Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
730 am EDT Monday may 4 2015
low pressure will track northeast into Quebec today with a trailing
cold front sinking south across Michigan. The frontal boundary will
approach the area and stall through Wednesday...then lift back as a
warm front on Thursday.
Near term /until 6 PM this evening/...
a surface trough extends from the plains...across the western Great
Lakes towards northern Quebec. Showers and thunderstorms have been
ongoing across the upper Midwest overnight where shortwave energy
aloft is interacting with low level moisture advection along this
boundary. Coverage of thunderstorms has greatly diminished over the
last few hours with a limited amount of instability. The
challenge for today is determining what effect the upstream
convection will have on timing of thunderstorms moving into the
As of 7 am...showers were decreasing along the outflow boundary
moving east across northern Indiana. A larger area of showers was
located in the Theta-E ridge across northern Illinois. Meanwhile an
upper level trough will move across Lake Superior today...with a
weak cold front pushing south across Michigan this afternoon. The
RUC shows the moisture advection pushing into Northwest Ohio
between 14-18z which could result in some leading showers during
the late morning towards Toledo. Showers during the morning could
also be triggered as the upstream mesoscale convective vortex arrives. Coverage of showers
and thunderstorms is expected to increase during the afternoon as
the front approaches and interacts with the moisture rich air.
Dewpoints will start the day in the 40s and will moisten as the
surface trough approaches. The low dewpoints will keep instability
on the lower side until later today...although never getting much
of 1200 j/kg. Upper level jet remains well north of the area so
shear will be a limiting factor for more organized thunderstorms.
The Storm Prediction Center has most of northwest and north
central Ohio in the marginal threat for severe weather as the
front approaches which is reasonable. Not expecting more than an
isolated strong storm or two with the primary threat being wind
gusts to 50 miles per hour. Tweaked highs down a degree or two in Northwest
Ohio where considerable cloud cover is expected...even this
morning. Areas farther east will see more sun before the clouds
Short term /6 PM this evening through Thursday night/...
will continue with likely probability of precipitation as the front sinks south into
Northern Ohio this evening. The push of middle-level dry air gets as
far south as Lake Erie...with the instability axis weakening overhead.
This should result in a decreasing trend to thunderstorms late
tonight. The next round of shortwave energy will move along the
stalled frontal boundary on Tuesday and should see scattered to
numerous coverage of showers and thunderstorms again. Lowered
highs on Tuesday across the north as winds develop off Lake Erie
and sufficient cloud cover has a limiting effect on temperatures.
A few of the southern counties may still reach the middle 70s.
The ridge starts to build aloft from Tuesday night into Wednesday
which should bring an end to convection. Will hold onto the low
20-30 percent probability of precipitation on Wednesday with some uncertainty on where the
stalled frontal boundary will reside at that time. By Thursday we
return to having a dry forecast as the cap strengthens overhead. The
warm front lifts back early Thursday which supports highs in the
middle 70s to near 80 for much of the area.
Long term /Friday through Sunday/...
upper level ridge looks like it will still be in control of the
region on Friday. However with an increase in low level
moisture...strong heating and the potential of some convergence
along a lake breeze and over the Central Highlands we will need to
mention some thunder in the grids. Since heights aloft are rather
high it will limit the coverage of any of the thunder. By Saturday a
cold front will move into the central Great Lakes and should be
enough to increase thunder chances across the west. A lake boundary
may also ignite a few storms across NE Ohio into northwest PA. There should
be a lull in thunderstorm activity after midnight Saturday night but
chances will increase on Sunday as the weakening cold front passes.
Current thinking is that the coverage will be scattered at best.
It continues to look like temperatures will remain above average
with highs generally within a couple degrees of 80. Cooler near the
Aviation /12z Monday through Friday/...
VFR conditions will continue until thunderstorms develop this
A cold front from the upper Great Lakes to the Central Plains will
move to the east and southeast through the day. Thunderstorms have
been decreasing in coverage as they pulled away from the cold front
this morning. The few showers that remain along the weakening
outflow boundary look as if they will dissipate before reaching Northwest
Ohio. Will remove their mention from the Toledo area. Otherwise
some convective debris cloudiness is expected across the region
today. The weakening outflow boundary and the cold front will
provide low level convergence to generate new thunderstorms early
to middle afternoon. The thunderstorms will then drift to the east
and southeast into the evening hours. Still uncertainty on when
the convection will develop and have a 6 hour window of time when
the thunder may occur (vcts). However we did attempt to provide a
best 2 hour window for convection for each location. This 2 hour
window is where we placed the IFR conditions.
Outlook...non VFR possible Tuesday into Tuesday night in
scattered showers and thunderstorms.
southwesterly winds will increase ahead of a cold front that will
move across Lake Erie this evening. These southwesterly winds should
be in the 10 to 20 knot range through the day with the larger waves
of 2 to 3 feet across the open waters. Winds and waves will decrease
tonight as the cold front stalls over northern or central Ohio. High
pressure over southern Canada will produce northeast to east winds
through Thursday. Most locations will keep wind speeds in the 5 to
10 knot range but some locally higher winds...maybe up to 15
knots...across the nearshore waters will likely occur Tuesday