Area Forecast Discussion
Issued by NWS Cleveland, OH

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545
FXUS61 KCLE 210610
AFDCLE

Area Forecast Discussion
National Weather Service Cleveland OH
210 AM EDT Mon May 21 2018

.SYNOPSIS...
High pressure northeast of the area will shift further east
tonight. Low pressure from the mid-Mississippi Valley will reach
northwest Ohio Tuesday morning lifting a warm front north across
the area Monday night and taking a cold front across Tuesday.
High pressure then settles across the region for mid week.

&&

.NEAR TERM /THROUGH TODAY/...
Only minor changes have been made to hourly temperatures and
cloud cover to reflect current trends.

Mesoscale models have done an excellent job handling the
showers that dissipated near Toledo and the convection across sw
Ohio. Have leaned heavily on these to modify the timing of the
dissipating morning showers and scattered thunderstorms that
will drift eastward across the region Monday morning into the
early afternoon.

Previous Discussion...
Any number of scenarios can evolve through Monday night and it
is a tough forecast for details. Stratus today has been slow to
lift, but we are getting holes for the late afternoon which has
helped improve temperatures by a few degrees. Eventually we will
get higher clouds move in overhead and then new development
toward Findlay/Marion closest to the quasi-stationary front
across southwest OH. A light shower or two may squeeze into
northwest OH this evening but will not result in more than a few
hundredths of an inch. Did bring in slight chance PoPs across
the southwest if there ends up being late night isolated showers
develop or move in from west-central OH. With partially clear
skies and the high to our north, will allow for a somewhat
cooler night tonight with lows ranging from some upper 40s
northeast OH/nw PA to the lower 50s elsewhere.

So, for Monday morning, most likely scenario is we will be dry.
High to our northeast will want to fend off intrusion of
showers. Upstream convection will likely be too far off and out
of reach for us, but left that possibility in there with morning
chance PoPs for the west/southwest counties. NAM models are the
most aggressive bringing dissipating activity into the west and
even central portions of the area before dissipating it.
Otherwise focus the likely PoPs on Monday afternoon/night as the
shortwave lifts across the area with a belt of stronger low and
mid level winds. Surface low tracks toward northwest OH by
Tuesday morning. Placement of warm front will be key. The
further north it gets the closer to the better shear it gets.
SPC slight risk is just southwest of the area. This will need to
be monitored.

Will maintain the gradient in temperatures across the area with
an east-northeast flow for much of Monday. This will keep the
immediate lakeshore and into Toledo in the 60s with 70s
elsewhere. Milder Monday night.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...
Low pressure will be near Lake Erie on Tuesday morning, moving
east of the lakes during the day. Coverage of showers on Tuesday
will have a lot to do with the evolution of the convection
Monday night and progress of the front. If vigorous convection
moves across the area Monday night, we may see very limited
coverage of showers and thunderstorms re-develop ahead of the
actual cold front on Tuesday. A solution similar to the NAM is
also possible which would suggest the front comes through faster
due to the stronger convection. If the coverage of convection
is not as high, some instability may re- develop across our
southern and eastern areas with showers and thunderstorms
possible during the afternoon ahead of the cold front. These
timing issues will also have an impact on temperatures Tuesday
which can be seen by the large spread in the MOS guidance. Have
gone with a blended approach for temperatures in the north,
leaning towards the warmer guidance in the south.

High pressure will build southeast into the Great Lakes region on
Wednesday with dry northwest flow aloft. Dry weather will continue
through Thursday with lots of sun and temperatures trending
warmer.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Upper level ridge will build east across the local area and
begin to amplify over the eastern seaboard by Saturday night.
This is in response to positively tilted trough diving into the
Mississippi Valley region during this time period. Surface high
pressure will persist across the local area Friday and then
shift off to the east coast by Friday night. There is still some
uncertainty in the models as to how the low pressure system
will influence our area and to what extent. GFS and the European
models show low pressure moving east with the upper level
trough into the central Great Lakes by the end of the period.
Both have slightly different tracks and speed. Canadian model
suggests a similar scenario but weaker in strength and a
possible tropical system developing in the Gulf of Mexico and
moving north into Mississippi and Alabama. If this scenario
occurs, then it appears the moisture will likely be cutoff from
the southeast states and the Gulf. Otherwise, the GFS and
European suggest a plume of moisture will stream north out of
the southeastern United States toward the local area. Due to the
uncertainties in the moisture source, will keep POPs on the
lower side and go with chance category Friday through Sunday.
Cape values begin to surge upward from south to north with a
plume into the southeast portions of the forecast area Friday
night and will mention isolated thunder there and showers
elsewhere. Day time heating will help in destabilizing the
atmosphere and produce thunder Saturday and the unstable
atmosphere will persist into Sunday. Temperatures will trend
upward through early part of the period and as threat for
showers and thunderstorms increases and cloud cover develops
with the storm system, temperatures will hold back a bit by
Sunday.

&&

.AVIATION /06Z Monday THROUGH Friday/...
A warm front will lift north into the area this
afternoon/evening. Sct/bkn VFR clouds will prevail into this
afternoon, with a few hours of MVFR ceilings at KTOL early.
Scattered showers and thunderstorms will move east across the
area late in the period as the front lifts through the area.
Lower confidence in coverage/timing at this point, but MVFR/IFR
reductions in TSRA certainly possible after 00Z. Winds will
generally be light and easterly through the period, then turning
southerly as the warm front moves through late.

OUTLOOK...Non VFR possible Monday night into Tuesday in showers
and thunderstorms. Some non-VFR may linger into Wednesday.

&&

.MARINE...
Aside from a chance of thunderstorms late Monday afternoon and
Monday night, generally good marine conditions expected through
Friday. Onshore winds are in place this afternoon with a ridge
over the lake. Winds will become easterly on Monday and increase
to 10-15 knots ahead of low pressure tracking out of the
Plains. Winds will shift around to the northwest on Tuesday
behind the passage of a weak cold front. High pressure will
build over the lake on Wednesday then shift east on Thursday,
with light winds becoming southerly by Friday.

&&

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

&&

$$
SYNOPSIS...Oudeman
NEAR TERM...Mullen/Oudeman
SHORT TERM...KEC
LONG TERM...Lombardy
AVIATION...Greenawalt
MARINE...KEC



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