Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service State College PA
814 PM EDT Sat Jul 30 2016

a plume of deep moisture on the west side of the subtropical ridge
will produce showers and thunderstorms over the region into early
Sunday. A weak trough will push the deep moisture to our east
Sunday. Behind this system it will slowly dry out. A ridge
building to our west early next week will work its way eastward
producing some hot weather later in the week. This surge of warm
air appears to be just ahead of what could be a real cold front
and a real break from the warm weather we have had for the past


Near term /until 8 am Sunday morning/...
fairly active mid to late afternoon with isolated severe reports
along with marginal heavy rain and flooding of poor drainage areas
in parts of the mid to lower susq River Valley. All areas had been
well worked over by late afternoon and rainfall transitioned to
more homogeneous light to locally moderate by early evening.
Quasistationary upper level trof over the central glaks and Ohio
Valley was helping to pool tropical precipitable water over the Delmarva and
southeast Piedmont regions this afternoon and evening...and
lifting weak shortwave over PA is pushing the back edge of large
shower and thunderstorm complex east of my area early this

To the west where instability remains...a broken line of showers
and storms is targeting the southwest corner of PA...and isolated
nearly stationary activity is lined up just northwest of the
northwest corner of Warren County.

This activity will continue to dissipate as the evening wears previous forecaster mentioned that the NCEP hrrrv2
appears to get 80 percent of the rain out of our area by about
0500 UTC. Expect isolated at worst coverage after midnight with
most areas remaining dry overnight...but with areas of fog
forming. Expect many areas to get below one mile visibility in the
pre dawn hours lasting through 7 am.


Short term /8 am Sunday morning through 6 PM Sunday/...
Sunday will feature more of the same...with a bit less coverage
the diminished deep layer moisture as the 2" precipitable water plume will have
been displaced off of the eastern Seaboard. This will allow temps
to warm several degrees higher than today's...which will spark
another round of afternoon and evening shra and tsra.


Long term /Sunday night through Saturday/...
short-waves sweeps to the coast but broad upper level trough
lingering across PA. The main trough axis lies through central PA
by 12z Monday and slowly progresses east through the day. With
the trough and cyclonic flow aloft scattered showers/isolated
thunderstorms are possible with best chances over the eastern
counties in the afternoon. High pressure builds in Monday night
and everything begins drying out. For Tuesday into Wednesday a sharp
upper level ridge is to our west over the Great Lake region with
the trough now off the coast, dry northwest flow and surface high
pressure across the region.

Short-wave weakens the ridge into Thursday. European model (ecmwf) takes this south
across Ohio into Virginia leaving PA dry. GFS is weaker and further
north with some convection over the PA mountains which it moves
east across PA through Thursday night. Stayed closer to the European model (ecmwf)
solution with no pops at this point. Both models agree on a more
rigorous cold front dropping southeast toward PA on Friday. This
will help surge the temperatures and humidity up ahead of it over
central PA Friday. Right now the timing is such that late day
convective storms will feed off the days heat and humidity and
roll through late in the day into the overnight. Models bring the
cold front southeast across PA overnight and then stall it near
the Mason-Dixon line for Saturday.


Aviation /00z Sunday through Thursday/...
rain tapering off to sct showers this evening as upper lvl
disturbance shifts east of the area. Partial clearing, combined
with wet ground and light wind, will promote areas of fog/low cigs
overnight. Blend of latest mdl guidance supports the idea of
fairly widespread IFR/LIFR conds overnight with onset btwn 02z-06z
based on latest lamp guidance and ncar ensemble.

Mdl soundings indicate fog/low cigs will lift by late am, with widespread
VFR likely by aftn. Sct shra/tsra are likely form during the aftn,
which could produce a brief vis reduction in spots thru early

Outlook... fog possible, then isold PM tsra impacts possible. fog possible. sig wx expected.

Thursday...isold PM tsra impacts possible western PA.


Ctp watches/warnings/advisories...


near term...grumm/devoir
short term...grumm
long term...Watson

National Weather Service Glossary of Abbreviations