Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Cleveland Ohio
119 am EDT Friday Jul 25 2014
cool and dry weather on tap to finish off the work week with high
pressure in control. A warm front will lift north into the Ohio
Valley on Saturday with a return of humidity and temperatures in
the 80s for the weekend.
Near term /through today/...
no major changes for the first evening update. Made a few minor
edits to the hourly temperature and sky grids. Overnight forecast
lows still appear to be on track.
a weak shortwave over the region is aiding in cloud
growth over the area despite large scale subsidence. Additional
mixing and dry air advecting into the region should dissipate any
lingering clouds by this evening. Overnight a cold pool will
settle over the region with h850 temperatures around 8-10c. This combined
with mostly clear skies and calm winds will support temperatures
bottoming out. The amount of continued mixing will continue to
play a part in how low the surface dew points get overnight which
could cause a 1-2 degree difference from forecasted. At this
time...have dewpoints dropping into the lower 50s to middle 40s in
higher terrain in northwest PA. Except for immediate
Lakeshore...temperatures will be in the lower 50s overnight.
Record low temperatures for July 25 are
49-Erie PA. Wouldn't be surprised if a record or two were set
given the right conditions.
Short term /tonight through Sunday night/...
the cold start to the day on Friday will make reaching temperatures above
the low/middle 70s difficult. The cold pool aloft will weaken
supporting temperatures a few degree warmer than today. The cold air aloft
and good solar heating will support generous cumulus development. Southwest
flow behind the exiting surface high will slowly increase dew
points. By Friday night a decent moisture influx on increasing SW
flow will support a rapid rise in humidity. There is a chance for
convection along the frontal boundary as it lifts north...but
given the amount of moisture recovery in the region it will likely
take advecting storms into the region or waiting until midday
Saturday for the better chance for rain. With the warm air
advection at the surface it won't take much to destabilize
conditions with the cold pool still aloft. The caveat may be the
amount of cloud cover and/or cap which will inhibit storm activity
until later in the day. Storm Prediction Center has the region outlooked for day 3 due
to the modest amount of shear and high instability. A strong
upper level trough slides over the upper lakes Sunday and move into
the Ohio Valley again keeping the chance for storms over the
region. Timing on some of the boundaries and perturbations moving
around the upper low is conflicting amongst the models making it
difficult to Pin Point when The Breaks in the rain will come.
Overall rainfall amounts look relatively modest for this time of
year with most areas receiving under an inch with locally higher
Long term /Monday through Thursday/...
by Monday a large trough will have been cut out across the eastern
U.S. So again we will be running temperatures that are a good 10+
degrees below normal with a slow recovery through the work week.
That final push of colder air arrives Monday with a cold front. With
800 mb temperatures dipping to around 8c scattered showers are a good bet with
and in the wake of the front. For the remainder of the week we stay
on the outer fringes of the upper trough and the surface high...so
run 20 or 30 percent precipitation chances through the week. It is not
until Thursday that enough heat and moisture return to add the
mention of thunder. Night lows will be cool too...with Wednesday
looking to be the coolest with the high overhead. Definitely 50s for
lows...if not a few upper 40s.
Aviation /06z Friday through Tuesday/...
high pressure will continue to dominate overnight with clear skies
and perhaps some patchy MVFR fog inland areas. Just a few cumulus
on Friday with some increasing high clouds. Light and variable
winds trending to light south or southwest later today. Onshore
flow will develop at Keri during the afternoon. A chance of
showers and thunderstorms return on Saturday.
Outlook...non VFR in showers and thunderstorms Sat through Monday.
will start out the afternoon with a choppy 2 to 4 Foot Lake as the
northeast winds subside quickly this evening. High pressure overhead
tonight and Friday will be fine day with light/variable winds and no
storms. South-southwest flow returns Friday night/Saturday with the
arrival of a warm front and the beginning of thunderstorm chances
that will run through Monday. One cold front crosses the Lake West
to east Saturday followed by another on Sunday and a third Monday.
Winds will shift from southerly to westerly with each of these
fronts...with a final shift to the northwest on Monday. The amount
of wind is uncertain...but could get a period of 15 to 20 knots over
the weekend. Monday will have a good cold push and will likely need
small craft advisories for the northwest flow. High pressure tries
to edge in from the west on Tuesday.