Area Forecast Discussion
Issued by NWS Cleveland, OH

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154
FXUS61 KCLE 200552
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1252 AM EST Mon Nov 20 2017

.SYNOPSIS...
High pressure centered over Texas will move northeast across
Tennessee and lower Ohio Valley Monday before moving off the mid
Atlantic Coast Monday night. Tuesday, low pressure moving
through Ontario will drive a cold front through the region
during the afternoon and evening. Wednesday, high pressure will
dominate the region.

&&

.NEAR TERM /THROUGH TODAY/...
Fairly noticeable downtrend with the lake effect bands over the
last hour, with little more than flurries for most of NE OH
outside of Ashtabula county. Backed off snow chances and amounts
where snow has diminished, with little to no additional snow
accumulation. Hi-res models starting to catch onto the drying
trend, with noted clearing of clouds across the western basin of
Lake Erie. Could still see some organized bands impacting
southern Erie for several hours, with an additional uptick
around 12Z as some better synoptic moisture moves across the
area, so will keep the headlines in tact. Otherwise, just minor
adjustments to the forecast with this update.

Original discussion...
Lake effect snow showers have expanded over the past couple
hours as the colder air continues to deepen across the area.
Forecast soundings on BUFKIT show that for the next 6 to 8 hours
the depth of the cold air remains fairly constant with cape and
moisture up to 700mb. Lift and instability is within the
favored dendritic growth zone and lake induced cape reaches
5-700j/kg. Moisture remains sufficient and shear is minimal. So
expect snow showers to continue/increase this afternoon into
evening. After about 9 to 10pm though, the inversion begins to
lower, winds begin to slowly back, and dendritic snow growth
diminishes. Instability however remains "moderate" so LES will
not shut down immediately. Could still see snow showers Monday
morning as warm advection/isentropic lift moves through the
area. Otherwise expect plenty of sunshine outside of nwrn PA
although during the afternoon expecting decreasing clouds there
as well as drier air and high pressure build in from the south.
Models continue to show dry air across the region Monday night
as high pressure moves off the mid Atlantic Coast.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
High pressure over the SERN states slides east allowing the next
system to move in from the NW.  Models continue to move low pressure
system across James Bay late Tuesday forcing the next cold front
across the forecast area.  Model timing coming into better agreement
with the front moving into NW OH late afternoon on Tuesday.  The
front moves across the forecast area ushering in colder conditions
and a little snow.  By daybreak Wednesday the 850 MB temps plunge to
-13c. With a W-NW flow best chance for snow will be int the
 snowbelt east of Cleveland. Do not expect much in the way of
 accumulations as ridge builds in quickly on Wednesday.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
For the second day in a row have not made many changes to long term.
Friday is still looking dry with precip chances then increasing for
the weekend.  Low pressure will pass to the north of lakes Friday
night and drag a cold front across the region.  Some light precip
could occur along the front with best chances over the eastern end
of the area.  There could be some lake effect behind this system as
both the GFS and ECMWF take 850 mb temps to neg 10 or colder by
early Sunday.  On Saturday some rain showers could occur downwind of
the lake but by early Sunday we could be looking at lake effect
snow.  For now will stick with chance pops for most of the weekend
with best chances obviously downwind of the lake.  Have used a blend
of guidance for temps.

&&

.AVIATION /06Z Monday THROUGH Friday/...
Most locations will be VFR through the day. The exception will
be downwind of Lake Erie across NE OH/NW PA. This is where some
MVFR snow showers will be possible. Most of this activity will
be focused across NW PA but could clip Ashtabula County through
mid morning. So at this point it appears only KERI could dip
briefly to MVFR in a snow shower. The cloud cover should thin
and eventually dissipate by late afternoon at all locations.

Winds will become southwest at all locations by 12Z. Strongest
near KERI with gusts to 30 knots possible. Winds will shift
closer to a southerly direction at several sites this evening
with some gustiness possible. If skies remain clear tonight
allowing winds to decouple slightly there is a possibility of
some low level wind shear.

OUTLOOK...A period of Non-VFR possible Tuesday evening into the
overnight in showers. The Non-VFR conditions will likely linger
across NE OH/NW PA into Wednesday evening.

&&

.MARINE...
Northwest winds to 30 knots will diminish to 20 to 25 tonight. Winds
will back to the SW Monday and to the S Monday night ahead of next
approaching system, but small craft advisory will continue as winds
remain at 15 to 25 knots.   Winds turn to the W to NW Tuesday night
as another cold front moves across Lake Erie.   Winds gradually
diminish Wednesday as high pressure gradually builds over the
Lake.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...Winter Weather Advisory until 1 PM EST this afternoon for
     PAZ002.
MARINE...Small Craft Advisory until 3 PM EST Wednesday for LEZ145>149.
     Small Craft Advisory until 4 AM EST early this morning for
     LEZ142>144.

&&

$$
SYNOPSIS...TK
NEAR TERM...Greenawalt/TK
SHORT TERM...DJB
LONG TERM...DJB
AVIATION...Mullen
MARINE...DJB



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