Area Forecast Discussion
Issued by NWS Cleveland, OH

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FXUS61 KCLE 211043
AFDCLE

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

.SYNOPSIS...
High pressure over the Great Lakes will shift east into New
England today. Low pressure over the Mid Mississippi Valley will
lift northeast into the southern Great Lakes tonight, bringing a
warm front north through the area. The low will shift northeast
into New England Tuesday, pushing a cold front southeast through
the area. High pressure will slowly build east across the Great
Lakes region Tuesday night through the end of the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
A few showers have popped up just southwest of the forecast
area, associated with some weak 850mb-700mb frontogenesis and
weak (150-250 j/kg) instability. Hi-res guidance shows this
activity weakening over the next few hours, but have added some
slight chance pops across the western part of the forecast area
this morning. Otherwise, no changes to the forecast.

Original discussion...
Somewhat active near term period expected across the region,
although high pressure pushing east across the Great Lakes this
morning should keep the region dry into this afternoon. Main
challenge to the forecast is onset of precip this
afternoon/evening, as low pressure over Missouri tracks
northeast into the southern Great Lakes. Convective activity
over the Mississippi valley will lift northward across Indiana
throughout the day, and currently expecting this activity to
remain west of the area until after 18Z. Hi-res guidance trends
some showers/storms associated with this activity into northwest
Ohio by 18-21Z, otherwise the bulk of the convective activity
will develop late this afternoon/evening as a warm front lifts
north into the area. This activity will track northeast across
the area through the evening into the overnight as the front
lifts north of the forecast area. Have generally slowed down
pops several hours through today/this evening based on the
latest guidance trends.

Somewhat of a conditional severe weather threat exists today
across northern Ohio. Decent mid level flow, mainly a potent
700mb jet tracking across northern Ohio this evening, will
provide deep layer shear values of 35-50 kts. The main question
is the northward extent of the instability in the warm sector.
Right now, only confident in destabilization along/south of a
Findlay to Mansfield line around 00Z, with a quick downtrend in
instability near/after 03Z as the front lifts north. There could
be a few initially discrete cells that develop early evening
with the better shear in place, but the shear will diminish as
well after 03Z as the mid level flow weakens across the area.
Feel comfortable with the SPC Day 1 Outlook with a marginal risk
for the western half of the area and the slight risk just
southwest of the forecast area.

After the front lift north of the area after 06Z, thinking there
might be a lull in precip across the area, with showers/storms
more scattered/isolated than widespread through the overnight.
Have backed down pops into the chance range into Tuesday
morning. The cold front will begin to move east-southeast across
the area Tuesday, with guidance trending a bit slower vs.
previous model runs. Have generally kept pops in the mid chance
to likely range from Tuesday afternoon. Another severe threat
exists across the southeast part of the area Tuesday afternoon,
highlighted by an SPC Day 2 marginal risk. A little more
uncertainty with the timing of the front and amount of
destabilization, however confident enough in likely pops with
development expected along/ahead of the front.

As far as temperatures, a tricky forecast for today with
easterly flow off the lake keeping temps several degrees cooler
downwind, especially in the Toledo area. Also some question for
temps south as the front may lift north to bump temps up a bit
early this evening. Have generally stayed close to a MOS
consensus, favoring the MAV vs. MET. Highs across much of the
area not downwind of the lake with reach the mid to upper 70s,
with mid to upper 60s near and downwind of the lake. No changes
to temps tonight or Tuesday.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
The cold front may not be east of the forecast area at the
start of Tuesday night but it should make progress. Will keep a
small chance pop in the eastern counties the first half of
Tuesday night.

High pressure will build in on Wednesday. The north wind will keep
the lakeshore a bit cool otherwise temps will likely be near normal
or a couple of degrees above normal. Fair weather cumulus is likely
Wednesday but the cumulus should be minimal by Thursday. Cirrus and
perhaps even some mid clouds will probably spill over the top of the
ridge by Thursday but I suspect it will still be mostly sunny.
Temperatures on Thursday will likely recover to 75 to 80.

The ridge aloft should max out on Friday. Difficult to say how
quickly a thunderstorm complex or thunderstorm debris from the upper
midwest will round the top of the ridge but the high heights will
likely shield us on Friday.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
By Saturday some activity will certainly try to sneak in from
the west as most of the models are progressive with the trough.
The forecast is complicated somewhat by a southern system and
tropical moisture which may spread north over the weekend. The
consensus is to favor more of a northward push and not so far
west as shown by the ECMWF. If any of the moisture can get this
far north it may take until Saturday night or Sunday. Do not
have the confidence to try and pin point a particular forecast
period of "likely" or higher pops yet, will generally forecast
40-50 pops over the weekend and include thunder. Temperatures
will be warm and dew points will come up and we will likely stay
in the warm sector all weekend although it could be close on
Sunday as the cool front begins to slide east.

&&

.AVIATION /06Z Monday THROUGH Friday/...
A warm front will lift north into the area this
afternoon/evening. Sct/bkn VFR clouds will prevail through this
afternoon. Scattered showers and thunderstorms will move east
across the area late this afternoon into the evening as the
front lifts through the area. Have backed off several hours on
SHRA/VCTS mention this evening due to the latest trends in the
models. Winds will generally be light and easterly through the
period, then turning southerly as the warm front moves through
late.

OUTLOOK...Non VFR possible Tuesday in showers and
thunderstorms, mainly across eastern sites. Some non-VFR may
linger into Wednesday.

&&

.MARINE...
ENE winds will try to pick up somewhat on Lake Erie today as the
pressure gradient tightens between low pressure over the Mississippi
Valley and high pressure over eastern Canada. Wind speeds should
stay below 20 knots and small craft advisory conditions are not
expected. The low pressure system will pass near Lake Erie late
tonight or Tuesday and winds will shift westerly. Winds will veer
more from the north as high pressure builds across the Great Lakes
mid week and while typically the northwest to north winds can become
brisk, it appears as though winds will not be all that strong. winds
will back to SSW late in the week as high pressure moves off to the
east.

&&

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

&&

$$
SYNOPSIS...Greenawalt
NEAR TERM...Greenawalt
SHORT TERM...Kosarik
LONG TERM...Kosarik
AVIATION...Greenawalt
MARINE...Kosarik


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