Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
408 PM EDT Friday Jul 3 2015
low pressure will move just south of the state later tonight and
Saturday. Weak high pressure will then build into the region for
later Saturday and Sunday. Drier weather continue into early next
week before unsettled conditions return for midweek.
Near term /until 6 am Saturday morning/...
most of the low clouds brought north by the weak low level upslope
flow have dissipated...while a more widespread cumulus field has
cooked up under the early July sunshine. Higher clouds are also
beginning to advect into the area ahead of the shortwave that is
approaching from the Ohio Valley.
A weak storm over northern Kentucky is expected to track east-northeast and
move along or just south of the Mason Dixon line later tonight
into Saturday. Models are in good agreement bringing a period of
light-moderate rain into the region tonight...into Saturday
morning. Ensembles use a 20-30kt south-southeast low level jet to bring a
brief surge in precipitable waters into the area. Rain/showers are made to
develop after about 20z/4pm over my southwestern zones...moving steadily
NE during the evening.
Overnight lows will be relatively mild from the upper 50s north
to middle 60s southeast.
Short term /6 am Saturday morning through 6 PM Saturday/...
short range model consensus timing of the surface low has it
moving off the New Jersey coast by early to middle afternoon Saturday. While
this bodes well for the steady rain to taper off and conditions to
improve for the second have of the day...a wedge of high pressure
ridging in from the northeast suggests that the low level
moisture may be hard to scour out...keeping US mainly cloudy and
Basin average quantitative precipitation forecast for the upcoming 12-18 hour event looks to
average between .50" - 1.00" over much of central PA with higher
amounts possible over The Laurels where the upslope component to
the deep layer flow should help to enhance the rainfall. The area
is pretty wet given recent rains so flash flood and headwater
guidance is rather low. However after collaborating with
surrounding offices we have decided against a watch at this time.
Have downplayed the chances for thunder...but the models do Cook
up a bit of instability so some embedded thunder cannot be ruled
At this time we are expecting the rain to taper to isolated showers
Saturday afternoon...leading to mainly favorable conditions for
evening outdoor activities and fireworks displays.
Highs on the 4th will be cool for the time of year. Upper 60s to
lower 70s will average some 5-10 degree cooler than normal.
Long term /Saturday night through Friday/...
surface low will track to our east by Sat night...with frontal
boundary stalling to our south. That will keep just very low probability of precipitation
across southern tier sun into Sun night. Temperatures across the south
will be near normals with some cloud cover around...while more sun
in the north will allow maximums to peak a bit above normal.
Ridge off the East Coast will gradually cede to a mean upper
trough centered west of PA for much of the week...resulting in
regular opportunities for rain. Ecens/gefs indicate the best chance
for rain will accompany passage of shortwave Tuesday night into Wednesday.
Diurnally-driven scattered convection returns Monday-Tuesday as weak return
flow kicks in. However...deep moisture and opportunity for
meaningful rainfall should hold off until approach of cold front
and positive precipitable water anomalies Wednesday. Temperatures will remain above normal
early this week.
Late week will feature westerly flow with tough to time shortwaves
sliding across keeping mention of rain chances ongoing. Temperatures slip
back to seasonal normals.
Aviation /20z Friday through Wednesday/...
all terminals are VFR as of Idaho day and will continue into the
evening before the approaching low pressure area over brings
widespread rain and reduced conditions later this evening into at
least early Saturday afternoon.
The rain will taper to just scattered showers by later
Saturday...but the low level moisture is expected to hang tough
keeping ceilings MVFR or lower into Sunday before improvement
begins to develop.
Sun...becoming VFR. No sig weather.
Mon-Tue...areas of MVFR with showers isolated thunder. Mainly
Wednesday...mainly VFR with rain showers possible.
near term...la corte
short term...la corte