387 
fxus61 kctp 301140 
afdctp 


Area forecast discussion 
National Weather Service State College PA 
740 am EDT Sat Aug 30 2008 


Synopsis... 
a cold front will drift slowly southeast across central PA during 
the day today. Sunshine and Summer-like temperatures will follow 
for the rest of the Labor Day weekend...and at least into the 
middle of next week...as a large area of high pressure settles 
over the region. 


&& 


Near term /until noon today/... 
line of showers and a few rumbles of thunder are moving through 
western PA...and should continue to move eastward this morning. The 
front seems to be farther west than this line...and the stable air 
over the eastern half of the area should lead to some weakening. 


Temperatures will remain very steady...as they are already very close to 
the dewpoints. Fog is not really dense at this time...with the low 
stratus over most of the region - and the approach of the showers 
should stir up the llvls a bit...so not anticipating a dense fog 
advisory this morning. 


Scattered showers should push to the southeast of ipt/unv/jst before noon. 


&& 


Short term /noon today through 6 PM Sunday/... 
wind shift associated with the cold front seems to occur in 
advance of the lower dewpoints across lower Ontario this 
morning...so expect a similar lag to the dry air infiltrating 
central PA this afternoon and evening. This double whammy of 
fronts could lead to more showers and perhaps a few thunderstorms 
across southern and eastern areas this afternoon. But...this will 
only occur if the plentiful low clouds in place break or slide out 
of the way for some decent solar heating to take place. While 
this is possible...it won't be likely. So will hold chance probability of precipitation 
across the southern half and east-central zones for this afternoon. 
Sref plumes paint a wide spread to the possible convective available potential energy this afternoon 
across the south with values from none to 1000 j/kg...with mean 
about 400. So...if there are breaks we could hear thunder. Will 
continue to mention thunder as well. The temperatures will be close to or 
even slightly above normal for this time of year. 


The front and the drier air behind it continue to look rather 
slow to push through completely...so will linger a low chance in the 
evening in the far southeast...and along the Maryland border. Then...most 
showers should be gone after 10 or 11 PM. Expect some fog to kick 
in as the skies clear. There could be enough of a light north 
breeze to keep it from getting bad...so will just mention as 
patchy fog for now. Mins might dip to the l40s in the northern mts...so 
valley fog is a given there. 


Sunday looks like a great day with low dewpoints and lots of 
sunshine. A few cumulus are possible in the NE...and some middle/high 
clouds possible in the south. Maxes will get a few degrees warmer on 
Sunday...putting the region squarely above normal. 


&& 


Long term /Sunday night through Friday/... 
we will see a return to warm and dry conds in the extended...as a 
ridge of hi pressure builds across the Middle-Atlantic States. The 06z 
gefs shows 500mb heights building to +1 Standard dev above normal from 
Sunday into Wednesday...which should lead to plenty of sunshine 
and above-normal temperatures. 


Once in place...the aforementioned hi pressure ridge will be slow to 
budge. However...a frontal boundary will gradually approach PA from 
the northwest late next week....accompanied by an increase in 
clouds and slightly higher probability of precipitation. This front seems to be a bit 
delayed by the models when compared to yesterday/S model 
runs...but still expect fnt to begin to impact regional weather by 
late next week. 


An additional variable in the extended period is what will come of 
the moisture from the suddenly very-active tropics. Right now...it 
appears that any moisture from Gustav and/or Hanna should not have 
an impact on central PA weather until the end of next week...at 
the earliest. 


&& 


Aviation /12z Saturday through Wednesday/... 
guidance appears to be aggressive with bringing dry air into most 
airfields across central PA...so have slowed the progression which 
will match reality. As a result of the slow arrival of relatively 
drier air minimal mixing height between 14-16z will linger IFR ceilings and 
MVFR/IFR visibilities with gradual improvement. A few terminals could 
linger through 17z before going MVFR. 


It appears a couple fronts exist with the first acting as a wind 
shift and providing low chance rain showers. This front will slowly push southeast 
across central PA airfields late morning/early afternoon. Linger rain showers 
for airfields at or above kmdt/klns this afternoon. Second and actually the 
main front is still held up in Michigan...with dry air associated. Dry 
air does not arrive until around sunset or 00z sun. Expect clear 
skies and light north flow to arrive...however challenges for 
airfields will arrise after 06z sun on whether fog will dev before 
dew points begin to fall from drier air filtering in. 


Second half of weekend will feature broad surface ridge building in 
and providing VFR conds for several days...or at least through Wednesday. At this time 
it appears the nocturnal hours Sat night/Sun night could be prime candidates 
to see valley fog develop. 


&& 


Ctp watches/warnings/advisories... 
none. 


&& 


$$ 
Synopsis...dangelo 
near term...dangelo 
short term...dangelo 
long term...evanego 
aviation...beachler