Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 220154
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
954 PM EDT Sat Oct 21 2017

.SYNOPSIS...
High pressure over the East Coast will start to move east by Monday
to allow a series of cold fronts to push east across the region
Monday night into Wednesday. High pressure will briefly be over the
area Thursday before a low tracks northeast into the Great Lakes
Friday and Saturday.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
Made minor tweaks to cloud cover and temperatures to reflect
current trends.

Previous Discussion...
The influence of high pressure to the east should keep the
lower levels of the airmass dry enough to prevent any rain thru
Sunday and maybe even Sunday night. As the upper trough moves
closer Sun night and lower levels start to moisten, sct shra
should start to push out of Indiana into western OH but may not
make it as far east as the I75 corridor. A SSW flow at upper
levels will continue to supply abundant cirrus for the area
tonight thru Sun.

Temps will stay well above normal so enjoy it as major changes are
on the way next week.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Upper level trough over the Rockies is forecast to close off
over the Mid- Mississippi Valley by Monday. At the surface, low
pressure will undergo considerable deepening as it moves
northeast across the central Great Lakes. Moisture from the Gulf
of Mexico will be transported north ahead of the trough. The
arrival of the deep moisture combined with strong dynamics
provides high confidence in a wet forecast on Monday afternoon
into Monday night. Models have sped up the timing of this system
and have raised pops in most areas to 90 or 100 percent
sometime in that window. Most areas will see over an inch of
rain and can not rule out some pockets of 1.50 or more. This
system will also pull a strong cold front east across the area
Monday night. The 12Z GEM/ECMWF have trended towards a deeper
low and more consolidated cold front while the NAM/GFS exhibit
more gradual cold advection through Tuesday. Lowered highs on
Monday by a couple degrees given the earlier onset of the rain.
Eastern areas will be a few degrees warmer on Tuesday as the
colder air continues to trickle in from the west. Another push
of cooler air arrives by Wednesday as a stronger trough digging
south out of Canada arrives. Highs on Wednesday will struggle to
get out of the 40s as 850mb temperatures drop to between 0 to
-2C.

Drier air aloft does gets wrapped around the upper level trough on
Tuesday but suspect enough low level moisture will remain for
lighter showers to persist triggered by shortwave energy and other
various troughs moving through. Another push of deeper moisture
accompanies the passage of the upper level trough axis on Wednesday
and should enhance showers, with likely pops downwind of Lake Erie.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
A highly amplified pattern will be in place across the CONUS with a
deep trough centered over the Ohio Valley at the start of the long
term. Precipitation from earlier in the day Wednesday will be
tapering off during the overnight hours with the best chances being
confined to the eastern half of the area. As winds turn on shore
Wednesday night we will see some lake effect/enhanced showers across
the Snowbelt. With temperatures expected to fall into the mid-30s
across inland areas of northeast Ohio and northwest Pennsylvania
Wednesday night, a chance of a few snow showers mixing in with the
rain can`t be ruled out.

Strong warm air advection arrives Thursday as a short wave ridge
moves overhead. This should dry out the area by Thursday afternoon
with highs generally in the middle and upper 50s. Temperatures will
continue to warm Friday as the ridge is slow to move off to the
east. The next front looks to arrive sometime next weekend, but the
models are in a significant disagreement with the timing of the cold
front. The ECMWF is around 48 hours slower than the GFS. With such a
highly amplified pattern in place it is more likely the large trough
out west becomes a closed low, which is the solution the ECMWF
favors compared to the much more progressive GFS. So have only went
with 20-30 percent PoPs and warmer temperatures (upper 50s/lower
60s) for Friday into Saturday.

&&

.AVIATION /00Z Sunday THROUGH Thursday/...
Variable amounts of middle and high level cloud cover will drift
across the region through the night into Sunday. Southerly winds
will be under 8 knots through the night. The southerly winds
increase across the west on Sunday with a few gusts around 20
knots possible.

OUTLOOK...Areas if Non-VFR in rain showers Sunday night through
Wednesday. Some snow may occur Wednesday into Wednesday night.

&&

.MARINE...
Marine conditions will remain relatively good into Monday with Small
Craft Advisory conditions developing Monday night through midweek.
Southerly flow of 10-15 knots through Sunday will increase to 20-30
knots by Monday night as an area of low pressure tracks north across
the lake. Winds will shift to the west with the passage of a cold
front before backing to southwest again on Tuesday. Models are
showing signs of trending towards a stronger cold front and can not
rule out a window of Gale conditions. Brisk conditions and continued
Small Craft Advisories will continue through mid-week as a series of
troughs bring much colder air to the region. Improving conditions
expected by Thursday as a ridge builds into the Great Lakes between
systems.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...None.
PA...None.
MARINE...None.

&&

$$
SYNOPSIS...Adams
NEAR TERM...Adams/Mullen
SHORT TERM...KEC
LONG TERM...Mottice
AVIATION...Mullen
MARINE...KEC



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