Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service State College PA
529 PM EDT Friday Jul 29 2016

an upper level trough will influence the region through early
next week...bringing daily chances of scattered showers and
thunderstorms. Most of the time will be dry in any one location
however. High pressure will build over the northeastern United
States by mid to late next week.


Near term /until 6 am Saturday morning/...
dying cold front pushing into northern PA early this evening,
producing enough lift to support sct convection ovr the northern
counties at 21z. Latest cams indicate focus for dwindling
convection will shift into the central counties toward sunset
as outflow bndry pushes south. Nocturnal cooling and lack of sig
forcing should result in nearly all the leftover showers
dissipating by midnight. Focus will then shift toward shortwave
approaching from the grt lks. Latest guidance supports an
increasing chc of showers assoc with this feature ovr the western
counties arnd dawn.

Low tonight mainly in the 60s some warmer spots in southeast and
cooler in northwest.


Short term /6 am Saturday morning through 6 PM Saturday/...
most guidance continues to show the plume of high precipitable water air coming
into PA Saturday. This favors increased chance of showers and
thunderstorms. Each hydrostatic model and it's convective
parameterization scheme (cps) have a different idea on the
evolution. The high precipitable water air and SW flow favors the chance of rain.
The 12z NAM maybe a excessive later Saturday into Sunday.

At this time the gefs 0.5 degree data implies the chance of rain
increases rapidly after 11 am Saturday and keeps climbing. It of
course has a big wet bias in convective cases. The gefs and all
the blends imply lowest pops in northwest and west and higher
central to eastern areas. Gefs is basically showing rain over all
of eastern and central PA by 21z.

Expect showers and thunderstorms with areas affected by intense
cores to see some better rainfall amounts. Most areas should not
see the widespread 0.5 to 1.0 inch amounts.

The rainfall peaks in the sref/gefs shortly after the cape peaks.
This implies mostly convective and cps is biasing forecasts.

The most intense rainfall is forecast mainly after 21z and early
overnight Saturday which is mainly in the next forecast period.


Long term /Saturday night through Friday/...
shortwave moves across PA Saturday night triggering showers and
possibly a thunderstorm. As that passes to the east, there should
be a break and then the main trough moves through with some
scattered convection likely late Sunday and Sunday night. Do not
believe it will be as wet as earlier advertised by models. Diminishing
pops into Monday as the upper level trough and cyclonic flow
slowly exits off the coast. Big ridge builds over the central US
and moves east to Ohio by Friday. This puts US into a drier
pattern with northwest flow. May see something move over the ridge but
then drop to the west and south of PA. Can't rule out some
afternoon clouds popping and maybe an isolated convective cell
over the higher terrain but that should be it. Temperatures will
start out in the normal range and warm toabove normal toward the
end of the week.


Aviation /21z Friday through Wednesday/...
VFR all about the air space. Issues this afternoon include some
very isolated rogue showers in central PA and more organized
showers in northwestern PA. Check radar before takeoff as some of
these showers will develop into thunderstorms.

Models imply rain and showers move in Saturday into Saturday
night. Shower with lower visibility and ceilings along with
isolated thunderstorms will be an issue from about midday Saturday
through midnight. Then more IFR in patchy fog where it rains.


Sat...showers and isolated thunderstorms IFR/MVFR then overnight fog.
Sun-Mon...scattered showers and isolated thunder.
Tuesday...improving conditions.


Ctp watches/warnings/advisories...


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

National Weather Service Glossary of Abbreviations