Area forecast discussion
National Weather Service State College PA
1204 PM EDT Wednesday Jun 19 2013
Synopsis...
the persistent/broad mean trough will be replaced by a upper
level ridge migrating eastward from the plains. This pattern
shift will bring some of the warmest air of the season to the
area...with the increasing heat and humidity arriving on schedule
with the official start of astronomical Summer early Friday morning.
Temperatures are forecast to remain above normal over the weekend
and into next week...with shower activity focused along west-east
oriented jet stream and frontal boundary extending from the upper
Midwest into the northeast U.S.
&&
Near term /through tonight/...
visible Sat imagery shows mostly sunny skies across central
PA late this morning...with fair weather cumulus cloud streets forming along
the nerly shear axis. Drier air mass and building subsidence inversion
should be sufficient to keep skies mostly sunny this afternoon.
500 mb heights will start to rise as the mean northestern Continental U.S. Trough finally
lifts out. High pressure will bring fair weather to the area today with low
humidity and temperatures about 3 to 5 degrees below seasonal normal.
Received several observer reports earlier this morning of min
temperatures in the upper 30s across northern tier counties. With clear
skies and low precipitable waters expected tonight...will make for another chilly
night overnight tonight especially across northern PA where nighttime
lows will fall into the upper 30s.
The GFS- based mav guidance has 36f for bfd suggesting some patchy
frost may even be possible. This is the lowest MOS guidance when
compared against the NAM/met...ec/ecm and is on the low end of the
18/00z ecens members.
&&
Short term /Thursday through Friday night/...
upper ridge over the plains states will shift eastward this period as
a deep closed low moves from the Pacific northwest into the northern rockies. 500 mb
heights climb above normal by Friday. Winds will veer around to the
south/southwest as the surface high moves off the middle-Atlantic coast. The
return flow will result in an increase in daytime temperatures and low level
mstr/dewpoints/humidity. The warmer pattern will arrive on
schedule with the first day of astronomical Summer /see climate
section for more details/. Model data suggests isolated diurnal
convection is possible along The Spine of the north-central appalchns
into the Laurel Highlands/S-cntrl ridges...but for the most part
expect most areas to stay rain-free. Capping inversion may be a
limiting/negative factor for terrain-induced thunderstorms later this week.
&&
Long term /Saturday through Tuesday/...
northern rockies 500mb trough will eject northeastward into the S-central Canadian
prairies over the weekend...allowing the subtropical ridge to
retrograde and expand westward back across the Southern Plains. With broad
subtropical ridging covering the southern 1/2 of the Continental U.S....the jet
stream will be confined along the US/Canadian border - which is
where it should be for this time of year. The global model and
ensemble guidance shows another weak trough developing over then
northeast states by the middle of next week...as the upper ridge
becomes more pronounced and builds northward across the Great Basin/inter
mountain west.
The main sensible weather impact this period should be the heat
and humidity...with above normal temperatures expected to last into the
middle of next week. A consensus of 19/00z medium range MOS guidance and
HPC shows maximum temperatures ranging between 80-85f across the alleghenies and
85-90f east of the mountains in the central ridges and susq valley. In the
summertime pattern...precipitation opportunities will be hard to pinpoint
and thus day 4-7 probability of precipitation came out looking very close to climatology with
modified diurnal trend.
&&
Aviation /16z Wednesday through Sunday/...
expect widespread VFR today as high pressure and dry air build
into the region. High pressure will control the weather into the
weekend.
Outlook...
Thu-Fri...no sig weather expected.
Sat-sun...isolated PM thunderstorms and rain impacts possible.
&&
Climate...
astronomical Summer begins at 104 am EDT on Friday June 21st.
&&
Ctp watches/warnings/advisories...
none.
&&
$$
Synopsis...gartner/steinbugl
near term...gartner/steinbugl
short term...steinbugl
long term...steinbugl
aviation...ceru/gartner
climate...steinbugl/gartner
