Area Forecast Discussion
Issued by NWS Cleveland, OH

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594
FXUS61 KCLE 180612
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
112 AM EST Sat Nov 18 2017

.SYNOPSIS...
Low pressure will move across the lower Great Lakes Saturday
bringing unsettled weather to the area for the weekend. A warm
front will lift north Saturday followed shortly thereafter by a
cold front. High pressure will build over the area Monday. The
next cold front will sweep across on Tuesday with high pressure
building in by Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Update...Have updated the PoPs now that we have a better handle
on the timing of the onset of rain. The leading edge of showers
and storms is across northwest Indiana as of ~7 PM. Expect
these to arrive along the I-75 corridor by midnight, the I-71
corridor by 3am, and along the OH/PA border by 4am or so. Some
moderate to perhaps heavy rain will be embedded within this
large swath of precipitation, especially associated with any
thunderstorm. Once the rain arrives the entire area will be in
for a wet night and a wet day Saturday. We may see a few breaks
late tonight into early Saturday before the precipitation
becomes widespread once again ahead of an approaching cold front.

Winds will increase tonight and further tomorrow into tomorrow
night. The wind advisory remains in effect for the entire area.
Some of the latest hi-res models are suggesting that at least
some SBCAPE (100-300 J/KG) will develop ahead of the surface
low and associated cold front Saturday afternoon into Saturday
evening. If we are able to get any breaks in the rain/clouds we
could see a strong to perhaps severe thunderstorm, mainly
across the southern half of the area. With the impressive shear
that will be in place it may not take much more than a heavy
shower to mix down some of the stronger winds.

Relevant previous discussion...
Rain/showers will expand in area and make it to the I-75
corridor by late evening/midnight ahead of the warm front.
Expect the rain to make it to PA before morning. Even after this
initial round makes it across, showers will continue to fill in
on Saturday during the brief time we will be in the warm
sector. This system has plenty of upper support and will be well
developed. Moisture transport will bring PWs up around an inch
to 1.5 inches. A few elevated/embedded thunderstorms cannot be
ruled out tonight. Thunderstorms also possible tomorrow closer
to the cold front. Moderate rainfall is expected tonight for
several hours and again Saturday with activity along the cold
front.

Winds will increase out of the south tonight and begin to gust.
The time frame for the highest gusts will be surrounding the
cold frontal passage Saturday night and in its wake with the
cold air advection. Have gone ahead and issued a Wind Advisory
for this period.

Temperatures early this evening will be the low for the night
with rising temperatures expected through mid afternoon
Saturday. The fall will begin Saturday night, but will take some
time before it can get cold enough for snow. Although there
maybe a little mix toward 7 am Sunday on the backside of the
precipitation, not expecting any accumulation up to that point.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Tricky forecast as the models continue to change for Sunday.  As has
been the case the past couple of model runs...the guidance is coming
in slightly warmer for Sunday. The new ECMWF is now slower than even
the GFS bringing in the coldest air. Both models have it about neg 5
at 850 mb at 12z but the GFS is about 2 deg colder by 00Z Monday.
Critical thicknesses are also slower to drop off. Will likely
start Sunday out with mixed precip and it may take most if not the
entire day for the immediate lakeshore to change over given the
strong northwest flow. This of course will keep accums down and
confident of not needing any headlines.  Will need at least chance
pops most of the area on Sunday as some snow showers from Lake
Michigan could reach the western end of the area.  A second trough
and shot of cold air will arrive Sunday night and best chances for a
couple quick inches of snow could come then...especially across
inland NW PA. The flow will become westerly on Monday which
will keep best snow chances over NW PA during the day. Even
there chances will diminish during the afternoon as ridging
occurs from the southwest and the atmosphere dries out. Tuesday
will be quiet.

Temps are also tricky as flow off of the lake will lead to a warm
start along the immediate lakeshore.  Highs there could be in the
mid 40s with falling temps during the day Sunday. Elsewhere
will use a blend of guidance for temps.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Cold front will sweep across the area Wednesday night but it appears
there will not be that much rain along and ahead of it. The main
precipitation will be in the wake of the front with some lake effect
rain/snow showers possible. These lake effect showers may linger
into Thursday morning before high pressure takes control of the
entire region. Conditions should remain dry into Friday.

Temperatures through the long term will generally be in the upper
30s to mid 40s.

&&

.AVIATION /06Z Saturday THROUGH Wednesday/...
Big changes on the way over the next 24 hours. Low pressure is
progged to move northeast across the southeast lower Michigan
and western Lake Erie. This storm system will force a warm front
to lift northeast across the area today. A secondary surge of
warm air will lift northeast later this afternoon across areas
southeast of Cleveland and east of Mansfield. The warm surge may
even lift northeast into Erie this evening. In the mean time,
expecting line of showers and embedded thunderstorms to move
east across the area this morning. There will be a short break
in the activity before another surge develops around 12Z in the
morning and pushes northeast along the developing warm front.
As cold front pushes east into the area, strong wind gusts are
possible in the most intense showers and thunderstorms and could
bring wind gusts to 45 knots or possibly higher to the surface
after 20Z across the area until about 02Z this evening. IFR with
brief LIFR possible with the cold front as well.

OUTLOOK...Non-VFR continues through Sunday and into Monday
across northeast Ohio and northwest Pennsylvania.

&&

.MARINE...
Will go ahead and put a Gale Warning up for the lake. It looks
like a pretty good set up so there is no sense in waiting. The
cold front will make it to about the Islands by sunset tomorrow
so will start the western basin a little sooner than the rest of
the lake. Strongest winds will occur overnight in the 06z to
09z time range. Could get some gusts close to storm force. The
new ECMWF is not quite as windy as the GFS so holding off on
anything stronger than a Gale seems prudent. Winds will come
down fairly quickly Sunday afternoon and will need a period of
small craft headlines once the Gale ends. The northwest flow
will become westerly on Monday. Winds may briefly become
southwest on Tuesday ahead of another cold front which will
cross the lake Tuesday night. Northwest flow will return behind
that feature and continue through the end of the period. Will
see small craft conditions much of the period from tomorrow
afternoon through the end of the period.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Wind Advisory from 7 PM this evening to 10 AM EST Sunday for
     OHZ009>014-019>023-027>033-036>038-047-089.
     Wind Advisory from 4 PM this afternoon to 7 AM EST Sunday for
     OHZ003-006>008-017-018.
PA...Wind Advisory from 7 PM this evening to 10 AM EST Sunday for
     PAZ001>003.
MARINE...Gale Warning from 4 PM this afternoon to 9 AM EST Sunday for
     LEZ142>144-162>164.
     Gale Warning from 7 PM this evening to 4 PM EST Sunday for
     LEZ145>149-165>169.

&&

$$
SYNOPSIS...Oudeman
NEAR TERM...Mottice/Oudeman
SHORT TERM...Kubina
LONG TERM...Mullen
AVIATION...Lombardy
MARINE...Kubina



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