Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 211129
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
629 AM EST Tue Nov 21 2017

.SYNOPSIS...
Low pressure north of Lake Superior will move eastward across
Ontario today. A cold front extending south from the low will
move across the region Tuesday evening. High pressure will
take control of the region on Wednesday and persist into
Thursday Night.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
Only minor changes have been made to hourly temperatures and
cloud cover to reflect current trends.

Strongest portion of the low level jet will lift out onto Lake
Erie through the morning. As the morning mix begins some of this
wind will move to the surface with gusts 30 to 35 mph common
through the morning.

Previous Discussion...
Gusty southwesterly winds will continue into the afternoon as
we await the arrival of a cold front. The cold front will cross
the are this evening. It should pick moisture up off of Lake
Erie with showers most numerous across NE OH/NW PA generally
from Cleveland to Erie. Temperatures drop quickly in the wake of
the front with rain changing over to snow after midnight. Any
accumulations will be on the light side. The greatest
accumulations may be an inch or 2 across the hills of NW PA,
generally from Edinboro to Wattsburg. High pressure will take
control of the area by Wednesday afternoon with any lake effect
snow showers across NW PA ending.

It will be warm today with highs 50 to 55. Cooler On Wednesday
with highs dipping back to the middle 30s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
Surface high pressure will be in control from Wednesday night
through Friday. Skies will initially be partly cloudy Wednesday
night, but as more and more of the moisture gets scoured out
Thursday into Friday, skies will become mostly clear. The one
exception will be across extreme northeast Ohio and northwest
Pennsylvania where the clouds will persist a bit longer. Overall the
weather looks benign for Thanksgiving day with southwest winds
around 10 to 15 mph and high temperatures in the upper 30s to near
40, except the middle 30s across inland northwest Pennsylvania.

Clouds will begin to increase from northwest to southeast Friday
evening into Friday night ahead of an approaching trough and
associated cold front. With the frontal passage holding off until
Friday night highs will be able to rise into the lower 40s across
inland northwest Pennsylvania and the middle to upper 40s elsewhere.

There won`t be a ton of moisture available ahead of this cold front,
so just how widespread the precipitation will be is still a bit of a
question. Currently have widespread chance PoPs across the region
with some likely PoPs over part of Lake Erie. The best chances for
precipitation will be across northern areas. Precipitation is
expected to remain in the form of rain through Friday night.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
Rain showers will be ongoing across the far eastern part of the
forecast area Saturday morning in the wake of the cold front. A
secondary cold front will filter in the colder air Saturday
afternoon. Winds will initially be out of the west-southwest
Saturday morning but will turn around to the northwest by late
Saturday evening into Saturday night as a large upper-level trough
becomes anchored over the region. This will kick off the lake-effect
snow machine with 850mb temperatures dropping to around -10C by
Saturday night. Precipitation should transition from a mix over to
all snow at some point Saturday night.

On and off lake-effect snow is then expected to continue from
Saturday night through Sunday night. Multiple short wave troughs
will round the base of the larger trough with the lake-effect snow
bands moving around with the passage of each short wave. Some
accumulating snow is expected across the Snowbelt as there will be
ample moisture available within the snow growth zone, inversion
heights topping out around 10k feet, a lake surface to 850mb delta T
of around 20C, and little directional shear. Still too far out to
get into any more specifics at this point.

The lake-effect snow should start coming to an end Monday as a large
ridge begins to move in from the west and a surface high moves in
from the southwest. This will back winds around to the west by
Monday afternoon and the southwest by Monday night. The combination
of the upper-level ridge and high pressure should make for dry
conditions once the lake-effect snow ends Monday with dry weather
continuing into Tuesday.

A bit of a roller coaster ride is in store for the temperatures
through the long term. Highs Saturday will be in the mid to upper
40s prior to the passage of the secondary cold front. Highs will
generally be around freezing Sunday and only a smidge warmer Monday.
As warm air advection returns Monday night into Tuesday highs will
rise back into the middle 40s for Tuesday. Low temperatures will be
in the 20s throughout the long term.

&&

.AVIATION /12Z Tuesday THROUGH Saturday/...
Strongest portion of the low level jet will move out onto Lake
Erie through the morning. Have placed a mention of low level
wind shear at all TAF sites with surface wind gusts under 25
knots. Looks like southwesterly winds around 2000 feet will be
around 45 knots. The gusty winds will continue into at least
early afternoon with 30 to 35 knots possible. Winds shift to
the northwest in the wake of the cold front and decrease
slightly.

Otherwise we will await the arrival of a cold front. Current
thinking is that the cold front crosses the area during the
evening with a period of showers. The better chances of showers
will be downwind of Lake Erie from Cleveland to Erie. MVFR
conditions are expected with the showers. The MVFR conditions
will persist into the overnight hours as temperatures drop. A
short period of lake effect snow will be possible across the
snowbelt of NE OH/NW PA. Away from this area ceilings will
slowly lift and dissipate.

OUTLOOK...Non-VFR conditions will likely linger across NE OH/NW
PA into Wednesday evening. The next chance for non-VFR
conditions looks like it will arrive with a cold front on
Saturday.

&&

.MARINE...
Small Craft Advisories remain in effect for the entire lake this
morning as strong southwest winds of 20 to 25 knots continue. Winds
may increase a touch more later this morning into early this
afternoon before they veer around to the west by this evening and
the northwest by tonight. The Small Craft Advisory for the Western
Basin has been extended through late this evening as winds will
continue to remain around 20 to 25 knots through the entire period
with waves increasing to 3 to 5 feet for a brief period this evening
into early tonight as winds turn around to the northwest. As winds
turn around to the northwest waves will increase everywhere along
the lakeshore so the Small Craft Advisory for the rest of the lake
continues through Wednesday.

Winds will gradually diminish to light west and southwest by
Wednesday night. Southwest flow will return and increase Thursday,
diminish slightly Thursday night, and strengthen once again for
Friday into the weekend. A small craft advisory will likely be
needed during this time period.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...Small Craft Advisory until 3 PM EST Wednesday for LEZ145>149.
     Small Craft Advisory until 10 PM EST this evening for
     LEZ142>144.

&&

$$
SYNOPSIS...Mullen
NEAR TERM...Mullen
SHORT TERM...Mottice
LONG TERM...Mottice
AVIATION...Mullen
MARINE...Mottice


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