Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
137 PM EDT Sat may 30 2015
moisture will spread north across the area today and interact with
a cold front approaching from the north. This frontal boundary
will stall in the vicinity of Lake Erie overnight with a wave of
low pressure tracking northeast along the boundary on Sunday. The
front will push south on Sunday night with high pressure building
overhead on Tuesday.
Near term /until 6 PM this evening/...
a few showers on the radar late this morning and more shower
activity is expected to develop. The majority of the shower and
thunderstorm activity will not develop until late this afternoon
and evening. Many breaks in the clouds allowing for quite a bit of
heating. Based on the high temperatures yesterday I believe the
current forecast highs are too low. With the late arrival of the
clouds and precipitation I believe we will warm into the middle 80s
in many locations. I will adjust the current high temperatures for
today into the middle 80s. No other changes.
Original discussion...the forecast area remains in the warm
sector ahead of a cold front approaching from the north. Water
vapor imagery shows a potent upper level trough pushing south
across Ontario while a plume of moisture can be seen spreading
north up the Mississippi Valley. This moisture which is just
starting to sneak into Northwest Indiana will be directed eastward with
time as the trough pushes south this afternoon. The surface front
itself will be slow to arrive...but moisture will increase this
afternoon and remnants from upstream activity may provide a
trigger for convection this afternoon. Some of the high resolution
models seem a little too fast with showers/thunderstorms
developing this morning and think activity will follow more of a
diurnal cycle...increasing in coverage this afternoon. Precipitable water values
are forecast to increase to around 1.70 inches as the deeper
moisture arrives. Instability may be a little better out ahead of
the front where more sun is likely. Models showing around 1000
j/kg of ml cape developing this afternoon and expect the greatest
coverage of thunderstorms to be focused immediately ahead of the
front from Northwest Ohio...extending NE towards Cleveland and
Erie by this evening. Storm motion today will be to the NE at
about 20 knots which will support training of storms. Due to the
threat of training...moderate storm motion and enhanced
precipitable water values...expecting some thunderstorms to
produce locally heavy rainfall. The coverage of the more robust
convection is still somewhat hard to determine so did not want to
go with any flood watches...especially given the recent dry
conditions...but will need to keep an eye on rainfall this
afternoon/evening. Added a mention of heavy rain possible with
thunderstorms to the favored areas. The Storm Prediction Center
also has the area in a marginal risk for severe storms with wind
gusts being the primary threat. This would be mainly in the form
of a wet microburst with limited organization today. One question
will be if convection tends to propagate to the south with time
towards the better instability. This is not real favorable given
the warm middle levels but will be something to watch and could
reduce threat of training...or at least shift it farther south.
Short term /6 PM this evening through Tuesday night/...
convection will likely continue into the evening with a decreasing trend
as we lose diurnal support...before the next wave rides north
along the front on Sunday. This should place a swath of rain on
the northwest flank of the low with thunderstorms possible in the
east ahead of it. Did raise temperatures in NE Ohio and lower them
towards Toledo. Models are placing a 1.50-2.00 maxima of rain to
the north of the storm track but this may end up clipping
Northwest Ohio or passing just north of our area. Depending on
how much rain we receive today...we may need to consider a Flood
Watch for Sunday if a secondary round of heavy rain is expected. A
limiting factor for the heavy rain could be the intrusion of a
middle-level dry slot as seen on the GFS so we are still trying to
pin down the track of the highest quantitative precipitation forecast.
The front will eventually be pulled south behind the departing
wave on Monday evening with any lingering precipitation becoming
light. Much cooler temperatures expected on Monday with highs
struggling to reach the low 60s. High pressure will build
southeast overhead on Tuesday with partly to mostly sunny skies
helping temperatures recover to the 70s except 60s near Lake Erie.
Long term /Wednesday through Friday/...
in general...the models have upper ridging over the area until
late Friday when a weak trough is shown moving east through the lakes.
Dry air is in place on Wednesday then by Friday enough moisture appears to
have moved back into the area for scattered rain showers/thunderstorms and rain to develop. Near
normal temperatures on Wednesday should increase to above normal by Friday as east
winds turn south.
Aviation /18z Saturday through Thursday/...
numerous showers and a few thunderstorms have developed
this afternoon. This trend will continue through the afternoon
with occassional showers and a few thunderstorms impacting the
taf locations. In general ceilings will remain VFR with brief MVFR
conditions in thunderstorms. Models continue to show a wave
developing on the frontal boundary as it moves into the northern
sections of the forecast area. MVFR to IFR conditions will be on
the north side of the front overnight. The southward progression
of the front before the wave develops will likely dictate the
areas of IFR tonight. Right now tol...cle and eri have the best
chances of seeing IFR conditions after 06z. MVFR and IFR will be
widespread by 10z. Showers will continue overnight as well.
Thunder will always be possible but the threat should diminish
during the night hours. Southwest winds this afternoon will shift
to the north and then northeast overnight.
Outlook...non VFR likely Sunday.
a cold front will drop southeast across Lake Erie this evening
causing SW winds of 10 to 20 knots to shift to northwest then NE and
increase to 15 to 25 knots for Sunday. Numerous thunderstorms and rain will occur with
the frontal passage so beware. A Small Craft Advisory will likely be needed for the
end of tonight through sun evening. Winds and waves will gradually diminish
Sun night into Tuesday as high pressure pushes into the lake. The high
should provide light east to NE winds on Wednesday as it begins to shift east
of the lake.