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-- Discussion containing changed information from previous version are highlighted. --
591
FXUS61 KCLE 150531
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1231 AM EST Sun Dec 15 2019

...06z Aviation Forecast Update...

.SYNOPSIS...
Low pressure currently over southern New York will continue to
move north tonight and deepen rapidly with a secondary cold
front moving southeast across the area early tonight. High
pressure will build southeast across the Midwest and Ohio Valley
on Sunday night. Another low pressure system will move
northeast across the Ohio Valley late Monday and Monday night
and off the New England coast by Tuesday. A ridge of high
pressure will build east across the eastern CONUS Wednesday
through Friday.

&&

.NEAR TERM /THROUGH TODAY/...
Update...Have made significant changes to the evening and
overnight forecast. Forecast soundings show a loss of ice in
the clouds overnight with only supercooled liquid clouds
remaining across the region. Overnight forcing is weak which
would favor a larger chance that any precip through the late
evening and overnight would be drizzle vs snow. As temps drop
this would become freezing drizzle. Have already seen pilot
reports of icing and and few obs of light rain. Will continue
with current advisory headlines across northwest PA and reword
text to include more zl and less snow. Will also keep the
warning. Although overnight snow will be limited, there is still
a window Sunday morning to redevelop snow off the lake with
dendrites again favored as colder air deepens. At this time,
elsewhere will wait for development and not issue any
additional advisories.


Original...A negatively tilted trough will continue to lift
north along the northeast CONUS. This trough is responsible for
forcing a deep low, currently located over southern New York.
This low is expected to continue almost due north (with a slight
east component) while undergoing significant cyclogenesis. This
has resulted in widespread precipitation, with a rain/snow mix
currently across northeast Ohio and northwest Pennsylvania.
Inland areas of northwest Pennsylvania and parts of inland
northeast Ohio have completely transitioned to all snow where
surface temperatures are a bit cooler. Precipitation associated
with this low pressure will end from west to east early this
evening into tonight. Beyond this, lake effect snow will develop
tonight as northwest flow aloft continues and temperatures at
850 mb decreases to a minimum of 12 deg Celsius by 15 UTC
Sunday. In addition lake effect, brief redevelopment of
scattered snow showers may occur across northern Ohio tonight,
adding to snow totals. Through 18 UTC Sunday, snow totals across
the Ohio lake effect snow belt are expected to be 1 to 4
inches, with highest amounts in hills. Snow totals in northwest
Pennsylvania are expected to be 5 to 9 inches with a very sharp
gradient along the lakeshore. Gusty winds of 30 to 40 mph may
introduce blowing snow and reduced visibility, especially closer
to the lakeshore. Because of snow totals, a Winter Storm
Warning has been issued for inland Erie County and a Winter
Weather Advisory for lakeshore Erie and Crawford Counties, both
of which are valid through 18 UTC Sunday.

Light lake effect snow showers may continue into the afternoon
but should be over by early Sunday night. High temperatures are
expected to be on the cool side, staying right around freezing.
Are next system comes in the form of low pressure developing
over the lower Mississippi Valley Sunday night. Precipitation
associated with this system will approach from the south late
Sunday night, likely staying as all snow through Sunday night.
There some uncertainty with the onset of snow on Sunday night
and the model trend right now is for most of the precipitation
to stay to our south. For that reason have stuck with a max 50
PoP through 12 UTC Monday.

&&

.SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/...
Southwesterly flow aloft persists Monday morning through daybreak
Tuesday as a trough aloft approaches from the west. Simultaneously,
a surface low should track from near AR to near south-central PA,
allowing our CWA to remain within the surface low`s cold sector.
Periods of widespread precipitation associated with warm air
advection and isentropic lift are expected on Monday and Monday
night. Temperatures at the surface and aloft will be critical in
determining precip type(s) at the surface. In general, a
rain/snow mix on Monday should change to all snow Monday night.
However, periods of sleet and/or freezing rain may also occur
and this potential will be watched closely. High temperatures
should reach the low to mid 30`s on Monday, while low
temperatures should reach the mid 20`s to lower 30`s Monday
night.

On Tuesday and Tuesday night, the surface low should continue moving
northeastward from near south-central PA to near the Canadian
Maritimes, allowing cold air advection to overtake our CWA.
Simultaneously, the trough aloft should settle eastward over our CWA
and merge with a potent mid- to upper-level low settling
southeastward over northern ON. Widespread wraparound snow should
end from west to east on Wednesday and transition to multiple bands
of lake effect snow across the snowbelt Tuesday night as a westerly
flow of progressively colder air crosses Lake Erie. High
temperatures in the low to mid 30`s on Tuesday should be followed by
lows reaching the upper teens or lower 20`s Tuesday night.

On Wednesday, northwesterly flow aloft is expected as the mid- to
upper-low moves from near Georgian Bay to northern New England and
high pressure at the surface and aloft builds from the west. Lake
effect snow should continue in the snowbelt as the low-level flow
veers from westerly to northwesterly and becomes even colder. Fair
weather is expected outside the lake snow. Wednesday will likely be
the coldest day of the week, with highs only reaching the 20`s.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
High pressure aloft builds eastward over our CWA Wednesday night
through Thursday night, causing northwesterly flow aloft to
eventually become westerly. Simultaneously, surface high pressure
crests over our region. Lingering lake effect snow in the snowbelt
should end by daybreak Thursday as the stabilizing high pressure
ridge allows lake-induced CAPE to diminish. Otherwise, fair weather
is expected across our CWA. Low temperatures in the teens to lower
20`s are expected overnight Wednesday night. On Thursday, afternoon
highs should reach the upper 20`s to mid 30`s. Lows should reach the
20`s Thursday night.

At this point, odds favor fair weather Friday through Saturday as
high pressure ridging at the surface and especially aloft should
remain in control over northern OH and northwest PA. Temperatures
should moderate during this period, including high temperatures
reaching the 30`s to lower 40`s.

&&

.AVIATION /06Z Sunday THROUGH Thursday/...
Widespread MVFR and IFR is expected through the rest of the
night into Sunday. MVFR is expected for the western TAF
locations and IFR is expected for the I-71 corridor eastward
into northeastern Ohio and NW Pennsylvania. Low ceilings between
700 feet to 1500 feet is expected along with areas of
drizzle/light snow with visibilities dropping between 2sm and
5sm at most locations across the northeastern Ohio. A band of
lake effect snow may develop late morning into the afternoon and
impact ERI later today. MVFR ceilings are expected through the
afternoon with ceiling lifting to around 5K feet by this
evening.


.OUTLOOK...Non-VFR possible Monday and Tuesday with periods of
rain and/or snow. Freezing rain may also be possible on Monday.
Non-VFR possible with lake effect snow on Tuesday and Wednesday.

&&

.MARINE...
Small Craft Advisories are in effect for Lake Erie today into
Sunday. Westerly winds as strong as 20 to 25 knots are expected
through tonight, resulting in waves as large as 4 to 8 feet,
especially east of The Islands. Westerly to southwesterly winds will
diminish gradually on Sunday and waves will lower gradually as a
northeastward-moving low pressure system pulls away from Lake Erie
and high pressure builds from the west. Quieter conditions should
affect the lake on Monday, while Small Craft Conditions may return
Tuesday into Wednesday as low pressure moves northeastward from the
Ohio Valley to Canadian Maritimes Tuesday and then extends a trough
over the lake into Wednesday.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...Winter Weather Advisory until 1 PM EST this afternoon for
     PAZ001-003.
     Winter Storm Warning until 1 PM EST this afternoon for PAZ002.
MARINE...Small Craft Advisory until 10 PM EST this evening for
     LEZ147>149.
     Small Craft Advisory until 10 AM EST this morning for LEZ143-
     144.
     Small Craft Advisory until 4 PM EST this afternoon for LEZ145-
     146.

&&

$$
SYNOPSIS...Saunders
NEAR TERM...Griffin/TK
SHORT TERM...Jaszka
LONG TERM...Jaszka
AVIATION...Griffin
MARINE...Jaszka