Area forecast discussion
National Weather Service State College PA
358 PM EDT Tuesday Jun 18 2013
Synopsis...
the persistent June pattern of a broad through over the middle-
Atlantic and northeast states is forecast to transition and be
replaced by a summertime upper level ridge migrating eastward from
the plains. A slightly cooler and less humid air mass will follow
in the wake of a cold front tonight into Thursday. Increasing heat
and humidity will arrive on schedule with the official start of
astronomical Summer...and last into the upcoming weekend.
&&
Near term /until 6 am Wednesday morning/...
best low level convergence is along the Turnpike and southern border.
Thus...expect highest chances for rain showers to be there early this
evening. A few more cumulus are building over the local area...where
heating has thus far been hampered by thick high cloud cover.
So...cannot pull all mentions of showers - especially with the RUC
insisting on making more/heavy showers over the ridge and
valley/middle susq before sunset. Tall cumulus over bfd will also warrant
at least isolated probability of precipitation in the Northern Hills for the next few hours as
well. Subsidence and clearing will come to the area from north-S
through the late evening and overnight. Winds do go calm in many
locations. So a little fog is possible - early in bfd before
dewpoints tank...and around the rest of the area later at
night...especially those places that did get wet today.
&&
Short term /6 am Wednesday morning through 6 PM Wednesday/...
last shortwave to enhance the trough overhead will run over the
region around sunrise...and then The Heights start to rise
steadily. Surface high pressure finally pushes far enough to the south
and into PA to remove most cloud cover and almost every bit of
probability of precipitation. Will just hang onto a slight chance over the highest terrain of
The Laurels/SC mts where enough moisture and elevated heating surfaces
may combine to pop off a rain showers or two. Temperatures will be a degree or two
lower Wednesday than Tuesday.
&&
Long term /Wednesday night through Tuesday/...
upper ridge over Central Plains will build eastward into PA Wednesday
night through Saturday...as 500 mb heights rise to 588dm. Center
of surface high slips southeast across Great Lakes and is located over
central PA on Wednesday night...setting up ideal radiational cooling
conditions. Dewpoints will still be lingering in the 50s across
southern PA...but much lower dewpoints north of I-80 will allow
temperatures to drop well into the 40s.
Starting Thursday...low level S-southwesterly return flow around surface high /drifting
off the East Coast/ will bring a gradual increase in low level moisture
through the end of the work week...with just a slight chance for an afternoon
pop-up/airmass type thunderstorm on Friday. Otherwise...sunny to mostly sunny
conditions will prevail as temperatures climb to seasonal normals on Thursday
and begin a string of above normal days on Friday.
Heat and humidity continue to increase heading into the weekend as
heights peak. Bigger surge of higher dewpoints slides in from the
west as heat continues to build...so a series of very warm and
humid days are in store for Sat into Tuesday...with overnight lows
remaining quite mild as well. With stagnant air and increasing
humidity on back side of surface high...held on to 20-30 probability of precipitation most
afternoons - with highest chances over western higher terrain of
isolated differential heating initiated storms.
Pattern also has a ring-of-fire look to it so will need to watch
for mesoscale convective system activity/ridge rollers sliding down from the northwest...though
latest models not quite as bullish on that. Ec overall producing
more convection than the GFS...but general areas are similar.
&&
Aviation /20z Tuesday through Sunday/...
scattered rain showers along the southern border may be joined by isolated/scattered rain showers over
the bulk of the area late this afternoon. But focusing mechanisms are
ill-defined at this time. Recent RUC runs continue to develop rain showers
over the central cos...and tall cumulus present over bfd. Will keep
vcsh in most airfields through 22-00z. Southern terminals may still
have some rain showers nearby through midnight...but covg will remain
sparse enough to not mention the in tafs.
MVFR ceilings and visibilities will again be a possibility tonight in fog -
especially where rain occurs. So some mentions of fog will be in the
tafs. High pressure then controls the weather into the weekend. Just a
very slight chance of a rain showers exists over the highest terrain on Wednesday.
But 99pct of the area will be dry and VFR.
Outlook...
Thu-Fri...no sig weather expected.
Sat-sun...isolated PM thunderstorms and rain impacts possible.
&&
Ctp watches/warnings/advisories...
none.
&&
$$
Synopsis...steinbugl
near term...dangelo
short term...dangelo
long term...rxr
aviation...dangelo
