday with highs in the lower to mid 30s.
Short term /Saturday night through Tuesday/...
overall upper level pattern trends toward becoming more zonal
across the Continental United States and result in fast moving
shots of moisture toward the area along with an upper level
positive vorticity maximum being ejected northeast out of the
A low pressure system will move northeast toward the area at a
fairly fast clip. A stationary front extending northeast from the
low will move little across the forecast area Saturday night through
Sunday night. The front eventually lifts northeast of the area
Monday as a warm front as the low moves northeast of the area.
Periodic shots of moisture will move northeast along the boundary
and bring with it a chance of precipitation Monday into Tuesday.
As the stationary front becomes a warm front and lifts north of the
area, we will start to see some warmer air move into the local
forecast area by Tuesday. Highs by Tuesday will push into the 40s.
Overnight lows will be back into the upper 30s across the area
Monday night in the warmer air.
Long term /Tuesday night through Friday/...
the long term begins Tuesday night with low pressure over
Quebec and a cold northwest low across the region. High pressure
will be building into the area from the southwest however with
the flow across the lake would expect lake snow in the snowbelt.
Better details as time nears however will have likely pops for
Ashtabula and northwest PA, slight chance or less elsewhere for
Tuesday night. Wednesday will shave Ashtabula out of the likely
pops as warm advection and drier air move in. For nwrn PA expect
best chance will be in the morning. Again, dry elsewhere.
Wednesday night and Thursday look dry as low pressure develops
in the Central Plains. Thursday night will bring chance to
likely pops back as the low and associated cold front move
through the area. Ahead of the system however 850mb temps above
zero so expect some precip as rain. Friday looks drier behind
the system however cold air again across the lake will bring
lake effect back to the snowbelt.
Aviation /18z Friday through Wednesday/...
MVFR clouds spreading west to east across the area as a
trough extending from low pressure over Northern Lake Huron
shifts east this afternoon. Light snow showers possible as lift
increases ahead of the trough this afternoon. Snow will
increase in the snowbelt as a weak cold front moves through this
evening and a westerly flow sets up off Lake Erie. The heaviest
snow is expected at eri who will see IFR and several inches of
snow overnight. Snow will increase again after 08z as deeper
moisture arrives and lake effect snow increases. We are watching
for a stronger band that may set up at eri but confidence is
low in timing.
Southwest winds will gust to 20-25 knots this afternoon. Winds
will become more westerly tonight behind the front.
Outlook...non-VFR possible Sunday night into Monday. Non-VFR
also possible in northeast Ohio and northwest Pennsylvania on
cold front will push east across the area this afternoon and allow
winds to increase from the west behind it. We are already seeing
winds at 15 to 25 knots on the lake at this time with a further
increase around 25 knots after frontal passage tonight. Winds are
expected to decrease fairly quickly during the afternoon Saturday.
Small Craft Advisory will remain in effect overnight but is expected
to be dropped during the afternoon Saturday as waves also subside.
Lake is expected to be relatively quiet through Monday but will
become disturbed again Monday night as winds increase out of the
southwest. A Small Craft Advisory will likely be needed again
Tuesday into Wednesday as a high pressure ridge tries to build down
toward the lake increasing the gradient across the area.
Ohio...Winter Weather Advisory until 4 PM EST Saturday for ohz014-089.
PA...Winter Weather Advisory until 4 PM EST Saturday for paz001-003.
Lake effect snow warning until 4 PM EST Saturday for paz002.
Marine...Small Craft Advisory until 4 PM EST Saturday for lez145>149.
Small Craft Advisory until 10 am EST Saturday for lez142>144.