Area Forecast Discussion
Issued by NWS Cleveland, OH

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207
FXUS61 KCLE 231731
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
131 PM EDT Sun Jul 23 2017

.SYNOPSIS...
A broad area of low pressure across the lower Great Lakes will
linger into early Monday. High pressure will then be able to
build across the region and bring lower humidity for the first
part of the new work week. The next cold front arriving from the
Upper Midwest and across the Great Lakes crosses the local area
on Thursday.

&&

.NEAR TERM /THROUGH MONDAY/...
Tricky forecast for this afternoon. A very humid airmass is in
place with an upper level trough swinging through the Great
Lakes today. A stationary front is draped from near Erie, PA
westward along the lakeshore to near Cleveland, then southwest
to the Findlay area. The only real noticeable difference along
this front is the light northerly winds on the north side and
the southwesterly winds south of the front. There is no
noticeable difference in temperatures or dewpoints across the
boundary. For this reason, forcing along this stationary front
will be minimal. However, an MCS passing well south of the area
could send some remnant circulation or outflow north into the
area. If this were to interact with the frontal boundary, it
could trigger thunderstorm development this afternoon.

Additionally, the 3-km NAM shows a weak 700-mb shortwave trough
moving across northern Ohio this afternoon into this evening.
There is some evidence of this in the GFS as well. As this
interacts with the weak stationary front, it could be enough to
trigger thunderstorms thanks to what will likely be a
moderately unstable airmass (1000-1500 J/Kg MLCAPE) in place.

The wind shear this afternoon will be relatively weak, with < 15
knots of 0-2 KM shear and around 25-30 knots of 0-6 KM shear.
This suggests multi-cell clusters would be the dominate type of
convection this afternoon. The main threats would be very heavy
rain (which could lead to flash flooding), strong winds, and
marginally severe hail.

The threat for showers and storms will come to and end from west
to east this evening into tonight. We could still see a few
lingering showers continue through the overnight hours across
far northeast Ohio into northwest Pennsylvania. One last
shortwave trough will move through the area Monday. This could
trigger a few more showers and storms throughout the afternoon
hours, though coverage is not expected to be too great. The best
chance will be across eastern Ohio into Pennsylvania. It may
just be more showers than anything on Monday with only a slight
chance for a few rumbles of thunder.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
Surface high pressure will drift off to the east on Tuesday.
Winds will likely remain from the east. A patch of cirrus may
brush the area otherwise it should be sunny with a few cosmetic
cumulus. High temperatures should average 75 to 80, a few
degrees below normal, with dew points in the 50s and comfortable
humidity.

Winds will come around from the south on Wednesday ahead of the
next front. It does not take long to warm up this time of year and
the forecast will be a degree or two warmer than most guidance with
forecast highs generally in the mid 80s.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
There is still some uncertainty on the timing of the next front.
A few of the models hint at a weak wave on the front which will
slow the progress. Will have a 40-60 pop in the forecast for
Thursday. The blended guidance has the winds coming around from the
northwest by late afternoon. I am not convinced the front will be
that quick, especially if there may be wave. Will keep a chance of
showers and thunderstorms in the forecast into Thursday night,
mainly east of I- 71.

Surface high pressure should build in from the west late in the week
although the trough aloft is progged to hang back across the Great
Lakes and northeast states. Occasionally this pattern can generate
a few rogue showers/thunderstorms if we cannot get the dewpoints
down. Will be optimistic at this time with a dry forecast by the
weekend and temperatures a few degrees below normal.

&&

.AVIATION /18Z Sunday THROUGH Friday/...
Showers and storms will develop this afternoon across the area.
A mix of VFR/MVFR conditions are expected outside of storms with
IFR/LIFR conditions expected in any thunderstorm. Storms can
contain strong and variable winds. Most convection should be
done in the west by 00Z and the east by 02Z or so. KERI could
see a few lingering showers through the night. Some fog will
likely develop tonight along with low ceilings. There may be a
brief break of VFR conditions by late morning before afternoon
CU develop and everywhere returns to MVFR CIGs. This should
happen by 15-16Z tomorrow.

OUTLOOK...Non-VFR in early morning fog/mist may continue during
the first half of the week. Non-VFR in thunderstorms with a cold
front Thursday.

&&

.MARINE...
Light northwest winds on western Lake Erie and light northeast winds
on eastern Lake Erie will transition to a mainly west to southwest
flow today ahead of a cold front dropping across the Great Lakes.
A series of weak surface troughs and weak fronts will cross he lake
today and Monday and mariners will have to remain alert for
thunderstorms. High pressure will finally build across the lake
Monday night into Tuesday. There will be a period of somewhat
stronger winds from monday evening into Tuesday morning as the
surface high builds across the lake. It is expected that winds and
waves will stay below small craft advisory criteria but it may be
close to small craft advisory conditions.

Winds will back to a more southerly direction Tuesday night and
then south to southwest Wednesday ahead of the next cold front.
The next front should drop across the lake on Thursday.

&&

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

&&

$$
SYNOPSIS...Oudeman
NEAR TERM...Mottice/Oudeman
SHORT TERM...Kosarik
LONG TERM...Kosarik
AVIATION...Mottice
MARINE...Kosarik



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