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FXUS61 KCLE 130609

Area Forecast Discussion
National Weather Service Cleveland OH
109 AM EST Fri Dec 13 2019

...06Z Aviation Update...

A low moving east across the upper Great Lakes will merge with 
a deepening low that moves up the East Coast on Friday and
Saturday. The associated cold front will move east across the
area on Saturday night. High pressure builds east across the
area on Sunday and Sunday night.


910 PM DISCUSSION...The near-term forecast remains valid. No 
updates appeared necessary late this evening.

643 PM DISCUSSION...Most of our near-term forecast remains 
valid. However, adjusted hourly temperatures and dew points 
through early Friday morning to better match observed trends. 
Also used NBM guidance to freshen sky cover through Friday 
morning given observed and expected trends. During this time 
frame, our skies will likely trend partly to mostly cloudy due 
to isentropic lift amidst sufficient mid- and upper-level 
moisture ahead of a longwave trough approaching from the west.

337 PM DISCUSSION...Quiet weather today will continue through 
tonight and much of the day tomorrow. High cirrus expected to 
linger across the area this evening before giving away to mostly
clear skies late tonight into tomorrow morning. Southerly winds
will remain elevated tonight into early tomorrow afternoon as 
pressure gradient remains tight over the area. Southerly winds 
should keep temperatures from decreasing too much tonight with 
low temperatures in the upper 20s and lower 30s.

As mentioned in the synopsis, low pressure over the Great Lakes
will merge with a deepening low that moves up the east Coast,
with low pressure of around 1000 mb situated over eastern
Pennsylvania by 12 UTC Saturday. Precipitation associated with
this deepening low will approach from the south, beginning to
enter our southern counties around 00 to 03 UTC. This is
anticipated to begin as mostly rain with some rain/snow mix in
northwest Ohio, where temperatures are expected to hover in the
mid to low 30s. As temperatures decrease slightly overnight, a
mix of rain/snow and even some areas of all snow will begin
creep into central and north-central Ohio late Friday night.
Only dusting of snow at most is expected through this period
where all snow occurs.


The short term begins Saturday with low pressure to our west over 
Illinois weakening and becoming absorbed in the developing broad 
coastal low centered along the Jersey Shore. The coastal low will 
already be dominant by this point however with deep moisture from 
the low wrapping west across much of the CWA. Temps at 850mb around 
0C to +2C so not low enough for snow. Expect temps across the 
central and eastern counties to be in the mid 30s in the morning 
where pops are best (likely to categorical) so will go with rain as 
the primary ptype. Far west where early morning surface temps are 
closer to 32, will allow for a few hours of a rain snow mix with low 
chance pops. This coastal low will continue to develop rapidly as it 
tracks northeast through New England Saturday night into Sunday as 
High pressure moves into the Northern Plains. Colder air will 
continue to funnel into the area between these two system, 
eventually arriving Saturday night taking 850mb temps down to -10C 
by Morning on Sunday as drier air moves in from the west. Saturday 
night precip should taper from the west as the effect of Lake Erie 
begin to dominate.  Will have likely to categorical pops for the 
snowbelt Saturday night into early Sunday and then drop to chance 
pops for the afternoon. Monday's storm will be interesting for the 
area.  For the day, differences between the GFS and ECMWF are not 
huge but a still big enough for the area to matter.  Both agree on 
bringing deep moisture into the area although the GFS is more 
aggressive.  Temps at 850mb by 00Z Tuesday are above 0C on the GFS 
but remain below freezing on the ECMWF. Will bring a chance of snow 
north into the area during the morning with snow changing to rain 
through the central portion of the area as warmer air moves north in 
the lower levels. Will keep the corners in snow for now. Highs 
Saturday around 40. Highs Sunday and Monday low to mid 30s.


The long term joins a winter storm currently in progress.  Of course 
the big question which cannot yet be answered is the details of the 
storm given model differences.  Monday night into Tuesday the GFS 
bring the surface low north across the eastern half of Ohio reaching 
central NY by 12Z Tuesday. The ECMWF track is slower and further 
east of the GFS track with the 12Z position in VA.  The GFS keeps 
the swath of most significant snow to our west and north while the 
ECMWF should be closer to the area but possibly to our southeast. Of 
course, lake effect should kick in behind the low beginning mainly 
Tuesday night as 850mb temps plunge toward -18C by Wednesday 12Z.
For now, starting Monday evening, the GFS does bring enough warm air 
into northwest Oh and nwrn PA to possibly give us a few hours of 
freezing rain so will put that possibility in. The rest of the area 
will begin as rain although given to colder ECMWF will also have it 
mixed with snow. As colder air move in, the remainder expect a 
transition to all snow overnight. Tuesday will continue with chance 
pops early, decreasing from the west during the afternoon as drier 
air moves in. Will have likely pops for snow showers off the lake 
Tuesday night into Wednesday. Thursday we should see a warmup as the 
Arctic air retreats.


.AVIATION /06Z 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 throughout the day Friday. 

The end of the TAF period, 0-6Z Saturday, looks to be quite
active with approaching rain showers from the south/southeast,
resulting in tanking ceilings and visibilities. Some MVFR 
pockets appear possible at CAK/YNG Friday afternoon, but 
expecting all TAF sites to fall to MVFR or IFR by late Friday
night into Saturday morning. LIFR ceilings are not out of the
question late Friday night into Saturday morning, especially at
CLE and eastwards.

.OUTLOOK...Non-VFR likely beginning Friday night and lingering
through Sunday due to rain and/or snow. Non-VFR possible on 
Monday and Tuesday with periods of rain and/or snow.


High pressure over the lake will move east tonight allowing 
southerly winds to increase to 15 to 20 knots or so across the 
nearshore with winds approaching 25 knots in the open waters.  For 
now will not issue a small craft advisory but conditions will 
approach criteria well away from shore. Winds drop back a bit on 
Friday as the pressure gradient relaxes. Winds will remain light 
Friday night through Saturday before increasing out of the northwest 
Saturday night to near 20 knots as low pressure deepens 
significantly across New England forcing a cold front across the 
lake. Expect another small craft advisory beginning Saturday night. 
Winds will remain 20 to 25 knots from the west to northwest Sunday 
in cold advection. Winds and waves diminish Sunday night as high 
pressure builds across the lake. Monday night into Tuesday deepening 
low pressure will move north through the Tennessee Valley across 
Ohio along a path just southeast of the lake.  Expect winds to 
increase from the east and southeast early Monday backing all the 
way to westerly as the low passes Tuesday. Winds will remain below 
gale through the period.




NEAR TERM...Jaszka/Saunders

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