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fxus61 kcle 131154 
afdcle

Area forecast discussion
National Weather Service Cleveland Ohio
654 am EST Fri Dec 13 2019

Synopsis...
a low moving east across the upper Great Lakes will weaken and
merge with a deepening low that is expected to move up the East
Coast later today and Saturday. The associated cold front will
move east across the area on Saturday night. High pressure will
build east across the area on Sunday and Sunday night.

&&

Near term /through Saturday/...
tweaked hourly temperatures to reflect slightly warmer across
the area this morning. Also tweaked sky cover to reflect the
continued clearing across the area this morning based on recent
satellite trends.

Previous discussion below...

Most areas have a good chance at seeing the sunrise this morning
as an influx of low and mid-level dry air has resulted in
clearing across the region overnight. The clearing will not
last long, however, as moisture returns from the southwest by
mid to late morning, leading to mid and high cloud cover
overspreading the area. Warm air advection will result in
slightly above normal temperatures across the area today in the
low to mid 40s.

Precipitation mainly in the form of rain will begin to
overspread the area from the southeast tonight and continue
through much of the day Saturday. A narrow window of a rain/snow
mix may be possible west of I-71 tonight into Saturday morning
as temperatures fall to the mid 30s. There will be a sharp
gradient in precipitation totals, with areas generally east and
southeast of Cleveland receiving anywhere from a quarter to a
half inch of rain, while areas out towards western and
southwestern Ohio may only see a few hundreds of an inch. As the
low moves off to the northeast, cold air will be funneled
behind the system into Northern Ohio and northwest Pennsylvania,
transitioning all precipitation to snow by Saturday night.

&&

Short term /Saturday night through Monday night/...
nearly zonal flow will persist across much of the western two thirds
of the lower 48 states. An exiting upper level trough of low
pressure will move east and out of the area Saturday night forcing a
deep surface low pressure to move northeast of the area. This
system will initially bring rain to the area Saturday and then as
cold air advection develops on the northwest side of the storm
track, the precipitation will transition over to all snow Saturday
evening.

A broad upper level ridge will force a brief surface high pressure
east across the area Sunday night into early Monday. The fair
weather will be very brief as upper level pattern remains fast
during this period.

A digging upper level trough will move quickly east across
the western half of the United States. The trough will deepen in
response to amplifying ridge along the West Coast by Monday night.
The positively tilted trough will rotate a potent positive vorticity
maximum through the middle Mississippi Valley region by Monday
causing cyclogenesis to occur over Texas. The surface low will then
track northeast through the Ohio Valley Monday night. The warm
sector will remain to the south of the forecast area and ample
moisture will stream north with the system Monday morning from
southwest to northeast. A mix of rain/snow will take place across
the area Monday into Monday night.

850 mb temperatures are expected to fall from around -6 degrees c to
around -10 degrees c by Sunday morning. As the next system
approaches Monday morning, mid level temperatures will warm back to
just above freezing across the southern half of the forecast area.
Will need to monitor temperatures through the column for the
possibility for freezing precipitation in the overrunning
precipitation threat. As low moves northeast of the area Monday
night, cold air advection returns in the mid levels as 850 mb
temperatures drop back to around -6 degrees c.

No real major changes in temperatures expected through this period
but some cold air advection will drop lows into the middle 20s by
Sunday night after highs Sunday in the lower to middle 30s. Highs
Monday and lows Monday night will be similar to Sunday and Sunday
night.

&&

Long term /Tuesday through Thursday/...
a deep digging upper level trough will push east across the
eastern United States. An upper level ridge is expected to
amplify across the Central Plains states. This will induce a
shortwave trough that will move southeast through the Great
Lakes region with a potent positive vorticity maximum by
Thursday night. This trough will develop a fast moving Alberta
clipper storm system that will move southeast through the Great
Lakes as well by Thursday afternoon. A quick shot of cold air
associated with the low pressure system followed by high
pressure will take place by the end of the forecast period.
Moisture associated with the upper level shortwave and surface
low will be limited and keep most of the precipitation threat
over the eastern portions of the forecast area. Western half of
the area should remain dry through the period. Most notable
impacts will be the cold air advection expected Tuesday night
into Wednesday with lows in the lower 20s and highs only in the
20s. Even colder temperatures are expected Wednesday night in
the teens. There will be somewhat of a break Thursday as a
return back to the upper 20s east and lower to middle 30s
elsewhere.

&&

Aviation /12z Friday through Tuesday/...
VFR across all taf sites through this morning with south to
southeasterly winds 5-10 knots across the area. The exception
is at eri where persistent southeasterly flow has resulted in
downslope winds of 10-15 knots with gusts of 20-25 knots which
should last through the afternoon.

The end of the taf period looks to be quite active with
approaching rain from the south/southeast starting around 3-6z
Saturday and continuing through the end of the taf period. The
heaviest rainfall should impact cle/yng/cak/eri and could result
in MVFR/IFR visibilities. Pockets of MVFR ceilings appear
possible at cak/yng early this afternoon, but expecting all taf
sites to fall to MVFR or IFR by late tonight into Saturday
morning. LIFR ceilings are not out of the question tonight into
Saturday morning, especially at cle and eastwards.

Outlook...non-VFR likely tonight through Sunday due to rain
and/or snow. Non-VFR possible on Monday and Tuesday with periods
of rain and/or snow.

&&

Marine...
southerly winds are expected today and will keep the highest waves
off the shoreline in the open waters. This is a result of low
pressure to the northwest of the forecast area. This low will
weaken as another system moves northeast up the Appalachian
Mountains tonight. A shift of the wind to a northerly direction
will take place Friday night into Saturday. A brisk northwest wind
will develop and it appears a Small Craft Advisory will likely be
needed late Friday night through early Sunday night. Winds diminish
to light and variable through Monday night and become westerly again
by Tuesday afternoon. Small Craft Advisory conditions will develop
in the afternoon Tuesday.

&&

Cle watches/warnings/advisories...
Ohio...none.
PA...none.
Marine...none.

&&

$$
Synopsis...kahn
near term...kahn

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