Area forecast discussion
National Weather Service State College PA
825 PM EDT Thursday may 23 2013
Synopsis...
a cold front will cross commonwealth tonight and early Friday.
An upper low will traverse the region on Friday...providing
cool...showery...almost blustery conditions. Canadian high
pressure will build over Pennsylvania from the Great Lakes and
bring improving and drier weather through the Memorial Day
weekend. Temperatures will trend colder over the next few
days...before moderating through the early to middle part of next
week.
&&
Near term /until 7 am Friday morning/...
showers grew into thunderstorms and rain for much of the area late this afternoon...but
it has quieted down considerably in the past hour or two. Light
rain is all that is left to the west of the line currently through
Bloomsburg/Carlisle. The line could still make some gusts into the
lower 40s before 10 PM...but the low-level stability is getting
high now as rain has proceeded the arrival of the line in the
lower susq. Farther to the west...the first blast of colder air is
already into Warren County...and dewpoints dropping quickly
through the 40s over Ohio and as low as 39 just across The Pond.
Scattered to numerous showers should continue into the night over
the northwestern half of the area...but there will be breaks in between
the showers...especially early. Deformation axis pivots across
central and northern PA very late tonight/early Friday
morning...continuing unsettled conditions. Only expecting a few
tens of an inch from this additional rainfall.
&&
Short term /7 am Friday morning through 6 PM Friday/...
a good chance of rain showers continues Friday as upper low cuts off
and propagates eastward. Cool air behind the surface cold front will
make for a very unpleasant day. Kept highest probability of precipitation across the
north central mountains in anticipation of orographic enhancement along
The Spine of the Appalachians. The arrival of much drier air
wrapping into the west side of developing cut off may shut off
any showers early in the day across Warren Colorado.
Well channeled northwest flow and a tightening surface pressure
gradient will result in a blustery day for late may. Northwest
winds should gust between 25-30kts during the afternoon. Temperatures in the
50s...combined with these gusty winds...will likely result in
apparent temperatures in the 40s during the afternoon across the alleghenies.
Brrr...
&&
Long term /Friday night through Thursday/...
main concern Friday night will be the potential of frost/freeze
headlines across the Allegheny plateau. Aforementioned pressure
gradient appears likely to keep the winds up Friday night...so
widespread frost seems unlikely. Hard to believe there will be a
widespread freeze this late in the season without a calm wind...so
have leaned on the warm side of MOS /closer to ec MOS/ and kept
temperatures just above freezing for most of the West Mountains Friday night.
Model trend continues to slow eastward progression of upper
low...so have kept mention of rain showers in the forecast through Friday night
across the eastern zones...and tapered them off later across the
central counties.
Eastern PA will remain on western periphery of upper low Sat/Sat
night. So...have increased the cloud forecast a bit over the eastern
counties and can/T completely rule out a stray rain showers over Sullivan
or Schuylkill Colorado. Elsewhere...confidence in a mostly sunny Saturday is
fairly high...as all model data pulls low precipitable water air southward across
central/western PA on Sat. However...despite strong may
sunshine...model 800 mb temperatures well blw normal should cap readings in the
l/M 60s across much of the area...with highs in the u50s likely
across the high terrain. Deep mixing should draw some gusty winds
to the surface again on Saturday. 800mb wind fields suggest much of
the area will see gusts between 25-30kts by afternoon.
Bulk of medium range guidance continues to indicate a high degree of
confidence in dry weather holding through Memorial Day...along with a
gradual warming trend...as upper low over new eng slowly lifts away
from the area. The models have slowed the progression of the
exiting low...so with northwest flow and colder air over the region with
light winds...there remains a chance for frost over the northwest mountains
Sunday night/Monday morning. The rest of the regions will be in
the low 40s.
By the middle of next week...a building upper level ridge is
advertised by the medium range guidance over the miss valley. Across
the east...surface high will pass off the coast...resulting in a
warmer SW flow. Some model diffs with respect to how fast the low
level moisture returns. However...have gradually introduced a chance of
diurnal convection in the Tuesday/Wednesday time frame.
&&
Aviation /00z Friday through Tuesday/...
adjusted tafs for bands of showers and isolated storms.
Much of the area just has middle level clouds and decent visibility
at the current time.
Expect conditions to go down hill later tonight...as the upper
level system digs southeast and starts to close off.
Friday will be a windy and cold day...with MVFR and IFR
conditions in many spots. For now...did bring conditions
back to VFR later in the after...given strong sun angle.
Weekend looks OK...but breezy.
Monday should be decent...as high builds over the area.
Could be a few showers and thunderstorms late Tuesday...as
strong warm front moves across the region. Strong storms
could form...given very strong warm advection and directional
wind shear. Back to Summer for a few days.
Have a good Holiday weekend.
Outlook...
Sat-Mon...VFR. No sig weather expected.
Tuesday...chance of showers and storms late.
&&
Ctp watches/warnings/advisories...
none.
&&
$$
Synopsis...dangelo/devoir
near term...dangelo
short term...devoir
long term...Fitzgerald/ceru
aviation...Martin
