Area Forecast Discussion
Issued by NWS Cleveland, OH

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000
FXUS61 KCLE 191620
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
1220 PM EDT Wed Jul 19 2017

.SYNOPSIS...
High pressure over the area will weaken slightly today and allow
a cold front across the central Great Lakes to approach the
area. The front will drop into the area tonight and remain
stalled across the region on Thursday. The front will move south
Thursday night as high pressure builds in for Friday.

&&

.NEAR TERM /THROUGH THURSDAY/...
Temps running 3 to 5 degrees hotter than ydy so bumped up
afternoon temps a couple of degrees.

Original...Today a cold front across the central Great Lakes
will move toward the area. By 00Z the front should be near a
Toronto to South Bend line and about to enter northwest Ohio.
The nam12 as well as the HRRR is depicting scattered convection
primarily in and around nwrn Ohio and possibly on the lake late
afternoon possibly lasting into early evening. Model CAPES at
00Z are around 1500-1900 j/kg in the northwest so convection is
certainly possible although expect focus will be well west where
moisture/instability and low level forcing is better. For now
will have chance pops northwest of a line from the islands to
wood county. Highs today mid to upper 80s. Tonight the NAM12
suggests the front drops into the area although manual progs
keep it north. Will side more with the new NAM2 guidance however
dont believe the front will be too active overnight. Thursday
however much better instability moves into the area with BUFKIT
forecast capes from 2500 to over 3000 j/kg. Also both the NAm
and the GFS show a short wave moving through the area in nwly
flow aloft. MAV pops are generally in the slight chance to low
chance category for Thursday while the NAM shows mostly likely
pops. For now will split the difference and go with high chance
pops for the afternoon. Highs again mid and upper 80s.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
Northwest flow will be in place across the Great Lakes by Thursday
night as the area of high pressure gets shunted off to the south and
east. A weak embedded shortwave trough and its associated surface
low will cut eastward across the southern Great Lakes Thursday
afternoon, dragging a cold front southeast through the area Thursday
evening into Thursday night. There will be plenty of moisture in
place with PW values generally greater than 1.5 inches. This will
lead to thunderstorm development along the front as it moves through
the area. Strong shear will be in place thanks to the 50+ knot
northwest flow aloft, and we should have ample instability (1500-
2000 J/KG MLCAPE) built up ahead of the front as surface dewpoints
surge into the lower 70s. This will mean a threat for severe storms
continuing into early Thursday night (potentially in the form of an
MCS). The primary threat would likely be wind damage as a linear
line of storms forms along the front and moves east-southeast
through the area. Some of the initial storms could also contain
severe hail as long as they are able to stay a little more isolated.

The cold front will stall out somewhere across central Ohio Thursday
night and slowly lift back north as a warm front Friday into Friday
night. We will see a continued chance of showers and storms along
and south of the northward moving warm front Friday and Friday
night. By Saturday, we will be well within the warm sector and
should see enough instability combine with the strong northwest flow
to trigger more showers and storms right on through Saturday night.

Temperatures should be around or slightly above normal through the
period, although any afternoon storms could inhibit highs from
reaching their potential. With dewpoints in the lower 70s, the heat
index will be quite high at times.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
A cold front will move southeast through the area Sunday, bringing
with it a continued chance for showers and storms. A trough over the
Great Lakes will be slow to move out, hanging around through Monday.
Will continue with a chance for some additional showers Monday until
a ridge begins to build in Monday night into Tuesday. This will
bring dry weather back to the region. Highs in the long term will
start off near normal, but will drop below normal behind Sunday`s
cold front. Highs Monday and Tuesday look to be in the mid to upper
70s.

&&

.AVIATION /12Z Wednesday THROUGH Sunday/...
A cold front across the central lakes will approach the area
during the day before stalling just to our north. Could see
isolated late afternoon thunderstorms with best chances west.
Given isolated nature have left out of TAFS for now except for
KTOL and KFDY with VCTS after 20Z. Otherwise aside from patchy
early morning MVFR fog both this morning and Thursday morning
expect VFR conditions across the area. Tonight with added
moisture and a front in the area could see a bit more fog. Did
take inland locations to IFR for a time around dawn Thursday.
Also with the front will likely see more thunderstorms in the
area Thursday afternoon and evening just beyond the TAF period.

OUTLOOK...Non-VFR possible Thursday night through Sunday in
early morning fog/mist or scattered thunderstorms.

&&

.MARINE...
Light southwest to west-southwest flow will continue until a cold
front moves southeast across Lake Erie Thursday night. The pressure
gradient will be weak enough that onshore flow will likely develop
over the immediate lakeshore the next couple of days. The northwest
flow behind the front will be light and short-lived, switching back
out of the southwest by Friday night.

Southwest winds will then continue through the weekend, increasing
slightly on Sunday as low pressure moves across the central Great
Lakes. The weather will be unsettled through much of the period,
especially from Thursday afternoon and beyond. Multiple rounds of
showers and storms are expected.

&&

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

&&

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


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