Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 220220
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1020 PM EDT Mon Aug 21 2017

.SYNOPSIS...
High pressure over the region will continue to move east of the
area tonight. Low pressure will move northeast across the Great
Lakes Tuesday, forcing a cold front through the region by
Tuesday night. High pressure will build east across the region
Wednesday through the first half of the weekend.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
An isolated storm or two remains in Crawford County PA with dry
conditions elsewhere. West of the area, low pressure is located
over northern Wisconsin with showers and thunderstorms
extending southwest into Kansas along the trough axis. The low
will deepen overnight as it tracks into southern Ontario ahead
of a deepening upper level trough. A low level jet will develop
across Illinois, Indiana, and Michigan which is where most of
the shower activity overnight is expected to be focused, so will
continue with fairly low pops for the overnight hours. LLJ
energy shifts into NW Ohio during the morning and will expect to
see scattered showers and thunderstorms across NW Ohio and Lake
Erie. Some breaks in the clouds are expected farther east which
should help the atmosphere destabilize. The Slight Risk for
severe thunderstorms still appears on track with stronger storms
more likely across southern and eastern areas. The time frame
for severe storms is focused during the afternoon ahead of the
approaching cold front.

Previous discussion...
Most of the models are indicating some type of prefrontal
trough/scattered convection moving into the area late in the
overnight into tomorrow morning. This may hamper the severe risk
across the area a bit, depending on the amount of cloud cover
and ongoing convection. Main synoptic front will not push into
the area until late Tuesday afternoon through Tuesday evening.
It is possible that the prefrontal trough will become the
dominant severe threat, pushing the bulk of the activity
southeast of the forecast area. Additional redevelopment is
possible along and just ahead of the main synoptic front, but
the severe threat would be considerably diminished. Timed pops
tomorrow to reflect this scenario, with the highest pops east of
the I-71 corridor during the afternoon.

No major changes to the temperatures through Tuesday, with a degree
or two drop for lows Tuesday night as cold front moves through the
area.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The short term begins Wednesday with models showing an upper
low over Ontario and cyclonic flow across the Great Lakes. A
short wave with some limited moisture will be dropping southeast
across the lakes and will move into the region during the
afternoon Wednesday. Looked at forecast sounding for KERI and is
shows low level lake cape and moisture below 700 mb in the
afternoon and evening. For this will have a band of chance pops
for showers from Wednesday afternoon through Wednesday night.
Thursday a rather sharp short wave rotates through the Great
Lakes so will continue chance pops most places. Thursday night
and Friday high pressure builds in so will keep forecast dry.
Temps below normal through the period.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
By Saturday large area of Canadian high pressure will extend
from james bay south across all of The Great Lakes. Models
continue to track the high slowly east across the Lakes. Expect
dry conditions with mostly sunny skies and mild temperatures
through the weekend. Models begin to diverge late in the period.
Models a little slower than ydy. ECMWF moves next system
through late Monday into Monday night while GFS continues strong
ridge over the Eastern Lakes. For now will continue with the
ECMWF solution and keep low chance pops going for next Monday.

&&

.AVIATION /00Z Tuesday THROUGH Saturday/...
An isolated shower/thunderstorm still near YNG with
thunderstorm activity decreasing quickly this evening. VFR
conditions expected for the overnight with high clouds
thickening and starting to lower. Continued with a mention of
LLWS at TOL/FDY as a low level jet clips NW Ohio while moving
from Indiana into Michigan. Chances for showers will increase
towards 10-12Z in NW Ohio as a trough approaches from the west
and moisture advection increases. Scattered showers are possible
through midday with coverage of thunderstorms increasing during
the afternoon as instability develops ahead of a cold front.
Some thunderstorms on Tuesday afternoon could be strong to
severe. Southwest winds will be breezy on Tuesday with gusts to
20-25 knots all sites. Winds will shift to the west and
eventually NW behind the cold front.

OUTLOOK...Non-VFR likely in scattered showers and thunderstorms
Tuesday night across eastern sites. Patchy morning BR possible
around sunrise, Thursday-Saturday.

&&

.MARINE...
High pressure now off the east coast as low pressure develops from
Nebraska and Iowa to Wisconsin. This low will strengthen overnight
as it moves northeast across the central Great Lakes.  The low will
reach southeast Ontario by Tuesday morning.  A trailing cold front
will cross the lake Tuesday afternoon and evening.  Expecting
southwest winds to increase on Tuesday to 15 to 25 knots ahead of
the front with winds dropping to 15 to 20 knots tuesday night as
they turn northwest behind the front. Will issue a small craft
advisory  for Lake Erie starting at 10am Tuesday lasting through
10am Wednesday. Winds will remain northwest on Wednesday at 15 knots
or so so there is a chance the small craft advisory may need to be
extended east third.  Either way the lake should continue rough
through the day.  Wednesday and Wednesday night through Saturday
high pressure will build across the lakes from central Canada. North
winds Thursday should turn more northeast Friday and Saturday. Again
would expect choppy conditions but at 5 to 15 knots expect waves
will be well under advisory levels.

&&

.CLE WATCHES/WARNINGS/ADVISORIES...
OH...Beach Hazards Statement from 9 AM EDT Tuesday through Tuesday
     evening for OHZ010>012-089.
PA...Beach Hazards Statement from 9 AM EDT Tuesday through Tuesday
     evening for PAZ001.
MARINE...Small Craft Advisory from 9 AM Tuesday to 10 AM EDT Wednesday
     for LEZ146>149.
     Small Craft Advisory from 9 AM Tuesday to 4 AM EDT Wednesday
     for LEZ142>145.

&&

$$
SYNOPSIS...Greenawalt
NEAR TERM...KEC/Greenawalt
SHORT TERM...TK
LONG TERM...DJB
AVIATION...KEC
MARINE...TK



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