Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1019 am 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 /through tonight/...
The fog has lifted but considerable low clouds are stuck in the
mountains of western Pennsylvania. A similar situation to the
east. Central areas are mostly clear
Temperatures will be near normal today. Not nearly as hot in the
south and east as earlier this week.
The cams suggest very few places will see any showers/rain today.
I used the blend for a background field which had at least
isolated showers everywhere. I put the hrrrv1 over this and it got
rid of most of that. The hrrrv1 has popcorn like showers over
central PA this afternoon. Nothing to focus on and slightly larger
popcorn in northwestern areas. So focused higher chance pops in
northwestern areas. No need to Chase convective parameterization
schemes crazy quantitative precipitation forecast in hydrostatic models. Screaming message very
isolated showers in central PA best chance in northwestern PA.
Hrrr only GOES into early evening. But it's quantitative precipitation forecast and radar
forecasts imply nothing to worry about well beyond midnight. The
ncar 3km efs probability matched mean quantitative precipitation forecast is similarly light on
quantitative precipitation forecast even in the northwest where it too has a very weak signal.
The ncar efs pretty much thinks we should be rain free until the
next forecast period.
Short term /Saturday/...
The NCEP forecasts systems are all confident in a plume of
moisture moving into southern and through southeastern PA Saturday
into Saturday night. Thus they are all robustly wet. Cams would
likely temper this and keep the rainfall in the plume of deeper
moisture and instability. The ncar 3km efs implies scattered
showers by 14z Saturday.
After 15z we are stuck using the NCEP models which have been too
wet. It's Summer and convection is not their forte. These systems
force one to consider rainfall over all of central and eastern PA
by 18z Saturday with lower pops to the east. The models release
the instability and "rainfall" in the higher precipitable water plume which
lingers into Sunday. Needless to say low confidence in widespread
rain event Saturday afternoon into Saturday night over most of
central and eastern PA. Since the gefs has over an inch in our
central and eastern counties we can assume there will be locally
moderate rainfall in the east with more focused convection. When
and where hard to pin down.
As this time period comes into the realm of the cams we will get a
better idea. The coarser models using cps's are not going to do
well and we know the rain will most likely be more focused than
indicated in these models.
Long term /Saturday night through Thursday/...
a second wave moves through in cyclonic flow Saturday night and Sunday
keeping the pops in the 50-70 range with highest chances over the
eastern counties. Short-wave moves to the coast Sunday night with
ridging building in across central PA helping clear things
out.Monday should be a drier day with sunshine and temps in the
80s.Hi pres ridge should hold through Wednesday though the GFS
tries to indicate maybe an isolated afternoon/evening shower or
thunderstorm over the Laurel Highlands both days.
Aviation /14z Friday through Tuesday/...
Fog is gone. Still some low clouds in west but burning off fast.
Patchy fog possible overnight. Thus some MVFR/IFR possible.
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.