Scientific Forecaster Discussion
fxus61 kcle 281403
Area forecast discussion
National Weather Service Cleveland Ohio
1003 am EDT Fri Jul 28 2017
a frontal boundary will very slowly drift to the southeast of
the region by the weekend as low pressure begins to strengthen
over the mid-Atlantic. This will provide unsettled weather for
Friday with conditions improving by the weekend as high pressure
becomes the dominant weather feature into next week. Another
system will approach the Great Lakes by the second half of the
Near term /through Saturday/...
forecast remains on track with a few showers developing from
near the North Shore of Lake Erie into northern Indiana. Still
expecting scattered showers to develop in Northwest Ohio where
low level convergence is focused downwind of the lake. Showers
will also expand in the east this afternoon where deeper
moisture will interact with lift ahead of the approaching
trough. Only minor tweaks made with the morning update.
Previous discussion... a cold front has stalled across the
southern portions of the County Warning Area overnight. It will
move little as we await the arrival of an upper level trough.
This trough will cross the region through the day. Middle level
lapse rates will be enough to warrant the at the mention of
thunder. The depth of the low level moisture is in question and
will limit the coverage of any convection. The better coverage
of showers and thunderstorms will be closer to the stalled
boundary and will likely be near and south of a line from
Meadville to Marion. These showers and thunderstorms should move
south and east of the region at some point during the evening.
High pressure will ridge into the area from the upper Great
Lakes overnight with drier air arriving with it. However the
cooler air flowing across Lake Erie will be enough to generate
some cloud cover over NE Ohio/northwest PA into Saturday morning.
Weak upper level ridging builds in response to low pressure
deepening to our east on Saturday. This should push the bulk of
the precipitation and thick cloud cover to our east. Cooler
conditions are expected as 850 mb temperatures fall to near 10
c. Dew points will also be lower than they have been over the
past few days.
Short term /Saturday night through Monday night/...
upper level trough will continue to slide off the East Coast early
in the forecast period. Large broad upper level ridge will begin to
advance east. Fair weather will be the dominant weather through this
period as surface high pressure builds east across the area. As the
high builds into the area along with upper level ridge, subsidence
will take place helping to clear skies out and bring with it some
more sunshine. After a somewhat chilly start Saturday night in the
50s across the area, we should see highs begin to recover again back
into the lower 80s in the west and lower to middle 70s in the east
Sunday. Due to the high being overhead, good radiational cooling
will take place allowing temperatures to drop into the 50s again
Sunday night. However, warm air advection will begin to take shape
Monday on the western side of the surface high with highs in the
middle 80s west to upper 70s east.
Long term /Tuesday through Thursday/...
amplification of the upper level high pressure and resultant ridge
over the western United States will take place. This will cause a
trough to dive southeast into the forecast area by Wednesday. The
troughiness is expected to have some limited moisture with it. At
the surface, a cold front will slide south toward the area Wednesday
and bring with it a chance for showers and thunderstorms. Due to
the warm air advection in place, there is enough support to produce
the thunderstorms across the area. Will keep pops minimal however
with and ahead of the cold front. The cold front is progged to
become diffuse and gradually dissipate over the forecast area
Thursday. Moisture associated with the upper level trough and
surface cold front will linger around. Temperatures will trend
gradually lower with each day due to the colder air in place with
the high pressure.
Aviation /12z Friday through Tuesday/...
patchy MVFR conditions were located across the region this
morning. Northeast flow off of Lake Erie will help to keep
moisture levels up through the day as an upper level trough
approaches. Lift with this feature will generate some showers
and thunderstorms through the afternoon but the coverage is
uncertain. The best chances of the showers/thunderstorms will be
near and southeast of a line from kgjk to ki43. So for now only
have a mention in the kyng taf and some vicinity wording at
kfdy, kmfd and kcak. Most of the MVFR conditions should be with
the showers/thunderstorms with any other MVFR ceilings lifting
late evening as the showers move into PA. Some of this cloud
cover will likely redevelop over NE Ohio and northwest PA as some cooler
air flows across Lake Erie.
Northeast winds will likely increase through the day as the
upper level trough passes. So expect to see winds in the 10 to
20 knot range with some gust up to 25 knots possible.
Outlook...non-VFR in low ceilings Friday night and could
persist into Saturday.
small craft flags will be flying once again as northeast flow sets
up through Saturday afternoon. Winds will diminish Saturday
afternoon and will likely be able to drop the small craft advisories
at that time. Otherwise, winds will become light and variable
through the rest of the forecast period as the high pressure becomes
the dominant weather feature across the area.
Ohio...beach hazards statement through Saturday afternoon for ohz003-
PA...beach hazards statement through Saturday afternoon for paz001.
Marine...Small Craft Advisory until 3 PM EDT Saturday for lez142>149.